JP3684394B2 - Water flow hole forming apparatus and method for forming water flow holes used for water flow hole formation for maintaining groundwater flow in impermeable walls - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water flow conservation technique for a groundwater flow that is blocked by a water shielding wall for constructing an underground part of a civil engineering or building structure. The present invention relates to a water hole forming apparatus and a method thereof.
[0002]
[Prior art]
When building a linear underground structure such as a subway or an underground road, if a deep wall is constructed continuously, free groundwater flow in the area may be blocked. FIG. 6 is a schematic diagram showing a state where the groundwater flow is blocked by the water blocking walls 100a and 100b. Here, the impermeable walls 100a and 100b are deeper than the flooring 107 in order to stabilize the excavation bottom ground, and are long penetrations 108 penetrating the permeable layers 105a and 105b to the impermeable layer 106b. For this reason, the groundwater flow 160a, 160b is blocked by the upstream impermeable wall 100b.
[0003]
When the groundwater flow 160a, b is blocked by the water-impervious walls 100a, b, the ground surface 150a on the downstream side causes ground subsidence due to a decrease in the groundwater level. Further, the fall of the groundwater level causes the standing tree 130a to wither and the well 120 to wither. Further, there is an influence such as settlement of the structure 110a such as a building.
[0004]
On the upstream side of the water-impervious wall 100b, the water level rises due to the blocking of the groundwater flow, and the wetness of the ground on the upstream surface 150b causes the root decay of the standing tree 130b, or the underground portion of the structure 110b. Water leakage may occur. In addition, since the circulation of groundwater flow is lost, the quality of the groundwater itself may deteriorate. Such influence on the surrounding environment appears during construction.
[0005]
Further, the impermeable walls 100a and 100b pass through the permeable layer 105b deeper than the flooring 107 so that the flooring 107 does not cause a floating phenomenon in which the underground structure floats due to the groundwater underneath. 106b is incorporated. For this reason, the underground water flow 160b deeper than the flooring 107 to be excavated for the construction of the structure is also blocked.
[0006]
In order to solve the above-mentioned problems, a method of restoring the groundwater flow at the top of the structure by removing the impermeable wall at the top of the structure after completion of the underground structure.
A method of drilling the wall surface of the cut-off part of the impermeable wall, inserting a water collecting pipe into the upstream permeable layer ground, and connecting it with the drain pipe inserted into the downstream permeable layer ground to restore the groundwater flow.
There is known a method of recovering a groundwater flow by digging a drainage well on both sides of the cut-off portion of the impermeable wall and connecting an upstream well and a downstream well in the ground.
However, in these groundwater flow maintenance methods, there is a problem that the groundwater flow 160a in the upper part of the flooring 107 that has been cut can be restored, but the groundwater flow 160b in a portion deeper than the flooring 107 cannot be restored.
[0007]
In addition, there is a problem that maintenance costs such as clogging of wells after construction are expensive.
[0008]
The inventor proposed in Japanese Patent Application No. 2000-205456 a mountain retaining wall having a groundwater flow maintenance function for forming a water passage at an arbitrary time and a construction method thereof for solving the above-mentioned problem. However, it takes time to break the anode of the pile core material that requires strength, and it is necessary to crush the solidified soil mortar that surrounds the pile core material, which makes it difficult to form reliable water holes. .
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems, and is blocking the groundwater flow for the maintenance of the groundwater flow blocked by the soil mortar impervious wall that is constructed in the construction of the underground excavation structure. It is an object of the present invention to provide a water hole forming apparatus and a water hole forming method for forming a water hole at an arbitrary time in a water shielding wall portion.
[0010]
In particular, the present invention provides a water-hole forming device that can easily and economically form water-holes at an arbitrary depth of a soil mortar impermeable wall.
[0011]
Moreover, the water-hole forming apparatus which can purify the harmful substance of a groundwater flow after water-hole formation is provided.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the water-hole forming device used for groundwater flow maintenance water-hole formation of the water-impervious wall according to claim 1 is a groundwater flow blocked by a water-impervious wall constructed when constructing an underground excavation structure. For the maintenance of the water-permeable wall forming device provided as a pile core material of the water-impervious wall in order to form a water-permeable hole at any time in the portion where the water-impervious wall blocks the groundwater flow,
The water flow hole forming device includes a pressure chamber connected to a pressure pipe for supplying a pressurized solution from the ground, a water flow cylinder provided on one or more sides of the pressure chamber and opened to the outside, It consists of a piston part that is slidably inserted into a water flow cylinder,
The piston part is connected to a piston body that slides outward in the water-cylinder cylinder by the pressure of the pressurized solution in the pressure chamber, and an electric wire inserted into the pressure pipe, and is anode-dissolved by applying a voltage. It is characterized by having a tip electric corrosion part.
