JP2012140789A - Microbubble liquid injecting device and method for injecting microbubble liquid into ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microbubble liquid injecting device capable of inhibiting the loss of microbubbles when injecting microbubble liquid into the ground and preventing the liquefaction of the ground, and to provide a method for injecting the microbubble liquid into the ground.SOLUTION: A liquid injecting device 20 includes a liquid supply device 34 for generating microbubbles, a liquid supply pipe 32 having an injection hole 32A, and an on-off valve 64 provided in the injection hole 32A. Herein, microbubble water first reaches the injection hole 32A in the state that the on-off valve 64 is closed, and the on-off valve 64 is subsequently opened to discharge the microbubble water when the pressure of the microbubble water exceeds set pressure. The discharged microbubble water is supplied into the ground 12 in a region where the injection hole 32A is disposed. Thus, the microbubbles are supplied into a liquefaction countermeasure layer S of the ground 12 without any loss and so the saturation grade of the ground 12 decreases to prevent the liquefaction.

Description

  The present invention relates to a microbubble liquid injection apparatus and a microbubble liquid injection method to the ground.

  The liquefaction of the ground is that when the water pressure of the sand ground becomes higher than the hydrostatic pressure due to the vibration caused by the earthquake (this water pressure is called excess pore water pressure), and when the excess pore water pressure becomes equal to the overpressure at each depth, This happens because the bonds are released and become floating. Here, as an example of a method for preventing liquefaction of the ground, there is a method of injecting ultrafine bubbles into the ground to lower the saturation of the ground to bring it into an unsaturated state (see Patent Document 1).

  In the liquefaction prevention method of Patent Document 1, when an excess pore water pressure is generated due to an increase in water pressure in the ground due to an earthquake, the void formed by the ultrafine bubbles is compressed to suppress the increase in water pressure and to be liquid. Is prevented.

  However, in the liquefaction prevention method of Patent Document 1, pressure release occurs in a pipe that feeds water containing ultrafine bubbles from the ground to the ground, and the ultrafine bubbles are lost in the middle, and the ultrafine bubbles are included in the ground. The water could not be injected.

JP 2008-2170

  An object of the present invention is to obtain a microbubble liquid injection apparatus and a microbubble liquid injection method to the ground that can suppress the loss of microbubbles and prevent liquefaction of the ground when the microbubble liquid is injected into the ground. And

  According to a first aspect of the present invention, there is provided a microbubble liquid injection device comprising: a microbubble generating means that pressurizes a liquid to generate a microbubble in the liquid; and a microbubble generating device that is inserted into a hole formed in the ground. A liquid supply pipe formed with a discharge port through which liquid containing microbubbles supplied in a pressurized state is discharged from the means, and the liquid supply pipe is provided in the discharge port and acts on the liquid containing the microbubbles in the liquid supply pipe An opening / closing valve that closes the discharge port until the applied pressure exceeds a set applied pressure and opens the discharge port when the set pressure is exceeded.

  According to the above configuration, the liquid supply pipe is inserted into the hole formed in the ground. Then, a liquid containing microbubbles (hereinafter referred to as microbubble liquid) is supplied from the microbubble generating means to the liquid supply pipe, and the microbubble liquid reaches the discharge port closed by the on-off valve. When the liquid pressure exceeds the set pressure, the on-off valve is opened and the microbubble liquid is discharged from the discharge port. The released microbubble liquid is supplied to the ground in the region where the discharge port is arranged by expanding the microbubble (bubble) when the pressure is released.

  Here, in the microbubble liquid, many microbubbles (bubbles) are generated when the pressure is released. Therefore, it is better to place the discharge port in the deep part of the ground and release the pressure. Compared to the case of injection, more microbubbles can be generated and injected into the ground. Thereby, since the microbubble liquid is supplied to the specific area of the ground without losing the microbubbles, the degree of saturation of the ground is lowered and liquefaction can be prevented.

  In the microbubble liquid injection device according to claim 2 of the present invention, a perforated pipe is inserted into the hole, the liquid supply pipe is suspended in the perforated pipe, and the perforated pipe includes Upper closing means suspended above the discharge port and expanding to close the perforated tube; and lower closing means suspended below the discharge port and expanding to close the perforated tube; , Is provided.

  According to the above configuration, the perforated tube above the discharge port is closed by the upper closing means, and the perforated tube below the discharge port is closed by the lower closing means. Furthermore, since the upper closing means and the lower closing means are suspended independently of the liquid supply pipe, the distance between the upper closing means and the lower closing means can be changed by adjusting the suspension length. Thereby, the specific area | region of the ground which supplies microbubble liquid can be changed.

  In the microbubble liquid injection device according to claim 3 of the present invention, a recirculation means is provided in the perforated tube to recirculate a part of the liquid containing the microbubbles discharged from the discharge port to the ground. . According to this configuration, even if the ground into which the liquid is injected becomes clogged and it becomes difficult to inject the microbubble liquid, a part of the microbubble liquid returns to the ground. It is possible to prevent the pressure in the vicinity of the discharge port from rising excessively. And it is not necessary to apply more load than necessary to the ground.

