EP4547480A2 - Biodegradable ground sealing sheet - Google Patents

Abstract

The invention relates to a plastics geo-mat, comprising an upper cover layer, a lower cover layer, and a middle filling layer, which is disposed between the upper cover layer and the lower cover layer and is composed of a filling layer material comprising a material capable of swelling. The invention is characterized in that the upper cover layer and/or the lower cover layer consists of or comprises a biodegradable material; the peeling resistance at a predefined time after the start of the biodegradation process is characterized by a residual degree of peeling resistance, which is formed by the square of a quotient of a reduced peeling resistance which the upper and lower cover layers and the connecting structure have at the predefined time and an initial peeling resistance which the upper and lower cover layers and the connecting structure have before the start of a biodegradation process.

Description

Biodegradable soil sealing membrane

The invention relates to a geosynthetic mat, comprising an upper cover layer, a lower cover layer, a middle filling layer arranged between the upper cover layer and the lower cover layer made of a filler layer material which comprises a swellable material, the filler layer material having a swelling behavior, and a connecting structure by means of which the upper and lower cover layers are mechanically connected to one another at several positions through the middle filler layer, the positions of the connection being spaced apart from one another, preferably at a regular distance from one another along positions following straight lines, so that the upper and lower cover layers have peel strength through the connection structure have to each other.

The filler layer material has a swelling behavior that is typically at a predetermined time after the start of the swelling process by a degree of swelling, which is determined by the ratio of the volume of the filler layer material, including the water absorbed therein, at the predetermined time to an initial volume of the filler layer material that the filler layer material has before the start of the swelling process, wherein the degree of swelling is determined by completely immersing the geosynthetic mat in a water bath over a period of time up to the predetermined time and determining the volume of the filler layer material before immersion and at the predetermined time. The degree of swelling therefore indicates the swelling ability of a material in unhindered conditions and can, for example be determined according to ASTM D5890. For example, a defined amount (2g) of dry filler layer material is placed in a 100ml measuring cylinder filled with 90ml water. Then fill up to 100ml with water. The filling layer material sinks to the bottom and an initial volume of the filling layer material can be read off the scale of the measuring cylinder immediately after filling in the filling layer material. The filling layer material then swells for a predetermined period of time, for example at least 16 hours. The swelling volume can then be read off by determining the height of the swollen filling layer material using the scaling on the measuring cylinder and the degree of swelling can be determined by forming a quotient with the initial volume.

A further aspect of the invention is a use of such a geoplastic mat and a method for producing such a geoplastic mat.

Geosynthetic mats of the aforementioned type are used to create a seal on a soil layer or within a soil; in other applications, such geosynthetic mats can also be used to additionally stabilize a soil layer and/or to protect a structure against mechanical or hydraulic influences or combinations thereof, for example in the area of a water or channel bank, an embankment, a barrier dam or a dike structure. They can also be used to protect other thin-layer waterproofing components.

The functional principle of such geosynthetic mats is that the middle filling layer, which is typically many times thicker than the upper cover layer and the lower cover layer, is not swollen and in no way hardened in the state immediately after production and therefore has a mechanical flexibility that prevents the material from rolling up Geosynthetic mat allowed to form a roll. On the one hand, this makes the geosynthetic mat transportable, and on the other hand, this flexibility allows the geosynthetic mat to nestle against a soil topology at the installation site. The geosynthetic mat is then rolled out at the installation site; In this case, by parallel, overlapping rolling out of several geosynthetic mats next to each other, a floor area can also be covered that is wider than the width of the geosynthetic mat transverse to its longitudinal direction, which corresponds to the rolling out direction.

After installation, the middle filling layer swells due to water absorption, which can be caused by the soil moisture at the installation site, and if necessary also by artificial moisture Water supply can be accelerated. This swelling causes a homogenization and a decrease in the air pore volume of the middle filling layer, whereby on the one hand it achieves the desired homogeneous and largely isotropic very low water permeability, characterized by the permeability kio, which is ideally less than 5x10 ^-10 and preferably less than 5x10 ^- after swelling of the middle filling layer. ¹¹ m/s can be. However, this homogenization and decrease in the air pore volume requires that the middle filling layer cannot expand unhindered, which requires the influence of the interconnected upper and lower cover layers as mechanical counterpressure, which brings about a desired limitation of the increase in volume. In certain installation situations or installation phases, such counterpressure can also be caused or increased by surface pressure on the upper cover layer, which is achieved by installing soil layers above the geosynthetic mat using its weight. The low water permeability achieved results in a sufficiently high sealing effect to be able to hold water in standing or flowing water, to provide landfill seals or to protect dike structures against moisture penetration.

The upper and lower cover layers and the connecting structure connecting these two cover layers therefore fulfill essential functions that are necessary for the use and properties of the geosynthetic mat. On the one hand, the cover layers and the connecting structure make the geosynthetic mat rollable and manageable and consequently retain its structure with the positioning of the middle filling layer between the two cover layers in a desired thickness even when rolled up after production, during transport and when laying at the installation site. Through the two cover layers and the connecting structure, a mechanical stabilization and therefore a mechanical counter-pressure against the swelling pressure of the middle filling layer is generated and maintained after the geosynthetic mat has been installed, whereby the middle filling layer develops a desired, dense structure when it swells. As a result of this swelling under the mechanical counterpressure, which is achieved by the narrowing of the middle filling layer between the two cover layers and the connecting structure, the inventors believe that the desired low permeability of the geosynthetic mat can only be achieved after the middle filling layer has swelled, and this low permeability should be in In the best case, this can be achieved regardless of whether a layer with a certain weight can be installed above the geoplastic mat or not. Finally, in installation situations in which a geosynthetic mat of the aforementioned type is installed at an angle, for example on a slope, the geosynthetic mat must have a shear strength in order to avoid that the geosynthetic mat itself represents or forms an unstable layer in the slope and consequently slides down the slope Geosynthetic mat could act as a separating layer. This shear strength is achieved by the connection structure between the upper and lower covering layers, thereby achieving a stable connection between the lower soil layer on which the lower covering layer rests and the upper soil layer resting on the upper covering layer.

Geosynthetic mats of the aforementioned type with properties which have good sealing, shear strength and mechanical resilience are known as clay sealing membranes, such as the bentonite mat from Naue GmbH & Co. KG and are described in EP 0 278 419 B1.

From DE19956783A1 a mat designed for covering carcasses is previously known, which was developed from the bentonite mat described in EP 0278419 B1. With this modified mat, the use of a virucidal or bactericidal powder instead of the sealing powder (e.g. bentonite) proposes a mat that effectively prevents active microorganisms from emerging from the grave site through a chemical-biological effect. The mat developed in this way therefore takes a route to providing a chemical-biological barrier against microorganisms instead of sealing by swelling by using appropriate virucidal/bactericidal fillers. This represents a special mat that is suitable for the specific purpose of covering carcasses and the associated microbial hazard, but cannot be used well for other purposes.

Another floor mat is known from DE60203517T2, which is based on the technology known from EP0278419B1. The aim of this floor mat is to ensure that the bentonite arranged in the intermediate layer can penetrate into the cavities and gaps in the adjacent floor area and only swell there. This is intended to fill these cavities and spaces. In order to achieve this, the top layer of the floor mat should dissolve when it comes into contact with the floor due to the influence of water. The technology of this floor mat therefore turns away from the principle of the floor mat originally described in EP0278419B1 with a swelling and compacting function of the bentonite within the intermediate layer and instead strives for rapid dissolution of the top layer so that the bentonite expands before it begins to swell the intermediate layer into the Cavities and spaces in the adjacent soil can move and then swell there. This floor mat is therefore suitable for special applications in which a layer of earth that is basically made up of sealing earth materials, but which has cavities and gaps, is to be sealed by sealing these defects. It is not suitable for other general sealing applications due to the rapid dissolution of the cover layer required.

Such previously known geosynthetic mats are installed for temporary or permanent sealing, for example to protect thin-layer plastic films, as an element with a separating function or to stabilize soil layers or surfaces. However, in some applications with morphologically variable geometry, long-term disadvantageous effects occur from an environmental protection point of view. On the one hand, when such geosynthetic mats are used permanently, sections of the geosynthetic mat can be separated by erosion processes and transported to other locations by wind or water flow and then represent pollution in an undesired location. When such geosynthetic mats are used temporarily, in some cases the geosynthetic mat can be isolated again from the ground be dismantled and then disposed of. In many cases, however, such an isolated expansion is not possible because layers of earth adhere to the geosynthetic mat or the geosynthetic mat is damaged during expansion. In such cases, a large amount of soil is often removed and the entire removed volume then has to be disposed of. Due to the synthetic components in this expanded volume, disposal falls into high pollutant classes and is correspondingly expensive.

The invention is based on the object of providing a geosynthetic mat which overcomes these aforementioned disadvantages and at least meets, preferably exceeds, the necessary mechanical properties and sealing properties of previously known geosynthetic mats.

This object is achieved according to the invention with a geosynthetic mat of the type mentioned at the beginning, in which the upper cover layer and / or the lower cover layer consist of a biodegradable material or include a biodegradable material, the peel strength being at a predetermined point in time after the start of the biodegradation process a residual peel strength degree is characterized by the square of a quotient of a reduced peel strength, which the upper and lower cover layer and the connecting structure at the predetermined time has, to an initial peel strength, which has the upper and lower cover layer and the connecting structure before the start of a biological degradation process, is formed, the residual peel strength in a composting test by completely inserting the geosynthetic mat into compost and composting in a temperature range that is above 25 ° C and is below 65°C, up to the predetermined time and measurement of peel strength in a peel test before pickling and at the predetermined time after removal from the compost or in a marine incubation test, with the following environmental conditions:; Temperature 30°C +/- 2°C; aerobic conditions in seawater with a salt content of 3.5% by weight +/- 1% by weight and measuring the peel strength in a peeling test before insertion and at the predetermined time after removal from the seawater, and the swelling behavior is characterized by a degree of swelling elevation, which is formed by the quotient of the volume of the filling layer material including the water absorbed therein at the predetermined time to an initial volume of the filling layer material before the start of swelling, the degree of swelling elevation being achieved by completely immersing a layer of filling layer material in a water bath and loading the layer of filling layer material is determined with a pressure of 4.5 N/m ² . According to the invention, the geosynthetic mat has a swelling-degradation ratio, which is formed from the degree of swelling elevation divided by the residual peel strength degree, is in a range between 1 and 5 within the first week after the simultaneous start of the swelling process and the biological degradation process and within each predetermined point in time from the beginning of the second to the end of the third month after the start of swelling and dismantling in a range between 1.5 and 25, preferably in a range with a lower limit of 2 and / or an upper limit of 15.