[0013]
The water flow hole forming apparatus used for water flow hole formation of the water shielding wall according to claim 2 is used to maintain the groundwater flow blocked by the water shielding wall constructed when constructing the underground excavation structure. In order to form a water passage hole at any time in the impermeable wall that blocks the flow, the passage that is connected to the upper and lower pile cores so that the impermeable wall is located at a depth that blocks the groundwater flow. A water hole forming device,
The water flow hole forming device includes a pressure chamber connected to a pressure pipe that supplies a pressurized solution from the ground, a water flow cylinder that is open to the outside and is provided on one or more sides of the pressure chamber, It consists of a piston part that is slidably inserted into a water flow cylinder,
The piston part is connected to a piston body that slides outward in the water-cylinder cylinder by the pressure of the pressurized solution in the pressure chamber, and an electric wire inserted into the pressure pipe, and is anode-dissolved by applying a voltage. It is characterized by having a tip electric corrosion part.
[0014]
A third aspect of the present invention is the second aspect of the present invention, wherein a plurality of the pressure chambers are connected, and an electrolytic corrosion barrier is provided between the upper and lower adjacent barriers of the pressure chamber, insulated from the barriers, and connected to the electrodes. At this time, a voltage is applied to the electrolytic erosion partition to dissolve the anode and open between the upper and lower pressure chambers so that water can pass through.
[0015]
Invention of Claim 4 is invention of Claim 1, 2, or 3, Comprising: The said water flow cylinder is provided with the sliding lock mechanism which stops sliding, when the said piston part is pushed out predetermined amount, The pressurized solution pushes out the other piston portion and prevents the external ground pressure from being pushed back.
[0016]
Invention of Claim 5 is invention of Claim 1, 2, 3 or 4, Comprising: The piston main body of the said piston part is formed in the length which penetrates the soil mortar layer around a pile core material, and is tip electrolytic corrosion The portion is formed in a conical shape that separates the soil mortar layer.
Invention of Claim 6 is invention of Claim 1, 2, 3, 4 or 5, Comprising: The said pressure chamber is a filter material which filters the harmful substance of a groundwater flow, when a water flow hole is formed. It is filled.
[0018]
According to the seventh aspect of the present invention, in order to preserve the groundwater flow blocked by the impermeable wall constructed during the construction of the underground excavation structure, the portion where the impermeable wall blocks the groundwater flow is passed at any time. A water hole forming method using the water hole forming device according to any one of claims 1 and 2 to form a water hole,
The water penetration hole forming device is set up together with the pile core material on the impermeable wall, filled with soil mortar, and the soil mortar is in the middle of curing, and the pressurized solution is supplied from the ground pressurized solution supply device through the pressure pipe to the pressure chamber. The piston portion is pushed out of the pressure chamber to remove the surrounding soil mortar, and then the electrolyte solution is filled into the pressure chamber through the pressure pipe at any time, and the negative electrode of the DC power source is By connecting a positive electrode to the tip erosion portion and applying a voltage to the pile core material, the metal of the tip erosion portion is anode-dissolved to form a water passage hole.
