JP2014156733A - Construction method of permeable foundation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction method of a permeable foundation which can be executed at a low cost without using a casing in foundation work including a permeability improvement measure to prevent liquefaction even for the ground subject to the liquefaction.SOLUTION: A construction method of a permeable foundation secures pore wall stability of a borehole with an impermeable membrane constructed by a stabilizer and then secures permeability by undoing the impermeable membrane constructed by the stabilizer when filling a permeable material 2 to construct a permeable layer.

Description

  The present invention relates to a method for constructing a water permeable foundation in which a water permeable material is buried in the ground in ground improvement work to be performed for liquefaction measures or pile work in liquefied ground.

  If the land is used without taking any countermeasures against poorly tightened sandy ground that may cause liquefaction due to an earthquake, serious damage may occur due to a decrease in ground stability. In addition, when the pile foundation is constructed, the horizontal ground reaction force of the pile foundation in the ground liquefied by the seismic force is reduced, so the pile bears most of the horizontal force from the existing structure. A large moment may be generated in the pile and the pile foundation may be destroyed.

  For such problems, as a typical method of ground improvement work for liquefaction countermeasure work, etc., drains made of materials with high water permeability such as crushed stone are columnar or wall-like in sandy ground There is a gravel drain construction method that aims to prevent excessive liquefaction by speeding up dissipation while suppressing the increase in excess pore water pressure that occurs during an earthquake.

  As for this gravel drain construction method, a casing auger system using construction machines and construction procedures as shown in FIGS. 5 and 6 is generally used. As a construction machine, a three-point crawler pile driving machine 9 including an earth auger 92, a casing pipe 91 with a screw, a crushed stone hopper 93, and the like is used.

  For this reason, the gravel drain construction method has a problem that construction in a narrow place is difficult, the influence of the surrounding environment due to vibration and noise is increased, and the use of large heavy machinery increases the cost.

  Various methods for preventing liquefaction have been proposed so far in order to prevent destruction of the pile foundation.

  Specifically, there is a pile structure that surrounds the pile with a crushed stone layer and releases excess pore water pressure in the crushed stone layer (hereinafter referred to as a drainage composite pile). For example, while pressing a casing pipe, A method has been proposed in which a steel pipe pile having a smaller diameter is installed inside the casing pipe when it is excavated and reaches the support ground, and the space between the casing pipe and the steel pipe pile is filled with crushed stone (for example, see Patent Document 1). ).

  In this construction method, there is a problem that the cost for inserting and removing the casing pipe is high, and that the cost increases rapidly as the excavation depth increases.

  As another construction method, a construction method has been proposed in which a bag body in which a drain material such as gravel is filled on a peripheral surface of an existing pile is used as a drain material (see, for example, Patent Document 2).

  According to this proposal, in order to install this pile body, a hole is drilled with an earth auger, etc., and a pile is inserted there, but a stable liquid is used for loosely stagnant sandy ground that causes liquefaction. When excavating with an earth auger without doing so, the hole wall collapses, so this method cannot be used in practice.

  As another construction method, in order to embed the supporting pile, an auger with a screw on the outer periphery is inserted into the ground, the pile is installed in the auger, and a gravel layer is formed in the pile and the auger. A construction method has been proposed (see, for example, Patent Document 3).

  According to this method, the larger the auger diameter, the greater the torque generated in pushing the auger. Therefore, the construction machine becomes very large and the construction diameter is limited.

  Furthermore, as another construction method, the casing is built while discharging the earth and sand to the softened ground, and then a pile foundation with an inner diameter smaller than the casing is built, and after filling the gap between the casing and the pile foundation with crushed stone, A drawing method has been proposed (see, for example, Patent Document 4).

  Regarding this construction method, as in the construction method (Patent Document 1), the cost of erection of the casing and the cost of removal of the casing are increased, and these costs are increased as the excavation depth is increased. There's a problem.