  According to a fourth aspect of the present invention, there is provided a method for injecting microbubble liquid into the ground, the hole forming step for forming a hole in the ground, and the hole so that the discharge port reaches the formation for injecting liquid containing microbubbles. Inserting a liquid supply pipe into the unit, supplying liquid containing microbubbles to the liquid supply pipe, opening an on-off valve that closes the discharge port, and injecting liquid containing microbubbles into the formation; Have

  According to the above configuration, the liquid supply pipe is inserted into the hole formed in the ground. Then, the micro bubble liquid is supplied to the liquid supply pipe, and the micro bubble liquid reaches the discharge port closed by the on-off valve. Here, for example, when the pressure of the microbubble liquid exceeds the set pressure, the on-off valve is opened and the microbubble liquid is discharged from the discharge port. The discharged microbubble liquid is supplied to the ground in the region where the discharge port is arranged while the pressure is released and the bubbles expand. Thereby, since the liquid is supplied to the specific region (the formation) of the ground without losing the microbubbles, the saturation of the ground is lowered and liquefaction can be prevented.

  Since the present invention is configured as described above, it is possible to suppress the loss of microbubbles and prevent liquefaction of the ground when the microbubble liquid is injected into the ground.

1 is a configuration diagram of a liquid injection system according to an embodiment of the present invention. It is a block diagram of the liquid injection apparatus which concerns on embodiment of this invention. (A) It is a fragmentary perspective view of the liquid injection apparatus which concerns on embodiment of this invention. (B) It is a cross-sectional view of the upper packer of the liquid injection apparatus according to the embodiment of the present invention. (A)-(C) It is process drawing which shows the installation process of the liquid injection apparatus which concerns on embodiment of this invention. It is a longitudinal cross-sectional view which shows the state which installed the liquid injection apparatus which concerns on embodiment of this invention in the hole of the ground. It is a schematic diagram which shows the injection | pouring state of the microbubble liquid to the ground by the liquid injection | pouring system which concerns on embodiment of this invention. (A) It is a schematic diagram which shows the presence state of the bubble in the microbubble liquid inject | poured into the ground by the liquid injection apparatus which concerns on embodiment of this invention. (B) It is a schematic diagram which shows the presence state of the bubble in the microbubble liquid inject | poured into the ground by the liquid injection apparatus which concerns on a comparative example. It is a graph which shows the relationship between the time when the microbubble liquid is inject | poured into the ground using the liquid injection | pouring system which concerns on embodiment of this invention, and the saturation of a ground.

  Embodiments of a microbubble liquid injection apparatus and a microbubble liquid injection method to the ground according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a liquid injection system 10 installed on the ground 12 and a building 14 as a structure built on the ground 12. The ground 12 is composed of a non-liquefied ground 16 as an impermeable layer and a soft ground 18 above the non-liquefied ground 16, and the building 14 is supported on the soft ground 18.

  In the soft ground 18 around the building 14, a water blocking wall 22 made of a continuous wall such as concrete or soil cement is constructed surrounding the building 14, and the lower end of the water blocking wall 22 is a non-liquefied ground 16. Has reached. In addition, an injection hole portion 24 as an example of a hole portion for injecting microbubble liquid is formed by excavation in a part of the soft ground 18 adjacent to the pair of side walls 14A and 14B of the building 14 on the side wall 14A side, A pumping hole portion 26 for pumping is formed on the side wall 14B side by excavation.

  Here, the microbubble liquid is a generic term for liquids including microbubbles (fine bubbles) having a diameter of 10 μm to 200 μm, and in the present embodiment, water containing microbubbles (hereinafter referred to as microbubbles) as an example of the microbubble liquid. Water). Microbubble water can be produced by a high pressure / decompression method in which a large amount of gas is dissolved in water under high pressure and re-bubbled by depressurization. The gas-liquid shearing method to generate is mentioned. In this embodiment, as an example, as will be described later, microbubble water is manufactured using a gas-liquid shearing method and supplied to the soft ground 18.

  The injection hole portion 24 is disposed opposite to the pumping hole portion 26 with the building 14 in between. In addition, although the injection hole part 24 and the pumping hole part 26 are formed in multiple numbers by the depth direction of FIG. 1, they are the same excavation state, respectively. For this reason, in the following description, one set of the injection hole 24 and the pumping hole 26 will be described, and description of the other injection hole 24 and the pumping hole 26 will be omitted.

  In the injection hole portion 24, a perforated tube 28 made of vinyl chloride and having a circular cross section is erected with the opening facing upward. The perforated tube 28 has a length approximately the same as the depth of the injection hole 24, and a through-hole 29 (see FIG. 5) described later is formed on the side wall at the position where microbubble water is injected. . In the following description, illustration of the through hole 29 of the perforated tube 28 is omitted except for FIG.

