JPH07158051A - Ground liquefaction preventing method - Google Patents

Abstract

PURPOSE:To prevent the liquefaction of a ground surely even on the ground right beneath an existing structure by pumping up ground-water from the bottom of the ground and filling a solidifier solution into the ground together with air. CONSTITUTION:Water shield walls 2 such as continuous soil walls, etc., are constructed around the ground to be improved from a ground surface to a desired depth. Also ground-water is pumped up from a ground 3 at the bottom of an existing structure 1 through a deep well 4 and a water drain pipe 5. At the same time, an under-water level 6 is lowered. Next slurry cement solidifier and solvent type solidifier are filled into the ground 3 together with air through a solidifier filling pipe 9. For cement system solidifier, a permeable ultra-fine particle cement is used. The solvent type solidifier is used after distillation so as to improve permeability. Then the ground strength is controlled by the amount of permeability of the solidifier. Since air remains between the solidifiers together with water after gathering water, liquefaction resistance can be further increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for preventing liquefaction of ground,
In particular, the present invention relates to a method for preventing the liquefaction of the ground immediately below the existing structure and the surrounding area.

[0002]

2. Description of the Related Art Liquefaction of the ground during an earthquake damages structures such as sinking, tilting and rising. In order to prevent such damage, it is effective to compact and solidify the ground, and there are already many construction results.

As a method for compacting the ground, a vibrating rod is penetrated into the ground or a weight is dropped, so that the ground is dynamically compacted by using so-called vibration, and a ground is applied to the ground to load the ground. There is a method of statically compacting by applying a force, and in the step of solidifying the ground, there are a method of mechanically mixing and stirring the solidifying material and the ground, and a method of injecting pressure into the ground.

A method for improving the ground directly below the existing structure is disclosed in, for example, Japanese Patent Laid-Open No. 56-111714.

This method comprises the steps of inserting an impermeable wall around the sand layer to be improved from the ground to reach the bottom edge of the sand layer, and inserting a water absorption pipe into the sand layer to suck water in the sand layer. And a step of injecting a solidifying agent solution into the sand layer.

[0006]

However, the dynamic method using the above-mentioned vibration may adversely affect the surrounding environment, and the static method using the embankment or the like requires a large amount of construction work for the embankment. In addition, there are restrictions such as the fact that the area directly below the existing structure cannot be improved.

Further, in the method of solidifying the ground, the work range is limited because a large machine is used, and when the solidifying agent solution is injected under pressure, there is a limit to the permeation ability of the material to be solidified. Therefore, there was a limitation in the range of improvement.

The present invention eliminates the above drawbacks.

[0009]

The method for preventing liquefaction of ground according to the present invention comprises a step of constructing an impermeable wall around the ground to be improved to a desired depth from the surface of the earth, and surrounded by this impermeable wall. It is characterized by comprising a step of pumping groundwater from the bottom of the ground and a step of injecting the solidifying agent solution into the ground together with air.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is an existing structure, 2 is an impermeable wall such as a sheet pile or a soil connecting wall which is driven to a desired depth from the ground surface around the ground of the existing structure 1, and 3 is to be improved. The ground 4 is a deep well located at the bottom of the ground to pump up groundwater in the ground 3.
Is a drainage pipe connected to the deep well 4, 6 is the groundwater level after pumping up groundwater, 7 is an improved width, 8 is an improved depth, and 9 is a slurry-like cement with its tip open in the ground 3. It is an injection pipe for injecting a system solidifying material or a solution-like solidifying agent.

In the present invention, the impermeable wall 2 as described above.
Groundwater is pumped from the bottom of the ground 3 of the existing structure 1 surrounded by the deep well 4 and the drain pipe 5.

As a result, the groundwater level 6 in the ground 3 to be improved is lowered as shown in FIG. 1, the ground 3 is in an unsaturated state, the effective stress of the ground is increased, and the liquefaction resistance of the ground is increased. become.

In the present invention, the solidifying agent injection pipe 9 is then used.
The solidifying agent is injected together with air into the ground 3 through the.
At this time, when a cement-based solidifying material is used, ultrafine particle cement with good permeability is used, and this concentration is made low by adding a separation preventing agent so that it can easily permeate. Furthermore, when a solution-type solidifying agent is used, it is diluted to improve the permeability. The strength of the hardened ground can be controlled by the permeation amount of the solidifying agent, but the usual liquefaction countermeasure is about 1 kgf / cm ^{2 in} uniaxial compressive strength.

Since the method for preventing liquefaction of the ground according to the present invention is as described above, the adhesion of the ground is increased, the liquefaction resistance of the ground is further increased, and the solidifying agent and the ground water injected and solidified. The liquefied strength of the ground that has been consolidated due to the lowering of the ground level is sufficiently increased, and it can be applied to the seismic reinforcement of existing structures. Further, even after the water is reconstituted, as shown in FIG. 2, water 1 is left between the sand particles 10 and between the hardened solidifying agents 11.
2 and air 13 are present together, and the degree of saturation in the soil is reduced by that much, so that liquefaction can be further prevented.

[0016]

As described above, according to the method for preventing liquefaction of the ground of the present invention, there is a great advantage that the liquefaction of the ground can be surely prevented even in the ground immediately below the existing structure.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method for preventing liquefaction of ground according to the present invention.

FIG. 2 is an explanatory view of soil obtained by the method for preventing liquefaction of ground according to the present invention.

[Explanation of symbols] 1 Existing structure 2 Impermeable wall 3 Ground 4 Deep well 5 Drain pipe 6 Groundwater level 7 Improvement width 8 Improvement depth 9 Injection pipe 10 Sand particles 11 Solidifying agent 12 Water 13 Air

Claims (1)

[Claims] 1. A step of constructing an impermeable wall around the ground to be improved to a desired depth from the surface of the earth, a step of pumping groundwater from the bottom of the ground surrounded by the impermeable wall, and solidifying in the ground. A method for preventing liquefaction of ground, comprising the step of injecting a chemical solution with air.