JPH0432894B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for filling voids that occur between a civil engineering structure and the ground, and more specifically, relates to a method for filling voids that may change over time. The present invention relates to a method for filling voids in soil, which is capable of filling voids with a water-absorbing and swelling polymeric material and closing the voids by following the deformation of the voids over a long period of time.

[Prior Art] Civil engineering structures are often constructed in areas where ground subsidence may occur, such as areas with low groundwater or soft ground. In such a case,
To prevent civil engineering structures from sinking with the ground, or from tilting due to uneven settlement, piles are driven that reach fixed points deep underground, and the structure is designed and constructed in such a way that the load of the structure is applied to them.
When such a construction method is adopted, the subsequent development of ground subsidence will result in the structure being lifted up, creating voids of various sizes to varying degrees between the structure and the ground. .

If groundwater exists, especially in places where there is a large hydraulic gradient due to rainfall, or if groundwater is constantly present, there is a possibility that water will flow into the voids and scour the soil, leading to a disaster. There is sex. The above-mentioned voids expand over time until restrictions on groundwater pumping and embankment loads reach equilibrium with ground stresses and settlement decreases.

In contrast, conventional techniques for filling voids include pouring and solidifying earth and sand or concrete, or for voids between structures, attaching elastic materials such as rubber in advance to areas where voids are expected to occur during construction. is taken.

[Problems to be solved by the invention] However, in the case of the former method of pouring concrete or earth and sand, although it is possible to fill the voids at the time of filling, it will only become clogged and solidified at that point, so it will not be possible in the future. It is essentially impossible to follow the continued expansion of the void. Further, the rubber filler used between structures can follow deformation to some extent, but its deformable range is narrow, and if the limit is exceeded, the filling effect becomes zero.

Therefore, although the prior art is effective at the time of filling, it has no effect on voids that enlarge and occur after that, and must be refilled when the voids are recognized to have occurred. Although the speed of gap expansion varies, there is no guarantee that a disaster will not occur at a point where the speed is high for the reasons mentioned above.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the conventional technology, and when the occurrence of voids is detected, simply injecting a predetermined amount of filler based on observation of the void shape and survey of the surrounding soil. Soil that can densely fill the voids for a long period of time immediately after injection, does not harm structures, and can prevent disasters caused by scouring of earth and sand caused by groundwater flow. An object of the present invention is to provide a method for filling voids.

[Means for Solving the Problems] The present invention, which can achieve the above objects, uses a polymeric material that absorbs water and expands as a filler, and fills it with soil according to predetermined specifications. This is a method of filling hollow spaces. The type and amount of the water-swelling polymeric material to be introduced here should be determined so that the initial pressure is less than the strength of the structure, and the potential is sufficient to close the maximum amount of void expansion expected during the life of the structure. This is the amount that can exhibit the amount of expansion. If there is groundwater in the surrounding area, a predetermined amount of filler may be simply poured into the void; if water is not constantly present in the surrounding area, water may be injected together with water or after filling to cause expansion. Further, when filling the void, a dummy filler such as earth and sand can be simultaneously introduced into the void.

Various known materials can be used as the water-absorbing and swelling polymer material to be filled here, but they are stable without being decomposed in the soil, and are toxic or other if mixed into groundwater. Materials are selected such that they do not pose a pollution problem.

[Function] The water-absorbing and swelling polymeric material filled into the soil voids according to the present invention absorbs moisture present in the surroundings, expands, and fills the voids. At this time, a fairly large pressure is generated, and the initial pressure is determined by the size of the gap and the quality and amount of the material introduced.
In the present invention, this initial pressure is set to be much smaller than the strength of the civil engineering structure.
Although it may compact the surrounding soil layer to increase its strength, it will not have a negative effect on the structure itself.

Normally, voids expand over time, on the order of years, but the filling material inside absorbs surrounding moisture and expands to follow the deformation of the void, so no voids occur. The void can always be closed.

The maximum amount of pore expansion can be determined in advance through soil surveys, etc., so simply adding the appropriate amount of filler will ensure that the pores are completely filled over a long period of time. . A material that expands upon absorption of water is an elastic body that can be greatly distorted.
The water permeability of the material itself becomes negligible because it is crushed and filled with honey by the self-pressure generated by water absorption. Also, the water that permeates through the material is absorbed by the material, so water does not seep through.

