JPH0442492B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The core material pulling method of the present invention is used in underground construction work in which a soil cement earth retaining wall is constructed and the ground is excavated, and the core material of the temporary earth retaining wall is removed after the construction is completed. It is used for construction work that cannot be left in the same location as it was constructed, or when the core material needs to be collected and reused for economic reasons.

[Conventional technology]

In the conventional core material pulling method, the following surface treatment has been performed on the surface of the core material in order to pull out the core material. Some of them are
A waxy wax with a low melting point is applied to the surface of the steel material. Waxy wax is applied to the steel material that serves as the core material, such as commercially available product name High Slide Wax TAP-1.
, TAP-2 or PS-5000 with a thickness of 1mm
The core material is applied in advance to a thickness of 2 mm, and the core material is pulled out after construction is completed using the slipping effect of the wax. A hydrophilic urethane resin coating is sprayed on the steel material in advance to a thickness of about 1 mm, and while it is buried in the soil for a long period of time, the urethane material reacts with the alkali in the mortar and turns into a gelatinous material. It exhibits a lubricating effect when pulling out the core material, making it easier to pull out.

There is also a construction method in which core steel materials are tied together, and as shown in FIG. Then, the crushing powder 9 is loaded and blasted, and the force of the blasting gas generated at that time is used to cut the edge of the core material and pull it out by loosening the flange part, which has been given a margin in advance. This is a construction method that makes it easier.

[Problem to be solved by the invention]

For continuous underground walls constructed as a means of ground improvement,
There are methods to improve the ground with soil cement, mud solidification method, mortar replacement method, and replacement method with concrete. In either case, the earth retaining wall material surrounding the core material has high strength, and the surrounding frictional resistance when pulled out is abnormally large, so it is often experienced that it is extremely difficult or impossible to pull out and recover the core material. ing.

In the conventional construction method, the waxy wax construction method described above applies a thinner coating thickness of 2 mm than 1 mm, so if the built-in core material is scratched, deformed, bent, warped, etc., the peripheral frictional resistance increases abnormally. Even short piles of 20 m or less may not be able to be pulled out. In the edge cutting method by blasting tied steel members, if there are no gaps in the overlapping part of the flanges over the entire length of the pile, movement of the steel members may occur.
The edges are not cut enough and it is difficult to pull out.

The method of spraying a hydrophilic urethane resin coating is
Because the spraying thickness is as thin as 1 mm, it is difficult to pull out for the same reason as the waxy wax method. In addition, even if a large pulling load is applied using a powerful drawing machine to a core material that has been erected without any treatment, rather than a core material that has been previously subjected to the steel surface treatment described above, the steel material that is the core material will not work properly. Its own cross-section fracture occurred and it was torn off.
It is also often experienced that it cannot be pulled out.

[Means to solve the problem]

In the invention described in item 1 of the present application, regarding the difference in density between the soil cement and the core material that has not yet hardened, the core material to be built is buried under its own weight without floating in the soil cement that has improved the ground. The condition is that. This is because when the soil cement density in the hole is higher than the density of the core material, the core material lifts up. When such a lifting phenomenon occurs, if an external force is forcibly applied to push it in, the lower end of the core material will move horizontally, causing the core material to bend or warp. If the core material is bent or warped, the core material will come into direct contact with the solidified soil mortar when it is pulled out, and the core material will not be able to be pulled out unless the soil mortar is destroyed. Therefore, the soil mortar density should be smaller than the density of the core material, but by changing the range from 1.05 g/cm ³ to 2 g/cm ³ ,
The core material's own weight makes it easy to build it into the soil mortar, and it is extremely important to prevent the core material from bending or warping in order to minimize the pulling resistance when pulling out the core material. .