  Further, the outer diameter of the perforated tube 28 is smaller than the hole diameter of the injection hole portion 24, and a gap having a preset width is formed between the perforated tube 28 and the injection hole portion 24. . Here, a liquefaction countermeasure layer S that requires microbubble water injection (air injection) is set in the soft ground 18 (the soft ground inside the water blocking wall 22 is 18A). A gravel layer 25 is formed in the gap between the perforated tube 28 and the injection hole portion 24 according to the depth of the liquefaction countermeasure layer S. The gravel layer 25 is sandwiched between clay layers 27 at the top and bottom, and microbubbles (air) of microbubble water passing through the gravel layer 25 are injected into the liquefaction countermeasure layer S without leaking upward. .

  On the other hand, the liquid injection system 10 includes a liquid injection device 20 as an example of a microbubble liquid injection device that injects microbubble water into the soft ground 18A surrounded by the water blocking wall 22 from the injection hole 24, and the soft ground 18 Water pump 30 for pumping groundwater from the pumping hole 26 to the ground, and an injection pipe (not shown) for injecting the groundwater pumped to the ground by the pump 30 into the perforated pipe 28 of the injection hole 24. Yes. A plurality of liquid injection devices 20 are provided according to the number of injection holes 24 and pumping holes 26.

  As shown in FIG. 2, the liquid injection device 20 includes a liquid supply pipe 32 suspended by a suspension means (not shown) in the perforated pipe 28, a liquid reflux pipe 33 as an example of a reflux means, and a liquid supply A liquid supply device 34 as an example of microbubble generating means for supplying microbubble water to the pipe 32, and an example of an upper closing means suspended above the lower ends of the liquid supply pipe 32 and the liquid reflux pipe 33 An upper packer 36 and a lower packer 38 as an example of a lower closing means suspended below the lower ends of the liquid supply pipe 32 and the liquid reflux pipe 33 are provided. Note that the liquid supply pipe 32 is made of a hard material only at the lower end portion, and the other parts are made of a vinyl tube.

  The liquid supply device 34 has a box-shaped housing 34A, and a connecting portion 42 to which one end of the liquid supply pipe 32 is connected is provided on the side wall of the housing 34A. Further, the liquid supply device 34 includes a micro bubble water generator 44 for supplying micro bubble water to the liquid supply pipe 32 connected to the connecting portion 42, a supply pipe 46, a pressure gauge 48, a control unit 50, and a flow meter. 52, an electromagnetic valve 54, and a timer 56 are provided.

  Further, the liquid supply device 34 is provided with a packer actuating device 60 that injects air into the upper packer 36 and the lower packer 38 via a pipe (not shown) or discharges air from the upper packer 36 and the lower packer 38. It has been. A connecting portion 43 to which one end of the liquid reflux pipe 33 is connected is provided on the side wall of the housing 34A. Further, the liquid supply device 34 is provided with a storage tank 62 in which water that has flowed through the liquid reflux pipe 33 is temporarily stored. Then, the water stored in the storage tank 62 is drained to the outside of the liquid supply device 34 or supplied to the microbubble water generator 44 (broken line T in FIG. 2) as necessary. Yes.

  In the housing 34 </ b> A of the liquid supply device 34, the connecting portion 42 and the microbubble water generator 44 are connected by a supply pipe 46. A pressure gauge 48, a flow meter 52, and a solenoid valve 54 are attached to the supply pipe 46 in order from the upstream side to the downstream side, with the microbubble water generator 44 side being the upstream side and the connecting portion 42 side being the downstream side. It has been.

  The microbubble water generator 44 operates by being supplied with power from a power source (not shown) and sends out microbubble water to the supply pipe 46. Here, as an example, a microbubble generator manufactured by Nikuni Corporation is used. This microbubble generator uses a gas-liquid shearing method, and a vortex turbomixer (not shown) sucks air from the atmosphere, stirs water, mixes it with water, dissolves it, and has a bubble diameter of about 10 μm. Micro bubbles are generated. The microbubble water generated in the microbubble water generator 44 is supplied to the supply pipe 46 in a pressurized state. As an example, the water injection pressure of microbubble water is 0.4 MPa.

  The pressure gauge 48 is for confirming whether or not the pressure of the microbubble water sent into the supply pipe 46 is the set pressure, and the flowmeter 52 is the microbubble water flowing through the supply pipe 46. It is for confirming that there is. In addition, a timer 56 is connected to the solenoid valve 54, and the switch is electrically turned on and off in accordance with the microbubble water supply time set in the timer 56 to open or shut off the supply pipe 46. .

  The controller 50 automatically turns on and off the operation switches of the microbubble water generator 44, the electromagnetic valve 54, and the packer actuator 60 based on a preset operation program. The time setting for the timer 56 is set via the control unit 50.

  On the other hand, one end (the ground side) of the liquid supply pipe 32 suspended in the perforated pipe 28 using suspension means (not shown) such as a crane is connected to the connection portion 42 of the liquid supply apparatus 34. . Similarly, one end (the ground side) of the liquid reflux pipe 33 suspended using the suspension means is coupled to the coupling portion 43 of the liquid supply device 34. In addition, the lower end part of the liquid reflux pipe 33 in the depth direction of the injection hole part 24 is opened, and the position of this opening is arranged to be the position of the gravel layer 25. The liquid reflux pipe 33 is provided with a flow meter 68 so that the flow rate of the microbubble water that has risen in the liquid reflux pipe 33 without being fed into the gravel layer 25 can be measured.