[Example] Hereinafter, the present invention will be explained in more detail based on the drawings. As described above, the present invention creates an initial pressure in the gap between the structure and the ground that is smaller than the strength of the structure, and is capable of closing the maximum amount of gap expansion expected during the service life. This is a method for filling voids in the soil, in which a water-absorbing and swelling polymeric material having a potential expansion amount of 1,000 yen is introduced, and the void is closed by absorbing water and expanding. The water-swelling polymeric material used here may be the water-swelling polymer compound itself, a composite obtained by blending it with a soft resin, rubber, etc., or a mixture thereof.
Furthermore, materials conventionally used for filling voids, such as earth and sand, concrete, etc., can be mixed with these water-absorbing and swelling polymeric materials.

A water-absorbing and swelling polymer compound refers to a substance that absorbs water and swells from several times to 1,000 times its own weight, but does not dissolve in water. For example, specific examples include saponified vinyl acetate-acrylic acid ester copolymer, saponified vinyl acetate-α,β-unsaturated dicarboxylic acid ester copolymer, crosslinked product of modified isobutylene-maleic anhydride copolymer, Examples include, but are not limited to, polyacrylic acid (salt) polymers having a crosslinked structure, saponified starch-acrylonitrile graft copolymers, and starch-acrylic acid (salt) copolymers.
The water-absorbing and swelling polymer compounds may be used alone or in combination of two or more. Among these, saponified vinyl acetate-acrylic acid ester copolymer is one of the most preferred because it has a high absorption capacity and excellent strength upon water absorption, has good weather resistance, and has no toxicity problems. Further, the soft resin or rubber composite compounded with a water-absorbing and swelling polymer compound is desirably adjusted so that it can absorb 2 to 300 times its own weight of water. Examples of soft resins include:
Ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, ethylene-acrylic ester copolymer, ethylene-acrylate copolymer,
Examples include vinyl chloride polymers, vinyl chloride copolymers, and urethane resins. Examples of the rubber include butadiene rubber, isoprene rubber, styrene-butadiene rubber, nitrile rubber, chloroprene rubber, epichlorohydrin rubber, natural rubber, EPDM, and the like.

Now, when the above-mentioned material is formed into granules and used, the filling specifications can be determined as follows. For example, a diagram plotting the generated pressure against the void ratio for a water-swelling polymer material made by mixing vinyl acetate-acrylic acid ester copolymer with styrene-butadiene rubber and adjusting it to absorb 50 times its own weight of water. is shown in Figure 1.
Here, the void magnification S is the ratio of the amount of voids to the volume of the material. A certain functional relationship is established between the pressure P generated by water absorption and expansion and the void magnification S.

S=f(P) Therefore, the minimum value of the void magnification is determined from the condition of generating an initial pressure smaller than the strength of the civil engineering structure (of course, taking into account safety factors, etc.), and this determines the minimum value of the void magnification. The maximum amount of water-swellable polymeric material that can be used is determined. Next, by surveying the surrounding soil, it is possible to calculate the maximum amount of void expansion that is expected to occur during the service life of the civil engineering structure. Small quantities can also be requested. Therefore, by selecting the material and its amount so as to satisfy the above two conditions, and filling the voids with the material, it is possible to prevent void changes from the time when the occurrence of voids is detected until the end of the service life of the civil engineering structure. This allows the gap to be closed at all times.

