ES2255666T3 - METHOD FOR CONSOLIDATING FOUNDATIONS. - Google Patents

Abstract

A method for consolidating foundation soils, comprising the operative steps of drilling a plurality of holes (1) in the soil, injecting into the soil through each hole (1) at least an at least an expanding substance (6) in one or more injection points (5) to compact the soil in proximity to said injection points (5) and monitoring the level of the soil to determine its rise. Moreover, for injection in each injection point (5), a minimum quantity of expanding substance (6) to be injected is determined, both as a function of the conditions of the soil in proximity to the injection point (5), and of the characteristics of the expanding substance (6), the quantity of expanding substance (6) injected into the soil is measured and compared to the determined minimum quantity. The injection of the expanding substance (6) is stopped when the injected quantity is at least equal to the minimum quantity, and the soil has risen by a predetermined minimum value, the consolidation being deemed to be effected in that moment. Advantageously, the expanding substance can expand less than five times. <IMAGE>

Description

Method to consolidate land of foundation.

The present invention relates to a method for consolidate foundation land, which is also used to build civil construction structures and artifacts of any type (hereinafter indicated globally as constructions) using expansive substances, in particular resins

So far, consolidation techniques with expansive resins have been based on a technology that used some fixed parameters such as operating procedures, and in the which expansive resin was studied more in view of the need to lift the structure quickly than from a real and definitive consolidation of the land.

Such resins constituted by mixtures of MDI polyols and isocyanates were initially used to lift sunken floors, for example as described in the patent of US invention 4,567,708.

Then, such resins progressively also used for injections under construction foundations, at different depths (see, for example, the request for Italian invention patent n. MI96A002520 and the corresponding European invention patents EP 851.064 and EP 941.388).

In particular, said invention patent publishes the use of expansive resins with the ability to expand into the air free at least five times its initial volume, combined with a monitoring of the elevation of the structure to consolidate. According to provided in said invention patent, consolidation should be consider achieved at the moment the structure begins to stand up.

Construction is usually monitored using a laser level and a millimeter sensor applied to the structure of the construction to consolidate.

So, so far the state of the art It provides two possibilities.

On the one hand, the injection, both below the plane of foundation as in depth, of the expansive resin by any method (that is, both multiple point injection vertically separated as within a vertical hole done in the field, as published for example in the patent of invention EP 851.064), but with the forecast to be monitored constantly the level of superior construction, giving for true that at the moment when construction begins to getting up has achieved a level of consolidation beyond minimum required for this intervention. It has been considered that when the dynamic thrust of the resin into the ground it discharged its power only upwards and therefore exceeded the force given by the static load of the construction, that was the moment when the underlying terrain could be considered, with reasonable certainty, consolidated.

On the other hand, the state of the art provides for use of an expansive resin able to increase its own volume of at least five times when expanding outdoors (for outdoor expansion means the expansion of the material freely without said material being confined within a default volume).

A small innovation, regarding described above, was provided by the invention patent EP 1,314,824, which simply publishes the use, to consolidate land requiring consolidation pressures greater than 500 kPa, of expansive resins capable of developing pressures greater than 500 kPa.

Anyway, such known technologies They have some drawbacks.

A first drawback is due to the fact that the consolidation moment is identified as the moment in which the land and / or construction that is at the top begin to get up.

Throughout his direct experience and Multi-year, the requesting party has observed that this system of finish the consolidation of the land has a high probability of error because it does not take into account the characteristics Geotechnics of the same terrain. To overcome this problem, they made different attempts carrying out geotechnical studies, in particular by conducting penetration measurement tests.

Such tests are usually performed by sampling in two or three points, adjacent to the construction to consolidate. In because the composition of the land can vary greatly speed even at short distances, the tests would have to perform them at each injection point, which is an operation complicated and, in some cases, impossible, apart from being highly onerous.

The consequence of such difficulties is the lack of a parameter that allows to determine with reasonable certainty when the land is consolidated and, by well, while injecting the expansive resin under a Construction structure sooner or later leads to its elevation, only in some cases such elevation corresponds to the final consolidation of the foundation ground, meaning by definitive consolidation of the land that state of compaction as to ensure, over time, a stable support to the structure that is at the top.