  Here, the lower end of the liquid supply pipe 32 in the perforated pipe 28 is open, and a discharge port 32A is formed. The liquid supply pipe 32 is disposed such that the position of the discharge port 32 </ b> A is the position of the gravel layer 25 in the depth direction of the injection hole portion 24. An opening / closing valve 64 is provided at the lower end of the liquid supply pipe 32 including the discharge port 32A.

  The on-off valve 64 is a throttle valve, and closes the discharge port 32A until the pressure applied to the microbubble water in the liquid supply pipe 32 exceeds the set pressure, and when the pressure exceeds the set pressure 32A. Is configured to open. Further, in the vicinity of the on-off valve 64, a water pressure gauge 66 for measuring the pressure of the microbubble water discharged from the discharge port 32A is provided. Water pressure data obtained by the water pressure gauge 66 is sent to the control unit 50 via a cable (not shown) and stored.

  As shown in FIG. 3A, a cylindrical upper packer 36 is extrapolated above the opening / closing valve 64 of the liquid supply pipe 32, and below the opening / closing valve of the liquid supply pipe 32. A cylindrical lower packer 38 is provided. Further, the above-described water pressure gauge 66 is disposed between the upper packer 36 and the lower packer 38.

  The upper packer 36 has a cylindrical shape as a whole, and is provided with annular disc portions 36A and 36B at the upper end and the lower end. An annular (tube-shaped) packer bag 36C made of an elastic material such as rubber that can expand or contract is provided between the disc portions 36A and 36B. An upper packer pipe (not shown) is connected to the packer bag 36C through the disc portion 36A, and the end of the upper packer pipe is connected to the packer operating device 60 (see FIG. 2). Has been.

  Further, one end of a plurality of wires 61 for suspending the upper packer 36 is attached to the upper surface of the disc portion 36A. The wires 61 are attached to, for example, four locations in the circumferential direction of the disc portion 36A, but here, only two wires 61 are shown, and the other wires 61 are not shown.

  FIG. 3B shows a cross-sectional view of the upper packer 36 of FIG. The packer bag 36C has an annular shape, and expands inward and outward as indicated by two-dot chain lines A and B when air is injected into the internal space 36D. Further, in the hole portion 36E of the packer bag 36C, wiring (not shown) of the liquid supply pipe 32, the lower packer pipe 41 for injecting air into the lower packer 38, and the water pressure gauge 66 (see FIG. 2). And are provided.

  On the other hand, as shown in FIG. 3A, the entire lower packer 38 has a cylindrical shape, and circular disk portions 38A and 38B are provided at the upper end portion and the lower end portion. An annular (tube-shaped) packer bag 38C made of an elastic material such as rubber that can expand or contract is provided between the disk portions 38A and 38B. The lower packer pipe 41 (see FIG. 3B) is connected to the packer bag 38C through the disc portion 38A, and the upper end of the lower packer pipe 41 is connected to the packer operating device 60 ( (See FIG. 2). Note that the lower end of the liquid supply pipe 32 is not inserted into the lower packer 38.

  Further, one end (lower end) of a plurality of chains 63 for suspending the lower packer 38 is attached to the upper surface of the disc portion 38A. The chains 63 are attached at, for example, four locations in the circumferential direction of the disc portion 38A. Here, only two chains 63 are illustrated, and the other chains 63 are not illustrated.

  Here, as for the upper packer 36 and the lower packer 38, the packer bags 36C and 38C expand when gas is fed from the packer operating device 60 (see FIG. 2) and pressure is applied. Further, the upper packer 36 and the lower packer 38 are contracted by decreasing the pressure when the packer actuating device 60 removes gas from the packer bags 36C and 38C. When the upper packer 36 and the lower packer 38 are suspended from the perforated tube 28, the packer bags 36C and 38C are in a contracted state.

  As shown in FIG. 2, the wire 61 having one end (lower end) attached to the upper packer 36 is wound at the other end (upper end) by a winding device 65 provided on the soft ground 18. Thus, the upper packer 36 is suspended in the perforated tube 28. On the other hand, the chain 63 having one end (lower end) attached to the lower packer 38 has the other end (upper end) attached to the lower surface of the disc portion 36B of the upper packer 36, so that the lower packer 38 is connected to the perforated tube. It is suspended in 28.

  Here, by operating the winding device 65, the installation position of the upper packer 36 and the installation position of the lower packer 38 in the depth direction in the perforated pipe 28 are changed. The upper packer 36 is installed at a position corresponding to the clay layer 27 above the gravel layer 25, and the lower packer 38 is installed at a position corresponding to the clay layer 27 below the gravel layer 25. Thereby, the range sandwiched between the upper packer 36 and the lower packer 38 is arranged to face the gravel layer 25.

