JP6066276B2 - Method and system for preventing liquefaction - Google Patents

Description

  The present invention relates to a liquefaction prevention method and system widely applied to various liquefied grounds including a liquefied ground spreading directly under existing structures such as embankments.

  Liquefaction of the ground is caused by the fact that when the vibration due to earthquake acts on the ground, the pore water pressure between the sand particles increases due to the shear deformation of the ground, and as the pore water pressure increases, the effective stress becomes zero. This is a phenomenon in which the stress cannot be transmitted and the fluidity becomes high, and is likely to occur in loose saturated sandy ground (hereinafter, the ground where liquefaction is likely to occur is called liquefied ground).

  As liquefaction progresses, the ground loses its vertical bearing capacity, leading to collapse of the building, and damage to the piles due to lateral flow of the ground occurs. It has come to be clearly recognized.

  Various countermeasures against such liquefaction damage have been researched and developed in the past, such as compacting the liquefied ground, injecting chemicals into the liquefied ground, improving the ground strength, and lowering the groundwater level. In addition to known countermeasures such as reducing the degree of saturation of the liquefied ground, water containing microbubbles (hereinafter simply referred to as microbubble-containing water) is injected into the liquefied ground. A method has also been developed to send fine bubbles into the soil particle gaps of the ground.

  Among these, according to countermeasures using microbubble-containing water, microbubbles absorb the increase in pore water pressure during earthquakes by reducing their volume, resulting in ground subsidence like countermeasures due to water level reduction. In addition, the ground can be prevented from being liquefied at a more reasonable cost than the countermeasure work by the drug injection.

JP 2007-2111537 A JP 2008-002170 A

  Here, in the countermeasure work using microbubble-containing water, even if the injected microbubbles disappear, the air contained in the microbubbles remains as normal bubbles in the soil particle gap, so the pore water pressure suppression action is Maintained to some extent.

  However, since the air in the bubbles diffuses into the atmosphere over time, the degree of saturation in the ground gradually increases along with this, and there is a problem that it becomes impossible to absorb the increase in pore water pressure during an earthquake.

  Such a problem can be solved by appropriately replenishing microbubbles to the liquefied ground. However, from the viewpoint of economy and the like, it is desirable that the action of preventing liquefaction can be maintained for a long time without performing maintenance and inspection.

  In particular, when trying to improve the liquefied ground that extends directly under long existing structures such as embankments where tracks are laid, the scope of countermeasures becomes enormous, and countermeasures that do not require subsequent maintenance costs are desired. It was.

  The present invention has been made in view of the above-described circumstances, and provides a liquefaction prevention method and system capable of maintaining the saturation level low over a long period of time when the saturation level is lowered to prevent liquefaction. The purpose is to do.

In order to achieve the above object, the liquefaction prevention method according to the present invention, as described in claim 1, shrinks or crushes as the surrounding pressure increases in the treatment area formed in the ground to be liquefaction-prevented. In the liquefaction prevention method of injecting a treatment liquid in which a possible micro hollow body is added to and mixed with a liquid,
The micro hollow body is an expansion / shrinkable hollow body that is encapsulated with air or other gas and is spherically formed of a resin film or a resin shell so that the micro hollow body can be expanded and contracted in accordance with fluctuations in ambient pressure. is there.

  In the liquefaction prevention method according to the present invention, the outer diameter of the micro hollow body is 50 μm or less.

  In the liquefaction prevention method according to the present invention, the treatment region is a region surrounded or sandwiched by a water shielding wall arranged in the ground.

  Further, the liquefaction prevention method according to the present invention includes the treatment liquid in the dewatering region so that air is trapped in the soil particle gap in the dewatering region generated in the pumping process after pumping up the groundwater in the treatment region. Is to inject.

  Further, the liquefaction prevention method according to the present invention performs the aeration process on the dehydration area after the pumping process and before the injection process, or decompression in the dehydration area and the subsequent air supply process Is to do.

Moreover, liquefaction prevention system according to the present invention as described in claim 6, capable of supplying the treatment a treatment liquid shrinkage or frangible microballoons with the periphery of the pressure increase is formed by adding and mixing the liquid In a liquefaction prevention system comprising: a liquid supply means; and an injection means for injecting the treatment liquid supplied from the treatment liquid supply means into a treatment region formed in a ground to be liquefaction-prevented,
The micro hollow body is an expansion / shrinkable hollow body that is encapsulated with air or other gas and is spherically formed of a resin film or a resin shell so that the micro hollow body can be expanded and contracted in accordance with fluctuations in ambient pressure. is there.

