JP5990443B2 - Ground improvement material injection method - Google Patents

Description

  The present invention relates to a method for injecting a ground improvement material into the ground in order to prevent liquefaction of the ground.

  In sandy ground with a high groundwater level, such as landfills, liquefaction occurs due to earthquake vibration, and manholes and sewer pipes are pushed up and protrude from the ground surface, and damage to the building can occur. ing. In order to prevent such a liquefaction phenomenon, improvement work must be performed on the ground where liquefaction is a concern.

  There are various conventional methods for preventing ground liquefaction. For example, a method of forming a ground improvement body in the ground by a deep mixing treatment method (see Patent Document 1), or a method of injecting a ground hardening material into the target ground at a high pressure to create a ground hardening material injection layer in the ground ( Patent Document 2) is known.

  The technique described in Patent Document 1 performs a step of jetting a high-pressure fluid jet containing air from an injection port of an injection tube penetrating into the ground and stirring while cutting the ground, and a step of raising the injection tube Thus, the ground improvement body is formed.

  In the technique described in Patent Document 2, an injection rod having a pair of superposition injection nozzles facing upwards and downwards is inserted into a target ground, and a hardener is injected at a high pressure from an upper nozzle and a lower nozzle, and a hardener injection layer is formed. Is to create.

JP 2012-62616 A JP 2012-41794 A

  For example, the ground targeted for liquefaction prevention is saturated ground, and groundwater exists in the ground. When applying a technique for injecting a ground improvement material such as a hardened material into the ground as described in Patent Document 1 and Patent Document 2 on the ground where groundwater exists in the ground, pressure is applied. The ground improvement material must be injected. Moreover, since the injection | pouring range of a ground improvement material becomes local (for example, the range of about 2.0 m), in order to perform ground improvement over a wide range, the location which should inject a ground improvement material increases. For this reason, there is a disadvantage that not only the construction period is long but also the construction cost is increased.

  Furthermore, in order to inject the ground improvement material under pressure, if the strength in the ground to be improved is not uniform, that is, if there are places where the ground strength is weak, avoid the places where the ground strength is strong, The ground improvement material is likely to enter only in places where the ground strength is weak. For this reason, the injection | pouring range of the ground improvement material became non-uniform | heterogenous, and the whole ground used for improvement could not be processed uniformly.

  The present invention has been proposed in view of the above-described circumstances, and an object thereof is to provide a method of injecting a ground improvement material capable of reliably and uniformly spreading the ground improvement material into the ground to be improved. To do.

  The ground improvement material injection method of the present invention includes, as main steps, a groundwater level lowering step, a ground improvement material injection step, a groundwater level recovery and a ground improvement material diffusion filling step.

The step of lowering the groundwater level is a step of temporarily lowering the groundwater level of the ground to be improved using a pumping means and discharging pore water in the soil particles . The step of injecting the ground improvement material is a step of injecting the ground improvement material into the ground using the injection means. In the process of groundwater level recovery and ground improvement material diffusion filling, the groundwater level of the ground is recovered by stopping the pumping means, and the process of injecting ground improvement material into the ground is continued to recover the groundwater level. This is a step of diffusing and filling the ground improvement material into the gaps of the soil particles from which the pore water has been discharged .

Also, before the step of lowering the groundwater level, in the ground to be improved , a step of providing a water blocking wall that surrounds at least one of the position where the groundwater flows in or the position where the ground improvement material is not desired to diffuse is performed. It is preferable to do.

  According to the method for injecting ground improvement material of the present invention, the ground improvement material is injected after the groundwater level in the ground is lowered, and the ground improvement material is diffused and filled into the ground as the groundwater level recovers. For this reason, since the ground improvement material can be injected with the same pressure over the entire ground, it becomes possible to form a uniform improved ground by uniformly diffusing and filling the ground improvement material into the gaps of the soil particles. .

  In addition, if the pumping means is stopped, the groundwater level will be restored in a short period of time, so diffusion filling of the ground improvement material can be performed in a short period of time, and the construction period will be shortened and the construction cost will be reduced compared to the conventional method Is possible.

  Moreover, an improvement range can be limited by providing a water blocking wall and performing the groundwater level lowering step and the ground improvement material injection / diffusion filling step. Therefore, not only the ground improvement material can be efficiently injected into the ground to be improved, but also the ground improvement material will not diffuse to the extent that the ground improvement material is not desired to be diffused. It becomes possible.