  As described above, the water pressure meter 66 is disposed between the upper packer 36 and the lower packer 38 and at a position corresponding to the gravel layer 25, and measures a change in water pressure at this position. The water pressure meter 66 can measure the water pressure by injecting ground water into the perforated pipe 28 after the upper packer 36 and the lower packer 38 are arranged in the perforated pipe 28.

  Further, the water pressure gauge 66 and the control unit 50 are electrically connected. The control unit 50 opens or shuts off the electromagnetic valve 54 according to the difference between the preset pressure setting value and the pressure measurement value measured by the water pressure gauge 66 to supply or stop supplying microbubble water. It has become.

  On the other hand, as shown in FIG. 1, a perforated tube 31 having a circular cross section made of vinyl chloride is erected in the pumping hole portion 26 with the opening facing upward. The perforated pipe 31 has the same length as the depth of the pumping hole portion 26, and a plurality of through holes (not shown) are formed on the side wall at the position where pumping is performed. Further, the outer diameter of the perforated pipe 31 is smaller than the diameter of the pumping hole portion 26, and a gap having a preset width is formed between the perforated pipe 31 and the pumping hole portion 26. . This gap is filled with the gravel layer 25 and the clay layer 27, but some earth and sand are also used.

  Further, in the perforated pipe 31, a pumping pump 35 that pumps up the ground water that has flowed into the pumping hole portion 26 is provided. The pumping pump 35 is electrically connected to the control unit 50 (see FIG. 2) of the liquid supply device 34, and the control unit 50 turns on and off the switch. In addition, one end (lower end) of a pumping pipe 35A extending from the pumping hole portion 26 toward the ground is connected to the pumping pump 35, and the other end (upper end) of the pumping pipe 35A is provided on the ground. Is connected to a pumping tank (not shown) in the pumping device 30. The pumping tank is connected to the above-mentioned injection pipe (not shown), and a delivery pump (not shown) for sending water stored therein to the injection pipe at a predetermined pressure is connected to the connection part of the injection pipe. Is provided. Here, the pumping device 30 is comprised by the pumping pump 35, the pumping pipe 35A, and the pumping tank.

  Next, the operation of the embodiment of the present invention will be described. First, the installation process of the liquid injection system 10 will be described.

  As shown in FIG. 1, the water blocking wall 22 is constructed from the soft ground 18 to the non-liquefied ground 16 so as to surround the building 14. Thereby, the movement of the water (ground water) between the surrounding ground outside the water blocking wall 22 and the soft ground 18A below the building 14 is blocked. And the installation process mentioned later is performed on the ground 12, and the liquid supply apparatus 34 and the pumping apparatus 30 are installed. Note that the soft ground 18A surrounded by the cut-off wall 22, or providing a liquefaction countermeasures layer S is determined in advance what depth.

  Subsequently, as shown in FIG. 4A, a plurality of injection holes 24 are formed in the soft ground 18A by an excavator (not shown) such as an auger. A perforated tube 28 is erected in the injection hole 24. Here, a gap is formed between the perforated tube 28 and the injection hole 24.

  Subsequently, as shown in FIG. 4B, clay is filled in the gap between the perforated tube 28 and the injection hole 24 to form a clay layer 27A. The clay is filled until the height of the upper surface of the formed clay layer 27A becomes the height of the lower surface of the liquefaction countermeasure layer S of the soft ground 18A.

  Subsequently, gravel is filled on the clay layer 27 </ b> A through the gap between the perforated pipe 28 and the injection hole 24 to form the gravel layer 25. In addition, gravel filling is performed until the height of the upper surface of the gravel layer 25 to be formed becomes the height of the upper surface of the liquefaction countermeasure layer S of the soft ground 18A. The gravel layer 25 is preliminarily selected from stones and sand so that air can be sufficiently transmitted therethrough.

  Subsequently, the gravel layer 25 is filled with clay through the gap between the perforated pipe 28 and the injection hole 24 to form a clay layer 27B. Thereby, the perforated pipe | tube 28 is fixed. The clay layer 27B does not have to be formed by filling clay up to the ground. After the layer thickness becomes such that air does not escape upward, the clay layer 27B may be filled with earth and sand when the injection hole portion 24 is excavated. Good.

  Subsequently, as shown in FIG. 4C, the liquid supply pipe 32, the liquid reflux pipe 33, the lower packer 38, and the upper packer 36 are integrally inserted into the perforated pipe 28. The position of the lower packer 38 is adjusted with respect to the upper packer 36 by adjusting the length of the chain 63 in advance, and the upper surface is held at a position where the upper surface becomes the lower surface of the liquefaction countermeasure layer S. Further, the position of the upper packer 36 is adjusted by drawing or winding the wire 61 by the winding device 65, and the lower packer 36 is held at a position where the lower surface becomes the upper surface of the liquefaction countermeasure layer S.

  Thus, since the upper packer 36 and the lower packer 38 are suspended independently of the liquid supply pipe 32, the distance between the upper packer 36 and the lower packer 38 can be changed by adjusting the suspension length. . Thereby, the liquefaction countermeasure layer S (specific area | region) of the soft ground 18A which supplies microbubble water can be changed. The position of the upper packer 36 is detected by the winding device 65 based on the winding amount of the wire 61.

