JPH0598627A - Improving method for soft ground - Google Patents

Abstract

PURPOSE:To effectively improve the soft ground even when there is an existing structure in the improvement object ground range. CONSTITUTION:The improvement object range of the soft ground A is surrounded with a continuous underground wall 1, deep wells 2 are drilled in the improvement object range, the ground surface of the improvement object range is covered with an airtight film body 5, then the air in the deep wells 2 is discharged to the outside with vacuum pumps 4 installed in the deep wells 2 to generate negative pressure. The underground water incorporated in the ground is discharged to the outside with underwater pumps 3 installed in the deep walls 2 to compact the ground. The improvement object range of the soft ground A having an existing structure is likewise surrounded with the continuous underground wall 1, the deep walls 2 are drilled in the improvement object range, and the ground surface is covered with the film body 5. Bentonite is fed to a contact section between the existing structure and the ground, then the air in the deep wells 2 is discharged to the outside with the vacuum pumps 4 to generate negative pressure. The underground water incorporated in the ground is discharged to the outside with the underwater pumps 3 to compact the ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving soft ground for the purpose of preventing liquefaction of soft ground such as sandy ground.

[0002]

2. Description of the Related Art Conventionally, the following methods have been used as a method for improving soft ground. <A> A method of constructing sand piles in soft ground and forcibly vibrating the sand with a vibro hammer to achieve consolidation.

<B> A method of inserting a pipe having good water permeability into the ground to dissipate excess pore water pressure when liquefaction occurs.

<C> A method of injecting a soil improvement material such as cement into the soil for improvement.

[0005]

In any of the above-mentioned conventional techniques, it is difficult to construct any existing method when there is an existing structure within the ground range to be improved. Especially, in the tank yard, which has become a problem in recent years, compaction work cannot be performed. Also, if there is an existing structure, it is difficult to compact it with a heavy machine just below it. Therefore, it is possible to inject the cement-based solidifying material, mix and stir to solidify, but this is economically disadvantageous.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can effectively improve soft ground, and in particular, it can be installed in the range of ground to be improved. It is an object of the present invention to provide a method for improving soft ground, which enables effective improvement even when a structure exists. That is, the present invention, the improvement target range of soft ground is surrounded by a continuous underground wall, a deep well is excavated in the improvement target range, and the ground surface of the improvement target range is coated with an airtight film body, The vacuum pump installed in the deep well discharges the air in the deep well to the outside to generate negative pressure, and at the same time, the submersible pump installed in the deep well discharges the groundwater contained in the ground to the outside. This is a method for improving soft ground by compacting the ground. In addition, the improvement target area of the soft ground where the existing structure exists is surrounded by a continuous underground wall, a deep well is excavated in the improvement target area, and the ground surface of the improvement target area is covered with an airtight film. Furthermore, after pouring bentonite into the contact part between the existing structure and the ground to intervene, the vacuum pump installed in the deep well discharges the air in the deep well to the outside to generate a negative pressure and simultaneously This is a method for improving soft ground, in which groundwater contained in the ground is discharged to the outside by a submersible pump installed in a well to compact the ground.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In addition, in the present embodiment, the improvement of the soft ground where the existing structure exists will be described as an example. <A> Construction of continuous underground wall FIG. 1 shows a case where the existing structure B is constructed on the soft ground A. The continuous underground wall 1 is constructed by surrounding the improvement target range of the soft ground A. The continuous underground wall 1 is constructed by a known method, and if possible, the impermeable layer C is rooted in the construction. When the impermeable layer C is deep, at least 25 underground
It is good to construct up to about m.

<B> Excavation of Deep Wells Next, a required number of deep wells 2 are excavated within the ground area to be improved. This deep well 2 is dug down to, for example, about 20 m underground. Further, in the deep well 2, a submersible pump 3 and a vacuum pump 4 are installed.

<C> Coating of film body After excavation of the deep well 2, the entire ground surface of the ground to be improved is covered with the film body 5 made of airtight vinyl or the like. Film body 5
The peripheral edge portion of is adhered to the upper end of the continuous underground wall 1 so that no gap is generated. Further, the discharge hoses of the submersible pump 3 and the vacuum pump 4 installed in the deep well 2 penetrate the film body 5 and draw it out to the outside, and the through hole of the film body 5 is closed with an adhesive or the like.

<D> Injecting bentonite The contact between the existing structure B and the soft ground A is also covered with the film 5, but if the film 5 is difficult to cover, the bentonite 6 is used.
There is also the case of pouring and intervening. As described above, the improvement target range ground is surrounded by the continuous underground wall 1, the film body 5, the bentonite 6, and the impermeable layer C in a sealed state. In addition to bentonite, clay, soil cement or the like may be used.

<E> Exhaust After the ground to be improved is surrounded as described above, the vacuum pump 4 installed in the deep well 2 discharges the air in the deep well 2 to the outside to generate a negative pressure. Then, since the ground to be improved is in a closed state, the air existing in the closed ground is discharged to the outside through the deep well 2, the atmospheric pressure is reduced, and the air is evacuated. Therefore, the entire ground to be improved can be firmly compacted.

<F> Draining / compacting At the same time as the above-described exhausting work, the submersible pump 3 installed in the deep well 2 collects groundwater in the deep well 2 and discharges it to the outside. As a result, the groundwater level is lowered, a load of about 1/2 of the lowered water level can be expected, and the ground can be compacted. As described above, according to the present invention, the soft ground can be surely improved by the dual effect of consolidation by vacuuming and compaction by lowering groundwater. When the existing structure B is not within the ground range to be improved, the entire ground surface can be covered with the film 5 and the ground can be improved in the same manner as above.

[0013]

Since the present invention is as described above, the following effects can be obtained. <B> By lowering the water level in the ground to be improved, it is possible to obtain a loading effect that is about 1/2 of the lowered water level. Furthermore, by reducing the air pressure in the ground to be improved,
Since the closed ground surrounded by the continuous underground wall and the membrane or bentonite is evacuated, the degree of vacuum can be expected as a loading effect. Therefore, a large load can be expected due to the decrease in the water level and the atmospheric pressure, the ground to be improved is firmly compacted, and effective improvement can be performed.

<B> The ground that is expected to be liquefied sometimes contains fine particles, and a clayey layer or silt layer may be interposed. The present invention is particularly effective on such a ground because a rapid consolidation effect can be expected.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

Claims (2)

[Claims] 1. The area to be improved on soft ground is surrounded by a continuous underground wall, a deep well is excavated in the area to be improved, and the ground surface in the area to be improved is covered with an airtight film, and then deep. The vacuum pump installed in the well discharges the air in the deep well to the outside to generate negative pressure, and at the same time, the submersible pump installed in the deep well discharges the groundwater contained in the ground to the outside. A method for improving soft ground by compacting the ground. 2. The improvement target area of the soft ground where the existing structure exists is surrounded by a continuous underground wall, a deep well is excavated in the improvement target area, and the ground surface of the improvement target area is an airtight film body. Then, bentonite is poured into the contact area between the existing structure and the ground to intervene, and then the vacuum pump installed in the deep well discharges the air in the deep well to the outside to generate a negative pressure. At the same time, a submersible pump installed in a deep well discharges the groundwater contained in the ground to the outside to compact the ground, which is a method for improving soft ground.