In order to achieve the above object, the invention in item 2 of this application uses polystyrene as the resin foam in the invention in item 1 of this application.
Polyester, polyurethane, polyethylene, polyvinyl chloride, acrylonitrile-butadiene copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, and low-density resin foam is used as the pasting material. The density of the core material can be adjusted by changing the thickness and attaching it to the steel material. Furthermore, the thickness of the resin foam to be attached to the steel material described in Section 3 is 15 mm rather than 6 mm, but this thickness is necessary for cutting the edges between the core material and the surrounding soil mortar, This is because if it is too thin, the edge cutting effect will not be as expected, and if it is thicker than 15 mm, the edge cutting width will become too large, which is not desirable from the standpoint of improving the strength of the ground.

To manufacture the core material having the structure described in item 4, first, viscous grease is applied to the steel material for the purpose of temporarily fixing the resin foam, and the resin foam is pressed and pasted. The resin foam is cut in advance to match the cross section of the steel material. In addition, all seams of the resin foam are fixed with adhesive tape, and the entire steel material is wrapped in a bag.

The grease to be used for applying the viscous grease described in item 5 may be one that is sticky enough to prevent the resin foam from falling off the steel material when the resin foam is attached to the steel material. It is used as an adhesive until it is pasted and the seam is fixed with adhesive tape.

The viscous grease described in item 6 has a consistency of 200 to 500 at 25°C and a dropping point of 95.
As long as it is a viscous grease that has properties ranging from ℃ to 300℃, any type of base oil may be used as long as it is water resistant, such as mineral oil, synthetic oil, or silicone oil. This is not intended to limit the invention.

The density of the coated steel described in item 7 is preferably adjusted from 2.1 ton/m ³ to 3.8 ton/m ³ , and from the above-mentioned effects, a coated steel with a density higher than that of unhardened soil mortar is manufactured. Generally, the density of unhardened soil mortar is 1.05ton/
m ³ to 1.8 ton/m ³ , and set the density range of the coated steel material that can easily settle naturally under the core material's own weight even if the core material is erected without uniform ground improvement through mortar mixing. .

The core material tip shoe according to the invention in Item 8 of the present application is made of a thin steel plate in a shape that covers the core material tip, and is attached when the core material is erected. The thickness of the thin steel plate is preferably 2.3 mm from 1.6 mm, and it is preferable to use the appropriate one depending on the size and weight of the core material, but there is no particular limit to the thickness or weight of this thin steel plate, and the thickness and weight of the thin steel plate used in the present invention are not limited. It does not stipulate the tip of the shoe.

[Effect]

As an illustration of the effect of the density difference in the invention of Section 1 of the present application, FIG.
Assuming G _A and the density of core material 1 as G _B , now G _A > G _B
When the following relationship is established, the core material 1 cannot be built up naturally by its own weight alone, and the core material 1 cannot be built into the soil mortar hole 2 unless pushing force P is applied.
When the core material 1 is pushed in by applying an external force, a reaction force F corresponding to the buoyancy will act between the core material 1 and the unhardened soil mortar, but since the core material 1 has elasticity, the lower end of the core material will move horizontally.
This becomes a bend or warp 1a of the built-in core material 1, and when the core material 1 is pulled out, the side part of the core material comes into direct contact with the solidified soil mortar 3a, so that the soil mortar cannot be destroyed. The core material 1 cannot be pulled out, and as a result, the core material 1 cannot be pulled out. Therefore, in order to erect core material 1 without deformation,
The relationship G _A < G _B is required.

The resin foam of the invention in Item 2 of the present application is interposed between the steel material serving as the core material and the soil mortar to prevent direct contact between the steel material and the soil mortar, and also reduces the density of the resin-coated steel material to 2.1 ton/m ³ It is useful to adjust to 3.8ton/ ^m3 . If the solidified soil mortar is in direct contact with the core material when the core material is pulled out,
The frictional resistance increases and the pull-out force of the core material increases. Furthermore, since the strength of the resin foam is lower than that of the soil mortar solidified with the core material, the resistance to external force when the core material is pulled out is small, and the core material is easily pulled out due to the destructive effect of the resin foam itself.