  The position of the inserted liquid supply pipe 32 and liquid reflux pipe 33 is detected by attaching a scale to the connected tube or the pipe itself. Here, the other end (upper end) of the liquid supply pipe 32 is connected to the connecting portion 42 (FIG. 2) of the liquid supply pipe 32 in a state where the on-off valve 64 (release port 32A) is inserted to a position facing the gravel layer 25. And the height position of the liquid supply pipe 32 is fixed. Similarly, the other end of the liquid reflux pipe 33 is connected and fixed to the connecting portion 43.

  Subsequently, the packer operating device 60 (see FIG. 2) is operated to inject air into the packer bags 36C and 38C (see FIG. 3A) of the upper packer 36 and the lower packer 38, respectively. The packer bags 36C and 38C into which air has been injected expand to seal the inside of the perforated tube 28 and are crimped to the perforated tube 28 to fix the position. The above-mentioned water pressure gauge 66 (see FIG. 2) is disposed between the upper packer 36 and the lower packer 38.

  In this way, by installing each part of the liquid injection device 20 (the liquid supply pipe 32, the liquid supply device 34, the upper packer 36, and the lower packer 38) on the soft ground 18A, as shown in FIG. The microbubbles (MB) can be sent to the liquefaction countermeasure layer S through the through holes 29 formed in the perforated pipe 28 and the gravel layer 25. In addition, the injected microbubbles MB (air) are prevented from escaping to the upper and lower portions of the upper packer 36 and the lower packer 38 in the perforated tube 28.

  On the other hand, as shown in FIG. 1, a plurality of pumping holes 26 are formed in the soft ground 18 </ b> A by an excavator (not shown) such as an auger on the opposite side of the injection hole 24 across the building 14. A perforated pipe 31 is erected in the pumping hole portion 26. Here, the perforated pipe 31 is fixed by filling the gap between the perforated pipe 31 and the pumping hole portion 26 with earth and sand.

  Subsequently, the pumping pipe 35 </ b> A and the pumping pump 35 are suspended by a crane (not shown) and inserted into the perforated pipe 31. Then, in a state where the pumping pump 35 is inserted to a position sufficiently deeper than the groundwater surface, the end (upper end) of the pumping pipe 35A is connected to a pumping tank (not shown), and the height position of the pumping pump 35 is fixed. The discharge port 32A (see FIG. 2) and the pumping pump 35 do not have to be at the same level. The pump 35 is preferably located at the same position or deeper than the discharge port 32A.

  Subsequently, one end of an injection pipe (not shown) is connected to the pumping tank in a state where each pumping tank is connected by a plurality of pipes. Here, the other end of the injection pipe is branched in advance in accordance with the plurality of injection holes 24, and the water sent from the pumping tank is inserted into each injection hole 24 to allow the perforated pipe 28. Injected into.

  Next, the microbubble injection operation to the soft ground 18A will be described.

  As shown in FIG. 6, the perforated pipe 28 above the opening / closing valve 64 is blocked by the expanded upper packer 36, and the perforated pipe 28 below the opening / closing valve 64 is blocked by the expanded lower packer 38. It is blocked. Here, in the liquid supply device 34, the microbubble water generator 44 (see FIG. 2) is driven by the control unit 50, whereby microbubble water is supplied into the liquid supply pipe 32. Hereinafter, microbubble water is described as W and microbubbles (fine bubbles) are described as MB.

  As shown in FIG. 2, in the liquid injection device 20, the space between the upper packer 36 and the lower packer 38 is submerged with microbubble water W and ground water (not shown), and the water pressure by these waters is measured by a water pressure gauge 66. Is done. Then, the control unit 50 supplies or stops supplying the microbubble water W to the liquid supply pipe 32 according to the difference between the preset pressure setting value and the pressure measurement value measured by the water pressure gauge 66.

  Here, when the soft ground 18A is clogged and it becomes difficult to inject the microbubble water W, the microbubble water W is excessively injected into the space between the upper packer 36 and the lower packer 38. However, the presence of the liquid reflux pipe 33 causes a part of the microbubble water W to return to the ground. Thereby, it is possible to prevent the pressure (water pressure) in the vicinity of the discharge port 32A from excessively rising due to the continuously supplied microbubble water W. And it is not necessary to apply more load than necessary to the soft ground 18A.

  The control unit 50 manages the injection amount of the microbubble water W injected into the soft ground 18A based on the difference between the flow rate measured by the flow meter 52 and the flow rate measured by the flow meter 68. Yes. Further, when the water pressure measured by the water pressure gauge 66 becomes higher than the set value, the control unit 50 closes the electromagnetic valve 54 and stops the supply of the microbubble water W. Due to these actions, the soft ground 18A is not subjected to an excessive load.