With the experience of thousands of interventions made, the requesting party has observed that in some cases the structure rises immediately with a few kilograms of expansive material injected into the significant bulb of pressures (for the definition of significant bulb of pressures, see below), while in other cases, despite the repeated injection of many kilograms of expansive material, the terrain does not rise or rises barely and successively returns to sink after a short period of time.

For example, if the sinking of the land was not caused by a sinking of the surface strata of the terrain, which are well consolidated, but by a sinking of the deeper strata, the injection of an expansive substance inside the superficial strata causes an immediate elevation  of the structure located at the top. If the only control which is done to verify that consolidation has been achieved It is based, as provided in EP 851.064 invention patents, EP 941,388 and EP 1,314,824, on the elevation of the land, remains Of course, immediately a mistake is made, since in reality there is only one false consolidation. The deep strata have not been consolidated and therefore in a short period of time they will cause the ground to sink again.

The diversity of results obtained in similar interventions, conducted in different places, depends of many concomitant factors, that is, type of terrain, presence or absence of cavities, amplitude of the plane of foundation, injection depth and amount of water contained in the ground.

Whereas, even in the presence of evidence geological, the type of terrain and its dynamic resistance can be precisely determined only partially, and that such data, of anyway, they are impossible to obtain or it is not economically feasible to verify them at all points where they should be performed the injections, to determine with reasonable certainty whether achieved consolidation is insufficient simply monitor the structure elevation. Therefore, it is indispensable determine the state of consolidation of the land in a way different and more reliable with respect to the methods currently known.

A second drawback of the techniques that are know today is related to the type of resin used

In accordance with the operating procedures currently used, although invention patents mentioned above provide for the use of resins with outdoor expansion coefficient of at least five times its initial volume, in practice the expansion coefficients of the effectively used resins are 15-25 times its initial volume (sector operators are convinced that the expansion speed is inversely proportional to capacity of expansion and that, in terms of consolidation, the best results are obtained with the lowest expansion speeds), to which corresponds an outdoor density (that is, a density after the resin has expanded outdoors) from 40-66 kg / m 3, and a resistance to compression in the range of 4 to 5 kg per centimeter square.

However, in the field it has been proven that resistance is merely theoretical, since those resins, expanded almost outdoors, they have an elastic behavior if They are subjected to compression.

In the frequent case where a resin with characteristics described above are injected below the foundations and within the foundation ground, and find empty due to washing, vertical cracks due to drying or cavities of any kind and nature, leads to its expansion momentarily until filling in the existing gaps as if was outdoors, assuming the characteristics of compressive strength described above.

In cases of this type, it has been proven that the consolidation provided by the resin is totally insufficient for ensure both the necessary lift to support the structure as the durability of the consolidation intervention.

It is no accident that the result of many consolidation interventions conducted with expansive resins of the type described above has been to provide an improvement momentary of the static conditions of the structure but not corroborated by its duration over time, since the expanded resin, requested by the load, slowly tended to compressed, albeit slowly, causing the reopening of the fissures in the structure located at the top.

In this situation, a technical task that constitutes the foundation of the present invention is that of provide a method to consolidate foundation lands that overcome the above mentioned inconveniences.

In particular a technical task of this invention is to provide a method to consolidate land of foundations in which it is determined whether their consolidation with greater certainty than in the methods of known consolidation.

Another technical task of the present invention is to provide a method to consolidate foundation lands to ensure the duration of the consolidation intervention at over time

The specified technical tasks and stated objectives are achieved substantially by a method to consolidate foundation lands as described in the claims that are ahead.

Other features and advantages of this invention will become even more apparent from the detailed description of some preferred executions, but not exclusive, of a method to consolidate foundation lands, described with reference to the attached drawings, in which:

- Figures 1, 2 and 3 illustrate, respectively, three successive operational steps of a method according to the present invention.

The method to consolidate foundation lands of the present invention comprises a first operative step in the which is made a plurality of holes (1) in the ground (2) a consolidate, properly distanced from each other, with a distance between the centers, for example, one meter. In the case of consolidation of an existing construction (3), the holes (1) they are made in close proximity to the foundations (4) thereof (figure one).