The invention is based on the following findings: Basically, the invention pursues the approach of replacing the synthetic components of the geosynthetic mat, which were unavoidably used in previous geosynthetic mats in particular to provide the upper and lower cover layer and the connecting structure, at least partially, preferably completely, with biodegradable materials to be replaced by the upper and lower cover layers and the connecting structure comprising a biodegradable material or consisting of such a biodegradable material. In the sense of the invention, a biodegradable material is to be understood as meaning a material that can be installed under the typical environmental conditions in a soil installation position, i.e. in a moist environment of a soil layer, which can consist of the main components earth, sand, clay and mixtures of these typical soil layer components a short or medium-term period, including a period of a few weeks to a few months, up to two years or several years, for example up to 10 years, is decomposed in a biological, chemical or biochemical process and thereby converted into components that are harmless to the environment.

The reduction in peel strength due to this biological degradation process, which is significant according to the invention, is determined according to the invention in a composting test; this can be done, for example, by a soil composting test with the following environmental conditions: temperature 50 ° C +/- 5 ° C; thermophilic conditions according to ISO 16929, or by a marine incubation test, with the following environmental conditions:; Temperature 30°C +/- 2°C; aerobic conditions in seawater with a salinity of 3.5 wt% +/- 1 wt%; be characterized. It should be understood here that the material used according to the invention has in particular a biodegradability according to the aforementioned soil composting test if it is intended for a soil layer sealing beyond flowing or standing water and has a biodegradability according to the aforementioned marine incubation test if it is intended for a Soil layer sealing in a body of water or on the bottom of a body of water is intended. The peel strength of a biodegradable material is determined over the biological degradation period in such a way that the geosynthetic mat is stored under the aforementioned environmental conditions of one of the two suitable tests for several different specific periods of time and after this period of time is subjected to a peeling test, for example a drum peeling test according to DIN 53295 or a peel test according to DIN EN 28510-1:2014 DE or according to ASTM D6496 in order to determine the progression of peel strength over time.

In particular, a composting environment in accordance with Section 5.1 of DIN EN ISO 16929:2018-04 can be provided, i.e. an environment with the following conditions in order to carry out the composting test: the geosynthetic mat is placed in fresh organic waste with a natural, ubiquitous microbial population, so that this Biowaste the geosynthetic mat at least 30cm on both sides. thick covered, Temperature, pH, moisture content and gas composition are monitored, the composting test is carried out in a container large enough for natural self-heating to take place, sufficient and uniform fumigation is carried out through an air supply system, the container can be placed in a climate chamber with a If the compost reaches temperatures above 65°C during the spontaneous thermophilic phase, the diversity of microorganisms can be reduced.

To restore the full range of thermophilic bacteria, the compost can be re-inoculated with mature compost (about 1% of the total initial mass of biowaste) of recent origin (maximum 3 months old).

For the composting test, homogeneous organic waste of the same age and origin is used, which is reduced to a particle size of a maximum of 50mm by shredding or sieving. Depending on the type of waste, 10%-60% of a filler made from structurally stable components such as wood chips or bark with a particle size of 10mm to 50mm is added. The organic waste must meet the following criteria: the C/N ratio of the mixture of fresh organic waste and filler is between 20 and 30, it can be balanced with urea if necessary, the moisture content is more than 50% by mass, but there is no free water before the loss on ignition of the dry residue is greater than 50% mass fraction, the pH value is above 5. In addition to the peel strength, according to the invention the swelling behavior is also taken into account as a property of the geosynthetic mat and the properties are adjusted in relation to the peel strength. According to the inventors' knowledge, the pure degree of swelling cannot be used as a characteristic variable for the desired long-term sealing properties of the geosynthetic mat for many applications because the degree of swelling does not adequately reflect the desired compaction properties of the middle filling layer. Instead, the middle filling layer is formed or characterized with a degree of swelling, which describes the increase in volume under a constant pressure, which is realized in the test as contact pressure on the material layer, for example by a plate or disk with a corresponding weight.

In principle, it should be understood that the degree of source elevation is taken into account over at least the first month and the following two months. In principle, the degree of swelling can also be taken into account over a longer period of time, which results in a good coordination of the properties, particularly in the case of slowly swelling middle fill layers. For some materials, it should be taken into account that they undergo an initial swelling when stored in air, for example because these materials come out of the production process very dry and capable of absorbing water. In such cases, it should be understood that the materials, in accordance with the realistic conditions of intermediate storage in air and the swelling that occurs, are only used in the test of the swelling behavior according to the invention in a state that then arises, in order to avoid falsification of the results due to unrepresentative initial effects, which could otherwise occur in the first hours or the first days of the swelling test.

The decisive factor for fulfilling the functions of the geosynthetic mat is, on the one hand, that the upper and lower cover layer and the connecting structure always maintain sufficient counterpressure against the swelling of the middle filling layer, which, in a timely manner, leads to sufficient compaction of the middle filling layer, particularly in the first few months This leads to the pores in the middle filling layer closing. In this way, the necessary tightness is achieved and can then be maintained over a long period of time, in particular after the swelling has asymptotically approached a maximum degree of swelling and the biological degradation has progressed to such an extent that the peel strength is significantly reduced or is close to zero. On the other hand, in many applications it is important that the geosynthetic mat provides the mechanical properties at any time after its installation that prevent slipping if installed on a slope. According to the inventors' knowledge, an initial small reduction in the peel strength in relation to the swelling is crucial in order to maintain the shear strength through the biodegradable structures in an early phase in which no stabilizing function of the middle filling layer has yet developed.

The period within which the desired properties, characterized by the swelling-degradation ratio, must be present can range from a few weeks to one or two years from the start of swelling and biodegradation.

Although the use of such biodegradable materials can in principle reduce or completely avoid the problem of contaminant transfer or pollution after removal of such a geosynthetic mat, the use of such biodegradable materials is hindered by the fact that the sealing effect of the geosynthetic mat is fundamentally not achieved due to biodegradation is because the necessary counterpressure is not generated or not sufficiently generated when the middle filler layer swells and as a result, after swelling, the permeability of the geosynthetic mat is too high, which does not achieve the desired sealing function. On the other hand, due to the biological degradation of the cover layers and the connecting structure, the shear strength of the geosynthetic mat is reduced to such an extent that slipping of slope layers occurs if the geosynthetic mat is installed at an angle on a slope. The use of biodegradable geotextiles is therefore seen as critical or unsuitable in many applications with regard to the time requirements for the mechanical bonding effect and DIN EN 12225 specifies test criteria for geosynthetics in order to demonstrate general resistance to microbial degradation.

The geosynthetic mat according to the invention overcomes these problems through a swelling behavior that is coordinated with the behavior of biological degradation. For this purpose, the composite of upper and lower cover layer and connecting structure is characterized according to a degree of residual peel strength, which this composite has due to a biological degradation rate after a certain biological degradation period, i.e. at a predetermined point in time after the start of the biological degradation process over a subsequent period of time. This residual peel strength therefore characterizes the composite of the two cover layers and the connecting structure in this way its peel strength decreases rapidly over time due to the biological degradation process, so it represents a curve that shows the peel strength of the biodegradable material over the time of biological degradation. The slope of the curve at any point in time can be defined as the degree of peel strength reduction. The further the biological degradation has progressed, the lower the degree of reduction in peel strength. The faster the biological degradation takes place, the steeper the curve of the degree of peel strength reduction falls over time and, consequently, the faster the peel strength of the composite decreases. The reduction in the degree of peel strength reduction can occur through biological degradation of the upper cover layer, the lower cover layer and/or the connecting structure or through a reduction in the fastening strength of the connecting structure in the upper or lower cover layer.

On the other hand, the filling layer material of the middle filling layer has a swelling capacity, which is characterized by water absorption and swelling capacity of the filling layer material. This ability to swell is characterized by the degree of swelling, which describes the increase in volume of the filling layer material at a certain point in time after the start of swelling in relation to the dry volume of the filling layer material before the start of swelling under a pressure load of 4.5N/m ² and results in a curve over time which shows the increase in the of the volume of the filling layer material over the swelling time. The higher the degree of swelling, the greater the ability of the filling layer material to swell under load. It should be understood that the degree of swelling elevation of the material is determined without restricting the path of the swelling movement, meaning that the material can increase its water content or volume unhindered when determining the degree of swelling elevation. In practice, this can be done by a force-controlled test or by placing a vertically freely movable plate weighing 4.5 kg per square meter on the fill layer material when determining the degree of swelling.

The swellable material of the middle filling layer and the biodegradable material of the upper and lower cover layer and possibly also the connecting structure are now designed in such a way that the relationship between the degree of swelling of the swellable material and the residual peel strength of the composite of the upper and lower cover layer and connecting structure over an initial period of a week in a range between 1 and 5 and from the beginning of the second to the end of the third month between 1.5 and 25, preferably between 2 and 15. Through these two temporally successive and coordinated material properties Middle filling layer on the one hand and the mechanical composite surrounding this middle filling layer on the other hand, it is achieved that in the initial phase of swelling of the middle filling layer, the upper and lower cover layer and the connecting structure between these two cover layers build up a sufficiently high mechanical counterpressure against the swelling pressure and maintain it over such a long period of time can ensure that the middle filling layer is sufficiently compacted during this swelling process. In addition, it is achieved that the upper and lower cover layer and, if applicable, the connecting structure have biologically degraded at a later point in time, when this swelling is largely or completely complete, thereby reducing pollutant pollution when the geosynthetic mat is removed or when parts of the geosynthetic mat are removed due to erosion can no longer occur.

According to the inventors' knowledge, with sufficient homogenization and a decrease in the air pore volume, the middle filling layer can develop a shear strength overall that is at least in the area of the shear strength of the geosynthetic mat immediately after installation, i.e. when the middle filling layer is not swollen and the initial peel strength of the composite of the upper and lower cover layer and the Connection structure lies or even exceeds it. This reliably prevents the risk of the slope slipping due to an unstable layer plane in the form of the geosynthetic mat.

Due to this composition and the ratio of the material properties with regard to the swelling behavior of the middle filling layer and the degradation of the mechanical properties of the upper and lower cover layer, the geosynthetic mat according to the invention achieves a sufficiently high level of tightness due to the achievable compaction, but at the same time avoids the risk of the slope slipping and thereby provides In the medium and long term, the desired hydraulic and mechanical properties are available without the associated pollution. The geosynthetic mat according to the invention can therefore, provided that the middle filling layer has or consists of appropriate environmentally friendly materials, be installed without the risk of local environmental pollution and an environmental hazard caused by erosion and movement to other locations and can be expanded and disposed of cost-effectively for temporary use.

