JPH06306847A - Countermeasure against liquefaction of underground structure - Google Patents

Abstract

PURPOSE:To work out a countermeasure against liquefaction of an underground structure by using a comparatively small-scale equipment without requiring a large scale equipment or work space, and improving a support foundation around or just under the underground structure. CONSTITUTION:A hole 7 is bored in the vertical direction in the ground by a boring device 3, and an injecting device 6 to inject a solidifying material to solidify a foundation in a cross shape through an injecting pipe 8, is inserted in a prescribed position of a nonliquefied layer 10 of the hole 7, and while injecting the solidifying material in a cross shape from the injecting device 6, the injecting device 6 is pulled up to the ground from a prescribed position along the hole 7, and a solidifying column 9 is formed in the ground. While moving this boring device 3 successively by a prescribed distance within a foundation improvement range around an underground structure 2, this solidifying material injecting processing is repeated, and plural solidifying columns 9 are created, and a compound foundation A is formed. By a similar method, a hole is bored in the bottom surface of the underground structure 2, and a solidifying column 9 is also formed in the foundation just under the underground structure 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquefaction countermeasure method for underground structures, and more particularly to a liquefaction countermeasure method for reducing liquefaction damage of underground structures installed in soft ground such as coastal areas. Regarding

[0002]

2. Description of the Related Art Conventional liquefaction countermeasure methods include methods such as ground compaction, grain size improvement and consolidation, and methods of changing stress conditions such as increase in effective stress and dissipation of excess pore water pressure. For example, a sand compaction method, a vibro flotation method, etc. are known. These are the methods used only for the ground, but the following methods are especially targeted for the liquefaction of the surrounding ground structure and supporting ground. (1) Deep mixing treatment method (D
JM), replacement method (CJG), etc. to suppress the shear deformation of the ground at the time of an earthquake, and prevent the outflow of water and sand to prevent subsidence. (2) A method of improving the ground around the underground structure to prevent the inflow of water and sand from the surrounding liquefied ground. In FIG. 4, the underground structure 2 provided directly below the road 1
In the case where the lower part is a liquefied layer, an arrow shows how the pore water pressure is locally generated and the wraparound of earth and sand is generated.

[0003]

The main cause of ups and downs of underground structures is the movement of sand and water due to the liquefaction of the supporting ground and surrounding ground of the underground structure. As a preventive measure against these problems, it has been proved effective to improve or replace the supporting ground and the surrounding ground to increase the shear strength. The conventional DJM and CJG method used in (1) above requires a relatively large space due to its large-scale equipment, so construction in a narrower space than the method (2) or There is a problem that it is difficult to apply it when it is installed directly under the existing structure.

Therefore, the present invention has been made in view of the above-mentioned problems, and does not require such a large-scale facility or working space, and provides a countermeasure against the liquefaction of the supporting ground around and beneath the underground structure. The purpose is to do.

[0005]

In order to achieve the above object, in the present invention, in a liquefaction countermeasure method for liquefaction countermeasures for an underground structure installed underground, a burial device is used to dig underground. A vertical hole is drilled in, and a spraying device that sprays solidifying material for solidifying the ground in a cross shape is inserted up to a predetermined position of the hole, and while spraying the solidifying material in a cross shape from the spraying device, the hole Along the line, the injection device is pulled up from the above-mentioned predetermined position to above the ground and directly under the underground structure to form a cross-shaped solidified column, and the boring device is separated by a predetermined distance from the periphery of the underground structure and the supporting ground immediately below. The solidifying material injection process is repeated while sequentially moving only.

[0006]

In the above liquefaction countermeasure method of the present invention, an injection device for injecting a solidifying material for solidifying the ground in a cross shape is inserted up to a predetermined position of the hole, and the solidifying material is injected in a cross shape from the injection device. However, the injection device was pulled up along the hole from the specified position to the ground and directly below the underground structure to form a cross-shaped solidified column, and the boring device was specified to the supporting ground around the underground structure and directly below it. While moving sequentially by distance,
Multiple solidified columns are formed by repeating this solidifying material injection process, so it is easy to solidify the solidified columns around the underground structure and in the supporting ground immediately below without requiring large-scale equipment or work space. Can be formed to form a composite ground in which the supporting ground and the solidified columns are a composite.

By forming a composite ground having the solidified pillars in the support ground, the density of the support ground, which is easily liquefied by itself as a whole, can be increased, the particle size can be hardly liquefied, and the soil particle skeleton can be obtained. The stability of can be improved. Therefore, it is possible to suppress shear deformation, shear strain, shear stress, etc. of the ground that occur when an earthquake occurs, and it is also possible to prevent ground subsidence after the earthquake by increasing the bearing strength of the supporting ground. In addition, these multiple solidification columns prevent the sand from wrapping around due to the difference in soil pressure directly beneath the ground and the underground structure, reduce the lift that acts on the underground structure when an earthquake occurs, and also function as a water blocking wall. Then the water supply is cut off and the excess pore water pressure is suppressed. In addition, the injection by the injection device can increase the density of the ground around the solidified columns and reduce the liquefaction damage of the underground structure when an earthquake occurs.