  Moreover, the liquefaction prevention system which concerns on this invention makes the said process area | region the area | region enclosed or pinched by the water-impervious wall arrange | positioned in the said ground.

  In order to apply countermeasures to the liquefied ground using the liquefaction prevention method and system according to the present invention, a treatment liquid in which a micro hollow body is added to and mixed with a liquid is liquefied from the treatment liquid supply means through the injection means. It injects into the processing area formed in the ground which becomes the object of prevention.

  The processing liquid may be prepared and stored by the processing liquid supply means, or a separately procured liquid may be stored in the processing liquid supply means. The micro hollow body can be shrunk or crushed as the surrounding pressure increases.

  In this way, the injected processing liquid permeates and diffuses into the processing area, and the existing groundwater in the processing area is replaced with the processing liquid, and the micro hollow body added to and mixed with the processing liquid becomes soil particles. Since it is dispersed in the gap, the volume of water in the soil particle gap is reduced by the volume of the fine hollow body, and as a result, the saturation of the treatment area is lowered.

  Therefore, after the above countermeasures are taken, if the pore water pressure increases due to the ground shear deformation due to the earthquake, the micro hollow body contracts or breaks due to the increase of the pore water pressure, which is the peripheral pressure, and the pore water pressure increases. Absorbs.

  Here, in the liquefaction prevention method and system according to the present invention, unlike conventional countermeasures for reducing saturation by microbubbles or bubbles, the pore water pressure suppression action by shrinkage or crushing of the micro hollow body has elapsed over time. Even so, it is possible to prevent liquefaction of the ground for a long time.

  The saturation in the present invention means the ratio of water in the soil particle gap, that is, the water saturation.

Relates microballoons, in the ground region has shifted to the soil particle structure once dense situations undergoing shear deformation of the ground caused by an earthquake, then since liquefaction is less likely to occur, the hollow microspheres, with the periphery of the pressure increase However, in the present invention, the micro hollow body is capable of expanding and contracting as the surrounding pressure fluctuates . If it does in this way, since the pore water pressure suppression effect | action by shrinkage | contraction of a micro hollow body is maintained irrespective of the condition of a soil particle structure, it becomes possible to prevent liquefaction over a long period of time.

The micro hollow body is an expandable / shrinkable hollow body in which air or other gas is enclosed and formed in a spherical shape with a resin film or a resin shell.

  The outer diameter of the micro hollow body is preferably 100 μm or less, and more preferably 50 μm. Although this depends on the depth of the groundwater level and the compaction situation, liquefaction is "sand with an average particle diameter (D50) of 0.02 to 2 mm, that is, fine sand and medium sand with a small uniformity coefficient. ”(“ Soil Mechanics ”, published by Fumio Oka, published by Asakura Shoten), for example, in order to allow a micro hollow body to diffuse through a soil particle gap on sand ground with a particle size of 1 mm, it takes 10 minutes. This is because it is considered necessary to be about 1/20 or less if possible.

  The injection means may be of any configuration as long as the treatment liquid can be injected into the treatment area in the ground, and is injected through an injection well disposed substantially vertically in the ground, and is substantially horizontal in the ground. It is possible to inject through a horizontal hole arranged in the ground, or through a curved hole arranged in the ground so that each end opens at two different positions on the ground surface in the ground. is there.

  In addition, when replacing the existing groundwater in the treatment area with the treatment liquid, the existing groundwater may be discharged to the surrounding ground by the pushing action due to the weight of the treatment liquid. If the treatment liquid supply means is configured so that the treatment liquid is prepared by adding and mixing the micro hollow body to the groundwater pumped by the pumping means, the existing groundwater can be effectively used. It is also possible to efficiently replace existing groundwater with the treatment liquid.

  The treatment area into which the treatment liquid is injected can be set to any area in the ground where liquefaction prevention is required, and if liquefaction prevention is necessary in the area where groundwater is accumulated, the retention The treatment liquid can be injected using the area as the treatment area.However, if there is a flow in the groundwater and there is a concern that the treatment liquid may spread around the groundwater, place a water-impervious wall in the ground, and It is desirable that a region surrounded or sandwiched by water walls is a processing region.

