JP6416532B2 - Liquefaction countermeasure method - Google Patents

Description

  The present invention relates to a liquefaction countermeasure method useful for liquefaction countermeasures such as sandy ground, and more particularly to a liquefaction countermeasure method for desaturating the ground (decreasing the degree of saturation of the ground).

Conventionally, various construction methods have been proposed as countermeasures for liquefaction of the ground, and among them, groundwater is drawn from the liquefied layer of the target ground for liquefaction countermeasures to lower the groundwater level and make the liquefied layer unsaturated. It is known that the groundwater lowering method is very effective in that it eliminates the liquefaction layer. In addition, in this method, in order to keep the groundwater level always low, it is necessary to continuously draw the groundwater, and there is a problem in that the construction requires a great deal of cost.
Thus, as a new liquefaction countermeasure method for desaturating the target ground, a liquefaction countermeasure method using microbubble water has been proposed by Patent Document 1 and the like. This method is to desaturate the target ground by injecting water (microbubble water) containing ultrafine bubbles with a diameter of several micrometers into the target ground. According to this method, the water was injected. In the process of microbubble water flowing through the gap in the liquefied layer of the target ground, the ultrafine bubbles are adsorbed and stay on the sand particles, and the adhesion of these ultrafine bubbles to the sand particle surface and By the combination, the saturation of the target ground is lowered, and as a result, the ground strength against liquefaction can be increased. It has been confirmed by laboratory tests and the like that the desaturation of the target ground using microbubble water is effective as a countermeasure against liquefaction.

JP 2008-2170 A

  However, in this liquefaction countermeasure method using micro-bubble water, fine bubbles in the ground near the ground surface escape to the ground through gaps in the ground due to their buoyancy and move by the lateral flow of groundwater. In order to dissipate, there is a problem that it is difficult to continuously ensure an effective unsaturated state (saturation degree of about 90 to 95%) in the ground near the ground surface.

  The present invention solves such a conventional problem, and can desaturate the target ground for liquefaction countermeasures to increase the liquefaction strength. Moreover, the target ground is unsaturated in the target ground. The amount of bubbles necessary to maintain the state (saturation level of about 90 to 95%) can be created and retained, and an effective unsaturated state can be continuously secured even in the ground near the ground surface. An object is to provide a liquefaction countermeasure method.

In order to achieve the above object, the liquefaction countermeasure method of the present invention is:
In the target ground for liquefaction measures, divide the range of a predetermined depth from the upper surface of the liquefied layer below the ground surface into upper and lower layers,
AE agent used as a concrete admixture in the lower layer: by mixing and stirring a material having a bubble effects including (AirEntrainingAgent air entraining agent), the lower a large number of bubbles created stagnation distillate is allowed in the lower unsaturated And
Inject and infiltrate the chemical into the upper layer to solidify the upper layer,
This is the gist.
In this case, the amount of bubbles in the lower layer is preferably adjusted by the amount of the material having bubble action.
In this case, it is preferable to inject and infiltrate the chemical solution around the lower layer, and solidify the periphery of the lower layer together with the upper layer .
In this case, it is preferable to pumping the groundwater of the lower layer when desaturate lower layer.
In this case, it is preferable to inject and penetrate a silica-based solution into the upper layer.

According to the liquefaction countermeasure method of the present invention, a range of a predetermined depth from the upper surface of the liquefied layer below the ground surface is divided into upper and lower layers in the target ground for liquefaction countermeasures, and the AE used as a concrete admixture in the lower layer. agent: by mixing and stirring a material having a bubble effects including (AirEntrainingAgent air entraining agent), desaturate the lower layer by distillation residence create many bubbles in the lower layer, and chemical causes the implanted penetrate the upper layer since solidifying the upper layer, the caking of the underlying desaturation and the upper layer, it is possible to increase the liquefaction strength of the target ground, moreover, in this case, that surrounds the lower layer of the top surface and surrounding the upper layer, It is possible to prevent the bubbles from dissipating by restricting the fine bubbles in the lower layer from passing through the gaps in the ground due to their buoyancy and moving by the flow of groundwater, and preventing the bubbles from dissipating. Can also be continuously ensure effective unsaturated state (about saturation 90% to 95%), it provides the present invention own particular effect that.

The figure which shows the outline | summary of the liquefaction countermeasure construction method in one embodiment of this invention The figure which shows the result of the sustainability test of the unsaturated state in the lower layer by the same construction method

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of a liquefaction countermeasure construction method for desaturating a target ground for liquefaction countermeasures and suppressing damage due to liquefaction of the target ground.
As shown in FIG. 1, in this liquefaction countermeasure construction method, a predetermined depth range from the upper surface (groundwater level) of the liquefied layer 1 below the ground surface to the upper and lower two layers 11 and 12 in the target ground for liquefaction countermeasures. Separately, a large number of bubbles are created and retained in the lower layer 11 to desaturate the lower layer 11, and the upper layer 12 is solidified by injecting and penetrating a chemical solution into the upper layer 12.