Japanese Patent Laid-Open No. 6-49840 JP-A-6-235215 Japanese Patent No. 3576259 Japanese Patent Laid-Open No. 10-25732

  The present invention eliminates the conventional problems from the background as described above, and does not use a casing in pile foundation work including measures for improving water permeability so as not to cause liquefaction even in the ground that is liable to cause liquefaction. An object is to provide a method for constructing a water-permeable foundation that can be constructed at low cost.

  The present invention is characterized by the following in order to solve the above problems.

  1stly, it is the construction method of a water permeable foundation, after ensuring the hole wall stability of an excavation hole with the water-impervious film formed with the stabilizing liquid, at the time of filling with the water-permeable material for providing a water permeable layer, The water-permeable film formed by the method is eliminated to ensure water permeability.

  Secondly, in the method for constructing a water permeable foundation according to the first aspect of the present invention, the stabilizing liquid is a swollen highly water-absorbing polymer stabilizing liquid for ground excavation including at least water and highly water-absorbing polymer particles swollen by absorbing water. Preferably there is.

  Third, in the method for constructing a water-permeable foundation according to the second aspect of the invention, the highly water-absorbing polymer particles swollen by absorbing water are preferably highly water-absorbing polymer particles having a crosslinked structure that does not release water by pressurization. .

  Fourth, in the method for constructing a water-permeable foundation according to the second or third invention, when the swelling superabsorbent polymer stabilizing liquid for ground excavation is mixed with an electrolytic substance such as concrete or salt, or an acidic or alkaline substance. In addition, it is preferable to be a swelled superabsorbent polymer stabilizing liquid for ground excavation to which a stabilizer capable of suppressing and recovering deterioration and quality of the swollen superabsorbent polymer stabilizing liquid for ground excavation is added.

  Fifth, in the method for constructing a water permeable foundation according to the fourth aspect of the present invention, it is preferable that the stabilizer is a stabilizer that lowers the electrolyte concentration.

  Sixth, in the method for constructing a water-permeable foundation according to the fourth or fifth invention, the stabilizer is preferably a neutralizing agent that neutralizes PH (hydrogen ion index concentration).

  Seventh, in the method for constructing a water-permeable foundation according to the fourth to sixth inventions, the stabilizer is dilute sulfuric acid, aluminum sulfate, aluminum hydroxide, magnesium hydroxide, polyacrylamide, polyvinyl alcohol, sodium polyacrylate, It is preferably at least one selected from polyethylene oxide, hydrogen carbonate and carbonate.

  Eighth, in the method for constructing a water permeable foundation according to the second to seventh inventions, the funnel viscosity (500 ml / 500 ml) of the swelling superabsorbent polymer stabilizing liquid for ground excavation is in the range of 19 to 120 seconds. preferable.

  Ninth, in the method for constructing a water-permeable foundation according to the fourth to eighth inventions, it is preferable that the electrical conductivity of the swelling superabsorbent polymer stabilizing liquid for ground excavation is 10 mS / cm or less.

  Tenth, in the construction method of a water-permeable foundation according to the first to ninth inventions, a sheath pipe having a diameter smaller than the diameter of the excavation hole is inserted, an in-situ pile is constructed in the sheath pipe, and the excavation hole and the sheath pipe are formed. It is preferable to provide a water-permeable layer between them.

  11thly, in the construction method of the water-permeable foundation of the said 1st-9th invention, it is preferable to build a concrete pile smaller than the diameter of a digging hole, and to provide a permeable layer between a digging hole and a concrete pile. .

  12thly, in the construction method of the water-permeable foundation of the said 1st-9th invention, it is preferable to build a steel pipe pile smaller than the diameter of a drilling hole, and to provide a water permeable layer between a drilling hole and a steel pipe pile. .

  13thly, in the construction method of the water permeable foundation of the first to ninth inventions, a water collection strainer pipe having a diameter smaller than the diameter of the excavation hole is built, and a water permeable layer is provided between the excavation hole and the water collection strainer pipe. It is preferable to use a well.

  14thly, in the construction method of the water permeable foundation according to the first to 13th aspects of the present invention, a horizontal drainage layer is provided on the ground part, connected to the constructed permeable layer, and the excess pore water is drained in the horizontal direction. It is preferable.