[0019]
The invention of claim 8 is an invention of a method for forming a water flow hole, wherein the impermeable wall prevents the underground water flow in order to preserve the underground water flow blocked by the impermeable wall constructed in the construction of the underground excavation structure. Pressurized pipe that is provided as a pile core material for a water-blocking wall to form a water passage hole at an arbitrary time in the blocked part , or is connected to upper and lower pile core materials and supplies a pressurized solution from the ground A pressure chamber connected to the pressure chamber, one or a plurality of water flow cylinders provided on both side surfaces of the pressure chamber and open to the outside, and a piston portion slidably fitted into the water flow cylinder. The piston part is connected to a piston body that slides outward in the water-cylinder cylinder by the pressure of the pressurized solution in the pressure chamber, and an electric wire inserted into the pressure pipe, and is anode-dissolved by applying a voltage. With the tip A water passing hole forming method using the pore forming apparatus,
The water penetration hole forming device is set up together with the pile core material on the impermeable wall, filled with soil mortar, and the soil mortar is in the middle of curing, and the pressurized solution is supplied from the ground pressurized solution supply device through the pressure pipe to the pressure chamber. The piston portion is pushed out of the pressure chamber to remove the surrounding soil mortar, and then the electrolyte solution is filled into the pressure chamber through the pressure pipe at any time, and the negative electrode of the DC power source is By connecting the positive electrode to the tip erosion part and applying voltage to the pile core material, the metal of the tip erosion part is dissolved in the anode to form a water passage hole. A positive electrode voltage is applied to dissolve the anode so that water can flow between the upper and lower pressure chambers.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a water passage forming device according to a first embodiment of the present invention, where (a) is a front view and (b) is a cross-sectional view.
[0021]
1 (a), a pile core steel pipe 20 is hermetically sealed by an upper sealing lid 21 and a bottom plate 29 provided at the bottom, and the inside of the pile core steel pipe 20 forms a pressure chamber 24. The pressure pipe 3a is connected to the sealing lid 21 via a valve 3b, and the water passage cylinder 22 opened to the outside on both sides of the pressure chamber 24 and the water passage cylinder 22 are slidable. The piston part 23 inserted in is provided.
[0022]
The said sealing lid 21 is provided with the connection terminal 21a of the electrode electric wire 13, and is detachably fixed to the pile core steel pipe 20 with the sealing bolt 21b. The pressurizing pipe 3a is connected to a pressurizing solution supply device 3 to be described later, and fills the pile core steel pipe 20 with the electrolyte solution 2 such as pressurizing water or saline to pressurize the pressure chamber 24.
[0023]
FIG.1 (b) shows the side surface cross section of (a). The pressure chamber 24 is provided with internal partition walls 27 and 27 for filling a filter for purifying the groundwater flow after completion of the water passage hole.
[0024]
As shown in the figure, the piston portion 23 is formed in a shape in which the piston tip protrudes, is inserted into the water-passing cylinder 22 and is stood on the water-impervious wall, and soil cement is poured into the periphery.
[0025]
Next, the structure of the water flow cylinder 22 and the piston part 23 will be described with reference to FIG. Fig.2 (a) shows the AA cross section of FIG.1 (b). (B) shows a state in which pressurized water is supplied from the pressurized pipe 3a and the pressurized water in the pressure chamber 24 pushes out the piston 23 and slides out from the water flow cylinder 22 to the outside.
[0026]
As shown in FIG. 2A, the piston portion 23 includes a piston main body 23a that is slidable in close contact with the water flow cylinder 22, and a tip electrolytic corrosion portion 23c provided at the tip thereof via an insulating material 23b. The pressurizing chamber 24 is open and has a sealed structure that receives pressure in the distal direction.
[0027]
The tip electric corrosion portion 23c is provided with an electrode terminal 23d and is connected via an expandable electric wire 13a that expands and contracts in accordance with the sliding of the electrode electric wire 13 and the piston portion.
[0028]
FIG. 2B shows a state in which the piston portion 23 protrudes from the water flow cylinder 22 by the pressure of pressurized water indicated by an arrow. At this time, a state is shown in which the sliding lock mechanism 25 is fixed at a predetermined sliding position. FIG. 2C shows the details of the sliding lock mechanism 25, and the piston main body 23a and the cylinder lock hole 25e provided in the water flow cylinder 22 are located at the same position. When the pin 23a is operated, the lock pin 25a is inserted into the piston lock hole 25d and fixed by the spring 25b urged by the spring locking metal 25c.
[0029]
Next, a second embodiment of the present invention will be described in detail with reference to FIG. Fig.3 (a) is a top view of 10 A of water flow hole formation apparatuses of 2nd Embodiment. In this embodiment, an H-section steel 40 (see FIG. 5) that is provided with pile core connecting portions 26 on both side surfaces of a rectangular water passage housing 20A and is generally used as a pile core material for the soil mortar impermeable wall 100 (FIG. 5). It has a structure that can be connected to 5) and buried in the underground permeable layer. 3a indicates a pressurized pipe.