The inventive ranges of the ratio between the degree of swelling and the degree of residual peel strength, which are maintained within the first three months, ensure a balanced development of the tightness of the geosynthetic mat Sources and the provision of mechanical strength for the soil layer are achieved even when installed on slopes and subject to corresponding shear forces.

It is particularly preferred if the swelling-degradation ratio is in a range between 1.2 and 5 within the first week after the simultaneous start of the swelling process and the biological degradation process from the third day. A particularly preferred swelling-degradation ratio in the first week for the installation of the geosynthetic mat with an overlying weighting soil layer is 1.25 to 4, preferably 1.25 to 3. A particularly preferred swelling-degradation ratio in the first week is for the installation of the geosynthetic mat without an overlying soil layer at 1 to 4, preferably at 1.2 to 3. In principle, the invention can preferably be implemented for different installation situations in such a way that the swelling-degradation ratio in the first week from the third day in a range which has a lower limit of 1, or 1.25 or 1.5 or 2 and which has an upper limit of 1.75 or 2 or 4 or 6.

From the beginning of the second to the end of the third month after the start of swelling and degradation, the swelling-degradation ratio is preferably in a range between 1.75 and 20, preferably in a range with a lower limit of 1.75 or 2 or 2, 5 or 3 and/or a cap of 25 or 20 or 15 or 10.

It is preferred if the swelling-degradation ratio from the third month to the end of the twelfth month after the start of the swelling process and the biodegradation process is in a range between 2 and 50, preferably in a range with a lower limit of 3 and/or has an upper limit of 30. With such a longer period of time, a long-term swelling and degradation process of the geosynthetic mat is recorded and the properties of the geosynthetic mat are such that optimal swelling and degradation behavior is achieved over this longer period of time.

According to the inventors' knowledge, various effects can be advantageously implemented through such a coordinated reduction in peel strength on the one hand and swelling on the other. A strong increase in weight and volume regularly occurs at the beginning of the swelling process and at this point a high counter pressure against the swelling pressure is required in order to achieve the densest possible structure in the middle filling layer. The swelling of the middle filling layer also causes a local compression and mechanical stabilization, which on the one hand results from the swelling under counter pressure itself, which occurs in many materials that are used for swellable middle filling layers can be made, but also results in a stabilized middle filling layer through a chemical process. For example, a layered silicate contained in the middle filling layer can be converted into another layered silicate during the swelling process, for example sodium bentonite can be converted into calcium bentonite, thereby providing greater strength and stability against shear forces from the middle filling layer itself. This conversion process in the middle filling layer therefore allows the peel strength of the stabilizing cover layer and connecting structure to be reduced as the degree of swelling increases, until the cover layer and the connecting structure are completely dismantled at a later point in time.

A typical example of this are middle fill layers that contain a mineral mixture known as bentonite with the main component montmorillonite in powder or granule form or consist of this mineral mixture. This mineral mixture can change from the initial state, which contains sodium bentonite components, into a swollen state, which contains converted calcium bentonite components and thereby increases in shear strength. According to the inventors' knowledge, the calcium ions required for this purpose are often already contained in bentonite in sufficient quantities for ion exchange, and in additional quantities in the surrounding soil, which can accelerate the process. Over time, the ion exchange from sodium (monovalent) to calcium (divalent) takes place. The environmental conditions determine how quickly this process takes place.

It is particularly preferred if the degree of swelling one week after the start of the swelling process is greater than 1.25, preferably greater than 1.5 or 2 and / or the degree of swelling one month after the start of the swelling process is greater than 1.5, preferably greater than is 2 or 3, and/or the residual peel strength degree three months after the start of the swelling process is less than 0.95, preferably less than 0.9 or 0.8 and/or the residual peel strength degree twelve months after the start of the swelling process is less than 0, 9, preferably less than 0.75 or 0.5. Basically, swelling behavior is to be understood as meaning that the middle filling layer swells to a relevant extent over time and biological degradation behavior is to be understood as meaning that the peel strength drops to a relevant extent over time. According to this training, not only is the ratio of swelling and biological degradation set in a certain range, but the swelling behavior and the reduction in mechanical strength due to biological degradation are also isolated in an advantageous range of values, which ensures favorable swelling and a time-appropriate biological Reduction achieved. For many applications, rapid swelling is necessary Establishing a tightness is initially important, whereas biological degradation can and should preferably take place over a longer period of time.

It is particularly preferred if the connecting structure comprises needling between the upper and lower cover layers or is formed by such needling. During needling, by piercing the cover layer with a barbed needle serving as a tool, several individual fibers are pulled from this cover layer through the middle filling layer and hooked into the opposite cover layer. Such needling can preferably be carried out if the pierced cover layer and/or the opposite cover layer is designed as a non-woven layer, i.e. as a layer with a disordered fiber structure, from which fibers can be pulled out during the needling process and can be anchored in the opposite layer, thereby to form the connection structure. However, needling is also possible if the anchoring cover layer is designed with ordered fiber structures, for example knitted, knitted or woven cover layers, with the needling preferably always starting from a fleece layer as the top cover layer, since the fibers in a fleece layer have good mobility perpendicular to the layer plane. In particular, a connecting structure can be provided by needling, which connects the upper and lower cover layers to one another at a large number of points distributed over the surface of the geosynthetic mat and spaced apart from one another, thereby creating a connection between the upper and lower cover layers that acts virtually over the entire surface both cover layers and can therefore be particularly effective against swelling pressure and shear forces. If the connecting structure, in particular the cover layer pierced to create the needling, comprises fibers made of a thermoplastic (e.g. PLA, PBS, PBAT), the fibers can be additionally anchored on the back of the second cover layer by melting and thus increase the initial internal shear bond of the geosynthetic mat. This can be done, for example, by means of a flame bar, which melts the fiber portions protruding outwards from the second cover layer, whereby they form small nodules which prevent or make it difficult for the fibers to be pulled out of the second cover layer in the direction of the first cover layer.

It is even further preferred if the upper and/or the lower cover layer and/or the connecting structure comprises fibers made of the biodegradable material or is formed by such biodegradable fibers. By designing fibers made of a biodegradable material, on the one hand good strength and the possibility of needling can be achieved, on the other hand such fibers can be particularly can be biodegraded in a well-targeted manner and thereby provide the desired ratio of the degree of swelling and the degree of residual peel strength.

Even further, it is preferred if the biodegradable material of the upper cover layer and the lower cover layer is different from each other, or the biodegradable material of the upper cover layer and the lower cover layer is the same. According to this embodiment, in a first embodiment, the biodegradable material of the upper and lower cover layers is different, which can be advantageous in certain installation situations and floor structures in order to adapt the geoplastic mat to local requirements on the top and bottom. In many applications, the second alternative is advantageous, in which the biodegradable material of the upper and lower cover layers match, i.e. the two cover layers are made of the same material. This embodiment enables a harmonious, similar degradation behavior of the upper and lower cover layers, a favorable selection of connection structures between the similar materials and is therefore well suited for many applications.

According to a further preferred embodiment, it is provided that the biodegradable material of the connecting structure is different from the biodegradable material of the upper cover layer and/or the lower cover layer, or the biodegradable material of the connecting structure is identical to the upper cover layer or the lower cover layer. In these two preferred embodiments, too, in certain installation situations, for example when a particularly high shear strength or a shear strength acting over a long period of time is required, the biodegradable material of the connecting structure can be different from that of the upper and / or lower cover layer for example, to achieve a slower biological degradation behavior of the connecting structure compared to the cover layers or one of the cover layers. Again, in many common installation situations, it is advantageous if the biodegradable material's connecting structure matches the upper or lower cover layer or both cover layers and this in turn achieves manufacturing advantages due to the sameness of the materials.

It is further preferred if the upper and/or the lower cover layer comprises a nonwoven layer made of the biodegradable material or is formed by such a nonwoven layer. If the cover layer is designed as such a fleece layer or includes such a fleece layer, this allows, on the one hand, a well-adhering support and shear force transmission from surrounding soil layers into the geosynthetic mat, since a fleece layer achieves sufficient shear force transmission to adjacent soil layers due to its surface structure. A nonwoven layer is also well suited for needling, as explained above, and can thereby enable the formation of an efficient connection structure. A fleece layer is to be understood as meaning a fiber layer in which the fibers are present in a disordered manner and which has medium-long to continuous fibers in the range from approx. 6cm to several meters or more. The nonwoven layer can preferably consist of fibers which have at least two, preferably more, different fiber strengths, whereby a different fiber strength is understood to mean a difference of at least 100%, i.e. a difference in which fibers with a first diameter and fibers with a second diameter, which is twice as large as the first diameter, is included in the fleece layer. Through such fleece layers with inhomogeneous fiber thicknesses, the biological degradation behavior can often be well adapted to the swelling behavior of the middle filling layer.

It is even further preferred if the upper and/or the lower cover layer comprises an ordered textile layer, in particular a knitted, woven or knitted textile layer made of the biodegradable material or is formed by such a textile layer. According to this embodiment, an upper or lower cover layer is provided with an ordered structure of the fibers, whereby a higher strength of the cover layer in the longitudinal and transverse directions is achieved, particularly in comparison to nonwoven layers, and furthermore a lower liquid permeability can often be achieved if a close-meshed arrangement of the Fibers are realized in the textile layer.

It is even further preferred if the middle filling layer comprises a mixture of the swellable material, such as a bentonite powder, in particular sodium bentonite, and a non-swellable additive, such as an inorganic bulk material, for example granules, in particular sand, glass granules, chalk or coal granules, or by a such mixture is formed. According to this embodiment, a mixture of swellable material and non-swellable tensile aggregate is arranged in the middle filling layer. Both materials are in the form of a bulk material and are preferably homogeneously mixed with one another. By adding such an additive, the resilience of the middle filling layer to shear forces can be significantly increased, according to the inventors' knowledge, and the mechanical properties of the geosynthetic mat can be influenced in an advantageous manner after extensive or complete biological degradation of the two cover layers and the connecting structure in such a way that a Installation and retention in steeper ones Slope locations become possible. The mixture can be designed in such a way that it has a proportion of at least 20% by weight of swellable material and at least 20% by weight of additive or at least 30% by weight, 40% by weight of swellable material and at least 30% by weight .-% or 40% by weight of additive.