The thickness of the pasting material described in item 3 is 6 mm to 15 mm.
However, if the steel material is curved, when a pull-out force is applied to the core material as shown in Fig. 4, it will compete with the mortar 3a solidified at the curved portion 1a, which is different from the conventional construction method. When there is only a thin coating like the high slide wax construction method, or when the coating is about 1 mm thick like the sprayed urethane construction method, there is no space between the core material and the solidified soil mortar, and the core material Frictional resistance increases as it comes into contact with solidified soil mortar. Particularly in the core material installation work during on-site construction, there are product errors within the permissible range of the core material itself, and there are also distortions caused by handling on site. Furthermore, when old wood is used, the distortion is particularly large, so it can be assumed that the built-in core material has settled in a form similar to that shown in Figure 4, although there may be differences in degree. Under these circumstances, the coating thickness of the core material should be 6 for short materials.
mm to 15 mm for long materials or large cross sections.

In the pasting of the covering material described in item 4, the resin foam is cut for each contact surface according to the cross section of the steel material, and by sticking it closely to the steel material, the steel material and the resin foam are bonded. to prevent uncured soil mortar from entering. In addition, since the joints of the individual resin foams are fixed with adhesive tape, it is possible to prevent unhardened soil mortar from entering through the joints, and to reliably cut the edge between the steel material and the soil mortar.

The application of the viscous grease described in item 5 serves as a glue that temporarily attaches the resin foam cut to match the cross section of the steel material to the steel material, and makes the seams between the foam adhesive. It acts as an adhesive until it is fixed with tape. In addition, the applied viscous grease acts as a lubricant against the rough surface friction between the steel material and the resin foam when the core material is pulled out, and can be pulled up with a small force when cutting the edge of the core material or pulling it up. It acts to make it possible. In this case, if the resin foam is attached to the steel surface with an adhesive that has a good adhesion effect instead of viscous grease, the resin foam that will be left in the ground when the core material is pulled up will be removed. Because of this, the resin foam itself has to be destroyed and pulled out when it is pulled out, which increases the pulling force accordingly. This results in the opposite of facilitating extraction.

That is, in the present invention, the viscous, grease-like state is extremely important as an adhesive for attaching the resin foam to the surface of the steel material.

The properties of the grease described in item 6 are extremely important, especially for carrying out the invention. In other words, when a steel material coated with waxy wax to a thickness of 1 mm to 2 mm is used as a core material without covering the steel material with a resin foam as in the present invention, the core material is placed in unhardened soil mortar. During construction, the wax must not be easily peeled off from the surface of the steel material by the soil mortar, and must remain unaltered on the surface of the steel material until the core material is removed. If the core material is pulled out, it will no longer have a lubricating effect, so in order to prevent it from falling off during erection, it is required to have a waxy hardness that will not easily fall off. However, rather than forming such a waxy solidified product, it is extremely preferable that the grease of the present invention has a consistency and a dropping point within appropriate ranges and has a viscous or butter-like consistency. It is easy to press and paste the resin foam onto the steel material from above, and once it is pasted, it will not fall off the steel surface due to the low density of the foam, and will be integrated with the steel material in the soil mortar. When it settles, it becomes . Moreover, even though the adhesive is kept so lightly, once construction begins in the soil mortar, the low-density resin foam will stick to the surface of the steel material due to the confining pressure of the surrounding fluid soil mortar. The resin foam sinks into the soil mortar while remaining attached to the surface of the steel material, and the resin foam is never peeled off from the surface of the steel material by the soil mortar. Furthermore, the resin foam, which is attached to the surface of the steel material due to the viscosity or butter-like nature of grease and its light adhesiveness, is easily left in the ground when the core material is pulled out, leaving only the steel material alone. However, the edges between the resin foam and the steel material can be cut very easily and without the need for much force. In this regard, when using a core material in which a resin foam is bonded to a steel material using a resin adhesive, such as an adhesive made by dissolving vinyl acetate resin in an ethyl acetate solvent, or an adhesive made by dissolving synthetic rubber in a trol solution, etc. , a considerable amount of force is required to separate the steel material and the resin foam, and for this reason, if the material is strongly adhered to the surface of the steel material, the resin foam itself may break, resulting in damage to the material in the future. It is particularly important to use the grease-like substance described in claim 6 as the adhesive material for pasting the resin foam used in the present invention, since the pulling force increases and it becomes difficult to pull out.