Further, since the solidifying material is provided by the spraying device so as to spray in a cross shape, and a plurality of cross-shaped solidifying pillars are formed around the underground structure, the second moment of area becomes high, The degree of ground improvement is improved. further,
Since the solidification material injection process is repeated while moving the boring device around the underground structure and the supporting ground immediately below it by a predetermined distance, a predetermined gap can be provided between the solidification columns. As a result, the excess pore water pressure can be dissipated in a short time after the earthquake.

[0009]

Embodiments of the present invention will be described with reference to the drawings. Road 1
In the ground right under, there is a common trench for the underground structure 2 below the groundwater level. In the present embodiment, this road 1 is an ordinary road that is already shared, there is not enough space around the road 1, it is difficult to carry in large-scale mechanical equipment, and there is a risk of liquefaction in the ground. The case is assumed.

A boring device 3, a high-pressure pump 4, and a chemical storage device 5 are installed on the road 1. The boring device 3 is for providing a hole 7 for inserting an injection device 6 described later in the ground. The chemical solution stored in the chemical solution storage device 5 is for improving and fixing the liquefied layer in the ground,
This chemical liquid is supplied into the ground by the high-pressure pump 4 via the injection pipe 8, and jetted into the ground by the injection device 6. This injection device 6 is installed at the tip of the injection pipe 8 and is provided with four injection holes (not shown) at 90-degree angles, and the chemical liquid is made into a cross shape as shown by the arrow in FIG. Jet jet.

As shown in FIG. 1 (e), while spraying the chemical liquid from the spraying device 6, the spraying device 6 is pulled out upward to remove the solidified and improved soil as shown in FIG. 1 (f). A solidified pillar 9 is formed. As shown in the plan view of FIG. 2B, the solidified columns 9 form a cross shape made of improved soil that has been solidified and improved. Next, the solidified pillars 9 of the supporting ground around and immediately below the underground structure 2 according to the present invention.
The improvement method by will be described in detail. Here, FIG.
As shown in FIG. 5, a plurality of cross-shaped solidifying columns 9 are provided on the support ground, which is a liquefied layer around and beneath the underground structure 2, to form the composite ground A.

First, with respect to the support ground which is a liquefaction layer in the ground, the range of the support ground to be improved, the arrangement or strength of the solidification columns 9 in the support ground, and the like are designed, and based on this, the injection device 6 is designed. Determines the composition of the material of the drug solution to be injected and injected. This chemical solution can be freely mixed so as to have a strength suitable for the supporting ground to be improved (Fig. 1).
(A)). Next, the boring device 3 is arranged within the improvement range of the supporting ground around the underground structure 2 on the road 1. Then, the boring device 3 starts the work of forming the hole 7 for inserting the injection device 6 (FIG. 2B).

Then, when the non-liquefied layer 10 which is the support layer for the liquefied layer in the ground is reached, the drilling operation of the insertion hole 7 is stopped (FIG. 1 (c)). After the stop, the injection pipe 8 having the injection device 6 attached at the tip is inserted into the insertion hole 7 to stop the injection device 6 at a predetermined position of the non-liquefied layer (FIG. 1 (d)). Next, the high pressure pump 4 and the chemical liquid storage device 5 are connected to the boring device 3. Then, the high-pressure pump 4 is operated to jet the chemical liquid from the chemical liquid storage device 5 through the injection pipe 8 from the injection device 6 in a cross shape.
While jetting the liquid medicine from the jetting device 6 in a cross shape, the jetting pipe 8 is pulled out toward the ground (Fig. 1).
(E)).

The injection pipe 8 is pulled out to the ground, and the injection device 6
After reaching the ground, solidified columns 9 having a width 9a are formed (FIG. 1 (f)). In this way, one solidified column 9 is formed in the ground, and when this solidified column 9 is viewed in plan,
It has a cross shape as shown in (b). Next, while the boring device 3 is sequentially moved within a required improvement range of the supporting ground around the underground structure 2 by a predetermined distance, the solidification column 9 described above is moved.
3 is repeated to form a plurality of cross-shaped solidified pillars 9 in a wall shape on the supporting ground around the underground structure 2 as shown in FIG. 3 (a).

On the other hand, by boring from the road 1,
The solidified pillars 9 are formed on the supporting ground around the underground structure 2, and at the same time, the underground structure 2 is also formed from the inside of the underground structure 2.
The solidified column 9 is formed immediately below. At this time, it is desirable that the boring device 3, the high-pressure pump 4, and the chemical solution storage device 5 used are as small and lightweight as possible so as to be suitable for work in the underground structure 2. With the boring device 3,
A hole is made in the bottom surface of the underground structure 2, and a hole is drilled in the support ground directly below the underground structure 2. Hole 7 is underground structure 2
Through the liquefied layer, which is the supporting ground, until reaching the non-liquefied layer 10, which is the supporting layer for the liquefied layer. When the non-liquefied layer 10 is reached, the boring operation is stopped, and the injection pipe 8 having the injection device 6 at the tip is inserted into the opened hole 7 and is lowered to the non-liquefied layer 10 and stopped. .