[0030]
FIG.3 (b) shows the BB cross section of Fig.3 (a). The water passage housing 20A is divided into two upper and lower pressure chambers 24a and 24b by an adjacent partition wall 28, and each pressure chamber 24a and 24b includes a water passage cylinder 22 opened on the opposite side wall. The piston portion 23 described in the first embodiment is inserted into the water flow cylinder 22.
[0031]
The adjacent partition wall 28 is provided with an electrolytic corrosion partition wall 28a through an insulating material 28b. The electrode wire 13c is connected to the electrolytic corrosion partition wall 28a.
[0032]
A pressure pipe 3a is connected to each of the pressure chambers 24a and 24b, and an electrode electric wire 13 is inserted into the pressure pipe 3a to be connected to an electrode terminal 23d provided at a tip electrolytic corrosion portion 23c of the piston portion 23. It is connected.
[0033]
In this embodiment, one water flow cylinder 22 is provided in each of the pressure chambers 24a and 24b partitioned by the adjacent partition wall 28, but a plurality of water flow cylinders 22 may be provided. The pressure chambers 24a and 24b partitioned by the adjacent partition wall 28 may be adjacent to the side surfaces. Furthermore, a plurality of water passage forming devices 10A can be arranged and provided at a depth at which the water shielding wall pile core material such as H-shaped steel blocks the water permeable layer in the ground.
[0034]
Next, it demonstrates according to FIG. 4 which shows the formation process of the water flow hole using 10 A of water flow hole formation apparatuses of this invention. Reference numerals in the description refer to the detailed drawings of FIGS. 1 to 3 or FIG. First,
(1) Excavate the location of the impermeable wall.
{Circle around (2)} The pile core material provided with the water flow hole forming device 10A of the present invention is put into the excavation hole.
(3) Pour the soil mortar 45 around the pile core.
(4) During the curing of the soil mortar 45, the ground pressurized solution supply device 3 is operated, and the pressurized water of the electrolyte solution 2 is supplied to the pressure chamber 24 through the pressure pipe 3a. The piston part 23 slides in the water flow cylinder 22 by the water pressure in the pressure chamber, and the external soil mortar 45 is pushed out and protrudes to the natural ground permeable layer.
(5) The negative electrode is applied to the pile core material from the DC power source 5 on the ground, and the positive electrode voltage is applied to the tip erosion portion 23c of the piston portion 23 filled with the electrolyte solution 2, and the tip erosion portion 23c is anodic dissolved and destroyed. . Here, the tip of the piston part 23 is opened, and the natural water permeable layer and the pressure chamber are formed so as to allow water to pass therethrough.
(6) At the time of restoration of the groundwater flow, an anode voltage is applied to the partition erosion portion of the adjacent partition wall from the direct current power source on the ground, and the partition erosion portion is anodic dissolved.
(7) The electrolyte solution 2 is recovered through the pressurized pipe 3a, and the pressure chamber is filled with a filter material having a groundwater purification action.
(8) A groundwater flow path from the natural groundwater permeable layer to the downstream natural groundwater permeable layer is formed to preserve the groundwater flow.
[0035]
FIG. 5 is a schematic cross-sectional view of the impermeable wall 100 in which the water passage forming device 10A of the present invention is arranged. In the figure, 5 is a DC power supply device arranged on the ground 150, and 3 is a pressurized solution supply device. The pile core material of the H-section steel 40 stood in the excavation hole 50 is provided with the water-hole forming device 10A of the present invention connected to the depth in contact with the water-permeable layers 105a and 105b. The pile core material is filled with soil mortar 45, and the piston portion 23 that protrudes by pushing the soil mortar in the step (4) reaches the water-permeable ground, and the tip that has blocked the tip in the step (5) A state in which the electrolytic corrosion portion 23c is broken by anodic dissolution is shown.
[0036]
In the above embodiment, the pile core steel pipe 20 and the water passage housing 20A have been described as rectangular, but the shape may be circular or polygonal as long as it is hollow and can form a pressure chamber. Moreover, although a water flow cylinder and a piston part were demonstrated also with the cylindrical shape, if a piston part is slidable, it will not stick to a shape.
[0037]
【The invention's effect】
According to the water flow hole forming apparatus used for groundwater flow maintenance water flow hole formation of the water blocking wall of the present invention, water can be easily and economically passed through the water blocking wall provided in the water permeable layer after the construction of the underground structure. Holes can be formed. In particular, a water passage hole can be formed at an arbitrary depth and position of the impermeable wall.