  As long as the groundwater in the treatment area does not flow into or out of the ground in a short period of time due to horizontal movement of groundwater between the treatment area and the surrounding ground, the impermeable wall However, it is not necessary for the lower end to penetrate the impermeable layer, and groundwater wraparound at the lower end due to relatively slow changes in the groundwater level such as seasonal factors is allowed.

  In this case, groundwater in the treatment area also rises and falls due to fluctuations in the groundwater level in the surrounding ground, and groundwater exchange occurs between the treatment area and the surrounding ground, resulting in a decrease in the concentration of micro hollow bodies in the treatment area, and saturation level. However, in such a case, the processing liquid may be supplied to the processing region as needed using the liquefaction prevention system according to the present invention. The same applies to the case where groundwater moves when no water barrier is provided.

  When the treatment area is an area surrounded or sandwiched by a water-impervious wall arranged in the ground, the groundwater in the treatment area is pumped before injecting the treatment liquid into the treatment area, and then pumped You may make it inject | pour a process liquid into this dehydration area | region so that air may be trapped in the soil particle gap of the dehydration area | region produced in the process.

  According to such a configuration, in addition to the decrease in the saturation due to the replacement of the existing groundwater with the treatment liquid containing the microhollow body, the decrease in the saturation due to the trapped air in the soil particle gap is added, and thus the microhollow body and Usually, the pore water pressure suppression effect by air bubbles or voids is further enhanced, and liquefaction below the existing structure can be more reliably prevented.

  Although the method for lowering the groundwater level in the pumping process is arbitrary, the groundwater level can be lowered in a short time by using the so-called vacuum deep well method that combines gravity drainage and forced drainage by decompression. Therefore, the liquefaction prevention work using the present invention can be realized in a short construction period.

  After pumping up the groundwater in the treatment area, the treatment liquid containing the fine hollow body may be injected as it is into the dewatering area generated in the pumping process, but after the pumping process and before the injection process. In addition, if the aeration treatment is performed on the dehydration region, or if the depressurization in the dehydration region and the subsequent air supply treatment are performed, the moisture remaining on the soil particle surface and the soil particle gap is also removed. More air is trapped in the gap between the soil particles as bubbles, and thus the degree of saturation can be further reduced.

  The aeration treatment can be performed by supplying air to the dehydration region, suction from the region, or a combination thereof, and for example, treatment using warm air is effective.

  On the other hand, in the depressurization in the dehydration region and the subsequent air supply process, the water evaporates almost completely due to the lowering of the boiling point of the water due to the reduced pressure, and air enters the corners of the soil particle gap by the air supply process in that state. For this reason, air tends to remain in the soil particle gap after the treatment liquid is injected.

  The depressurization in the dehydration region can be performed by making the dehydration region airtight by laying an airtight sheet on the ground surface and drawing out the air existing in the space in the dehydration region with a vacuum pump.

The schematic diagram of the liquefaction prevention system concerning a 1st embodiment. It is the figure which showed the effect | action of the liquefaction prevention system which concerns on 1st Embodiment, (a) is sectional drawing which showed the state with which the gap 23 of the soil particle 22 is filled with groundwater, (b) is groundwater. Sectional drawing which showed a mode that the micro hollow body 21 in this processing liquid was disperse | distributed to the gap | interval 23 while being replaced by the processing liquid. Schematic of the liquefaction prevention system which concerns on a modification. Schematic of the liquefaction prevention system which concerns on another modification. It is the schematic of the liquefaction prevention system which concerns on another modification, (a) is a vertical sectional view, (b) is the arrow view seen from the AA line direction. Explanatory drawing which showed the procedure which implements the liquefaction prevention method which concerns on 2nd Embodiment. Explanatory drawing which showed the procedure of implementing the liquefaction prevention method which concerns on 2nd Embodiment continuously.