  Fifteenth, in the method for constructing a water permeable foundation according to the first to fourteenth aspects of the present invention, in order to provide a water permeable layer inside the excavation hole, the water permeable material is filled with an electrolytic substance together with a water permeable material. It is preferable to eliminate the water barrier property of the water barrier film and construct a water permeable layer.

  Sixteenthly, in the water permeable foundation construction method of the fifteenth aspect of the invention, the electrolytic substance is preferably at least one selected from calcium chloride, citric acid, sodium hydroxide and sodium chloride.

  According to the foundation construction method of the present invention, in pile foundation work including measures for improving water permeability so as not to cause liquefaction even in ground that is liable to be liquefied, water permeability that can be constructed at low cost without using a casing. A method for constructing a sex foundation can be provided.

It is the schematic which showed the process of the construction method of the water-permeable foundation of this invention. It is the schematic which showed the process of the construction method of the water-permeable foundation in the case of constructing a pile. It is the schematic which showed the process of the construction method of the water-permeable foundation in the case of constructing an expanded pile. It is the graph which showed the relationship between electrolytic substance concentration and the amount of water absorption. It is the schematic which showed the construction machine of the general gravel drain. It is the schematic which showed the construction process of the general gravel drain.

  The present invention is a method for constructing a water permeable foundation used in foundation work having a drainage layer for preventing liquefaction such as gravel drain method, which is performed on a ground which is liable to be liquefied. The hole wall stability of the excavation hole is improved by a water-impervious film formed by a swollen highly water-absorbing polymer stabilizing liquid for ground excavation (hereinafter simply referred to as a polymer stabilizing liquid) containing superabsorbent polymer particles swollen by water absorption. After securing, when filling with a water permeable material for providing a water permeable layer, the water imperviousness of the water impervious film is eliminated by using an electrolytic substance to ensure water permeability. is there.

  Hereinafter, the construction method of the water-permeable foundation of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an embodiment in which the water permeable foundation construction method of the present invention is applied to the gravel drain construction method.

  In FIG. 1 (1), first, excavation is performed to a predetermined depth by an earth drill excavator 3 on sand ground or the like that may be liquefied. Then, when excavation is completed to a predetermined depth, the bucket 4 is pulled up as shown in FIG.

  In the present invention, at the time of excavation, excavation is performed using at least water and the polymer stabilizing liquid 1 containing the highly water-absorbing polymer particles swollen by absorbing water.

  As the stabilizing liquid for excavation, a bentonite-based stabilizing liquid, a bubble stabilizing liquid, or the like is usually used. However, when a bentonite-based stabilizing liquid is used, a poorly permeable film is formed around the drilling hole. When a water-permeable material is introduced into the stabilizing liquid, the bentonite-based stabilizing liquid and the water-permeable material are mixed and do not function as a water-permeable layer. For this reason, bentonite-based stabilizers cannot be used to construct a water-permeable foundation.

  Further, when the bubble stabilizing liquid is used, the bubble stabilizing liquid is a mixture of excavated soil, bubbles, and water, and has a specific gravity of 1.3 or more, so that it is difficult to replace it with a water-permeable material. Therefore, it is not possible to use a bubble stabilizer for the construction of a water-permeable foundation.

  In contrast, the polymer stabilizing liquid 1 including water and highly water-absorbing polymer particles swollen by absorbing water has a function of forming a water-impervious film during excavation and ensuring the wall stability of the excavation hole. However, at the time of construction of the water permeable layer, the volume of the superabsorbent polymer particles is reduced by reaction with the electrolytic substance, and the water permeability can be ensured by reducing the viscosity thereof. It can use suitably.

  The highly water-absorbing polymer particles used in the present invention are hydrophilic polymers having a cross-linked structure, have a water absorption of 10 times or more of their own weight, and are difficult to separate even under pressure. It is defined in JIS K 7223.