[0038]
Moreover, since a water passage hole to the permeable layer ground can be formed during the curing of the soil mortar, reliable groundwater flow maintenance can be performed.
[0039]
According to the second aspect of the present invention, the water flow path to the outside is formed in advance, and the adjacent partition wall is anodic dissolved and penetrated at an arbitrary time, thereby further reliably controlling the recovery of the groundwater flow. be able to.
[0040]
Furthermore, since a water purification filter can be arrange | positioned inside a water flow hole, water quality purification can be performed with the restoration | recovery of a groundwater flow.
[Brief description of the drawings]
FIG. 1 shows a configuration of a water passage forming device according to a first embodiment of the present invention, wherein (a) is a front view and (b) is a cross-sectional view.
2A is a cross-sectional view showing an AA cross section of FIG. 1B, FIG. 2B is a view showing a state in which a piston portion protrudes, and FIG. 2C is an enlarged view showing details of a sliding lock mechanism. FIG.
FIGS. 3A and 3B show a configuration of a water passage hole forming apparatus according to a second embodiment of the present invention, in which FIG. 3A is a plan view and FIG. 3B is a cross-sectional view along line BB in FIG.
FIG. 4 is a diagram showing a process of forming water holes using the water hole forming apparatus of the present invention.
FIG. 5 is a schematic cross-sectional view of a water-impervious wall in which the water passage forming device of the present invention is arranged.
FIG. 6 is a schematic diagram showing a state where a groundwater flow is blocked by a water blocking wall.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Water flow hole 1a Water flow hole formation location 2 Electrolyte solution 3 Pressurized solution supply apparatus 3a Pressure pipe 3b Valve 5 DC power supply 10, 10A Water flow hole formation apparatus 13 Electrode electric wire 13a Telescopic electric wire 20 Pile core steel pipe 20A Water flow hole Enclosure 21 Sealing lid 21a Connection terminal 21b Sealing bolt 22 Water-cylinder 22 Tip electrical corrosion portion 22a Pipe connection hole 22b Wire connection terminal 22c Bottom plate 22d Insulation material 22e Electrode plate 23 Piston portion 23a Piston body 23b Insulation material 23c Tip electrical corrosion portion 23d Electrode terminals 24, 24a, 24b Pressure chamber 25 Sliding lock mechanism 25a Lock pin 25b Spring 25c Spring locking metal 25d Piston lock hole 26 Cylinder lock hole 26 Pile core connecting part 27 Internal partition wall 28 Adjacent partition wall 28a Electrical corrosion partition wall 28b Insulating material 29 Bottom plate 30 Water pipe 40 H-section steel 45 Soil mortar 1 00, 100a, 100b Impervious walls, soil mortar impermeable walls 105, 105a, 105b Permeable layers 106, 106a, 106b Impervious layers 160a, 160b Groundwater flow 107 Flooring 108 Rooting 110, 110a, 110b Structures 130, 130a , 130b Standing trees 150, 150a, 150b Ground surface, ground part

Claims (8)

In order to preserve the groundwater flow that is blocked by the impermeable walls that are constructed during the construction of the underground excavation structure, it is necessary to form a water passage hole at any time in the part where the impermeable walls block the groundwater flow. A water hole forming device provided as a pile core material for water walls,
The water flow hole forming device includes a pressure chamber connected to a pressure pipe for supplying a pressurized solution from the ground, a water flow cylinder provided on one or more sides of the pressure chamber and opened to the outside, It consists of a piston part that is slidably inserted into a water flow cylinder,
The piston part is connected to a piston body that slides outward in the water-cylinder cylinder by the pressure of the pressurized solution in the pressure chamber, and an electric wire inserted into the pressure pipe, and is anode-dissolved by applying a voltage. The water-hole forming device used for forming a water-hole for maintaining a groundwater flow in a water-impervious wall, comprising: In order to conserve the groundwater flow blocked by the water-impervious wall constructed during the construction of the underground excavation structure, in order to form a water passage at any time in the water-impervious wall blocking the groundwater flow, A water hole forming device arranged to be connected to the upper and lower pile cores so that the water wall is located at a depth at which the groundwater flow is blocked,
The water flow hole forming device includes a pressure chamber connected to a pressure pipe that supplies a pressurized solution from the ground, a water flow cylinder that is open to the outside and is provided on one or more sides of the pressure chamber, It consists of a piston part that is slidably inserted into a water flow cylinder,