  Embodiments of a liquefaction prevention method and system according to the present invention will be described below with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a diagram showing a liquefaction prevention system according to the first embodiment. As shown in the figure, the liquefaction prevention system 1 according to the present embodiment is intended for liquefaction prevention in the ground range extending below the embankment 9 as an existing structure constructed on the ground surface of the ground 2. As the treatment liquid supply means for producing the treatment liquid and storing the produced treatment liquid, the impermeable walls 3 and 3 disposed in the ground 2 so that the ground range is sandwiched laterally. A mixing tank 4, an injection well 6 as an injection means for injecting the processing liquid supplied from the mixing tank 4 into the processing region 5 in the ground 2 sandwiched between the water shielding walls 3, 3, and groundwater in the processing region 5 The pumping well 7 pumps up the water with a vacuum pump 8, and the pumping well constitutes a pumping means together with the vacuum pump 8.

  The mixing tank 4 stirs and mixes the groundwater in a state where a micro hollow body is added to the existing groundwater pumped from the processing region 5 through the pumping well 7, and prepares and stores the processing liquid and injects the processing liquid. It can be supplied to the well 6.

  The micro hollow body is composed of an expandable / shrinkable hollow body in which air or other gas is enclosed and formed in a spherical shape with a resin film or resin shell, and has an outer diameter of 50 μm or less.

  The micro hollow body may be formed of, for example, a plastic sphere sold under the trade name “EXPANCEL” (registered trademark) by Nippon Philite Co., Ltd.

  In order to prevent liquefaction using the liquefaction prevention system 1 according to this embodiment, first, the impermeable walls 3 and 3 are arranged in the ground 2 to be liquefied.

  The impermeable wall 3 only needs to extend downward to a depth at which it is desired to prevent liquefaction, and it is not necessary for the lower end to penetrate the impermeable layer 10. In addition, the impermeable wall 3 can be comprised by a sheet pile, for example.

  On the other hand, the injection well 6 and the pumping well 7 are built in the treatment region 5 sandwiched between the impermeable walls 3 and 3. The injection well 6 and the pumping well 7 are arranged substantially vertically so that they face each other.

  Next, the existing groundwater pumped from the treatment area 5 through the pumping well 7 is poured into the mixing tank 4 and a micro hollow body is added to the groundwater, and then these are stirred and mixed to mix the inside of the mixing tank 4. A processing solution is prepared and stored.

  Next, the processing liquid stored in the mixing tank 4 is supplied to the injection well 6 and the processing liquid is injected into the processing region 5 through the injection well.

  As described above, the treatment liquid is added to the micro hollow body in the ground water in the treatment region 5 pumped through the pumping well 7 and mixed and stirred, and this is injected into the treatment region 5 through the injection well 6. This operation is performed until all existing groundwater existing at a depth shallower than the lower ends of the impermeable walls 3 and 3 is replaced. The series of operations such as pumping, mixing and mixing and pouring should be performed in a state where the water level in the treatment area 5 is matched with the groundwater level of the surrounding ground so that groundwater exchange with the surrounding ground does not occur. desirable.

  When the processing liquid is injected into the processing area 5 in this way, the injected processing liquid permeates and diffuses into the processing area 5 in a form that replaces the existing groundwater in the processing area 5, and accordingly, FIG. As shown, since the micro hollow body 21 added and mixed in the treatment liquid is dispersed in the gaps 23 of the soil particles 22, the volume of water in the soil particle gaps 23 is reduced by the volume occupied by the micro hollow bodies 21. As a result, the saturation of the processing area 5 is lowered.

  For this reason, when the pore water pressure increases due to the ground shear deformation due to the earthquake after the above countermeasure work is taken, the micro hollow body contracts due to the increase in the pore water pressure, which is the peripheral pressure, and the increase in the pore water pressure is reduced. Absorb.

  In addition, when groundwater exchange occurs between the surrounding ground due to the fluctuation of the groundwater level in the surrounding ground, and the amount of the minute hollow body is thereby reduced, the liquefaction prevention system 1 is used to treat the processing liquid. 5 may be supplied at any time to lower the degree of saturation in the processing region.

  As described above, according to the liquefaction prevention method and system 1 according to the present embodiment, unlike conventional countermeasures for reducing the degree of saturation by microbubbles or bubbles, the pore water pressure suppressing action by contraction of the micro hollow body However, it is possible to prevent the ground 2 from being liquefied for a long period of time.

  In the present embodiment, it is assumed that the embankment 9 that is an existing structure is present on the ground surface. However, the liquefaction prevention method and system according to the present invention are not premised on the existence of an existing structure. The present invention can also be applied when there is no structure.