Said holes (1) can be made both vertical as inclined with respect to the vertical line, in particular way of extending below the plane of foundation.

Advantageously, the holes (1) involve to the significant pressure bulb of the foundations (4), where the significant pressure bulb is the area of the underlying terrain to the foundation plane, affected by a pressure, exerted by the same foundations (4), of significant value. Conventionally, the significant pressure bulb is identified by a band of ground underlying the foundation plane, as wide as the base of the foundations (4) and deep twice its depth (to from the foundations).

In the second step of the method are identified, along each orifice (1), one or more injection points (5), in correspondence of which subsequently the expanding substance (6) will be injected into the ground to compact the same ground.

Alternatively, the injection can also involve the entire hole (1), which thus coincides with the injection point (5).

As you can see in the attached drawings, in the case of injection points (5) that do not match all the hole (1), for each injection point (5) advantageously a tube (7) whose end is inserted into the hole (1) lower is in correspondence of the injection point (5), and whose upper end (9) is accessible from the outside by part of an operator (10). Logically, the hole (1) must be made with a sufficient diameter to allow the introduction of a quantity of tubes (7) equal to the number of points of injection (5).

Before starting to inject the substance expansive (6), it is necessary to determine a minimum amount of expansive substance (6) to be injected into each injection site (5), depending on the terrain conditions near the injection point (5) and the characteristics of the substance expansive (6).

During the injection stage it is necessary reach or exceed said minimum amount, to ensure that the land on which the weight of a construction rests (3) is has consolidated definitively and is stable.

In particular, according to the preferred manner of Execution of the present invention, the minimum amount of substance expansive (6) to be injected into each injection point (5) is determined based on the degree of soil moisture in correspondence of the respective injection point (5), in consideration of the fact that as the content of water the ground becomes more prone to deform and, by consequently, its resistance decreases.

Therefore, before being able to determine the minimum amount of expansive substance (6) to inject, it is necessary to carry out a preliminary operational step during which the degree of soil moisture is measured in correspondence of each injection point (5).

According to the preferred execution, the Measurement of the degree of soil moisture is achieved by measuring the electrical resistance of the same terrain, since there is a narrow correlation between the water content in the soil and its resistance electric

As already noted, inside the holes (1) tubes (7) are introduced for injection, which They are usually made of copper or aluminum, both materials with Good electrical conductivity

So, in consideration of the correlation existing between the electrical resistance of the ground and its degree of humidity, it is enough to connect, with an appropriate instrument (11), to two adjacent tubes (7) placed on the ground, to be able to measure the electrical resistance of the ground between them and so determine the degree of soil moisture in that area (figure 2).

Advantageously, anyway, in a evolved version of the present invention, only the end of Each tube (7) is made of conductive material, so that accurately locate the measurement at the exact injection point (5).

Performing the measurement between each pair of points adjacent injection (5) (horizontally and vertically) is possible determine the electrical resistance of the terrain in that area.

For example, if for a hole (1) they have planned two injection points at different depths, to each of them will be possible to measure the electrical resistance both in relation to the injection point (5) lower and higher, and a the two injection points (5) located on its sides in the plane horizontal (or, anyway, to the two injection points (5) more close to it). Calculating the weighted average of the values obtained in this way, it will be possible to determine with good precision the electrical resistance of that area of the land and, by consequently, the degree of humidity.

Depending on the needs, the amount of Measures taken can be adapted to each operational case. For example, resistance could be measured in relation to a single point of injection (5) for each hole (1).

As already noted, the minimum amount of expansive substance (6) to be injected depends on the characteristics of the expansive substance (6), in particular of its ability to expansion.

The following Table 1 shows the coefficients of Outdoor expansion of seven types of expansive substance (6), consisting of a resin of the type described below, designated generically with the letters A, B, C, D, E, F and G.

TABLE 1

Type of resin TO B C D AND F G Resin expansion coefficient used 4.8 4.6 4.4 4.2 4.0 3.5 3.0 Density after outdoor expansion of the resin 208 218 228 238 250 286 333 used Kg / m 3

The following Table 2, on the other hand, shows the minimum amount to be injected for each of the resins of the Table 1, depending on the electrical resistance of the ground (and, by therefore, of its degree of humidity).