It is even further preferred if the middle filling layer comprises a hardening or hardening liquid, in particular a hard oil such as linseed oil or tung oil, the liquid preferably only being present in a partial area such as a partial cross section of the middle filling layer. By adding such a hardening or hardening liquid, the mechanical resilience, in particular against shear loads on the middle filling layer or against erosion effects acting on the surface, can be further increased and the biological degradation of the cover layers and the connecting structure can be compensated for. A hardening liquid is to be understood as meaning a liquid that changes from a liquid to a solid state, for example through polymer crosslinking or through evaporation of solvent components. On the other hand, a liquid that leads to hardening is understood to mean a liquid that reacts with other components of the middle filling layer and thereby promotes hardening of the middle filling layer. The liquid can be distributed over the entire middle filling layer and the entire cross section of the middle filling layer, but it can also only be applied in partial areas, for example at points, in grid strips, longitudinal strips or transverse strips of the geosynthetic mat. Likewise, the liquid can only be present over a partial cross section of the middle filling layer, for example only in a surface area of the middle filling layer or in a central area of the cross section of the middle filling layer.

It is further preferred if the geosynthetic mat is formed by an upper barrier layer arranged adjacent to the upper cover layer and/or a lower barrier layer arranged adjacent to the lower cover layer, each barrier layer being formed by a film, in particular by a film made of a biodegradable material, wherein preferably the upper barrier layer is arranged between the upper cover layer and the middle filler layer, the lower barrier layer between the lower cover layer and the middle filler layer, the upper cover layer between the upper barrier layer and the middle filler layer, or the lower cover layer between the lower barrier layer and the middle filler layer. Such a barrier layer can prevent substances that accelerate or inhibit swelling from penetrating the middle filler layer from layers of earth adjacent to the geosynthetic mat and thereby influence the swelling behavior of the middle filler layer unfavorably and unpredictably. So will through such a The barrier layer ensures that a planned slow swelling behavior from the rising earth moisture or targeted irrigation is possible, which is appropriate to the biological degradation behavior of the connecting structure and the cover layers. Such a barrier layer can be provided by a polyethylene film, but films made of biodegradable plastics can also be used for the barrier layer; in particular, biodegradable materials can be used here for the barrier layer, which are the same as the upper or lower cover layer. The barrier layer can be applied during the manufacturing process of the geosynthetic mat in the form of a coating (inline extrusion) or applied as a finished film by laminating, gluing or similar.

According to a further preferred embodiment, it is provided that the biodegradable material of the upper cover layer, the lower cover layer and / or the connecting structure comprises fibers or consists of fibers which have a fiber core strand made of a first biodegradable material and a fiber core strand sheathing surrounding the fiber core strand made of a second biodegradable material, wherein the first biodegradable material has a first biodegradation rate that is higher than a second biodegradation rate of the second biodegradable material. According to this embodiment, the upper and lower cover layers and/or the connecting structure contain fibers which are constructed from a fiber core strand and a fiber core strand covering, wherein the fiber core strand and the fiber core strand covering are constructed from two materials which have different rates of biodegradation behavior. According to the inventors, this design of the fibers achieves a significant advantage in that the degradation behavior of the fiber and thus its reduction in tensile strength takes place discontinuously through such a design, i.e. with two consecutive different degradation phases. In a first phase, the fiber core strand coating is first biologically degraded, whereas the fiber core strand is not yet subject to any or only a slight biological degradation because it is still protected by the fiber core strand coating from the influences that would cause such a biological degradation, for example the impact of radiation, liquid. The fiber core strand therefore retains its mechanical properties completely or almost completely in this first phase, so that if the fiber is dominantly characterized in its mechanical properties by the mechanical properties of the fiber core strand, then in this first phase of the biological degradation of the fiber core strand coating the fiber is not or hardly at all loses mechanical properties. Only after the fiber core strand coating has been dismantled is the Fiber core strand biodegrades and consequently the mechanical properties of the fiber are significantly reduced. The fiber constructed in this way initially shows a very delayed reduction in its mechanical properties, which then increases at a certain point in time. This is advantageous for the geosynthetic mat according to the invention in many applications, since sufficient mechanical strength can be provided by the cover layers and the connecting structure over a certain period of time, which can correspond, for example, to the typical swelling behavior or the typical conversion behavior of a middle filling layer, but after this period of time then a rapid biological and complete degradation of the cover layers and the connecting structure is achieved with a corresponding reduction in mechanical strength.

It is further preferred if the first biodegradable material comprises a natural fiber such as coconut fiber, jute fiber, hemp fiber, bamboo fiber or flax fiber or a biodegradable synthetic fiber made of PBS, PBAT, PLA or a polymer blend of at least two of these materials or that the biodegradable material is a Mixture of fiber cores made of natural fibers and synthetic fibers, preferably the weight proportion of the synthetic fibers being greater than 30%, in particular greater than 50%. The use of these fiber materials or mixtures of these fiber materials has proven to be particularly suitable for many applications in order to achieve the mechanical strengths and biodegradation rates required for a geosynthetic mat with a swellable material in the middle fill layer.

It is even further preferred if the second biodegradable material comprises a cellulose-based plastic, a starch blend, lyocell, succinic acid (PBS), a biodegradable polyester such as polybutyrate adipate terephthalate (PBAT) or polylactic acid (PLA). These materials have proven particularly useful as coating materials because they exhibit sufficiently slow biodegradation behavior, but at the same time can be easily applied as a coating in liquid form. It should be understood that the fibers in the cover layer or the connecting structure can be designed in such a way that they have already been coated before the fiber material is processed into the cover layer, i.e. the cover layers have been made from coated fibers. Alternatively, it can also be provided to produce the cover layers from uncoated fibers, i.e. only from the fiber core strands, and then to coat the cover layer as a whole with the second biodegradable material in order to also cover cut fiber ends and to solidify the cover layer through connecting effects at crossing points Fibers to achieve through the second biodegradable material. It is even further preferred if the middle filling layer has a permeability between 1x10 ^-5 to 1x10 ^-9 m/s. According to this embodiment, the geosynthetic mat is provided with a middle filling layer which has a permeability that is initially not sufficient in the production state before installation in order to thereby achieve a reliable sealing of soil layers. According to the inventors' knowledge, such permeability can initially be tolerated in many applications or is even desirable in order to achieve seepage of the geosynthetic mat in an initial phase after installation. During this seepage, particles contained in the water that seeps through the geosynthetic mat are deposited in the middle filling layer and, in the manner of a clogging filter, lead to a compaction and sealing of the middle filling layer, i.e. a colmation process takes place, which causes the structure of a filter cake in or on the middle filling layer. This allows a favorable sealing effect to be achieved at a particularly high level of sealing with a particularly low permeability of the geosynthetic mat. In the first phase, the geosynthetic mat only acts as a leakage barrier and only reaches its final tightness after a certain seepage phase, which it then maintains. According to the inventors' knowledge, this structure of the geosynthetic mat is particularly suitable for creating a seal in the beds of liquid-carrying flows, such as streams, rivers, and in doing so taking advantage of the fact that the liquid in the stream or river contains corresponding particles that are used for Sealing can act, carried. According to one aspect of the invention, this also includes a geosynthetic membrane in which the middle filling layer consists of a material that has only a very low swellability or a non-swellable material - i.e. a material with a swelling degree of 1 over the entire installation period. For example, a middle filling layer made of sand or other pourable mineral materials can be used for such a sealing effect through colmation.

A further aspect of the invention is a geosynthetic sheet comprising at least one layer that comprises fibers or is formed by fibers, in which the fibers have a fiber core strand made of a first biodegradable material and a fiber core strand sheathing made of a second biodegradable material that envelops the fiber core strand, wherein the first biodegradable material has a first biodegradation rate and the second biodegradable material has a second biodegradation rate that is different, in particular higher, than the first biodegradation rate of the first biodegradable material. In the sense of the invention, under a geosynthetic sheet, as well as under a geosynthetic mat, a structure that has dimensions in a longitudinal direction and a transverse direction that are many times higher than its thickness. A geoplastic mat and a geosynthetic sheet can have dimensions, particularly in the longitudinal direction, that are a multiple of their dimensions in the transverse direction, i.e. they can be significantly longer than they are wider. Typically, geosynthetic mats and geosynthetic sheets are transported in a rolled-up or folded state and then rolled out or unfolded at an installation site in order to be able to lay them lengthwise. In the understanding of the invention, a geosynthetic mat should differ from a geosynthetic sheet in that the geosynthetic mat has several layers, whereas a geosynthetic sheet can also have only a single layer, but can also be constructed in multiple layers if necessary.

The geosynthetic membrane according to the invention is characterized in that it is formed from fibers that have at least a two-layer structure or has such fibers. The fibers have a fiber core strand and a fiber core strand covering that envelops this fiber core strand. The fiber core strand and the fiber core strand coating consist of two different biodegradable materials which have a different biodegradation rate from one another, i.e. are biodegraded in such a way that under the same biodegradation conditions the first material is biodegraded either faster or slower than the second material. It is preferred that the second material has a biological degradation rate that is lower than the biological degradation rate of the first material, i.e. the second material biodegrades more slowly than the first material.

As before in connection with the geosynthetic mat, which can also have fibers or a layer of fibers which are designed in at least two layers in this way, such a fiber design can result in a more favorable course of the mechanical strength during the biological degradation of the fibers or the layer. which is made from the fibers, can be achieved, in particular in such a way that the fibers maintain a high mechanical strength over a longer period of time in a first phase, namely while only the fiber core strand coating is biodegraded, whereas then, after the fiber core strand coating has been broken down, the mechanical strength of the fibers decreases rapidly in a second phase when the fiber core strand is then broken down. It should be understood that these properties and also the further developments on this, which were previously explained in relation to the geosynthetic mat, are also applicable to the geosynthetic sheet and reference is made accordingly. According to a preferred embodiment, it is provided that the fibers in the layer are present as a disordered structure, in particular as a nonwoven layer, or as an ordered structure, in particular as a knitted, woven or knitted textile layer. Accordingly, the special fibers of this geosynthetic sheet can be present as a disordered structure, for example as a fleece layer, which results in the properties and advantages explained above, which also arise in connection with the geosynthetic mat explained above. Alternatively, the fibers can also be processed as an ordered structure, i.e. knitted, woven or knitted or arranged in another direction, whereby an ordered structure, as previously understood for the geosynthetic mat, is to be understood as meaning a structure that has a regularly repeating pattern geometric pattern of the course of the fibers, typically along a rectilinear direction or two rectilinear, intersecting directions. With regard to the ordered structure, reference is also made to the properties and advantages that were previously explained about the geosynthetic mat.