  In the present embodiment, the groundwater is pumped through the vacuum pump 8 and the pumping well 7 in order to use the groundwater in the processing region 5 to prepare the processing liquid. About water, it may replace with the groundwater of the process area 5, and may be procured separately. In this case, the vacuum pump 8 and the pumping well 7 can be omitted. In this modification, the existing groundwater is discharged from the lower side of the impermeable wall 3 to the periphery while being pushed down by the injected processing liquid.

  Further, in the present embodiment, the processing liquid is injected into the processing region 5 through the injection well 6, but instead, as shown in FIG. In addition to excavating 31 and forming a horizontal hole 32 from within the shaft, a perforated pipe 33 is disposed in the horizontal hole, and the processing liquid in the mixing tank 4 is injected into the processing region 5 through the perforated pipe. It can be constituted as follows.

  In addition, such a modification is also a modification using freshly procured water instead of the groundwater in the treatment area 5 for the water required for the preparation of the treatment liquid. As described above, it is pushed down to the injected treatment liquid. In this way, the existing groundwater is discharged from below the impermeable wall 3 to the periphery, so that the vacuum pump 8 and the pumping well 7 are unnecessary.

  Moreover, as shown in FIG. 4, in the same figure, each edge part opens on one side and the other side of the embankment 9 so that each edge part opens in two different positions on the ground surface in the ground 2. As shown in FIG. 4, while forming the curved hole 41 in the treatment area 5 and pumping the existing groundwater in the treatment area 5 through one end of the perforated pipe 42 arranged in the curved hole, in FIG. After preparing a processing liquid in which a micro hollow body is added and mixed in the pumped groundwater in the mixing tank 4, the processing area 5 is passed through the other end of the perforated pipe 42 from the mixing tank, in FIG. Can be configured to be injected.

  Here, the curved hole can be appropriately formed using a curved drilling technique known in the field of chemical injection such as curved boring, curved boring, and curved drilling. For example, a flexible rod is formed on the ground. While grasping with the installed drilling machine and feeding the rod diagonally downward with the drilling machine, the ground 2 is excavated with the excavating bit attached to the tip of the rod to form the curved hole 41 and in the vicinity of the rod tip What is necessary is just to manage the shape of the curved hole 41 with attitude | position detection sensors or position detection sensors, such as the provided gyro.

  Moreover, in this embodiment, although the impermeable walls 3 and 3 are arrange | positioned in the ground 2 and the area | region in the ground 2 pinched | interposed into this impermeable wall was made into the process area 5, in this invention, the impermeable wall of Arrangement is arbitrary, and when groundwater is stagnant in the target range of liquefaction prevention that spreads below the embankment 9, the configuration of the embodiment may be omitted and the water shielding walls 3 and 3 may be omitted. Absent.

  In such a modification, instead of the configuration of the present embodiment in which the injection well 6 and the pumping well 7 are opposed to each other so that the treatment liquid is replaced with the existing groundwater even without a water shielding wall, for example, FIG. As shown, it is possible to adopt a configuration in which the injection well 6 is installed in the approximate center of the processing region 5 and a plurality of pumping wells 7 are installed so as to surround the injection well 6 along the periphery of the processing region. .

  According to such a configuration, since the diffusion of the treatment liquid to the surroundings is prevented, the injected treatment liquid can be appropriately replaced with existing groundwater.

[Second Embodiment]
Next, a second embodiment will be described. Note that components that are substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  6 and 7 are explanatory views showing a state in which the liquefaction prevention method according to the present embodiment is performed. As shown in FIG. 6, in order to implement the liquefaction prevention method according to this embodiment, as shown in FIG. 6 (a), the liquefaction prevention range extending below the embankment 9 in the ground 2 is in advance. The impermeable walls 3 and 3 are arranged in the ground so as to be sandwiched between the injection well 6 and the pumping well 7 in the treatment region 5 sandwiched between the impermeable walls. The injection well 6 and the pumping well 7 are arranged substantially vertically so that they face each other.

  In order to implement the liquefaction prevention method according to this embodiment, first, groundwater in the treatment area 5 is pumped through the pumping well 7.