If the amount of expansion of the void is not so large, it is desirable to simultaneously fill the void with another material, such as earth and sand, as a dummy filler (expanding material), considering the economic effect. For example, as schematically shown in FIG. 2, a gap 14 between the civil engineering structure 10 and the ground 12
Suppose that is formed. A dummy filler 16 such as earth and sand and a water-absorbing and swelling polymeric material 18 are placed into the void 14 . The size W ₁ of the void during filling is determined by actual investigation. On the other hand, if the amount of dummy filler 16 is Z and the amount of water-swellable polymer material 18 is X, then the amount of each input must be S _MIN < (W ₁ - Z)/X ... (1) Must be. Here, S _MIN is the minimum value of the void magnification that produces an initial pressure smaller than the strength of the civil engineering structure. Further, the maximum void volume W ₂ that is expected to increase during the service life of the civil engineering structure 10 can be determined from a ground survey or a soil test. Assuming that the maximum swelling ratio of the water-absorbing and swelling polymer material 18 is A, in order for the voids to be filled even when they become the largest, W ₂ −Z<A・X ...(2) must be satisfied. Must be. Here, the maximum swelling ratio A is a value determined by the characteristics of the material. Therefore the above
From the simultaneous inequalities (1) and (2), the amount Z of the dummy filler 16
and the range of the amount X of the water-absorbing and swelling polymeric material 18 can be determined. The dummy filler 16 is also pressurized and consolidated, but if its properties are determined from soil tests and included in the maximum pore expansion amount, the above equation will not be affected at all.

The present invention fills a water-absorbing and swelling polymeric material based on such specifications. This material that expands upon absorption of water is an elastic body that can be greatly deformed, and the generated pressure compresses the gaps between the particles and tightly fills them, resulting in negligible water permeability.
On the other hand, if the material still retains its water-absorbing ability, the water that permeates through the material will be absorbed by the material and will not penetrate.

If the amount of voids to be generated is expected to be extremely large, it is preferable to fill the voids in a multilayered manner as shown in FIGS. 3A and 3B. FIG. 3A is an explanatory diagram when a filler is introduced immediately after a void is discovered, and FIG. 3B is a diagram showing a state when the amount of void has expanded. If the void created between the civil engineering structure 10 and the ground 12 is expected to become very large over time, it is necessary to use a dummy filler 16 such as earth and sand with a high water absorption and swelling property. The molecular material 18 is alternately divided into multiple layers. The water-absorbing and swelling polymeric material 18 continues to absorb surrounding water and expand as long as there are voids. At this time, water is supplied from the ground 12 or near the structure 10,
The water-swelling polymeric material expands more easily at the periphery than at the center. As a result of the expansion of the surrounding area, there is a possibility that it becomes difficult for water to reach the inside. In other words, even though the material itself still has the ability to expand, a state may occur where the material is unable to expand because it is difficult for water to penetrate inside the material. Such problems can be solved by using a multilayer packing structure as in this embodiment. In other words, since the dummy filler 18 such as earth and sand existing between them becomes a passage for water to penetrate, the water-absorbing and swelling polymer material 18 divided into multiple layers
As shown in FIG. 3B, it expands almost uniformly and can completely close a large gap. In this case, when the water-absorbing and swelling polymer material expands, the intervening layer of earth and sand is consolidated by the generated pressure, and the earth and sand is held down by the pressure, so there is no risk of it flowing out.

[Effects of the Invention] Since the present invention is a method for filling voids in soil configured as described above, when the presence of a void is detected, the method is determined based on the measurement of the void volume and the surrounding soil test, etc. Just add the specified filling material,
It can follow the changes in deformation of voids over time and close them at all times to stop water, preventing various disasters from occurring, and once filled, there is no need to refill even if ground movement occurs. Because there is no such thing, it has excellent effects such as extremely good workability.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the generated pressure and the void ratio of a water-swellable polymeric material made of a mixture of vinyl acetate-acrylic acid ester copolymer and styrene-butadiene rubber, and Figure 2 is a diagram showing the relationship between the generated pressure and the void ratio of a water-swelling polymer material made of a mixture of vinyl acetate-acrylic acid ester copolymer and styrene-butadiene rubber. A schematic diagram of filling a void and FIGS. 3A and 3B are explanatory diagrams showing other embodiments of the method of the present invention, respectively. 10... Civil engineering structure, 12... Ground, 14...
void, 16... dummy filler, 18... water-absorbing and swelling polymer material.

Claims (1)

[Claims] 1. Water absorption and swelling property that creates an initial pressure in the void between the civil engineering structure and the ground that is smaller than the strength of the civil engineering structure and has a potential expansion amount that is sufficient to close the expected maximum amount of void expansion. A method for filling voids in soil, which comprises introducing a polymeric material and causing it to absorb water and expand to close the void.