The geosynthetic sheet can then be further developed by covering the fibers on the circumference and at the end with the fiber core strand covering, in particular by producing the layer layer in a process in which, in a first step, a fiber core layer layer is produced from fiber core strands and in a subsequent second step Fiber core strands of the fiber core layer layer are coated with a covering material. Such a configuration with a circumferential and end-side covering of the fiber core strand with the fiber core strand wrapping can be achieved in particular by first producing the layer layer from the fiber core strands, for example by processing it into a fleece or woven, knitted or knitted and then the pre-produced one Layer layer made of the fiber core strands is coated with the fiber core strand coating, for example by immersing it in a liquid or wetting it with a liquid in a spraying or coating process, thereby achieving an all-round coating of the fibers. In order to achieve the biodegradation properties in the desired manner, this is advantageous and therefore preferred over processes in which the fibers are completely pre-produced and then processed, because in this processing method the frontal fiber core strand cross-sectional ends are exposed due to the necessary separation of the fibers and would therefore be susceptible to rapid biodegradation.

Another aspect of the invention is a geosynthetic mat of the structure and functionality explained above, in which the upper and / or the lower cover layer Geosynthetic membrane has the structure and functionality described above or is formed by such a geosynthetic membrane. As explained above, the properties of such a geosynthetic sheet with the two-layer fibers contained therein can be used particularly advantageously for the geosynthetic mat according to the invention.

A still further aspect is the use of a geosynthetic mat of the construction described above or a geosynthetic sheet of the construction described above to produce a sealing layer in the ground or at the bottom of a body of water. As already explained above, the geosynthetic mat according to the invention and the geosynthetic sheet according to the invention are particularly suitable for producing a sealing layer in the ground and are also suitable for producing such a sealing layer at the bottom of a body of water. The balanced properties of providing mechanical peel strength for a first phase of swelling of the middle filling layer are particularly effective and can achieve a secure seal, whereas the biological degradation of the cover layers and the connecting structure and an additional barrier layer, if necessary, reduce the environmental impact when expanding the Geosynthetic mat or geosynthetic sheet or in the event of erosion-related removal of parts of the geosynthetic mat or sheet can be significantly reduced or completely avoided.

The use can be advantageously developed by rolling out the geosynthetic mat in a first step and impregnating the geosynthetic mat with a liquid, in particular with a hard oil, in a subsequent second step. In this method of use, the geosynthetic mat or geosynthetic sheet is first almost completely prefabricated by producing the layers, arranging them to one another and connecting them to one another and then rolling up the geosynthetic mat or sheet prefabricated in this way in order to be able to transport it. After transport to the installation site, the geosynthetic mat or sheet is then rolled out in order to lay it and then wetted at the installation site with a liquid that influences the further mechanical and/or biological behavior. This impregnation of the geosynthetic mat or sheet only at a second point in time, which follows the time of production of the geosynthetic mat or sheet, prevents the properties of the geosynthetic mat or sheet from changing during any storage or transport that has already taken place Impregnation with the liquid can change, but it is achieved that the desired functional and structural properties are influenced by the First start using the liquid at the installation site, following the wetting with the liquid that takes place there.

It should be understood that this impregnation can also consist of the coating of fiber core strands that were processed in pre-production to form a cover layer, a connecting structure or the like in the geosynthetic mat or sheet and which are then provided with an additional coating on site to advantageously influence the biological degradation behavior and the mechanical properties.

The wetting/impregnation can in particular be carried out in such a way that it is selected depending on the environmental conditions at the installation site that were previously measured, for example by adapting a layer thickness to such environmental conditions or by selecting the liquid with which the impregnation takes place from several different ones Available liquids are selected or mixed from them. The environmental conditions that can influence this selection or impregnation intensity are, for example, a moisture content of the soil, a pH value of the soil, a concentration of substances in the soil that accelerate or slow down the biodegradation process, the intensity of UV radiation at the installation site and other influencing factors . Basically, it should be understood that in these types of use with pre-wetting, the point in time from which the swelling-degradation ratio is determined and lies in the ranges mentioned must be determined from the impregnation of the geosynthetic mat, even if the liquid with which the impregnation is carried out may not yet trigger biological degradation.

According to a further preferred development of the use according to the invention, it can be provided that the geosynthetic mat is impregnated at a first time before installation with a liquid which causes the middle filling layer to pre-swell and is installed in an installation position at an installation location at a subsequent second time and in the installed position, swells due to the supply of liquid, especially from the surrounding soil. According to this embodiment, it is provided that the geosynthetic mat or sheet is impregnated with a liquid before it is laid, which causes the middle filling layer to pre-swell. Pre-swelling is understood to mean limited swelling in which the material of the middle filling layer has not yet exhausted its maximum swelling capacity, i.e. has not yet swelled to the maximum, but rather has only exhausted part of this swelling capacity. Such impregnation with a liquid for this pre-swelling can, for example, take place during the production of the Geosynthetic mat or sheet can also be used alternatively in such a way that at a first point in time the geosynthetic mat is produced and at a second point in time the geosynthetic mat is impregnated for pre-swelling, for example shortly before delivery or transport of the geosynthetic mat to the installation site, so that any changes in the geosynthetic mat during storage between the time of production and the time of transport are avoided. The pre-swelling can be promoted in a favorable manner and can serve to positively influence the initial swelling behavior of the geosynthetic mat immediately after installation in the first few days or weeks and thereby avoid unfavorable structural changes or changes in mechanical properties.

The liquid with which the geosynthetic mat is impregnated at the first time can correspond to or be similar to the liquid that also causes the swelling at the installation site, for example consisting of impregnation with water. In other applications, however, the liquid with which it is impregnated at the first time can also be different from the liquid with which the geosynthetic mat is wetted at the installation site, i.e. in particular have a different composition or contain additives that promote pre-swelling, for example have the effect that pre-swelling is promoted, but biological degradation is inhibited or prevented in order to prevent premature biological degradation of the cover layers and the connecting structure due to the impregnation at the first point in time.

It is then preferably provided that the geosynthetic mat is first brought into a transportable state after impregnation, in particular for this purpose it is rolled up or folded and can then be transported to the installation site. In principle, it is preferred to carry out uniform impregnation at the first point in time before the geosynthetic mat is in a transportable state in order to avoid the geosynthetic mat being impregnated differently in a spatially resolved manner.

The use according to the invention can be further developed in the use of the geosynthetic mat to produce a sealing layer at the bottom of a body of water, or in the use of the geosynthetic mat to produce a seal in a soil layer by placing the geosynthetic mat at a first point in time on the bottom of the body of water or in the area of the water bottom or is installed in a soil layer and the upper cover layer of the geosynthetic mat has an open porosity and, as a further improvement, the outer surface of the upper one Cover layer has an outward-facing roughness structure and the geosynthetic mat is placed on the bottom of the water in such a way that the outer surface of the upper cover layer points upwards, and furthermore the middle filling layer has a permeability between 1x10 ^-5 to 1x10 ^-9 m / s and that in Particles carried in the body of water above the body of water get caught in the pore structure, further favorably influenced by a reduced flow velocity and reduced drag stress as a result of the roughness structure, and migrate through the upper cover layer into the middle filler layer, so that particles deposited in the middle filler layer and the upper cover layer come out of the water form a sealing layer which, at a second time subsequent to the biodegradation of the top cover layer, provides a supplementary sealing effect within the swollen middle fill layer and an additional sealing layer at the location of the degraded top cover layer.

According to this advantageous use, the geosynthetic mat is used in such a way that the middle filling layer initially has a certain permeability value in a defined range of values and thereby allows the passage of liquid. This permeability is combined with an open porosity and consequently permeability of the upper cover layer and preferably also of the lower cover layer, further improved by an outwardly facing roughness structure of the outer surface of the upper cover layer, which is, for example, due to the typical roughness of a fleece layer or one made by weaving, knitting or knitting produced ordered structure of the cover layer can be provided. This ensures that liquid flows through the middle filling layer in a first phase after installation and that particles that are in the liquid can settle in the middle filling layer and the upper or lower cover layer and thereby reduce the permeability. This flow and the associated settling of particles from the liquid flowing through it in the geosynthetic mat consequently causes a gradual sealing of the geosynthetic mat in this first phase after installation, which continuously changes to a state in which the permeability is reduced to such an extent that hardly any more or there is no longer any flow through and the geosynthetic mat is sealed at this point. This sealing effect caused by particles at the installation site during a first phase is known as so-called colmation and can be used advantageously for the overall properties, particularly through the construction of the geosynthetic mat. By constructing the geosynthetic mat in this way and using the colmation, it is not necessary for the middle filling layer to swell so much and for it to be necessary to work with such a high counter pressure against the swelling behavior within the geosynthetic mat that this swelling behavior alone creates the desired tightness provides. This relieves the requirements for the peel strength of the upper and lower cover layer and the connecting structure and also makes it possible to design the middle filler layer in such a way that it only has a limited swelling behavior, for example to provide the middle filler layer with additives which increase the shear strength of the middle filler layer. The design and use according to the invention therefore makes it possible to provide a middle filling layer with increased shear strength, to reduce the mechanical requirements on the upper and lower cover layer and the connecting structure, also with regard to their biological degradation behavior and the resulting peel strength, and at the same time a very low permeability in permanent use the geo plastic mat.

It is particularly preferred if the use is carried out in such a way that before the geosynthetic mat is placed on the bottom of the water, the amount of particles carried in the water per water volume is determined as the particle quantity density and the geosynthetic mat is designed in such a way that the swelling-degradation Ratio and/or the degree of residual peel strength and/or the thickness of the upper cover layer is formed as a function of this particle quantity density, in particular in such a way that the swelling-degradation ratio is made smaller, the degree of residual peel strength is made greater and/or the thickness of the upper cover layer the smaller the particle density is, the higher the particle density. According to this embodiment, before the geosynthetic mat is installed, the properties of the water are determined, in particular the amount of particles carried in the water per volume of the water, i.e. the particle density in the water. This can include the number of particles, but can alternatively or additionally also include the size of the particles that are carried in the body of water. Depending on this determined parameter of the water in relation to the amount of particles, the geosynthetic mat is then designed to be adapted to it, whereby this adapted training can consist of the properties of the upper cover layer and / or the properties of the middle filling layer being adapted in order to achieve an ideal colmation effect achieve this and adapt the geosynthetic mat ideally to this. In bodies of water in which a particularly large number of particles are carried, a middle filling layer with a lower degree of swelling can be used in the geoplastic mat than in bodies of water that only have a low particle density. In the same way, the properties of the upper cover layer can be adjusted, for example in waters that have a high particle density, rapid biological degradation with a correspondingly high degree of peel strength reduction can be used, since in this case a rapid sealing effect due to the colmation effect can be expected and consequently a Counter pressure against the swelling of the middle filling layer does not play as important a role as in waters with low particle concentrations, which require such swelling behavior for a good sealing effect of the geosynthetic mat. Furthermore, the surface of the cover layer can be adapted in terms of the roughness structure so that, depending on the water-specific flow conditions and drag tension on the surface of the mat, a deposition and incorporation of particles into the mat can take place reliably.