The average data shown in this table is refer to standard land, such as land clayey or clayey-sandy with presence of sand and / or gravel, with few small cavities. Further, the table was determined for injection points (5) located at a reciprocal distance of one meter.

TABLE 2

4

In general, the table should be obtained empirically for each type of terrain and each type of substance expansive (6), through field tests, in In particular, it will be necessary to check with appropriate evidence if a given amount of resin injected at each injection point (5) a good compaction has been achieved or not (see also indicated below about the monitoring of the level of ground).

In this way, if a table similar to Table 2 for each type of terrain, once measure the resistance of the land to consolidate in correspondence of each injection point (5), for each of them you can easily determine the minimum value of expansive substance (6) to inject

In general, the minimum amount of substance expansive (6) to be injected into each injection point (5) increases as air expandability decreases free of the expansive substance (6), and as the electrical resistance of the ground at that point of injection (5).

After the above the operator (10) can start injecting the expansive substance (6) into the ground in correspondence of each injection point (5).

During the injection, the method of the present invention also provides for continuous monitoring of the level of land and / or a construction (3) that rests on it to determine the elevation of the same land, and to measure the amount of expansive substance (6) injected into the ground, and compare said value with the value of the minimum quantity to be injected, determined for that injection point (5).

As can be seen in Figure 3, the operator (10) performs the injection by means of a gun (12) fed, through an injection pump (not shown), from a tank (not shown) of the expansive substance (6) (or from several tanks, through several pumps, when the expansive substance (6) is obtained by mixing two or more components at the point of injection (5).

Both the injection pump and the ducts (13) that extend between the tank and the gun are heated suitably to keep the expansive substance (6) at its optimum temperature, according to known modalities.

Advantageously, the operator (10) can have a viewfinder (14) that allows you to visualize the values of the amount of substance (6) injected and the ground elevation or construction (3).

The injection of the expansive substance (6) is stops when the amount injected is at least equal to the amount minimum, provided that the land and / or construction (3) that is supported on it they have risen from a minimum value default, which is usually not less than 1 mm.

In general, the minimum default value is not a constant, but must be determined for each intervention according to the magnitude of consolidation required (this value, in particular, it varies with the magnitude of the different subsidence of the land that require consolidation intervention). Said value minimum, therefore, may vary even from one point to another in the Same intervention.

To ensure a consolidation result yet better, however, if, before reaching the minimum amount of expansive substance (6), the land and / or construction (3) that is supports on it has risen of a magnitude that exceeds a default maximum value (also variable of an intervention to another, similar to the default minimum value) beyond which runs the risk of damaging the construction (3), the step injection is canceled and the steps described are repeated until here in a new injection point (5). Said new point of injection can be selected in the same hole (1) at a different depth, in an extension of it, or in a new hole (1) made in proximity to it.

This procedure can be repeated several times. until an injection point (5) is identified at which can inject an amount of expansive substance (6) at least equal to the minimum predetermined amount.

The security check described above is especially when, however, a subsidence of the land, the surface strata of that land they are well consolidated, and the deepest strata were the that have sunk (as described above with respect to disadvantages of the techniques that are currently used).

In this case, all injections will have to carried out at great depth.

According to the preferred method execution of the present invention, an expansive substance should be used (6) in a position to expand its own outdoor volume less that five times, and therefore has, after his outdoor expansion, a density of at least 200 kg per meter cubic. Preferably, said expansive substance (6) has a expansion coefficient between three and five times.

Advantageously, said type of substance used expansive (6) has, after its outdoor expansion, a compressive strength of at least 5 kg per centimeter square, and preferably at least 9 kg per square centimeter, with a deformation of less than 0.5%.

Preferably, the expansive substance (6) is a resin that expands by means of a chemical reaction, and that It consists of a mixture of two components, a polyol / polyether such as for example Eterol 317 / X1 polyol manufactured by the Polychem System Company, and an MDI-based isocyanate, such such as the MDI Desmodur VKS 20F isocyanate manufactured by Bayer company.