After that, the boring device 3 is attached to the high pressure pump 4
Also, the chemical liquid storage device 5 is connected, the chemical liquid is sent to the injection device 6 through the injection pipe 8, and the chemical liquid is injected from the injection device 6 in a cross shape. While spraying the liquid medicine from the spraying device 6 in a cross shape, the spray pipe 8 is pulled upward until it reaches just below the bottom surface of the underground structure 2 to form a cross-shaped solidified column 9 directly below the underground structure 2. After that, the injection pipe 8 is completely pulled out to remove the boring device, and then the hole in the bottom surface of the underground structure 2 is closed to form the cross-shaped solidified column 9 directly below the underground structure 2. .

Next, while the boring device 3 is sequentially moved over the bottom surface of the underground structure 2 within a required improvement range of the support ground directly under the underground structure 2 by a predetermined distance, the work for forming the solidified column 9 is performed. By repeating this, as shown in FIG. 3 (a), a plurality of cross-shaped solidified columns 9 are formed on the support ground immediately below the underground structure 2. Thus, as shown in the cross-sectional view of FIG. 3A, the solidification pillars 9 formed in a wall shape on the supporting ground around the underground structure 2 directly under the road 1 cause the ground generated at the time of the earthquake. The amount of shear deformation, shear strain, shear stress, etc. of can be suppressed. Further, the solidified pillars 9 formed immediately below the underground structure 2 enhance the bearing capacity of the supporting ground that supports the underground structure 2, and can prevent ground subsidence after an earthquake or a drop in groundwater level. .

Further, as shown in FIG. 3B, the solidification column 9
A predetermined gap 11 is provided between the solidification column 9 and the solidification column 9.
The gap 11 enables the excess pore water pressure generated by the earthquake to be dissipated in a short time. Incidentally, FIG.
In (a), the drawing is complicated when the insertion hole 7 of the solidified column 9 and the gap 11 are drawn at the same time, so the gap 11 is omitted.

[0019]

According to the present invention, while solidifying material is jetted in a cross shape, the injection device is pulled up to above the ground and directly below the underground structure to support the formation of the solidified column around and below the underground structure. Unlike the conventional DJM and CJG construction methods, large-scale equipment and work space are not required, because relatively small-scale equipment such as boring equipment, high-pressure pumps and chemical storage equipment is used in the ground. Further, it is possible to easily form the solidified columns around and immediately below the underground structure to form a composite ground composed of the support ground and the solidified columns. Further, the solidified columns can suppress shear deformation, shear strain, shear stress, etc. of the ground that occur during an earthquake, and at the same time increase the bearing strength of the supporting ground to prevent ground subsidence.

Furthermore, the solidified column can prevent the sand from wrapping around due to the difference in soil pressure between the surrounding ground and the ground structure immediately below, and reduce the lift acting on the ground structure during an earthquake. Further, the solidified column also functions as a water blocking wall to cut off the supply of water and suppress excess pore water pressure. Moreover, the density of the ground around the solidified columns can be increased by the injection by the injection device. In addition, even in normal time,
It also has the effect of preventing dense subsidence due to a decrease in groundwater level.

[Brief description of drawings]

FIG. 1 is sectional views (a) to (f) showing a procedure for forming a solidified column according to the present invention.

FIG. 2 is an explanatory view (a) showing an injection direction of the injection device according to the present invention. The plane explanatory view (b) of a solidification pillar.

FIG. 3 is a vertical cross-sectional explanatory view (a) showing a solidified column according to the present invention formed around and immediately below an underground structure. FIG. 3B is a plan cross-sectional explanatory view showing a state in which solidified columns formed around and immediately below the underground structure are arranged with a predetermined gap.

FIG. 4 is a schematic diagram showing a liquefaction phenomenon that occurs when there is no solidification column.

[Explanation of symbols]

 1 Road 2 Underground Structure 3 Boring Device 4 High Pressure Pump 5 Chemical Liquid Storage Device 6 Injection Device 7 Hole 8 Injection Pipe 9 Solidification Column

Claims (1)

[Claims] 1. A liquefaction countermeasure method for liquefaction countermeasures for an underground structure installed in the ground, a solidifying material for solidifying the ground by making a vertical hole in the ground by a boring device. Inserting an injection device for injecting a cross shape to a predetermined position of the hole, while injecting the solidifying material from the injection device in a cross shape, the injection device is injected along the hole from the predetermined position to the ground and underground structure. Characterized by repeating the above solidifying material injection process while pulling up to just below the object to form a cross-shaped solidified column and sequentially moving the boring device by a predetermined distance with respect to the surrounding of the underground structure and the supporting ground immediately below Measures against liquefaction of underground structures.