A further aspect of the invention is a method for producing a geosynthetic mat, with the steps: providing a first geosynthetic layer, applying a middle filler layer made of a filler layer material that includes a swellable material to the first geosynthetic layer, the filler layer material having a swelling behavior, laying down a second geosynthetic layer on the middle filling layer, connecting the first to the second geosynthetic layer through the middle filling layer by means of a connecting structure, in particular by needling, in which a layer made of a first biodegradable material is provided as the first geoplastic layer and a layer made of a second biodegradable material is provided as the second geoplastic layer is placed, the upper and lower cover layers having a connection to one another characterized by a peel strength, which is characterized by a residual degree of peel strength at the predetermined time after the start of the biological degradation process, which is determined by the square number of a quotient of a reduced peel strength, which is the upper and lower cover layer and the connecting structure at the predetermined time, to an initial peel strength, which has the upper and lower cover layer and the connecting structure before the start of a biological degradation process, is formed, wherein the residual peel strength level in a composting test by completely placing the geosynthetic mat in compost and composting in a temperature range that is above 25 ° C and below 65 ° C up to the predetermined time and measuring the peel strength in a peel test before insertion and at the predetermined time after removal from the compost, and wherein the swelling behavior is characterized by a degree of swelling elevation, which is formed by the quotient of the volume of the filling layer material including the water absorbed therein at the predetermined time to an initial volume of the filling layer material before the start of swelling, the degree of swelling elevation being achieved by completely immersing a layer of filling layer material in a water bath and loading the layer of filling layer material is determined with a pressure of 4.5 N/m ² and at which a swelling-degradation ratio is formed from the degree of swelling divided by the The degree of residual peel strength within the first week after the simultaneous start of the swelling process and the biological degradation process is in a range between 1 and 5 and within each predetermined time from the beginning of the second to the end of the third month after the start of swelling and degradation in a range between 1, 5 and 25, preferably in a range with a lower limit of 2 and / or an upper limit of 15.

With regard to the manufacturing process, it should be understood that the properties of the geosynthetic mat with regard to the degree of residual peel strength and the degree of swelling lifting and the swelling-degradation ratio formed therefrom over time and in terms of their height can be as previously explained in relation to the geosynthetic mat.

Furthermore, a specific roughness structure of the surface can be produced by placing a structural material with a degradation behavior of the first or second cover layer or a third degradation rate, and needling the structural material with the geosynthetic layers. The method according to the invention can be used in particular to produce a geosynthetic mat with the properties described above and allows a geosynthetic mat to be provided which is suitable for the previously described use at the installation site.

It should be understood that the steps carried out in the method preferably lead to the previously explained structural and functional properties and advantages of the geosynthetic mat according to the invention and enable the previously explained use. In this respect, with regard to these process steps, reference is made to the previous explanation of the corresponding properties and advantages.

The previously explained method and the previously explained development of the method according to the invention can preferably be developed in such a way that the first and/or the second biodegradable material is designed in fiber form, in particular as fibers which have a fiber core strand made of a first biodegradable material and a the fiber core strand covering made of a second biodegradable material, wherein the first biodegradable material has a first biodegradation rate that is higher than a second biodegradation rate of the second biodegradable material. According to this process development, the first and/or the second biodegradable material is formed from fibers which are constructed in two layers, i.e. have a fiber core strand and a fiber core strand covering, whereby the fiber core strand covering can already be present before the respective layers or the connecting structure are made from the fibers or can be applied subsequently in the production process or can also be applied on site at the installation site. In this regard, reference is made to the previous explanation of corresponding fibers in use in the geosynthetic mat according to the invention or a corresponding geosynthetic sheet.

The method can be further developed by producing the first and/or the second cover layer from the fiber core strands in a first step and, in a subsequent second step, covering the fiber core strands in the first and/or second cover layer with the fiber core strand covering. According to this development, the fiber core strand covering is only applied after the cover layer has been produced from the fiber core strands, thereby achieving a comprehensive coating of the fiber core strands, including on any front cut edges. Reference is also made to the previous description in this regard.

It is even further preferred if the upper and/or the lower cover layer, the middle filling layer or the entire geosynthetic mat are impregnated with a liquid, in particular with a hardening liquid such as a hard oil. This production step of impregnation with a liquid such as a hard oil can in turn take place immediately during the production of the geosynthetic mat at the production site, but can also take place subsequently, for example immediately before the geosynthetic mat is transported to an installation site or after the geosynthetic mat is transported to the installation site, for example already with the geosynthetic mat laid out. The previously explained advantages of time-delayed impregnation with the liquid also apply to the method according to the invention in this regard.

It is further preferred if a non-swellable additive, in particular sand, is also applied when the middle filler layer is applied. By applying a non-swellable tensile aggregate, on the one hand the swelling behavior of the middle filling layer can be influenced, for example to promote colmation effect, on the other hand the shear strength of the middle filling layer is increased and thereby the suitability of the geosynthetic mat for installation in shear-loaded installation situations, such as on slopes, is improved, which particularly after biological degradation of the upper and lower cover layer and the connecting structure has an advantageous effect.

Preferred embodiments of the invention are explained with reference to the accompanying figures. Show it: 1 shows a schematic, perspective and partially sectioned representation of a geoplastic mat according to the invention, partially fanned out according to layer layers,

Figure 2 is a cross-sectional longitudinal view of a second embodiment of a geosynthetic mat according to the invention,

Figure 3 is a perspective, sectioned view of a fiber for producing a geosynthetic mat according to the invention,

4 shows a second embodiment of a fiber for producing a geosynthetic mat according to the invention in a longitudinal sectional side view,

Figure 5 shows a schematic diagram of the course of the peel strength and the swelling over time of a geosynthetic mat according to the invention.

Referring first to FIG. 1, a preferred embodiment of the geosynthetic mat according to the invention is constructed from a total of five layers. The top layer is a first sealing layer 10, which is made from a biodegradable plastic as a liquid-tight film and covers the upper surface of the geosynthetic mat as a fluid barrier.

An upper cover layer in the form of a fleece layer 20 is arranged below and adjacent to this upper sealing layer 10. This fleece layer is made up of disordered fibers and typically has a thickness that is greater than the sealing layer 10, in particular three to ten times greater than the thickness of the sealing layer 10.

A middle filling layer in the form of a layered silicate layer made of sodium bentonite is arranged below and adjacent to the upper cover layer 20. The thickness of this middle filling layer 30 is greater than the thickness of the fleece layer 20, typically by a factor of 5 to 20 greater than the thickness of the fleece layer 20. This middle filling layer is composed of a mixture of sodium bentonite particles and sand particles and, depending on the application, can be impregnated, for example with a Linseed oil. Thanks to this composition, the middle filling layer is able to initially have basic strength and impermeability to groundwater and to further increase this strength and impermeability to water by swelling the sodium bentonite in the composition with surrounding moisture such as soil moisture. Through this swelling process, the sodium bentonite is converted into calcium bentonite, which solidifies the middle filling layer effects. It is to be understood that the middle filling layer can also be composed in a different way and even then has an initial basic strength and initial tightness, which can increase due to swelling from surrounding moisture. For example, the middle filling layer can be composed exclusively of a swellable material such as bentonite or a layered silicate, or additives other than sand can be used. Impregnation with linseed oil can be replaced or supplemented by other liquids such as hard oils or such impregnation can be dispensed with.

Below the middle filling layer 30 there is a second sealing layer 40 which is designed to match the first sealing layer 10. The first sealing layer 10 and the second sealing layer 40 prevent swelling-accelerating or swelling-hindering active ingredients from the surrounding soil layers from reaching the middle filling layer immediately after installation of the geosynthetic mat and thereby adversely affecting the swelling behavior.

Finally, a geotextile layer 50, which is composed of woven fibers, is arranged below and adjacent to the second sealing layer 40. The fibers in the geotextile layer 50 are therefore aligned with one another in an orderly manner, here in a rectangular grid pattern, and ensure good longitudinal and transverse loading capacity of the geosynthetic mat.

The entire geosynthetic mat is fixed to one another by needling 11 in the thickness direction, i.e. perpendicular to its longitudinal and transverse extent. The needling fixation includes a large number of individual needling, which are distributed over the entire geosynthetic mat and can be arranged, for example, in columns and rows or pseudo-randomly to one another. Through this needling, the upper and lower cover layers are connected flatly and the composite of upper and lower cover layers and needling therefore has resistance to peeling of the upper cover layer or the lower cover layer from the composite, i.e. peel resistance.

The needling can be effected in terms of production technology by piercing a needle with barbs vertically through the geosynthetic mat and thereby taking fibers from the nonwoven layer 20 and/or the geotextile layer 50 and pulling these fibers vertically through the geosynthetic mat. These fibers get caught in the geotextile layer 50 and the fleece layer and can also get caught in the sealing layers 10 and 40. This entanglement and entanglement can be caused by a Welding or nodulation can be additionally reinforced in order to strengthen the attachment through needling. Instead of such needling, other methods for fixing the layers in the geosynthetic mat to one another can also be used, for example the geoplastic mat can be sewn, for example by sewing with a fiber in the same pattern as the needling and thereby the sewing thread perpendicular to the several points is guided through the geosynthetic mat and thereby fixes and stabilizes the layers to one another. For use in channels and bodies of water involving colmation effects, layer 10 can be replaced by a surface roughness structure and layer 40 can be omitted in order to achieve an initial flow.

It is to be understood that the geosynthetic mat extends in a longitudinal direction LR and a transverse direction QR and can in particular be wound up along the longitudinal direction LR. The edges of the geosynthetic mat can be sealed in such a way that the first sealing layer 10 and the fleece layer 20 as well as the lower sealing layer 40 and the textile layer 50 protrude laterally beyond the middle filling layer when viewed in the transverse direction and these protruding areas are sewn together in order to also enclose the middle filling layer laterally .

