JP2536638B2 - Ground improvement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention does not cause liquefaction before and after building a building by reducing the saturation of groundwater in the ground even when subjected to repeated loads such as earthquakes. The present invention relates to a ground improvement method for improving the ground.

[Conventional technology]

Loose sand ground with saturated groundwater is likely to be liquefied in the event of an earthquake and damage the buildings on the ground. In order to prevent liquefaction, there is an idea that the degree of saturation of the ground, which is an absolute condition for liquefaction, is reduced, or the strength is increased by consolidation or compaction. Among them, as a method of reducing the saturation of the ground, there is a method of lowering the groundwater level to make unsaturated soil.

[Problems to be Solved by the Invention]

By the way, most of the above-mentioned methods of consolidation and compaction are large-scale construction, and pollution such as vibration and noise is always generated, and it is difficult to be a countermeasure method for existing structures. The consolidation method by injection can be used as a countermeasure method for existing structures, but it is difficult to use due to its economical efficiency.

Furthermore, the above-described method for reducing the degree of saturation has difficulty in long-term maintenance of the pump for pumping groundwater.

The present invention was developed in view of the above circumstances, and an object thereof is to provide a construction method that can be applied to an existing building, can form unsaturated ground without pumping groundwater, and has low pollution.

[Means for solving the problem]

In order to achieve the above object, in the present invention, an injection pipe is inserted into the ground where groundwater is closer to saturation than the surface of the ground, and a foaming material having foamability is injected into the ground through the injection pipe, It is designed to be foamed.

〔Example〕

Hereinafter, description will be given based on the illustrated embodiment. First, the first
As shown in the figure, boreholes are drilled from the ground surface 1 and the building mat 2 into the ground where the groundwater is close to saturation, and the required number of boreholes 3 are provided. Next, the injection pipe 4 is built in the boring hole 3, and the filter material 5 is put into the gap between the boring hole 3 and the injection pipe 4. A water-impermeable filler 6 is installed near the surface of the earth (Figs. 2 and 3). By passing a foaming liquid (a mixture of a foam material 7, a surface-active material and water) through the injection pipe 4, the foam material 7 is injected into the ground through the injection hole 4a of the injection pipe 4 to generate bubbles 8 in the ground. Give birth.

The foam material having foamability includes a chemical foam material that chemically reacts with water in the ground to form a gas (for example, isocyanates) and a chemical foam material that decomposes to generate a gas (for example, various kinds). Hydrogen carbonate, various inorganic peroxides, various inorganic peracids, etc.), and a physical foaming material (for example, carbonated water etc.) that generates a gas by a physical change.

If these foam materials are liquid, they may be directly injected or mixed with water and injected. In the case of a solid, it is mixed with water to form a liquid and injected. The type of foam material and the injection form are properly selected in consideration of the injection property into the ground. Also, 2
You may use together more than one kind of foam material. In either case, it is preferable to add a foam stabilizer so that the generated bubbles are stable for a long time.

The state of the ground when the foam material 7 is injected is shown in FIG. 4 (A),
Shown in (B) and (C). When the foam material 7 is injected in a liquid state into the ground that is close to saturation and is filled with groundwater 10 in the space between the sand particles 9 shown in FIG. (A), the foam material 7 becomes, for example, an oil droplet shape as shown in FIG. , Or dispersed in groundwater or dissolved and enter the gap of the sand particles 9. Further, the bubble material 7 is gasified and fine gas bubbles are coalesced to form bubbles 8 in the gap as shown in FIG.

Since the foam material 7 is injected in a liquid state and has not been foamed, it has good fluidity, and is easily evenly dispersed and diffused in a relatively wide area in the ground to be gasified in the ground, and to be filled in a gap filled with water. It makes it possible to create stable air bubbles throughout and efficiently reduce the saturation of groundwater.

FIG. 5 shows the arrangement pattern of the injection tube 4. In addition to being vertically installed in the ground, the injection pipe 4 may be installed obliquely, or may be installed horizontally by excavation, backfilling, or the like. If the injection pipe 4 is installed in the ground even after the injection, it can be re-injected when the bubbles 8 in the soil are reduced.

〔The invention's effect〕

As described above, according to the present invention, since the unsaturated ground has artificially created bubbles between the sand particles in the ground and the value of the pore water pressure coefficient is reduced, excessive pore water pressure is generated even when subjected to repeated loads such as earthquakes. Can be prevented. It can also be applied to existing buildings and creates unsaturated soil without pumping groundwater, so there is no risk of pollution.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a state in which a boring hole is drilled,
FIG. 2 is an enlarged vertical cross-sectional view showing a state where the injection pipe is inserted into the boring hole to inject the foam material, FIG. 3 is a vertical cross-sectional view showing a state after the foam material is injected, and FIG. 4 is a foam material. FIG. 5 is an enlarged perspective view showing a state in the ground from before injection to after injection, and FIG. 5 is a vertical cross-sectional view showing a pattern of installation of an injection pipe. 1 ... ground surface, 2 ... building mat, 3 ... boring hole, 4 ... injection tube, 5 ... filter material, 6 ... impermeable water filling material, 7 ... foam material, 8 ... air bubbles, 9 ... sand particles,
10 …… Water.

Claims (1)

(57) [Claims] 1. An injection pipe is inserted into the ground where groundwater is more saturated than the surface of the ground, and a foaming foam material is injected into the ground through the injection pipe in a liquid state to foam in the ground. Ground improvement method.