The density of the core material described in item 7 is from 2.1ton/ ^m3 .
By adjusting to 3.8 ton/m ³ , core material can be easily built into unhardened soil mortar. This is for the reason mentioned above, and allows the core material to be easily and precisely set up, which in turn makes it easier to pull out the core material.

The shoe 13 at the tip of the invention in Item 8 of the present application is a protective shoe made of resin foam that is attached to the lower end of the core material, and when the core material hits the ground during erection, the core material penetrates into the ground to a predetermined depth. It also works to prevent the resin foam attached to the steel material from peeling off when the core material is laid down.

〔Example〕

Examples shown in the drawings will be described below.

FIG. 5 is a pile-laying diagram of the MIP column-row earth retaining wall 2, which was constructed using an earth auger drilling machine (not shown). The construction method for MIP is to rotate and insert an earth auger into the soil, and at the same time inject cement milk from the hollow pipe tip of the earth auger core to loosen the ground and mix the soil and cement milk in the hole. A column-row earth retaining wall is formed by constructing an H-shaped steel or I-shaped steel that becomes the core material 1. Depending on the circumstances of the construction work, the core material 1 has two types: a pile 5 to be left as is (the part without diagonal lines), and a pull-out pile 4 (the part with diagonal lines) to collect the core material.

Referring to FIG. 1, which is a perspective view of the core material 1, the core material 1 is to be built into soil cement. The divided resin foam 11 is pasted over the entire area where the steel material 10 contacts the soil cement using adhesive grease (not shown), and the entire surface of the joint is fixed with adhesive tape 12 shown in Figure 2. .
Further, a steel plate shoe 13 shown in FIG. 3 is attached to the tip of the core material to complete the installation of the core material.

This fully equipped core material is quietly placed into the soil cement hole that has already been constructed in the ground. Referring to FIG. 4, which is a schematic diagram of the core material built into the soil mortar hole, 1a is the bent portion of the core material 1, 2 is the soil mortar hole, 3a is the soil mortar that will be destroyed when pulled out, and P is the soil mortar that is destroyed when pulled out. Pushing force for sinking the core material, F
Referring to FIG. 7, which is a cross-sectional view of the steel material tying construction method showing the buoyancy generated in the core material, 8 is the tying steel material, 9 is the crushing agent, and H is the hollow portion.

In areas subject to vibration and noise regulations, core material is pulled out using hydraulic jacks and multiple pulleys, but in areas where vibration and noise are permissible, a vibro-type pulling machine may be used. In this example, a multiple pulley system was adopted to pull out the core material. The results of the on-site pullout test are shown in the table in Figure 6.
When pulling out the core material, which is 450 x 200 x 9 x 14 mm and is covered with resin foam and has a length of 18 m, the average value of the pullout load is 116 tons based on the data from the three test piles. This is 3.8t/m ² when converted to the contact area of the steel material. In Figure 6, No. 39, No. 40, and No. 41 are the serial numbers assigned to the MIP pile-up diagram in Figure 5. The first load is the load required for edge cutting of the core material, and the second load is indicates that the pull-out load is reduced due to slipping between the steel material and the resin foam that constitute the core material.

This caused the edge of the bond between the I-shaped steel and the resin foam to break.

The resistance caused by soil cement bending has been reduced.

The resistance due to bending and twisting of the core material has been reduced.

For these reasons, it is thought that the force that resists the core material being pulled out the second time is mainly due to the frictional force between the resin foam and the I-shaped steel generated by the lateral pressure. Because resin foam has a resilience against deformation, an average pullout load of 116 tons was required even after the edge broke the second time.