  On the other hand, as shown in FIG. 6, in the liquid supply pipe 32, the on-off valve 64 is closed until the applied pressure acting on the supplied microbubble water W reaches the set applied pressure. The on-off valve 64 is opened. Then, by opening the on-off valve 64, the microbubble water W is discharged from the discharge port 32A (see FIG. 2). Note that the microbubble water W is so small that the microbubble MB cannot be visually recognized when the on-off valve 64 is closed and pressurized, but the on-off valve 64 is opened and the pressure is released (large). At atmospheric pressure), it expands and the bubble diameter is enlarged, so that it is visually recognized as a cloudy state.

  Subsequently, the microbubble water W discharged from the discharge port 32A into the space partitioned by the upper packer 36 and the lower packer 38 passes through the through hole 29 (see FIG. 5) of the perforated tube 28 and the gravel layer 25, It is injected (supplied) into the liquefaction countermeasure layer S of the soft ground 18A. Here, since the on-off valve 64 is opened in a region close to the liquefaction countermeasure layer S, the microbubble water is supplied to the liquefaction countermeasure layer S without losing the microbubbles MB in the microbubble water. Thereby, in the liquefaction countermeasure layer S of the soft ground 18A into which the microbubble water W is injected, the saturation of the gap is reduced from 100% due to the microbubbles MB included in the microbubble water W.

  FIG. 7B shows a microbubble water generator 100 and a liquid supply pipe 102 extending from the microbubble water generator 100 to the liquefaction countermeasure layer S as a comparative example. FIG. 7B schematically shows the presence state of the microbubbles MB at the upper and lower ends of the liquid supply pipe 102. In the comparative example, the pressure is released in the liquid supply pipe 102. For this reason, the microbubble MB generated in the microbubble water generator 100 is present in a predetermined bubble diameter when the pressure is released, but gradually contracts while flowing in the liquid supply pipe 102 and is injected into the liquefaction countermeasure layer S. At that time, it will be lost, or it will become ineffective (decrease) in liquefaction countermeasures.

  On the other hand, as shown in FIG. 7A, in this embodiment, the liquid supply pipe 32 is closed until the on-off valve 64 reaches a predetermined pressure, so that the microbubbles MB generated in the liquid supply device 34 are opened and closed. The pressurized state is maintained up to the valve 64, and the pressure is released from the discharge port 32 </ b> A with a small bubble diameter.

  Since the microbubble water W has a feature that many microbubbles (bubbles) are generated when the pressure is released, the discharge port 32A is arranged in the deep part of the ground (liquefaction countermeasure layer S) as in this embodiment. Thus, more microbubbles are injected into the liquefaction countermeasure layer S than when the microbubble water W whose pressure is released on the ground is injected into the liquefaction countermeasure layer S as in the comparative example. be able to. Thereby, it is possible to suppress the loss of the microbubbles MB when the microbubble water W is injected into the liquefaction countermeasure layer S.

  Here, as shown in FIG. 6, in the present embodiment, when an earthquake occurs in the ground 12 in the state where the microbubbles MB (fine bubbles) exist in the gap between the liquefaction countermeasure layers S and the degree of saturation is lowered, In the anti-oxidation layer S, the increase of the pore water pressure is suppressed by the contraction of the bubbles of the microbubble MB. Accordingly, the state in which the sand particles are kept in contact with each other is maintained, and the sand particles are prevented from freely moving in the water, so that the soft ground 18A can be prevented from being liquefied. As a feature of the microbubble MB, since the rising speed in water is slower than that of normal (mm order) bubbles, the time existing in the liquefaction countermeasure layer S also becomes longer. Thereby, the residence time of the bubbles in the liquefaction countermeasure layer S can be made longer than when air is simply fed into the soft ground 18A.

  In addition, since groundwater is continuously pumped on the pumping device 30 side, a difference (gradient) in the water level is generated, so that the microbubble water W supplied to the liquefaction countermeasure layer S permeates the pumping pump 35 side. It is supplied to a wide range of soft ground 18A. Then, the groundwater pumped up to the ground is injected into the injection hole 24.

  FIG. 8 is a graph showing the relationship between the injection time of the microbubble water W into the soft ground 18A (see FIG. 6) and the saturation level of the soft ground 18A. The graph GA is that of the present embodiment, and the graph GB is that of a comparative example (see FIG. 7B). The degree of saturation of the soft ground 18A is expressed as a ratio of how much ground water fills the gap between the earth and sand in the soft ground 18A, and is saturated when all the gap between the earth and sand is filled with ground water. The degree is 100%. For example, the saturation can be obtained by measuring the specific resistance of the soft ground 18A.

  As shown in FIG. 8, in the graph GA, when the injection time of the microbubble water W into the soft ground 18A (see FIG. 6) is increased from 0 to t1, t2 (t1 <t2), the saturation of the soft ground 18A is It decreases from 100% to A% and B% (A> B). Thereby, it turns out that 18 A of soft ground will be in an unsaturated state by inject | pouring microbubble water W (microbubble MB) into the soft ground 18A. The unsaturated state is a state in which microbubbles (fine bubbles) enter the gap between the earth and sand and the occupancy ratio of the earth and sand gap space by the groundwater is reduced.