  Next, the existing groundwater pumped up from the treatment area 5 is poured into the mixing tank 4 and a micro hollow body is added to the groundwater, and then the processing liquid is prepared and stored in the mixing tank 4 by stirring and mixing them. To do.

  As in the first embodiment, the micro hollow body is composed of an expandable / shrinkable hollow body in which air or other gas is enclosed and formed in a spherical shape with a resin film or resin shell, and its outer diameter is 50 μm or less. May be used.

  The pumping of the groundwater through the pumping well 7 can be performed by using, for example, a so-called vacuum deep well method using both gravity drainage and forced drainage, and according to such a method, the groundwater level is lowered in a short time. It is possible.

  If the groundwater level in the treatment area 5 is lowered below the liquefaction prevention range due to the above-mentioned pumping, the water level after the pumping with respect to the dewatering area 12 ranging from the groundwater level before pumping to the groundwater level after pumping. Aeration treatment is performed while maintaining

  In the aeration process, as shown in FIG. 6 (b), an air compressor (not shown) connected to the injection well 6 is used to send air from the injection well into the dehydration region 12 and to the pumping well 7. A vacuum pump (not shown) is used to suck air in the dewatering region 12 from the pumping well.

  If it does in this way, the water | moisture content adhering and remaining on the soil particle surface in the dehydration area | region 12 and a soil particle gap will volatilize, and this moisture will be removed in the form entrained by the air flow which flows through a soil particle gap. In addition, in order to promote the volatilization of the moisture remaining on the surface of the soil particles and the space between the soil particles, aeration treatment may be performed using warm air.

  Next, as shown in FIG. 7, the processing liquid stored in the mixing tank 4 is injected into the processing region 5 through the injection well 6.

  When the treatment liquid is injected into the treatment area 5, the dehydration area 12 becomes a condensate area filled with the treatment liquid containing the minute hollow body. In this condensate area, the treatment liquid is contained in the treatment area 5. Along with the permeation and diffusion, the micro hollow body 21 added and mixed in the treatment liquid as described with reference to FIG. 2 is dispersed in the gaps 23 of the soil particles 22, so the volume of water in the soil particle gaps 23 is Only the volume occupied by the minute hollow body 21 is reduced, and as a result, the saturation of the processing region 5 is lowered.

  In addition, part of the air that occupied the soil particle gap before the treatment liquid was injected is trapped in the soil particle gap when the treatment liquid is injected, and remains as bubbles or voids. In the embodiment, moisture is removed from the soil particle gaps in the dewatering region 12 by the above-described aeration treatment, and most of the soil particle gaps are occupied by air. Trapped and remain as bubbles or voids, and the saturation of the processing region 5 further decreases.

  For this reason, when the pore water pressure increases due to the ground shear deformation due to the earthquake after the above countermeasure work is taken, the micro hollow body contracts due to the increase in the pore water pressure, which is the peripheral pressure, and the increase in the pore water pressure is reduced. Absorb.

  If groundwater exchange occurs with the surrounding ground due to changes in the groundwater level in the surrounding ground, thereby reducing the abundance of micro hollow bodies, the processing liquid is treated using, for example, the liquefaction prevention system 1. What is necessary is just to make it reduce the saturation in this process area | region by supplying to the area | region 5 at any time.

  As described above, according to the liquefaction prevention method according to the present embodiment, unlike conventional countermeasures that reduce the degree of saturation by microbubbles or bubbles, the pore water pressure suppression action due to the contraction of the micro hollow body takes time. Since it is maintained even after the lapse of time, liquefaction of the ground 2 can be prevented for a long time.

  Moreover, according to the liquefaction prevention method according to the present embodiment, the ground water in the treatment region 5 is once pumped before injecting the treatment liquid containing the minute hollow body, and the dehydration region 12 generated in the pumping step is removed. Since the treatment liquid was injected again into the dewatering region so that air was trapped in the soil particle gap, in addition to the decrease in saturation due to the replacement of the existing groundwater with the treatment liquid, air was introduced into the soil particle gap. A reduction in the saturation due to the trapping is added, and thus the pore water pressure suppression action by the fine hollow body, the bubbles or the voids is further enhanced, and the liquefaction below the embankment 9 can be more reliably prevented.

