JP2814930B2 - Soil liquefaction prevention method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing liquefaction of a ground which may liquefy during an earthquake.

[0002]

2. Description of the Related Art As a method for preventing liquefaction of the ground, various methods are classified into methods based on the principle of the method, such as a method of increasing ground density, a consolidation / replacement method, a method of lowering groundwater level, a method of dispersing pore water pressure, and a method of suppressing shear deformation. It has been known. Among them, the shear deformation suppression method is considered to be a particularly useful method because it has little effect on the surroundings due to the construction and can be applied to the ground where the existing structure exists.

[0003] In the shear deformation suppressing method, the ground which may be liquefied during an earthquake is closed in a cylindrical or prismatic shape, and the closed inner ground is restrained to suppress shear deformation during the earthquake to liquefy the ground. A continuous underground wall, a sheet pile, etc. are adopted as the closing work.

[0004]

The conventional method for suppressing shear deformation merely surrounds the target ground with a cut-off work, and the following points are concerned when adopting this method.

[0005] (1) The effect of suppressing the shear deformation of the internal ground due to the cutoff work is mainly caused by (a) the shear resistance due to the cutoff work, and (b) the increase in the rigidity of the internal ground due to the load applied to the structure. When applying the shear deformation control method to the ground-structure system where the effect of (b) can hardly be expected due to factors such as a small load on the object, it is necessary to maximize the effect of (a). In addition, measures such as increasing the thickness of the closing work (continuous underground wall, sheet pile, etc.) and using a material having high rigidity are required, which leads to an increase in construction costs.

[0006] (2) The lower end of the closing work is supported by the supporting ground, but the upper end is free and not sufficiently fixed. When trying to increase the degree of fixation of the upper end (1)
In the same way as above, it is necessary to take measures such as increasing the wall thickness of the closing work or using a material having high rigidity, which leads to excessive design and an increase in construction costs.

(3) In the event of an earthquake, the ground is subjected to shearing force in all directions in a horizontal plane and liquefies. Therefore, it is desirable that the cutoff work has a structure that equally resists in all directions in the horizontal plane, that is, a cylindrical shape. If it cannot be made cylindrical, it will be necessary to reinforce the closing work.

[0008]

SUMMARY OF THE INVENTION The present invention has been completed in view of the above-mentioned problems, and it is possible to reduce excessive design and increase construction costs by appropriately reinforcing a closing work of appropriate quality. An object of the present invention is to provide a method for preventing ground liquefaction by a shear deformation suppressing method that can be carried out without inviting.

That is, according to the first aspect of the present invention, the target ground is closed in a cylindrical shape, and a lower end of the target ground reaches the support ground, and a lower end is constructed obliquely downward in the cylinder from the upper end of the lower end. A method for preventing liquefaction of the ground, characterized by constructing a slope-improved construction of an inverted conical shape extending so that the lower end thereof reaches the support ground. The invention according to claim 2, wherein the target ground is cut off into a prismatic shape , Constructing a cut-off work whose lower end reaches the support ground, and constructing an inverted pyramid-shaped oblique improvement work that extends diagonally downward into the prism from the upper end of the cut-off work so that its lower end reaches the support ground. A method for preventing liquefaction of the ground, wherein the invention according to claim 3 shuts off the target ground in a cylindrical or prismatic shape, constructs a cutoff in which the lower end reaches the supporting ground, and opposes the cutoff. Connect the upper ends to each other with steel A liquefaction prevention method of the ground, characterized and.

In the present invention, even when the shape of the cut-off work is a desirable cylindrical shape, the cut-off work is reinforced by connecting to the upper end portion of the cut-off work to construct an inverted conical oblique improvement work. Without taking measures such as increasing the wall thickness of the deadline or using a material with high rigidity, the shear deformation control method can be implemented at a low construction cost as a whole.

In the case where the shape of the cut-off work is an undesired prism, a diagonal improvement work is similarly constructed so that the cut-off work resists equally in all directions in the horizontal plane. Also in this case, since the resistance to the shearing force can be adjusted by constructing the oblique improvement work, it is not necessary to take measures such as increasing the wall thickness or using a material having high rigidity in the cutoff work. In addition, it is judged that the condition of the target ground is relatively good and it is not necessary to construct the slope improvement work, and if no structure is built on the target ground, the opposing upper ends of the cutoff work will be , The liquefaction of the ground inside the cutoff work can be prevented by taking a simple operation of fixing the upper ends of the cutoff work to each other.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 and FIG. 2 are schematic perspective views of constructing a closing work for cylindrically closing an object ground where an existing structure is present, and constructing an inverted conical oblique improvement work on the closed inner ground. FIG. 3 is a schematic plan view showing the types of the inverted conical oblique improvement works to be constructed, and FIG. 4A is a diagram showing the construction of a cut-off work for cutting the target ground where the existing structure is present into a prismatic shape. FIG. 4B is a schematic perspective view showing the construction of the inverted pyramid-shaped oblique improvement work on the obtained internal ground, FIG. 4B is a schematic plan view showing the oblique improvement work at that time, and FIG. 5 does not include an existing structure. It is a schematic perspective view which constructs the closing work which closes a target ground in a cylindrical shape, and mutually connects the opposing upper ends of the constructed closing work with steel materials.