  Moreover, in FIG. 8, it has shown that injection | pouring of the micro bubble water W is stopped at the time t3, and has shown that injection | pouring of the micro bubble water W is restarted at the time t4. Since the injection of the microbubble water W is stopped between the time t3 and the time t4, the saturation of the ground is increased by the gradual loss of the microbubble MB. On the other hand, after the time t4, since the injection of the microbubble water W is resumed, the saturation level of the ground is lowered.

  On the other hand, in the graph GB of the comparative example, the decrease in saturation is smaller than that in the present embodiment. As described above, the microbubble MB is lost or saturated while the microbubble water flows down the liquid supply pipe 102 after releasing the pressure on the microbubble water generator 100 (see FIG. 7B). When the microbubble water is injected into the liquefaction countermeasure layer S, there is no microbubble MB enough to sufficiently reduce the saturation (deficient). )

  Here, as described above, in FIG. 6, when the groundwater of the soft ground 18 </ b> A around the perforated pipe 31 is pumped up by the pumping pump 35, the groundwater level L in the soft ground 18 </ b> A is higher on the injection hole portion 24 side. The pumping hole 26 side is lowered. As described above, since the ground surface level L is inclined from the injection hole 24 toward the pumping hole 26, the groundwater including the microbubble water W around the injection hole 24 moves toward the pumping hole 26. To do. Due to the flow of the groundwater, the microbubbles MB injected into the soft ground 18A move to a position close to the pumping hole portion 26. Thereby, the width | variety of the liquefaction countermeasure layer S can be made wider (it sets far), and the microbubble MB can be hold | maintained in the soft ground 18A.

  Since the water pumped up by the pump 35 is injected or drained into the perforated pipe 28 of the injection hole 24 by an injection pipe (not shown), the total amount of ground water in the soft ground 18A does not change much. For this reason, in the liquid injection system 10, ground subsidence due to a decrease in groundwater around the pumping hole portion 26 can be prevented. In addition, the operation | movement which returns water to the injection | pouring side is not necessarily performed. For example, if the injection hole portion 24 and the pumping hole portion 26 are close to each other, the amount of pumped water is small, and thus the pumped water may not be returned to the injection side.

  In addition, this invention is not limited to said embodiment.

  The number of the injection hole portions 24 and the pumping hole portions 26 can be freely selected from one or a plurality of two or more. Further, the expansion or contraction of the packer bags 36C and 38C in the upper packer 36 and the lower packer 38 may be performed using not only air but also a liquid. Further, when a plurality of liquefaction countermeasure layers S should be set in the depth direction, a plurality of sets may be provided with the upper packer 36 and the lower packer 38 as one set in accordance with the set position of the liquefaction countermeasure layer S.

  In the supply (injection) of microbubble water to the soft ground 18A, the liquid reflux pipe 33 may not be used in a period when there is no problem with the clogging of the soft ground 18A. Further, the liquid supply pipe 32 is fixed by adjusting the depth position of the discharge port 32A of the liquid supply pipe 32 to the depth position of the liquefaction countermeasure layer S, or the liquid is placed above and below the discharge port 32A and the opening / closing valve 64. When the flange portion that extends outward from the side surface of the supply pipe 32 is provided, the upper packer 36 and the lower packer 38 may not be used.

12 Ground 20 Liquid injection device (an example of a micro bubble liquid injection device)
24 injection hole (an example of a hole)
28 perforated pipe 32 liquid supply pipe 32A discharge port 33 liquid reflux pipe (an example of reflux means)
34 Liquid supply device (an example of microbubble generating means)
36 Upper packer (example of upper closing means)
38 Lower packer (an example of lower closing means)
64 On-off valve

Claims (4)

Microbubble generating means for pressurizing a liquid to generate microbubbles in the liquid;
A liquid supply pipe formed with a discharge port through which liquid containing microbubbles is inserted from a hole formed in the ground and supplied in a pressurized state from the microbubble generating means;
The discharge port is closed until the applied pressure applied to the liquid containing the microbubbles in the liquid supply pipe exceeds the set pressure, and when the set pressure is exceeded, the discharge port is provided. An on-off valve that opens
A micro-bubble liquid injection device. A perforated tube is inserted into the hole,
The liquid supply pipe is suspended in the perforated pipe,
In the perforated pipe,
Upper closing means that is suspended above the discharge port and expands the diameter to close the perforated tube;
Lower closing means that hangs below the discharge port and expands the diameter to close the perforated pipe,
The microbubble liquid injection device according to claim 1, further comprising:   The microbubble liquid injection device according to claim 1 or 2, wherein a recirculation unit is provided in the perforated tube to recirculate a part of the liquid containing the microbubbles discharged from the discharge port to the ground. . A hole forming step for forming a hole in the ground;
Inserting a liquid supply pipe into the hole so that the discharge port reaches the formation into which liquid containing microbubbles is injected;
Supplying liquid containing microbubbles to the liquid supply pipe, opening an on-off valve that closes the discharge port, and injecting liquid containing microbubbles into the formation;
A method of injecting microbubble liquid into the ground having