According to a different execution of the method of consolidation of the present invention, within different points Injection (5) two or more expansive substances are injected with Different expansion capacities. Preferably, of all modes, all expansive substances to be used will have a expansion coefficient less than five.

In particular, for a hole (1) where they have been planned two injection points (5) superimposed, in each of said two injection points (5) superimposed can be inject two different expansive substances (6), chosen from so that the expansive substance (6) injected within the point of Injection (5) deeper have greater expandability that the expansive substance (6) injected within the point of injection (5) less deep.

The operational steps described above can be directly carry out an operator (10), or with the help of a programmable electronic control unit that, for example, can memorize the data corresponding to the electrical resistance of the terrain determining for each point the minimum amount of substance (6) to inject, monitor the ground level and the amount of substance (6) injected and disable the substance supply (6) when the above conditions are reached, or once has exceeded the maximum default elevation value.

In this way, the present invention achieves important advantages

First, the method to consolidate Foundation grounds of the present invention ensures the possibility of determining, with greater certainty than the methods of known consolidation, the time when the terrain can be considered consolidated.

In this way, it is ensured over time the duration of the consolidation intervention.

In addition, considering that on average it is calculated that on foundations on the ground is discharged a minimum of 0.2-0.3 kg per square centimeter at a maximum of 3-3.5 kg per square centimeter, you have a lift of at least 9 kg per square centimeter (as is ensured by the method of the present invention using substances expansive able to expand less than five times), and said term means that said load bearing capacity is guaranteed with deformations below 0.5%, which satisfies widely all the safety margins required by the building regulations.

This load bearing capacity was confirmed by conducting tests on samples of expanded material at atmospheric pressure (outdoors).

Comparative tests conducted on resins expansive ones that are currently used, with a coefficient of 15-25 times expansion that implies resistance to theoretical compression that varies from 4 to 5 kg per centimeter square, have shown that the application of a load of 4-5 kg per square centimeter to be sampled from such expanded open-air resins cause deformation in proportion to the applied load, which highlights its indisputable elastic behavior

In addition, the correlation between the quality of the consolidation and the amount of water on the ground has proved, in numerous tests conducted, to be an optimal choice which combines ease of execution with information reliability obtained in this way.

In addition, it should be noted that this invention is relatively easy to realize and that the cost related to the embodiment of the invention is not very high, compared to industry standards.

The invention thus conceived can be subjected to numerous variants and modifications, without departing from the scope of the inventive concept that characterizes it.

All components can be replaced by other technically equivalent elements and, in practice, all the materials used, as well as the shapes and dimensions of the various components, they can be any depending on the needs.

Claims (25)