Fig. 2 shows a second embodiment of a geosynthetic mat according to the invention in a cross-sectional longitudinal view. Here too, a middle filling layer 130 is arranged centrally. Above and below each adjacent to this middle filling layer, a first sealing layer 110 and a second sealing layer 140 are arranged, which are consequently placed directly adjacent to the middle filling layer, in contrast to the first embodiment of FIG. 1. A fleece layer 120 is then arranged above the first sealing layer as the upper cover layer and a textile layer 150 is arranged below the second sealing layer 140 as the lower cover layer. Again, the individual layers of the geoplastic mat are fixed and secured to one another by needling 111; Furthermore, it can be seen that the upper cover layer, the first sealing layer, the second sealing layer and the lower cover layer protrude laterally in the transverse direction and are sewn or needled together along a side edge in order to also close the middle filling layer laterally.

Fig. 3 shows a fiber from which the connecting structure, for example as a needling 11, the nonwoven layer 20, 120 or the textile layer 50, 150 can be formed or which can be included in such a layer. The fiber includes a fiber core strand 210, which consists of a first biodegradable material. To the Fiber core strand is arranged as a cylindrical casing, a fiber core strand casing 220, which consists of a second biodegradable material. The first biodegradable material has higher strength and a faster biodegradation rate than the second biodegradable material. If the fiber constructed in two layers is fed into a biological degradation process and at the same time is supposed to absorb mechanical loads over a limited period of time, this results in a favorable course of the mechanical resilience of this fiber. During this process, the mechanical resilience is initially only reduced slightly or not at all because only the fiber core strand coating biodegrades, which makes no significant contribution to the mechanical properties. Only after the fiber core strand covering 220 has been dismantled is the fiber core strand 210 also dismantled, which then leads to a rapid reduction in the mechanical strength of this fiber.

Fig. 4 shows a longitudinal sectional side view of a short or medium-length fiber according to the invention. This fiber also includes a fiber core strand 310, which is covered by a fiber core strand sheath 320. Fiber core strand and fiber core strand covering 310, 320 are designed in a similar way with regard to their mechanical properties and their biological degradation rate as in the previously explained embodiment according to FIG. 3. As can be seen from FIG on the front sides. This is achieved by applying the fiber core strand coating only after processing and cutting of the fiber core strand 310, thereby achieving an all-round coating that is favorable for biological and mechanical degradation behavior.

Fig. 5 shows schematically the course of the peel strength S(t) of a composite of two fleece layers needled together, which is made up of fibers according to Fig. 3 or Fig. 4 and consequently comprises or consists of fibers which have a fiber core strand and a fiber core strand covering . As can be seen from the course of this curve, the curve initially only drops slightly over a first period of time, which therefore corresponds to only a small reduction in tensile strength. Only at a point in time t, at which the fiber core strand coating has largely completely biodegraded, does the peel strength of the composite then fall more steeply, because from this point in time t the fiber core strand biodegrades and the peel strength of the fiber, which is significantly influenced by it, is thereby reduced. In this exemplary embodiment, the overall peel strength of the composite is influenced by the biological degradation of the fibers in the upper and lower cover layers and the connecting structure, i.e. the needling. It should be understood that in other interconnected systems also isolated Degradation behavior can significantly or solely influence the drop in peel strength, for example when a non-biodegradable connecting structure connects two cover layers, one or both of which are biodegradable, such as can be achieved by sewing. In this case, the peel strength is only influenced by the anchoring strength of the connecting structure in the biodegradable cover layer.

5 also shows the swelling behavior of a middle filling layer, in the form of the curve Q(t) as the degree of swelling of the middle filling layer. As can be seen, after an initial short delay, the middle fill layer initially increases rapidly in volume, corresponding to a rapid initial swelling, and then transitions to a slower increase in volume corresponding to a slower swelling, which then asymptotically approaches a final swelling state.

From Fig. 5 it can also be seen that a geosynthetic mat, which would have a layer as the upper and lower cover layer, which is made from fibers which would have the peel strength behavior according to S (t) and which are also needled with such fibers, by a Middle filling layer with a swelling behavior according to Q(t), during the significant part of the swelling of the middle filling layer would still have a high peel strength and could therefore counteract the swelling pressure with a sufficiently high counterpressure in order to achieve the desired good homogenization and removal of the air pores of the middle filling layer through swelling achieve. Only after the swelling has largely been completed and only minor increases in volume and weight of the middle filling layer due to residual swelling are the biodegradable fibers of the upper and lower cover layer and the needling then in the phase of rapid biological degradation and consequently of rapid reduction in peel strength - i.e. a high degree of peel strength reduction. At this point, there is no longer any need to apply significant counter pressure to prevent swelling, but the geosynthetic mat then benefits from a middle fill layer that has already swollen and sealed in a favorable manner.

The calculation of the swelling-degradation ratio is explained in more detail below using four examples:

1.) Volume of the middle filling layer swelling in the swelling lifting test under a load of 45Pa after one week of swelling is 40 liters, after three months 50 liters. The volume before swelling began was 20 liters. This results in a doubling of the volume within a week, i.e. a source elevation of 2 and a Source elevation of 2.5 after three months; The peel strength at the beginning of the composting test is 120N/10cm, this remains virtually unchanged within the first week and the peel strength after three months of composting is 90N/10cm. This results in a 25% reduction in peel strength after three months, i.e. a residual peel strength of 0.56. This results in a swelling-degradation ratio of 2 after one week and a swelling-degradation ratio of 4.4 after three months.

2.) Volume of the middle filling layer swelling under a load of 45Pa in the swelling lifting test is 60 liters after one week of swelling, 80 liters after three months and then no longer increases significantly. The volume before swelling began was 20 liters. This results in a tripling of the volume within a week, i.e. a source elevation level of 3 and a source elevation level of 4 after three or more months; The peel strength at the start of the composting trial is 120N/10cm, this reduces to 1 15N/10cm within the first week, the peel strength after three months of composting is 60N/10cm and drops to 40N/10cm by the twelfth month. This results in an approximately 4% reduction to a residual peel strength of 0.96 within the first week, a 50% reduction in peel strength after three months, i.e. a residual peel strength of 0.25 and a residual peel strength of 0.1 after twelve months. This results in a swelling-degradation ratio of 3.1 after one week, which increases to 16 after three months and to 36 after twelve months.

3.) Volume of the middle filling layer swelling under a load of 45Pa in the swelling lifting test after one week of swelling is 30 liters, after three months 40 liters and after twelve months also 40 liters. The volume before swelling began was 20 liters. This results in a source elevation of 1.5 after one week and a source elevation of 2 after three and twelve months; The peel strength at the beginning of the composting test is 120N/10cm, this remains virtually unchanged within the first week and the peel strength after three months of composting is 90N/10cm and drops to 60N/10cm by the twelfth month. This results in a residual peel strength of 0.56 after three months and a residual peel strength of 0.25 after twelve months. This results in a swelling-degradation ratio of 1.5 after one week, which increases to 3.6 after three months and to 8 after twelve months.

4.) Volume of the middle filling layer swelling in the swelling lifting test under a load of 45Pa is 40 liters after one week of swelling, 60 liters after three months and 80 liters after twelve months. The volume before swelling began was 20 liters. This results in a source elevation level of 2 after one week and a source elevation level of 3 after three months and from 4 to twelve months; The peel strength at the beginning of the composting test is 120N/1 Ocm, this reduces to 110N/10cm within the first week, the peel strength after three months of composting is 40N/10cm and drops to 20N/10cm by the twelfth month. This results in a residual peel strength of 0.84 after one week, a residual peel strength of 0.1 1 after three months and a residual peel strength of 0.03 after twelve months. This results in a swelling-degradation ratio of 2.4 after one week, which rises to 27 after three months and to 133 after twelve months.

In the present examples, Examples 1, 2 and 3 therefore represent geosynthetic mats which have particularly preferred properties according to the invention and achieve good sealing behavior. The geosynthetic mat according to Example 4 has a rapid swelling behavior in relation to rapid biological degradation and the associated loss of peel strength, this according to the invention

Although a geosynthetic mat may still achieve good sealing behavior under heavy loads from an overlying soil layer, it is less suitable if such a weight load is not present to compensate for rapid biological degradation, because then there is too little swelling counter pressure to achieve a good seal achieve.