Due to this restoring force, the compressed material expands and fills the voids in the I-shaped steel part, so even if the steel material is pulled out, the water-stopping properties will not be impaired.

This shows that if the construction is carried out with the utmost care, it is possible to bring the pull-out load closer to 116 tons.

There is an example of a published example in which the core material pulled out using High Slide Wax was 170t to 200t, which is an average of 5t/m ² per unit area.
In addition, with the hydrophilic urethane spraying method, the actual work is
The result was 6t/ ^m2 . Compared to these examples, according to the present invention, it was 3.8t/m ³ , so compared to the conventional construction method, this construction method made it possible to easily pull out with a small load, and when pulling out, Can be safely installed without damaging the core material.

〔Effect of the invention〕

Nowadays, in the design and construction of structures based on recent urban planning, it is expected that underground structures will become more popular and expanded, and the steel materials of continuous earth retaining walls built for temporary earth retention can be easily pulled out and recovered after construction is completed. It made it possible to do so.

In the future, this construction method will be extremely effective in construction projects that require the removal of core materials, or in cases where removal becomes necessary due to agreements with adjacent landowners during construction work. Furthermore, since the pulling force is small, it is sufficient to prepare a small pulling machine, which brings about many effects such as reducing construction costs and shortening the construction period.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of the core material, FIG. 2 is a cross-sectional view of the core material taken along line S--S in FIG. 1, and FIG. 3 is a perspective view of a steel shoe shoe attached to the tip of the core material. FIG. 4 is a schematic diagram of the core material installed in the soil mortar hole. Figure 5 shows the pile-down surface of the MIP column earth retaining wall.
FIG. 6 shows the effects of the present invention, and is a table showing the result data of a core material pull-out test. FIG. 7 is a sectional view of a known steel tying method. 1... Core material, 10... Steel material, 11... Resin foam.

Claims (1)

[Scope of Claims] 1. In the construction of a continuous underground soil retaining wall in which a reinforcing core material is built into a continuous underground soil cement wall,
When inserting the core material into soil cement that has not hardened yet in the hole, first apply viscous or butter-like grease around the steel material used as the core material, and then apply the resin foam to the surface of the steel material so that the surface of the steel material is not exposed. The difference in density between soil cement and the core material is 1.05g/ ^cm3.
By adjusting the density of the unhardened soil cement so that it is within the range of 2 g/cm ³ , the core material can be built easily, and the covering effect of the resin foam allows the core material to bond with the surrounding soil cement. A core material drawing method that is characterized by cutting the edges of the steel material, and effectively using grease to lubricate the steel material when the core material is being pulled out, thereby making it easier to draw out the steel material. 2 In the core material drawing method described in paragraph 1, the resin foam to be pasted around the steel material forming the core material is
A core material drawing method characterized by being polystyrene, polyester, polyurethane, polyethylene, polyvinyl chloride, acrylonitrile, butadiene copolymer, styrene/acrylonitrile copolymer, or acrylonitrile/butadiene/styrene copolymer. 3. The core material drawing method according to item 2, wherein the resin foam has a thickness of 15 mm rather than 6 mm. 4. The core material drawing method according to item 1, characterized in that the structure consists of a steel material covered with a resin foam. 5. The method according to item 4, characterized in that when pasting the resin foam, a viscous or butter-like sticky grease is applied to the surface of the steel material in advance, and then the resin foam is pressed and pasted. Core material pulling method. 6. The adhesive described in item 5, wherein the adhesive is a viscous or butter-like grease having a consistency of 200 to 500 at 25°C and a dropping point of 95°C to 300°C. core material pultrusion method. 7. The core material drawing method according to item 1, characterized in that a core material having a structure covered with a resin foam and having a density adjusted from 2.1 ton/m ³ to 3.8 ton/m ³ is used. 8. The core material pulling method according to item 1, characterized in that a shoe is attached to the tip of the core material having a structure covered with a resin foam.