  The type of superabsorbent polymer particles can be used without particular limitation as long as the above conditions are satisfied, and examples thereof include starch-based, cellulose-based, and synthetic polymer-based superabsorbent polymers. . Among these, sodium polyacrylate highly water-absorbing polymer particles can be particularly preferably used in terms of both performance and cost.

Polyacrylic acid sodium superabsorbent polymer particles are a cross-linked product of sodium salt of acrylic acid polymer with a three-dimensional network structure that is lightly crosslinked by adding a crosslinking agent to sodium acrylate (CH ₂ = CH-COONa). It is a gel. There are various types of crosslinking agents.

  This sodium polyacrylate superabsorbent polymer particle is known to absorb sodium and dissociate sodium ions in the gel, and if pure water produces a degree of swelling that is 100 to 1000 times its own weight. Yes.

  Moreover, the water absorption of the sodium polyacrylate highly water-absorbing polymer particles is such that if a large amount of a crosslinking agent is added to sodium acrylate, the gel becomes hard and the water absorption decreases. Further, when the amount of the crosslinking agent is decreased, the gel becomes soft and the water absorption amount increases.

  Furthermore, as a special sodium polyacrylate superabsorbent polymer particle, the surface of the superabsorbent polymer particle polymerized with a crosslinking agent is further cross-linked, and the sodium polyacrylate superabsorbent polymer of shell and core double structure There are particles.

  In the case of the sodium polyacrylate highly water-absorbing polymer particles having a dual structure of shell and core, the thicker the shell, the harder the gel and the smaller the water absorption. The thinner the shell, the softer the gel and the greater the water absorption.

  In addition, the above shell and core are usually crosslinked by an ester bond, but there are also sodium polyacrylate superabsorbent polymer particles in which the core bond is an ether bond excellent in alkali resistance and electrolytic substance resistance. In the present invention, this ether bond is more preferable.

  In addition to the above characteristics, dissociation of sodium ions in the polyacrylic acid sodium superabsorbent polymer particles also depends on conditions such as pH and salt concentration where the gel is placed, so other superabsorbent polymers depending on the use conditions Particles can be appropriately selected and used in combination.

  Usually, since the polymer stabilizer may be used at a deep depth, it is necessary to select highly water-absorbing polymer particles having a crosslinked structure that is less likely to be deformed with little decrease in water holding power depending on the applied pressure, and In order to clog gaps between particles such as sandy ground with poor tightening that may cause liquefaction, it is desirable that the particle size after swelling is 3 mm or less and the particle size distribution is good.

  In the present invention, when sodium polyacrylate highly water-absorbing polymer particles are used, any polymer can be used without particular limitation as long as the above conditions are satisfied. What adjusted the water absorbing polymer particle to said conditions can be used suitably.

  Moreover, an inorganic material can be added to the polymer stabilizer 1 used in the present invention as a weighting material.

  As the inorganic material as the weighting material used in the present invention, fine sand, fine barite or ceramic crushed material can be used.

  In addition to the addition of the inorganic material to the polymer stabilizing liquid 1 in advance, the addition of the weighting material is performed in addition to the inorganic material or without the inorganic material. Can also be used as a weighting material.

  As the particle size of the weighting material, those having a maximum particle size of 2.0 mm or less, preferably 1.0 mm or less can be suitably used.

  By setting it as this particle size range, a stable water shielding layer can be formed.

  The polymer stabilizing solution 1 used in the present invention is prepared by adjusting the specific gravity to 1.20 or less, preferably 0.95 to 1.20, with water and a weighting material added to the superabsorbent polymer particles. It is. In addition, in the polymer stabilizing liquid 1 in which the inorganic material as the weighting material is not added in advance and the fine particles of the ground mixed from the sandy ground during excavation are used as the weighting material, the specific gravity is 1.00 to 1.. What was adjusted to the range of 20 can be used. This specific gravity can be adjusted by the following formula (1).

The mass of the superabsorbent polymer particles expanded by adding water to the superabsorbent polymer particles before water absorption is W _P4 , the volume is V _P4 , the specific gravity is ρ _P4, and the added mass of the weighting material of the polymer stabilizer 1 is W _{When S 1} , the volume is V _S , and the specific gravity is ρ _S , the specific gravity ρ _C of the polymer stabilizer 1 is expressed by the following formula (1).