1. Method to consolidate land of foundation, which includes the operational steps of: - realization of a plurality of holes (1) in the ground; - injection into the field, through said holes (1), of at least one expansive substance (6) in one or more injection points (5) to compact the ground in proximity of said injection points (5); Y - monitoring of the ground level and / or a construction (3) that relies on it to determine its elevation; characterized by the fact that it also includes, for injection at each injection point (5), the operational steps of: - determination of a minimum amount of expansive substance (6) to be injected, both depending on the degree of soil moisture corresponding to the respective point of injection (5), as of the outdoor expandability of the expansive substance (6); - measurement of the amount of substance (6) injected into the ground; Y - comparison of the amount of substance (6) injected with respect to said minimum amount; the injection of the expansive substance (6) being stopped when the amount injected is at least equal to said minimum quantity, and said land and / or construction (3) that is supported on it it has risen from a predetermined minimum value, whereas at that time consolidation has been achieved. 2. Method for consolidating foundation lands according to claim 1, characterized in that it also comprises, before said step of determining the minimum quantity of expansive substance (6) to be injected, the operative step of measuring the humidity degree of the ground in correspondence of the injection point (5). 3. Method for consolidating foundation lands according to claim 2, characterized in that said step for measuring the degree of soil moisture is carried out by measuring the electrical resistance thereof.
ground. 4. Method for consolidating foundation lands according to claim 3, characterized in that the electrical resistance of the ground is measured between a pair of adjacent injection points (5). 5. Method for consolidating foundation lands according to claim 3, characterized in that the electrical resistance of the ground is measured between pairs of adjacent holes (1). Method for consolidating foundation grounds according to any one of claims 3 to 5, characterized in that the minimum quantity of expansive substance (6) to be injected into each injection point (5) increases as the electrical resistance of the ground at that point of injection (5). 7. Method for consolidating foundations according to any one of the preceding claims, characterized in that the minimum amount of expansive substance (6) to be injected into each injection point (5) increases as the expansion capacity decreases. outdoor substance expands
siva (6). 8. Method for consolidating foundation grounds according to any one of the preceding claims, characterized in that said expansive substance (5) is in a position to expand its volume in the open air less than five times. 9. Method for consolidating foundations according to any one of the preceding claims, characterized in that said expansive substance (6) is able to expand its volume in the open air between three and five times. 10. Method for consolidating foundation lands according to any one of the preceding claims, characterized in that said expansive substance (6) has, after its expansion in the open air, a density greater than 200 kg per cubic meter. 11. Method for consolidating foundations according to any one of the preceding claims, characterized by the fact that for said injection step an expansive substance (6) is used which, after its expansion in the open air, has a compressive strength of at least 5 kg per square centimeter with a deformation of less than 0.5%. 12. Method for consolidating foundation grounds according to claim 11, characterized in that the expansive substance (6), after its expansion in the open air, has a compressive strength of at least 9 kg per square centimeter with a deformation less than 0.5%. 13. Method for consolidating foundation grounds according to any one of the preceding claims, characterized in that said expansive substance (6) is expanded by means of a chemical reaction. 14. Method for consolidating foundations according to any one of the preceding claims, characterized in that said expansive substance (6) comprises a mixture of polyols / polyethers and isocyanate based on MDI. 15. Method for consolidating foundation lands according to any one of the preceding claims, characterized in that said holes (1) are made in a vertical line. 16. Method for consolidating foundation lands according to any one of the preceding claims, characterized in that said holes (1) are made inclined with respect to the vertical line. 17. Method for consolidating foundation grounds according to any one of the preceding claims, characterized in that for each hole (1) multiple injections of expansive substance (6) are made in correspondence of injection points (5) located at different depths . 18. Method for consolidating foundation grounds according to any one of the preceding claims 1 to 16, characterized in that for each hole (1) a single injection of expansive substance (6) is made along the entire length of the orifice (1), said orifice (1) coinciding with a single injection point (5). 19. Method for consolidating foundation lands according to any one of the preceding claims, characterized in that said predetermined minimum elevation value is at least 1 mm. 20. Method for consolidating foundation lands according to any one of the preceding claims, characterized in that said injection points (5) are located below foundations (4) of a construction (3) to be consolidated. 21. Method for consolidating foundation lands according to any one of the preceding claims, characterized in that said injection points (5) are located within the significant pressure bulb of the foundations (4) of a construction (3) to be consolidated. . 22. Method for consolidating foundations according to any one of the preceding claims, characterized by the fact that it provides for the injection of two or more of said expansive substances (6) with different expansion capacities, within different injection points ( 5). 23. Method for consolidating foundation lands according to claim 22, characterized in that at least one orifice (1) has been provided with two superimposed injection points (5), and by the fact that in each of said points of Injection (5) superimposed two different expansive substances (6) have been injected, the expansive substance (6) injected at the deepest injection point (5) having a greater expandability than the expansive substance (6) injected at the point Injection (5) less deep. 24. Method for consolidating foundation lands according to any one of the preceding claims, characterized in that if the land and / or the construction (3) that rests on it have been raised from a value that exceeds a predetermined maximum value before injecting said minimum quantity of expansive substance (6), said injection step is canceled and another new injection point (5) is identified and for said new injection point (5) all operational steps are carried out. 25. Method for consolidating foundation grounds according to claim 24, characterized in that the identification of a new orifice (1) is repeated until for an injection point (5) the injection of the expansive substance (6) stops because the amount injected is at least equal to said minimum amount, and said land and / or construction (3) that rests on it have been raised from said predetermined minimum value.