In this case, the liquefied layer 1 below the ground surface extends from the upper surface of the liquefied layer to a depth of about several meters, and a part of the upper surface side of the liquefied layer 1, here the upper surface of the liquefied layer 1 is used. The range of 1 m from the top surface of the liquefied layer 1 is the upper layer 12, and the range of 1 m from the lower surface of the upper layer 12 is the lower layer 11.
In the construction procedure, first, bubbles are created and retained in the lower layer 11 to desaturate the lower layer 11, and then the upper layer 12 is injected and penetrated to solidify the upper layer 12.

In the construction of the lower layer 11, bubbles are entrained in the lower layer 11 by stirring and mixing a material having a bubble effect in the lower layer 11. In this case, the amount of bubbles in the lower layer 11 is adjusted by the amount of the material having a bubble effect. Moreover, in construction of this lower layer 11, since this ground 11 is desaturated by entraining a bubble to the lower layer 11, the groundwater of the lower layer 11 is pumped up in parallel.
Here, an AE agent (Air Entraining Agent) used as a concrete admixture is used as a material having a bubble effect. As is well known, the AE agent can be mixed with concrete in advance to generate a large number of fine air bubbles in the concrete. In this construction method, the bubble action of this AE agent is utilized.
A construction machine such as a backhoe is used as the base machine for the construction machine, and a trencher type stirring mixer is attached to the tip of the backhoe arm.
The supply of the AE agent to the lower layer 11 uses a feed pump, a hose, a material injection nozzle or the like. In this case, the hose is extended to the target ground from the supply source (storage container etc.) of the AE agent via the feed pump, the material injection nozzle is connected to the tip of the hose, and this material injection nozzle is connected to the stirring mixer or the vicinity thereof. To place.
And in this construction, the backhoe is moved on the target ground, the backhoe is stopped at every predetermined position, and the AE agent and the lower layer 11 are connected by the trencher type stirring mixer and the AE agent supply equipment. Stir and mix. In this case, the trencher type stirring mixer at the tip of the arm extending from the backhoe is driven to rotate in the vertical direction in a substantially vertical posture, penetrates into the lower layer 11 from the ground surface of the target ground, and supplies the AE agent in parallel therewith. While injecting the AE agent sent from the source by the feed pump and the hose into the lower layer 11 from the material injection nozzle, the AE agent and the lower layer 11 are stirred and mixed with the stirring mixer while taking in air. The air bubbles are entrained in the lower layer 11.
In this manner, the AE agent, the soil particles of the lower layer 11, and the groundwater are stirred and mixed together with the air, and a large number of fine bubbles are generated and retained in the lower layer 11. At this time, the amount of entrained air increases in proportion to the added amount of the AE agent. Therefore, if the added amount of the AE agent is increased, the amount of air bubbles increases, and the amount of bubbles in the lower layer 11 increases depending on the added amount of the AE agent. It is possible to adjust the amount. In addition, the bubble which consists of this AE agent has a property which is hard to tear. In this way, bubbles are generated and retained in the lower layer 11, so that the degree of saturation of the lower layer 11 is lowered and the unsaturated state in the lower layer 11 is continuously maintained. In addition, there is little influence on an environment on the property of AE agent.

  For reference, FIG. 2 shows the result of the sustainability test of the unsaturated state in the ground by this construction method. In this case, an AE agent 1% solution was used. From this test result, it is recognized that this construction method can continuously ensure an unsaturated state (unsaturation level of 95% or less) in the ground.

In the construction of the upper layer 12, the ground layer is consolidated by injecting and infiltrating a chemical into the upper layer 12 using a technique for improving the shallow layer.
Here, a silica-based solution is used as the chemical solution.
A drilling machine or the like is used as the construction machine.
Supplying the silica-based solution to the upper layer 12 uses an injection tube, an injection hose, or the like. In this case, the injection hose can be extended to the target ground from the silica-based solution supply source (chemical solution tank).
In this construction, first, a hole drilling machine is set at each predetermined position on the target ground, the upper layer 12 is drilled from the ground surface, and an injection pipe is built into the drilled hole. Then, a silica-based solution is injected through an injection hose through the hole. As a result, the silica-based solution penetrates into the gaps between the soil particles in the upper layer 12, pushes water out of the gaps, and is replaced with a jelly-like substance, and an improved body is formed in the upper layer 12. This construction is performed in a range from the upper layer 12 to the periphery of the lower layer 11, and the periphery of the lower layer 11 is solidified integrally with the upper layer 12.
By this shallow layer improvement, an improved body is constructed in the upper layer 12 of the liquefied layer of the target ground, so that the strength of the upper layer 12 is increased, and this improved body is formed in a bowl shape as a whole. Since the unsaturated lower layer 11 is held in the lower layer 11, the fine bubbles in the lower layer 11 are restricted from moving to the ground through the gaps in the ground 11 due to their buoyancy and moving by the lateral flow of groundwater. Is not dissipated, the unsaturated state of the ground 11 is maintained for a long time, and the strength of the lower layer 11 is increased.