Explanatory drawing of the injection method of the ground improvement material which concerns on embodiment of this invention. In the injection method of the ground improvement material which concerns on embodiment of this invention, the schematic diagram which shows the process of inject | pouring a ground improvement material into a ground and carrying out the diffusion filling. The schematic diagram which shows an example of the pumping means used with the injection method of the ground improvement material which concerns on embodiment of this invention. The schematic diagram which shows an example of the injection | pouring means used with the injection | pouring method of the ground improvement material which concerns on embodiment of this invention.

  Hereinafter, an embodiment of a method for injecting a ground improvement material of the present invention will be described with reference to the drawings. 1 to 4 illustrate a method of injecting a ground improvement material according to an embodiment of the present invention. FIG. 1 is an explanatory diagram of a method of injecting a ground improvement material. FIG. 2 is a diagram of injecting a ground improvement material into the ground. FIG. 3 is a schematic diagram showing an example of pumping means, and FIG. 4 is a schematic diagram showing an example of injection means.

<Outline of injection method of ground improvement material>
In Japan, liquefaction of the ground occurs due to the occurrence of a massive plate boundary earthquake, and large scale damage is expected due to this phenomenon. In fact, during the Great East Japan Earthquake, liquefaction occurred in landfills, embankments, banking, and revetments, causing various damage. For this reason, it is desirable to take measures against liquefaction as soon as possible in preparation for a large-scale earthquake that is expected to occur in the near future.

  The ground improvement material injecting method according to the embodiment of the present invention is the method of injecting the ground improvement material after reducing the groundwater level in the ground to be improved, and then injecting the ground improvement material injected along with the recovery of the groundwater level into the ground. It is a method of diffusing and filling inside, and it is possible to perform ground improvement appropriately and reliably without large-scale construction.

  In the embodiment shown below, the groundwater level is lowered in the saturated ground, the ground is once desaturated, and the ground improvement material is injected into the unsaturated ground to restore (increase) the groundwater level. Along with this, the ground improvement material is diffused and filled into the ground and explained as an example of the construction for countermeasures against liquefaction, but the ground improvement material injection method of the present invention is not only applied to the countermeasures against liquefaction. It can be widely applied to construction for injecting ground improvement materials.

<Pumping means>
In the method for injecting ground improvement material according to the embodiment of the present invention, as shown in FIGS. 1 and 3, the well 10 and the groundwater pumping pump 20 for pumping function as pumping means. Any pump may be used as the groundwater pumping pump 20 for pumping water as long as the groundwater level in the ground can be lowered. For example, a gravity drainage type pumping pump installed at the bottom of the well 10 can be used, or a negative pressure pump that pumps water by generating a negative pressure in the well 10 can be used.

  In the case of using a negative pressure pump, the groundwater level can be lowered in a shorter time. Moreover, the number of the wells 10 can be appropriately changed according to the geology of the ground to be improved, the groundwater discharge situation, the improvement range, and the like. In addition, the groundwater pumped by the groundwater pump 20 is stored in the storage tank 30 and discharged after an appropriate water quality improvement process (for example, muddy water process).

<Injection means>
In the ground improvement material injection method according to the embodiment of the present invention, as shown in FIGS. 1 and 4, an injection device (ground improvement) in which an injection tube 40 is inserted into the ground to be improved and connected to the injection tube 40. The ground improvement material is injected into the ground using the material tank 50 and the injection pump 60).

  More specifically, for example, the ground improvement material is stored in the ground improvement material tank 50, the ground improvement material is sent to the injection pipe 40 by the injection pump 60, and the tip portion of the injection pipe 40 inserted into the ground. The ground improvement material is injected into the ground by ejecting from the injection port 41 provided in the vicinity. In order to spread the ground improvement material widely in the ground, the ground improvement material may be injected while the injection tube 40 is pulled out. Moreover, the injection port 41 can be provided in the several places of the length direction of the injection pipe 40, and a ground improvement material can also be spread widely in the ground.

  The injection means may be a device that can inject a ground improvement material into the ground, use a commonly used device, or improve according to the type of ground improvement material to be injected. Can be used. As a general injection means, a device for performing drilling and chemical material injection using a double tube strainer, and after performing drilling using a casing, an injection tube 40 is inserted into the hole to perform chemical injection. There are various devices such as a device, a device that performs bending boring and injects a chemical material.

<Ground improvement material>
The ground improvement material used in the present invention is required to have a long gel time in order to permeate and diffuse into the ground, but as long as this condition is satisfied, any suspension type, solution type, high viscosity material, etc. A ground improvement material may be used.