  In addition, according to the liquefaction prevention method according to the present embodiment, since the dehydration region 12 is subjected to the aeration process after the pumping process and before the injection process, Moisture that remains attached is removed, and more air is trapped in the soil particle gaps as bubbles or voids, thus making it possible to further reduce the degree of saturation.

  In the present embodiment, it is assumed that the embankment 9 that is an existing structure is present on the ground surface. However, the liquefaction prevention method according to the present invention is not based on the existence of an existing structure, but an existing structure. It can also be applied when no exists.

  In the present embodiment, the processing liquid is prepared using the groundwater pumped from the processing area 5, but instead of this, water for preparing the processing liquid may be procured separately. .

  In the present embodiment, the injection well 6 and the pumping well 7 are used to perform air supply and suction for aeration treatment, but instead, an air supply well or a suction well. May be provided for exclusive use.

  In the present embodiment, the injection well for injecting the processing liquid is a vertically arranged well. Instead, the well is described with reference to the perforated tube 33 described in FIG. 3 of the first embodiment and FIG. A configuration in which the processing liquid is injected through the perforated tube 42 is possible.

  In this embodiment, when the treatment liquid containing the micro hollow body is injected into the dehydration region 12, the aeration treatment is performed in advance so that air is easily trapped in the gap between the soil particles. If sufficient moisture removal is possible, this may be omitted. Conversely, if sufficient moisture removal cannot be achieved by simple ventilation, instead of ventilation, You may make it perform the subsequent air supply process.

  In this way, moisture is evaporated almost completely due to a drop in the boiling point of water due to reduced pressure, and air enters the corners of the soil particle gap by performing the air supply treatment in this state, so that a micro hollow body is included. Air is more easily trapped in the soil particle gap after the treatment liquid is injected.

  The depressurization in the dehydration region 12 is performed by air-tightening the dehydration region 12 by laying an airtight sheet on the surface of the embankment 9 or the surface of the ground 2 spreading on both sides of the embankment 9, and the air present in the space in the dehydration region What is necessary is just to pull out with a vacuum pump.

1 Liquefaction prevention system 2 Ground 3 Water-impervious wall 4 Mixing tank (treatment liquid supply means)
5 Process area 6 Injection well (injection means)
7 Pumping well 12 Dewatering area 21 Micro hollow body 32 Horizontal hole (injection means)
33, 42 Perforated tube (injection means)
41 Curved hole (injection means)

Claims (7)

In the liquefaction prevention method of injecting a treatment liquid in which a micro hollow body that can be shrunk or crushed in accordance with an increase in ambient pressure is added to a liquid in a treatment region formed on the ground to be liquefaction-prevented,
The micro-hollow body is an expansion / contraction hollow body in which air or other gas is enclosed and formed in a spherical shape with a resin film or a resin shell so that the micro-hollow body can be expanded and contracted in accordance with fluctuations in ambient pressure. A characteristic liquefaction prevention method. The method for preventing liquefaction according to claim 1, wherein an outer diameter of the micro hollow body is 50 μm or less. The liquefaction prevention method according to claim 1 or 2, wherein the treatment region is a region surrounded or sandwiched by a water-impervious wall disposed in the ground. The liquefaction prevention method according to claim 3 , wherein after the groundwater in the treatment area is pumped, the treatment liquid is injected into the dewatering area so that air is trapped in the soil particle gaps of the dewatering area generated in the pumping process. . The liquefaction prevention method according to claim 4 , wherein after the pumping step and before the pouring step, the dehydration region is subjected to aeration treatment, or the depressurization in the dehydration region and the subsequent air supply treatment are performed. A processing liquid supply means capable of supplying a processing liquid obtained by adding and mixing a micro hollow body that can be shrunk or crushed with an increase in the ambient pressure into the liquid, and liquefying the processing liquid supplied from the processing liquid supply means In a liquefaction prevention system comprising an injection means for injecting into a treatment region formed in the ground to be prevented,
The micro-hollow body is an expansion / contraction hollow body in which air or other gas is enclosed and formed in a spherical shape with a resin film or a resin shell so that the micro-hollow body can be expanded and contracted in accordance with fluctuations in ambient pressure. Characterized liquefaction prevention system. The liquefaction prevention system according to claim 6, wherein the treatment area is an area surrounded or sandwiched by a water-impervious wall disposed in the ground.

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