In addition, regarding the specific gravity adjustment in the case where the weight material is not added, the weight added material W _S , the volume V _S , and the specific gravity ρ _S may be calculated as zero.

  The viscosity of the polymer stabilizing solution 1 used in the present invention is adjusted so that the funnel viscosity (500 ml / 500 ml) is within a range of 19 to 120 seconds, preferably 22 to 30 seconds, depending on the amount of the superabsorbent polymer particles added. It is a thing. Here, the funnel viscosity is a viscosity measured using a Marsh Funnel viscometer that measures the viscosity according to the outflow time (seconds) required to discharge 500 ml of the sample liquid placed in a 500 ml funnel-shaped container.

  In addition, an auxiliary can be added to the polymer stabilizing solution 1 used in the present invention for the purpose of improving the pore wall stability and adjusting the viscosity of the polymer stabilizing solution 1.

  Furthermore, the polymer stabilizer 1 used in the present invention can suppress or recover the deterioration of the property and quality of the polymer stabilizer 1 when an electrolytic substance such as concrete or salt, or an acidic or alkaline substance is mixed. Stabilizers can be added.

  Stabilizers include dilute sulfuric acid, aluminum sulfate, aluminum hydroxide, magnesium hydroxide, polyacrylamide, polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, sodium hydrogen carbonate, calcium hydrogen carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate Or at least one selected from carbonates such as sodium carbonate, calcium carbonate, potassium carbonate, and ammonium carbonate.

  In the excavation process, when electrolytic substances such as concrete and salt are mixed in the polymer stabilizing liquid 1 and the concentration of the electrolytic substance increases, the water absorption ratio of the superabsorbent polymer particles in the polymer stabilizing liquid 1 decreases, and the water that has been absorbed The properties and quality of the polymer stabilizer 1 such as the funnel viscosity and the amount of drainage are rapidly deteriorated.

  In such a situation, by adding a stabilizer in advance, an increase in the concentration of the electrolytic substance can be suppressed, and deterioration of the properties and quality of the polymer stabilizer 1 can be prevented.

  Moreover, by adding a stabilizer to the polymer stabilizer 1 that has deteriorated due to the mixing of the electrolyte, the concentration of the electrolyte is lowered, the released water is reabsorbed, and the properties and quality of the polymer stabilizer 1 are restored. You can also

  Furthermore, when the concrete is mixed and becomes alkaline, the properties and quality of the polymer stabilizer 1 are deteriorated. Therefore, by adding a stabilizer as a neutralizing agent and neutralizing PH (hydrogen ion index concentration), Properties and quality can be recovered.

  In the above-mentioned polymer stabilizer 1 used in the present invention, the electric conductivity is desirably 10 mS / cm or less.

  By excavating using the polymer stabilizing solution 1 having the characteristics as described above, it is possible to ensure the hole wall stability of the excavation hole without using a casing.

  Next, as shown in FIG. 1 (3), the polymer stabilizing liquid 1 in the excavation hole is filled with the water-permeable material 2 using the treme tube 3. The water-permeable material 2 can be used without particular limitation as long as it is a water-permeable material 2 having water permeability that suppresses an increase in the interval water pressure accompanying liquefaction that occurs during an earthquake. Examples of the water-permeable material 2 include crushed stone and sand. be able to.

  In addition, filling of the water permeable material 2 is performed by replacing the polymer stabilizing liquid 1 used in the excavation process of FIGS. 1 (1) and 1 (2). A water film is formed.

  Therefore, in the present invention, the electrolytic substance is filled together with the water permeable material 2 in order to eliminate the water shielding property of the water shielding film after the water permeable material 2 is filled.

  When an electrolytic substance is added to the polymer stabilizer 1, the superabsorbent polymer particles release the water taken in depending on the type of electrolytic substance and the electrolytic substance concentration of each electrolytic substance, as shown in the graph of FIG. Thus, the volume can be reduced to form a gap in the water permeable material 2, and the viscosity of the superabsorbent polymer particles can be reduced, so that the water barrier property of the water barrier film can be eliminated.