Claims

Claims: Geosynthetic mat, comprising: an upper cover layer, a lower cover layer, a middle filling layer arranged between the upper cover layer and the lower cover layer made of a filler layer material which comprises a swellable material, the filler layer material having a swelling behavior, a connecting structure by means of which the upper and the lower cover layer are mechanically connected to one another at several positions through the middle filling layer, the positions of the connection being spaced apart from one another, preferably at a regular distance from one another along a straight line, so that the upper and lower cover layers have a peel strength to one another due to the connection structure , characterized in that the upper cover layer and/or the lower cover layer consist of a biodegradable material or comprise a biodegradable material, wherein the peel strength at a predetermined time after the start of the biodegradation process is characterized by a residual peel strength degree, which is determined by the square of a Quotients are formed from a reduced peel strength, which has the upper and lower cover layer and the connecting structure at the predetermined time, to an initial peel strength, which has the upper and lower cover layer and the connection structure before the start of a biodegradation process, wherein the residual peel strength degree o in a composting test by completely placing the geosynthetic mat in compost and composting in a temperature range that is above 25 ° C and below 65 ° C until the predetermined time and measuring the peel strength in a peel test before insertion and at the predetermined time after removal the compost, or o in a marine incubation test, with the following environmental conditions:; Temperature 30°C +/- 2°C; aerobic Conditions in seawater with a salinity of 3.5% by weight +/- 1% by weight and measurement of peel strength in a peel test before pickling and at the predetermined time after removal from the seawater; is determined, and wherein the swelling behavior is characterized by a degree of swelling elevation, which is formed by the quotient of the volume of the filler layer material including the water absorbed therein at the predetermined time to an initial volume of the filler layer material before the start of swelling, the degree of swelling elevation being formed by complete immersion of a filler layer material layer in a water bath and loading the filling layer material layer with a pressure of 4.5 N/m ² is determined, in which a swelling-degradation ratio, which is formed from the degree of swelling divided by the degree of residual peel strength, within the first week after the simultaneous start of the Swelling process and the biological degradation process is in a range between 1 and 5 and from the beginning of the second to the end of the third month after the start of swelling and degradation in a range between 1.5 and 25, preferably in a range with a lower limit of 2 and /or an upper limit of 15. 2. Geo plastic mat according to claim 1, characterized in that the swelling-degradation ratio from the third month to the end of the twelfth month after the start of the swelling process and the biological degradation process is in a range between 2 and 50, preferably in a range with a lower limit of 3 and/or an upper limit of 30. 3. Geosynthetic mat according to one of the preceding claims, characterized in that the degree of swelling one week after the start of the swelling process is greater than 1.25, and / or the degree of swelling one month after the start of the swelling process is greater than 1.5, and / or the residual peel strength level three months after the start of the swelling process is less than 0.95, and/or the residual peel strength level twelve months after the start of the swelling process is less than 0.75. Geosynthetic mat according to one of the preceding claims, characterized in that the connecting structure comprises needling between the upper and lower cover layers or is formed by such needling. Geosynthetic mat according to one of the preceding claims, characterized in that the upper and/or the lower cover layer and/or the connecting structure comprises fibers made of the biodegradable material or is formed by such biodegradable fibers. Geosynthetic mat according to one of the preceding claims, characterized in that the biodegradable material of the upper cover layer and the lower cover layer is different from one another, or the biodegradable material of the upper cover layer and the lower cover layer is the same. Geosynthetic mat according to one of the preceding claims, characterized in that the biodegradable material of the connecting structure is different from the biodegradable material of the upper cover layer and/or the lower cover layer, or the biodegradable material of the connecting structure is identical to the upper cover layer or the lower cover layer is. Geosynthetic mat according to one of the preceding claims, characterized in that the upper and/or the lower cover layer comprises a fleece layer made of the biodegradable material or is formed by such a fleece layer. Geosynthetic mat according to one of the preceding claims, characterized in that the upper and / or the lower cover layer is an ordered textile layer, in particular a knitted, woven or knitted one Textile layer made of the biodegradable material or is formed by such a textile layer. 10. Geosynthetic mat according to one of the preceding claims, characterized in that the filler layer material comprises a mixture of the swellable material, such as a bentonite powder, in particular sodium bentonite, and a non-swellable additive, such as an inorganic bulk material, in particular sand, glass granules, chalk or coal granules or is formed by such a mixture. 1 1 . Geosynthetic mat according to one of the preceding claims, characterized in that the middle filling layer comprises a hardening or hardening liquid, in particular, for example, a hard oil or wax or varnish based on, for example, linseed oil or tung oil, the liquid also only in a partial area such as a partial cross section the middle filling layer may be present. 12. Geosynthetic mat according to one of the preceding claims, characterized by an upper barrier layer arranged adjacent to the upper cover layer and / or a lower barrier layer arranged adjacent to the lower cover layer, each barrier layer being formed by a film, in particular by a film made of a biodegradable material, wherein preferably the upper barrier layer is arranged between the upper cover layer and the middle filler layer, the lower barrier layer between the lower cover layer and the middle filler layer, the upper cover layer between the upper barrier layer and the middle filler layer, or the lower cover layer between the lower barrier layer and the middle filler layer. 13. Geosynthetic mat according to one of the preceding claims, characterized in that the biodegradable material of the respective barrier layer is identical or different to the biodegradable material of the upper or lower cover layer to which the film is adjacent. 14. Geosynthetic mat according to one of the preceding claims, characterized in that the biodegradable material of the upper cover layer, the lower cover layer and / or the connecting structure comprises fibers or consists of fibers which comprise a fiber core strand made of a first biodegradable material and a fiber core strand encasing Fiber core strand covering made of a second biodegradable material, wherein the first biodegradable material has a first biodegradation rate that is higher than a second biodegradation rate of the second biodegradable material. 15. Geosynthetic mat according to the preceding claim, characterized in that the first biodegradable material comprises a natural fiber such as coconut fiber, jute fiber, hemp fiber, bamboo fiber or flax fiber or a biodegradable synthetic fiber made of PBS, PBAT, PLA or a polymer blend of at least two of these materials or consists of such, or that the biodegradable material comprises a mixture of fiber cores made of natural fibers and synthetic fibers, the weight proportion of the synthetic fibers preferably being greater than 30%, in particular greater than 50%. 16. Geosynthetic mat according to one of the preceding claims, characterized in that the second biodegradable material is a cellulose-based plastic, a starch blend, Lyocell, succinic acid (PBS), a biodegradable polyester such as polybutyrate adipate terephthalate (PBAT) or polylactic acid (PLA) or comprises or consists of a wax. 17. Geosynthetic mat according to one of the preceding claims, characterized in that the middle filling layer is characterized by a permeability between 1x10 ^-5 to 1x10 ^-9 m / s. 18. Geosynthetic membrane, comprising at least one layer that comprises fibers or is formed by fibers, characterized in that the fibers comprise a fiber core strand made of a first biodegradable material and a fiber core strand sheathing made of a second biodegradable material that envelops the fiber core strand have, wherein the first biodegradable material has a first biodegradation rate and the second biodegradable material has a second biodegradation rate that is different, in particular higher, than the first biodegradation rate of the first biodegradable material. 19. Geosynthetic membrane according to claim 17, characterized in that the fibers in the layer layer Present as a disordered structure, in particular as a fleece layer, or Present as an ordered structure, in particular as a knitted, woven or knitted textile layer. 20. Geosynthetic membrane according to claim 18 or 19, characterized in that the fibers are surrounded on the circumference and at the end with the fiber core strand covering, in particular by producing the layer layer in a process in which, in a first step, a fiber core layer layer is produced from fiber core strands and in one In the subsequent second step, the fiber core strands of the fiber core layer layer are coated with a covering material. 21. Geosynthetic mat according to one of claims 1-17, characterized in that the upper and / or the lower cover layer comprises a geosynthetic sheet according to one of claims 18, 19 or 20 or is formed by such a geosynthetic sheet. 22. Use of a geosynthetic mat according to one of the preceding claims 1-21 for producing a sealing layer in the ground or at the bottom of a body of water. 23. Use according to claim 22, characterized in that in a first step the geosynthetic mat is rolled out and in a subsequent second step the geoplastic mat is impregnated with a liquid, in particular with an oil, preferably a hard oil or resin or a varnish based thereon. 24. Use according to claim 22 or 23, characterized in that the geosynthetic mat is impregnated at a first time before laying with a liquid which causes a partial pre-swelling of the middle filling layer and is installed at an installation location in an installation position at a subsequent second time and in the installation position by supplying liquid, in particular the surrounding soil. Use according to claim 24, characterized in that the geosynthetic mat is brought into a transportable state after the first point in time, in particular rolled up and transported to the installation site. Use according to one of claims 22 to 25 for producing a sealing layer at the bottom of a body of water, characterized in that the geosynthetic mat is placed on a body of water at a first point in time, that the upper cover layer of the geosynthetic mat has an open porosity and the outer surface of the upper cover layer has one has an outward-facing roughness structure and the geosynthetic mat is placed on the bottom of the water in such a way that the outer surface of the upper cover layer faces upwards, and that the middle filling layer has a permeability between 1x10 ^-5 to 1x10 ^-9 m / s and that in the water above Particles carried by the water get caught in the roughness structure and migrate through the upper cover layer into the middle filling layer, so that particles from the water deposited in the middle filling layer and the upper cover layer form a sealing layer, which at a second point in time, after the biological degradation of the upper cover layer lies, a supplementary sealing effect within the swollen middle filler layer and an additional sealing layer at the location of the dismantled top cover layer. Use according to claim 26, characterized in that before placing the geosynthetic mat on the bottom of the water, the amount of particles carried in the water per water volume is determined as particle quantity density and the geosynthetic mat is designed in such a way that the swelling-degradation ratio and / or the residual peel strength and/or the thickness of the upper cover layer is designed as a function of this particle quantity density, in particular in such a way that the swelling-degradation ratio is made larger, the degree of residual peel strength is made smaller and/or the thickness of the upper cover layer is made smaller, the higher the particle quantity density is. Process for producing a geosynthetic mat, with the steps: Providing an initial geosynthetic layer, Applying a middle filler layer made of a filler layer material that includes a swellable material to the first geosynthetic layer, the filler layer material having a swelling behavior, Placing a second geosynthetic layer on the middle fill layer, Connecting the first to the second geosynthetic layer through the middle filling layer by means of a connecting structure, in particular by needling, characterized in that a layer made of a first biodegradable material is provided as the first geosynthetic layer and a layer made of a second biodegradable material is placed as the second geosynthetic layer , wherein the upper and lower cover layers have a connection to one another characterized by a peel strength, which is characterized by a residual degree of peel strength at the predetermined time after the start of the biodegradation process, which is determined by the square of a quotient of a reduced peel strength, which is the upper and lower cover layer and the connecting structure at the predetermined time, to an initial peel strength, which has the upper and lower cover layer and the connecting structure before the start of a biodegradation process, is formed, wherein the residual peel strength level in a composting test by completely inserting the geosynthetic mat into compost and composting in a temperature range that is above 25 ° C and below 65 ° C, up to the predetermined time and measurement of the peel strength in a peel test before insertion and at the predetermined time after removal from the compost, the swelling behavior being determined by a degree of swelling is characterized, which is formed by the quotient of the volume of the filling layer material including the water absorbed therein at the predetermined time to an initial volume of the filling layer material before the start of swelling, where - M - the degree of swelling is determined by completely immersing a layer of filling layer material in a water bath and loading the layer of filling layer with a pressure of 4.5 N / m ² , and in which a swelling-degradation ratio is formed from the degree of swelling divided by the The degree of residual peel strength within the first week after the simultaneous start of the swelling process and the biological degradation process is in a range between 1 and 5 and within each predetermined time from the beginning of the second to the end of the third month after the start of swelling and degradation in a range between 1, 5 and 25, preferably in a range with a lower limit of 2 and / or an upper limit of 15. Method according to claim 28 or the preamble of claim 28, wherein a layer made of a first biodegradable material is provided as the first geosynthetic layer and a layer made of a second biodegradable material is placed as the second geosynthetic layer, characterized in that the first and / or that second biodegradable material is formed in fiber form, in particular as fibers which have a fiber core strand made of a first biodegradable material and a fiber core strand coating made of a second biodegradable material, wherein the first biodegradable material has a first biodegradation rate that is higher than a second biodegradation rate of the second biodegradable material. Method according to claim 29, characterized in that the first and/or the second cover layer is produced from the fiber core strands in a first step and in a subsequent second step the fiber core strands in the first and/or second cover layer are covered with the fiber core strand covering. Method according to one of claims 29-30, characterized in that the upper and / or the lower cover layer, the middle filling layer or the entire geosynthetic mat with a liquid, in particular a water-repellent liquid such as preferably oil, preferably with a hardening water-repellent liquid such as a hard oil or be impregnated with a varnish based on it. Method according to one of claims 29-31, characterized in that when applying the middle filling layer, a non-swellable additive, in particular sand, is also applied.