<Process of ground improvement material injection method>
In the method for injecting ground improvement material according to the embodiment of the present invention, as shown in FIG. 1 (a), in the ground in a saturated state, groundwater in the ground is discharged using pumping means (well 10 and groundwater pumping pump 20). Pump water and lower the groundwater level as shown in FIG. When the groundwater level drops, the ground that was previously saturated becomes desaturated.

  When the groundwater level is lowered to a predetermined position (depth), as shown in FIG. 1C, the ground improvement material is injected into the ground using the injection means (injection pipe 40 and injection pump 60). Subsequently, as shown in FIG. 1 (d), the groundwater pump 20 is stopped to recover the groundwater level, and the ground improvement material is diffused and filled into the ground as the groundwater level recovers (rises). In addition, it is preferable to continue the injection of the ground improvement material until the ground improvement material reaches the ground after the groundwater pumping pump 20 is stopped.

  Moreover, in the method for injecting ground improvement material according to the embodiment of the present invention, the step of providing the water blocking wall 70 surrounding at least a part of the ground to be improved is performed before the step of lowering the groundwater level. Is preferred. For example, as shown in FIGS. 3 and 4, the water blocking wall 70 is installed so as to surround the ground to be improved. However, the water blocking wall 70 does not surround the entire periphery of the ground to be improved. It is possible to provide the water blocking wall 70 only at the position where the water flows in, or to provide the water blocking wall 70 only at a position where the ground improvement material is not desired to be diffused.

<Diffusion filling of ground improvement material>
As shown in FIG. 2A, pore water 90 exists between the soil particles 80 in the ground to be improved by the ground improvement material injection method according to the embodiment of the present invention. Then, when the pumping means is operated to lower the groundwater level of the ground to be improved, the pore water 90 existing between the soil particles 80 is discharged as shown in FIG. Arise. Air exists in the gap 100.

  Then, when the pumping means is stopped and the groundwater level of the ground is restored, as shown in FIG. 2 (c), the ground improvement material 110 is diffused and filled into the gap 100 from which the pore water 90 has been discharged. Thereby, the shear strength of the ground is increased, the generation of excessive pore water pressure is suppressed, and the liquefaction strength of the ground is improved.

<Comparison with conventional technology>
The ground improvement material injection method of the present invention is based on a new concept that is completely different from the conventional ground improvement material injection method in which the ground improvement material is forcibly injected into the ground to be improved by applying pressure. It is. That is, in the method for injecting ground improvement material according to the present invention, the groundwater level of the ground is once lowered, the pore water 90 in the soil particles 80 is discharged, and then the groundwater level is recovered, thereby recovering (increasing the groundwater level). ) Is characterized in that the ground improvement material is diffused and filled in the ground (in the gaps of the soil particles).

  The ground improvement material injection method of the present invention can be applied to various uses using the conventional chemical solution injection method (ground improvement material injection method), and is particularly effective in preventing liquefaction where uniformity of the improved ground is required. When applied to applications such as water stoppage, the excellent effects of the present invention can be sufficiently exhibited.

  In addition, by applying conventional groundwater level lowering technology and chemical material injection technology, it is only necessary to inject ground improvement material by lowering the groundwater level in the ground, and then restore the groundwater level, shortening the construction period, Various excellent effects such as reduction of construction costs can be achieved.

DESCRIPTION OF SYMBOLS 10 Well 20 Groundwater pump 30 Storage tank 40 Injection pipe 41 Inlet 50 Ground improvement material tank 60 Injection pump 70 Water blocking wall 80 Soil particle 90 Pore water 100 Crevice 110 Ground improvement material

Claims (2)

Using the pumping means, once reducing the groundwater level of the ground to be improved , and discharging the pore water in the soil particles ;
A step of injecting a ground improvement material into the ground using an injection means;
By stopping the pumping means, the groundwater level of the ground is recovered and the step of injecting a ground improvement material into the ground is continued, and the soil from which the pore water has been discharged with the recovery of the groundwater level Diffusing and filling the ground improvement material in the gaps between the particles ;
A method for injecting a ground improvement material, comprising: Prior to the step of lowering the groundwater level, in the ground to be improved , a step of providing a water blocking wall that surrounds at least one of the position where the groundwater flows in or the position where the ground improvement material is not desired to diffuse is performed. The method for injecting a ground improvement material according to claim 1.

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