  The electrolytic substance used in the present invention can be used without particular limitation as long as it is an electrolytic substance that releases water by being added to the polymer stabilizing solution 1, and examples of the acidic substance include hydrochloric acid, sulfuric acid, nitric acid, citric acid, and the like. Examples of basic substances include sodium hydroxide, potassium hydroxide, and calcium hydroxide, and examples of salts include calcium chloride, sodium chloride, and potassium chloride. Among these, calcium chloride can be preferably used in consideration of the environmental load and economical aspects after the release of water.

  In the specific example of the filling of the electrolytic substance, for example, when the composition of the polymer stabilizer 1 is 0.2% superabsorbent polymer particles, 4.8% weighting material, and 95.0% water, by adding calcium chloride It has been confirmed that the stable liquid is separated into a solid of 95% calcium chloride aqueous solution, 5% weighting material and superabsorbent polymer particles.

  The polymer stabilizing liquid 1 filled with the water-permeable material 2 and the electrolytic substance as described above and separated into a solid and a liquid is discarded, so that the disposal becomes easy and the processing cost is very high. It can be kept inexpensive. Alternatively, the superabsorbent polymer particles can be separated and recovered from the recovered polymer stabilizing solution 1 and re-absorbed by reabsorbing water.

  Thus, the water-imperviousness of the water-impervious film is eliminated together with the filling of the water-permeable material 2, and a water-permeable layer made of the water-permeable material 2 is formed as shown in FIG. 1 (4), thereby constructing the water-permeable foundation of the present invention. be able to.

  According to the process of the present invention described in detail above, after ensuring the hole wall stability during excavation by the pre-boring method using the polymer stabilizing liquid 1 without the casing, the polymer stabilizing liquid 1 is used when the water-permeable material 2 is filled. Water permeability can be ensured by eliminating the formed water shielding film with an electrolytic substance.

  And in the improvement work of the liquefied ground and the drainage combined pile work in the liquefied ground, by eliminating the casing that was the premise of the conventional construction method, to realize excellent workability and low cost Can do.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

  For example, as shown in FIG. 2, after excavation using the polymer stabilizing liquid 1 in the steps of FIGS. 2 (1) and 2 (2), a pile 6 having a diameter smaller than the diameter of the excavation hole is placed (FIG. 2). 2 (3)), the water-permeable material 2 and the electrolytic substance are filled between the excavation hole and the pile 6 (FIG. 2 (4)), and a water-permeable layer made of the water-permeable material 2 can be constructed around the pile 6 ( FIG. 2 (5)).

  Further, as shown in FIG. 3, excavation is performed using the polymer stabilizing liquid 1 so as to become the expanded bottom 7 until reaching the support layer 8 of the hard ground deeper than the sand ground or the like which may be liquefied (see FIG. 3). 3 (1)), the pile 6 can be driven to the support layer 8 (FIG. 3 (2)), and a water-permeable layer made of the water-permeable material 2 can be constructed around the pile 6 (FIG. 3 (3)). .

  The piles 6 to be placed shown in FIGS. 2 and 3 can be appropriately set according to the characteristics of the sand ground or the structure to be built on the upper part. In-situ piles can be built inside, concrete piles and steel pipe piles can be built.

  Moreover, the pile 6 in FIG. 2 can be constructed by changing to a water collection strainer pipe, and a well provided with a water permeable layer made of the water permeable material 2 around the water collection strainer pipe can be constructed.

  Furthermore, in the construction method of the water permeable foundation of the present invention, a horizontal drainage layer is provided on the ground part, and connected to the constructed water permeable layer, and the excess pore water can be drained in the horizontal direction.

  As a result, the groundwater that has risen up the permeable layer at the time of the earthquake is further dispersed in the drainage layer having a large area, and damage due to shaping can be surely prevented.