As described above, in this liquefaction countermeasure construction method, a predetermined depth range from the upper surface of the liquefaction layer 1 below the ground surface is divided into upper and lower two layers 11 and 12 in the target ground for liquefaction countermeasures. A large number of air bubbles are created and retained to desaturate the lower layer 11, and the upper layer 12 is injected and infiltrated to solidify the ground of the upper layer 12. Therefore, the lower layer 11 is desaturated and the upper layer 12 is consolidated. The liquefaction strength of the target ground can be increased.
Moreover, according to this construction method, since the amount of bubbles in the lower layer 11 can be adjusted by the amount of AE agent added, the unsaturated state (saturation level of about 90 to 95%) of the ground 11 is continuously maintained in the lower layer 11. It is possible to reliably create and retain an amount of bubbles necessary for securing, and to continuously ensure an effective unsaturated state even in the ground near the ground surface.
Further, according to this construction method, the upper surface and the periphery of the lower layer 11 are surrounded by the improved body of the upper layer 12, so that the fine bubbles in the lower layer 11 escape to the ground through the gap in the ground by the buoyancy and move by the flow of groundwater. It is possible to prevent the bubbles from being dissipated by restricting the occurrence of bubbles, and to maintain the unsaturated state of the ground 11 for a long time and to maintain the strength of the target ground for a long time.

  In this embodiment, an AE agent used as a concrete admixture is used for a material having a bubble effect. However, as long as it has a bubble effect, it may be replaced with another material as long as it does not adversely affect the environment. Also good.

Further, in this embodiment, a large number of bubbles are created and retained in the lower layer 11 and the lower layer 11 is desaturated. However, a large number of bubbles are formed in the lower layer 11 using water containing fine bubbles such as microbubble water. May be injected and permeated. When the lower layer 11 is desaturated using microbubble water, a hole drilling machine is set at each predetermined position on the target ground, the upper layer 12 is drilled from the ground surface, and then the microhole is placed in each hole. It is only necessary to insert a bubble generating nozzle, inject microbubble water generated and supplied by a microbubble generator into each hole, and permeate into the surrounding ground from each hole. In this case, desaturation of the lower layer 11 and solidification of the upper layer 12 (shallow layer improvement) can be performed by the same construction machine.
As already described in the background art section, the microbubble water is adsorbed and retained by the ultrafine bubbles on the sand particles in the process of flowing through the gaps in the lower layer 11. Since the degree of saturation of the lower layer 11 is reduced by adhesion to the gas bubbles and bonding of bubbles, the liquefaction strength of the target ground can be increased by the desaturation of the lower layer 11 and the consolidation of the upper layer 12.
Even in this case, by surrounding the upper surface and the periphery of the lower layer 11 with the improved body of the upper layer 12, fine bubbles in the lower layer 11 escape to the ground through the gap in the ground 11 due to the buoyancy, or groundwater ( It is possible to prevent the bubbles from dissipating by restricting the movement by the flow (in the lateral direction), and maintaining the unsaturated state of the lower layer 11 for a long time, thereby maintaining the liquefaction strength of the target ground for a long time. can do.

1 Liquefaction layer 11 Lower layer 12 Upper layer

Claims (5)

In the target ground for liquefaction measures, divide the range of a predetermined depth from the upper surface of the liquefied layer below the ground surface into upper and lower layers,
AE agent used as a concrete admixture in the lower layer: by mixing and stirring a material having a bubble effects including (AirEntrainingAgent air entraining agent), the lower a large number of bubbles created stagnation distillate is allowed in the lower unsaturated And
Inject and infiltrate the chemical into the upper layer to solidify the upper layer,
A liquefaction countermeasure method characterized by this. The liquefaction countermeasure method according to claim 1, wherein the amount of bubbles in the lower layer is adjusted by the amount of the material having bubble action . The liquefaction countermeasure method according to claim 1 or 2 , wherein a chemical solution is injected and infiltrated around the lower layer, and the periphery of the lower layer is solidified together with the upper layer . The liquefaction countermeasure method according to any one of claims 1 to 3 , wherein when the lower layer is desaturated, the groundwater of the lower layer is pumped up . Liquefaction measures method according to any one of claims 1 to 4 solution silica is injected penetrate the upper layer.