The piston part is connected to a piston body that slides outward in the water-cylinder cylinder by the pressure of the pressurized solution in the pressure chamber, and an electric wire inserted into the pressure pipe, and is anode-dissolved by applying a voltage. The water-hole forming device used for forming a water-hole for maintaining a groundwater flow in a water-impervious wall. A plurality of the pressure chambers are connected, and the partition walls are insulated from the partition walls at the upper and lower adjacent partition walls of the pressure chambers, and have an electrolytic corrosion partition connected to the electrodes. The water hole forming device used for forming a water hole for maintaining a groundwater flow in a water shielding wall according to claim 2, wherein the pressure chambers are opened to allow water to pass therethrough. The water flow cylinder is provided with a sliding lock mechanism that stops sliding when the piston portion is pushed out by a predetermined amount so that the pressurized solution pushes out another piston portion and pushes back the external ground pressure. The water-hole forming apparatus used for groundwater flow maintenance water-hole formation of the water-impervious wall according to any one of claims 1, 2, and 3, wherein The piston main body of the piston part is formed to have a length penetrating a soil mortar layer around the pile core material, and the tip erosion part is formed in a conical shape for pushing the soil mortar layer. The water flow hole formation apparatus used for groundwater flow maintenance water hole formation of the impermeable wall in any one of 2, 3, or 4. The said pressure chamber is filled with the filter material which filters the harmful | toxic substance of a groundwater flow, when a water flow hole is formed, The claim 1, 2, 3, 4 or 5 characterized by the above-mentioned. Water flow hole forming device used to form a water flow hole for maintaining the groundwater flow in the impermeable wall. In order to preserve the groundwater flow blocked by the impervious wall constructed during the construction of the underground excavation structure, a request is made to form a water passage at any time in the part where the impervious wall blocks the groundwater flow. A water hole forming method using the water hole forming device according to any one of Items 1 and 2,
The water penetration hole forming device is set up together with the pile core material on the impermeable wall, filled with soil mortar, and the soil mortar is in the middle of curing, and the pressurized solution is supplied from the ground pressurized solution supply device through the pressure pipe to the pressure chamber. The piston portion is pushed out of the pressure chamber to remove the surrounding soil mortar, and then the electrolyte solution is filled into the pressure chamber through the pressure pipe at any time, and the negative electrode of the DC power source is A water-hole forming method, wherein a positive electrode is connected to a pile core material and a voltage is applied to form a water-hole by anodic dissolution of the metal at the tip-electrolytic portion. For preservation of blocked groundwater flow by seepage control wall being construction upon ZoTsuki underground digging construct barrier to form a water passing hole at any time the portion impervious wall is cut off groundwater flow A pressure chamber provided as a pile core material for a water wall, or connected to upper and lower pile core materials, connected to a pressure pipe for supplying a pressurized solution from the ground, and one or both on both sides of the pressure chamber A plurality of water flow cylinders that are open to the outside and a piston portion that is slidably fitted into the water flow cylinder, and the piston portion is formed by the pressure of the pressurized solution in the pressure chamber. Water flow using a water flow hole forming device comprising a piston body that slides inside and an electric wire inserted into the pressurized pipe and a tip electrolytic corrosion portion that is anode-dissolved by application of voltage A hole forming method comprising:
The water penetration hole forming device is set up together with the pile core material on the impermeable wall, filled with soil mortar, and the soil mortar is in the middle of curing, and the pressurized solution is supplied from the ground pressurized solution supply device through the pressure pipe to the pressure chamber. The piston portion is pushed out of the pressure chamber to remove the surrounding soil mortar, and then the electrolyte solution is filled into the pressure chamber through the pressure pipe at any time, and the negative electrode of the DC power source is By connecting the positive electrode to the tip erosion part and applying voltage to the pile core material, the metal of the tip erosion part is dissolved in the anode to form a water passage hole. A method for forming a water passage hole, comprising applying a positive voltage to dissolve the anode and opening between the upper and lower pressure chambers so as to allow water to pass therethrough.

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