DESCRIPTION OF SYMBOLS 1 Swelling superabsorbent polymer stabilization liquid for ground excavation 2 Water-permeable material 3 Earth drill excavator 4 Bucket 5 Tremy pipe 6 Pile 7 Bottom expansion 8 Support layer 9 Three-point crawler pile driver 91 Casing pipe 92 Earth auger 93 Hopper for crushed stone

Claims (16)

  A method for constructing a water-permeable foundation, which is formed by a stabilizing liquid when filling a water-permeable material for providing a water-permeable layer after securing the hole wall stability of a drilling hole by a water-shielding film formed by the stabilizing liquid. A method for constructing a water-permeable foundation characterized in that the water-permeable film is eliminated to ensure water permeability.   2. The method for constructing a water-permeable foundation according to claim 1, wherein the stabilizing liquid is at least water and a swollen highly water-absorbing polymer stabilizing liquid for ground excavation containing water-absorbing polymer particles swollen by water absorption. .   The method for constructing a water-permeable foundation according to claim 2, wherein the water-absorbing polymer particles swollen by water absorption are water-absorbing polymer particles having a crosslinked structure that does not release water by pressurization.   Swelling superabsorbent polymer stabilization liquid for ground excavation is mixed with electrolytic substances such as concrete and salt, and acidic and alkaline substances. The method for constructing a water-permeable foundation according to claim 2 or 3, wherein the stabilizing liquid is a swelling superabsorbent polymer for ground excavation to which a stabilizer capable of recovery is added.   The method for constructing a water-permeable foundation according to claim 4, wherein the stabilizer is a stabilizer for reducing the electrolyte concentration.   The method for constructing a water-permeable foundation according to claim 4 or 5, wherein the stabilizer is a neutralizing agent that neutralizes PH (hydrogen ion exponential concentration).   The stabilizer is at least one selected from dilute sulfuric acid, aluminum sulfate, aluminum hydroxide, magnesium hydroxide, polyacrylamide, polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, bicarbonate, carbonate. The construction method of the water-permeable foundation as described in any one of Claims 4-6.   The construction of a water-permeable foundation according to any one of claims 2 to 7, wherein the funnel viscosity (500 ml / 500 ml) of the swelling superabsorbent polymer for ground excavation is in the range of 19 to 120 seconds. Method.   The method of constructing a water-permeable foundation according to any one of claims 4 to 8, wherein the electrical conductivity of the swelling superabsorbent polymer stabilizing liquid for ground excavation is 10 mS / cm or less.   The sheath pipe having a diameter smaller than the diameter of the excavation hole is inserted, an in-situ pile is constructed in the sheath pipe, and a water permeable layer is provided between the excavation hole and the sheath pipe. The construction method of the water-permeable foundation as described in claim | item.   The method for constructing a permeable foundation according to any one of claims 1 to 9, wherein a concrete pile having a diameter smaller than the diameter of the excavation hole is built, and a permeable layer is provided between the excavation hole and the concrete pile. .   The method for constructing a permeable foundation according to any one of claims 1 to 9, wherein a steel pipe pile having a diameter smaller than the diameter of the excavation hole is installed, and a water permeable layer is provided between the excavation hole and the steel pipe pile. .   10. A water collection strainer pipe having a diameter smaller than the diameter of the excavation hole is built, and a water permeable layer is provided between the excavation hole and the water collection strainer pipe to form a well. Construction method for water permeable foundation.   The water-permeable foundation according to any one of claims 1 to 13, wherein a horizontal drainage layer is provided on the ground part, connected to the constructed water-permeable layer, and excess pore water is drained in the horizontal direction. How to build.   In order to provide a water-permeable layer inside the excavation hole, the water-imperviousness of the water-impervious film formed by the stabilizing liquid is eliminated by filling the electrolytic material together with the water-permeable material, and the water-permeable layer is constructed. Item 15. A method for constructing a water-permeable foundation according to any one of Items 1 to 14. The method for constructing a water-permeable foundation according to claim 15, wherein the electrolytic substance is at least one selected from calcium chloride, citric acid, sodium hydroxide, and sodium chloride.