FIG. 1 is a perspective view showing the construction of a cut-off work 3 and an oblique improvement work 4 so as to surround the periphery of an existing structure 2. First, as shown in FIG. 1 (b), a continuous underground wall is constructed in a cylindrical shape. Or, the sheet pile is driven into a cylindrical shape, and the target ground 1 below the periphery of the existing structure 2 is closed in a cylindrical shape. Next, as shown in (c), a diagonal improvement 4 having a shape in which two inverted cones are overlapped is constructed, and as shown in (a), the whole is constructed.

The case of FIG. 2 is almost the same as that of FIG. 1, except that the shape of the oblique improvement 4 is one inverted cone.

In both cases of FIGS. 1 and 2, the slope improvement work 4 is a method similar to the continuous underground wall construction method, or a pile 5 or a sheet pile is driven in an oblique direction, and an intermediate position between the driven pile 5 and the sheet pile is used. The part may be consolidated by a method similar to the continuous underground wall construction method to form a wall on the entire surface of the conical slope (see FIG. 3 (a)), or may be constructed along the conical slope. A form in which the formation of the intermediate wall is omitted by simply driving the pile 5, the sheet pile, the earth anchor, etc. in the oblique direction (FIG. 3)
(See (b) and (c)). In this case, a plurality of piles 5, sheet piles, earth anchors, and the like, which are driven obliquely along the conical slope, constitute the oblique improvement work 4. In addition, the conical shape (height, angle, etc.) formed by the oblique improvement work 4 and the position and number of the pile 5 to be driven, the sheet pile, the earth anchor, and the like are appropriately selected according to the condition of the target ground. It is necessary to construct so that the lower end of the slope improvement work 4 reaches the supporting ground.

FIG. 4 shows the construction of a prismatic closing work 3 surrounding the existing structure 2 and a plurality of piles 5 which are driven obliquely along the pyramidal slope.
This is an example of reinforcing with a sheet pile, earth anchor, etc., and when it is impossible to close the target ground 1 below the existing structure 2 into a cylindrical shape due to the surrounding situation, construct a continuous underground wall in a prismatic shape This is an example of closing. A plurality of piles 5, sheet piles, earth anchors, etc. are driven along the pyramid-shaped slope in an oblique direction until reaching the support ground, thereby reinforcing the cut-off work 3.

FIG. 5 shows the construction of a deadline 3 for cylindrically closing the target ground 1 where the existing structure 2 does not exist, and the upper ends of the constructed deadlines which are opposed to each other are fixed to each other with steel 6. This is an example applied to the target ground 1 in which the condition of the target ground 1 is relatively good and it is determined that it is not necessary to construct a slope improvement work. Although the existing structure 2 is illustrated to facilitate understanding, it is needless to say that the structure is built on the ground after the shear deformation suppressing method is applied.

[0019]

According to the method of the present invention, the liquefaction of the ground can be prevented without excessively designing or increasing the construction cost by appropriately reinforcing the closing work of appropriate quality. In addition, it is possible to have a structure that resists less desirable prismatic cut-off work equally in all directions in the horizontal plane, and it can be handled in the same way as cylindrical cut-off work, so selection of the ground shape Wider.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of constructing a closing work for closing a target ground where an existing structure is present in a cylindrical shape, and constructing an inverted conical oblique improvement work on the closed inner ground.

FIG. 2 is a schematic perspective view of constructing a closing work for closing a target ground where an existing structure is present in a cylindrical shape, and constructing an inverted conical oblique improvement work on the closed inner ground.

FIG. 3 is a schematic plan view showing types of an inverted conical oblique improvement work to be constructed.

FIG. 4 (a) is a schematic perspective view of constructing a closing work for closing a target ground where an existing structure is present in a prismatic shape, and constructing an inverted pyramid-shaped oblique improvement work on the closed internal ground; (B)
Is a schematic plan view showing the oblique improvement work at that time.

FIG. 5 is a schematic perspective view of constructing a closing work for closing a target ground having no existing structure in a cylindrical shape, and connecting mutually opposed upper ends of the constructed closing work with steel materials.

[Explanation of symbols]

1..Target ground, 2..Existing structure, 3..Closing work,
4 ・ ・ Improvement work, 5 ・ Pile, 6 ・ Steel.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) E02D 27/34 E02D 3/00

Claims (3)

(57) [Claims] 1. A target ground is cut off in a cylindrical shape, a cut-off work whose lower end reaches a supporting ground is constructed, and an inverted conical oblique improvement work which extends obliquely downward into a cylinder from an upper end of the cut-off work is provided. Soil liquefaction prevention method characterized by construction so that the lower end reaches the supporting ground 2. A target ground is cut off in the form of a prism, a cut-off work whose lower end reaches the supporting ground is constructed, and an inverted pyramid-shaped oblique improvement work that extends obliquely downward into the prism from the upper end of the cut-off work, Soil liquefaction prevention method characterized by construction so that the lower end reaches the supporting ground 3. The ground, wherein the target ground is cut off into a cylindrical or prismatic shape, a cut-off work whose lower end reaches the supporting ground is constructed, and the opposing upper end portions of the cut-off work are connected to each other by a steel material. Liquefaction prevention method