JPH10219671A - Ground sideways flow preventive construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a structure such as a building constructed on the weak ground or the like from being influenced by sideways flow of liquefied ground due to earthquake or the like by improving the ground over a ranged up to a sliding surface in the ground. SOLUTION: A footing 3 of a structure 2 constructed in the vicinity of a bulkhead 1 is composed of piles 4 whose tip parts 4a are embedded in an unliquefied layer G2 under a liquefied layer G1 of the ground G. When the bulkhead 1 moves by an earthquake, a boundary surface between a part G1' where the occurrence of a sideways flow is anticipated in the liquefied layer G1 and a part G1" where the occurrence of the sideways flow is not anticipated, is used as a sliding surface, and is formed as a surface by connecting a lower end part A of the bulkhead 1 and the ground surface B in the vicinity of a side surface 2a on the opposite side of the bulkhead 1 in the structure 2. Therefore, when a ground is improved over a range L containing a part up to a sliding surface S in the liquefied layer G1 from an under surface of the structure 2, the sideways flow is neither caused in the ground improved range L, nor earth and sand under the structure 2 flow out, and damage of the structure 2 can be prevented.

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 a lateral flow of a ground which is suitable for use as a foundation of various structures such as buildings on soft ground.

[0002]

2. Description of the Related Art As is well known, the foundation of various structures such as buildings constructed on soft ground loses its supporting force when the ground below liquefies due to an earthquake. We use piles that reach the underground hard support layer, and make ground improvements.

By the way, in the 1995 Hyogoken-Nanbu Earthquake, the foundations of structures such as buildings and bridges suffered severe damage even though the above liquefaction countermeasures were taken. did. This damage was due to lateral flow (horizontal displacement) due to liquefaction of the ground, which caused the foundation to move and cause the bridge to fall on the bridge, and the foundation pile to be deformed and damaged in the building. It is clear.

[0004] The damage caused by the lateral flow of the ground is as follows.
In particular, it is remarkably recognized in structures near the revetment. This is because, as shown in FIG. 3, the seawall 1 moves due to the inertial force of the earthquake and the rigidity decrease due to the liquefaction of the liquefied layer G1 of the ground G, and is dragged by the large lateral flow of the ground G accompanying the seawall 1. Thus, it is determined that the foundation 3 of the structure 2 was damaged.

[0005]

However, the above-mentioned conventional techniques have the following problems.
First, in order to prevent the lateral flow of the ground G near the revetment 1, it is first necessary to reinforce the revetment 1 so as not to move due to an earthquake. In many cases, the owner of the structure 2 such as a building is not the same,
In this case, the owner of the structure 2 cannot take measures.

Therefore, the owner of the structure 2 may take other measures such as strengthening the ground G by various ground improvement methods or the like. If it is attempted to completely prevent even flow, both the construction period and construction cost will be extremely enormous.

When the pile 4 is used as the foundation 3, the diameter of the pile 4 may be increased or a material having high hardness may be used to avoid damage due to lateral flow as described above. It is also conceivable to increase the rigidity of No. 4. However, if the pile 4 is not damaged by a strong earthquake such as seismic intensity 7, not only will the cost increase significantly but also a large amount of material will be required. At present, it is difficult to obtain a sufficient pile displacement suppressing effect with the conventional technology.

[0008] The present invention has been made in view of the above points, to maintain its function without being damaged even if lateral flow occurs due to liquefaction of the ground due to an earthquake or the like. It is an object of the present invention to provide a method for preventing lateral flow of the ground that can be performed.

[0009]

The invention according to claim 1 is
In order to prevent lateral flow due to liquefaction of the ground due to an earthquake or the like, a feature is to improve the ground to a slip surface in the ground.

According to a second aspect of the present invention, in the method for preventing lateral flow of the ground according to the first aspect, the slip surface is provided on a ground surface of a structure located near the revetment on a side opposite to the revetment, It is characterized by a surface connecting the lower end of the revetment.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for preventing lateral flow of the ground according to the present invention will be described below with reference to FIG. Here, the ground lateral flow prevention method according to the present invention,
For example, description will be made using an example in which the present invention is applied to a structure having a pile foundation.

As shown in FIG. 1, a structure 2 constructed near a revetment 1 has a foundation 3 made of piles 4, 4,. The tip 4a of each pile 4 is embedded in the non-liquefied layer G2 below the liquefied layer G1 of the ground G.

[0013] In order to apply the soil lateral flow prevention method to the foundation 3, the ground is improved by, for example, injecting a cement-based material into a predetermined range L of the liquefied layer G 1 below the structure 2. .

The range L in which the ground improvement is performed is a portion below the structure 2 and including the lower surface of the structure 2 to the slip surface S in the liquefied layer G1. The slip surface S is defined as a portion G1 ′ where lateral flow is expected to occur in the liquefied layer G1 and a portion G1 ″ where lateral flow is not expected to occur in the liquefied layer G1 when the seawall 1 moves due to an earthquake. Here, the slip surface S is, for example, a lower end A of the revetment 1 and a side surface 2 of the structure 2 opposite to the revetment 1.
The surface is connected to the ground surface B near a.

By performing the ground improvement in the predetermined range L in this manner, the slip surface S can be made discontinuous, and even if the revetment 1 moves due to the earthquake, the liquefied layer G
The lateral flow due to liquefaction 1 is in the range L
It occurs only on the revetment 1 side. Therefore, in the range L where the ground improvement has been performed, no lateral flow occurs, and the sediment below the structure 2 does not flow away, thereby preventing the foundation 3 and the structure 2 from being damaged by movement or damage. Can be prevented.

At this time, the range L in which the ground improvement is performed is not the entire liquefied layer G1, but the lower surface of the structure 2 and the sliding surface S
Since only the part including the above is included, the construction period and construction cost can be greatly reduced.

In the above-described embodiment, the range L in which the ground improvement is performed is defined as a portion below the structure 2 up to a certain depth, but this is, for example, as shown in FIG. May be a range L ′ from the lower surface to the surface that is parallel to the expected slip surface S and slightly lower than this. By doing so, the above effect can be made even more remarkable.

Further, the slip surface S is, for example, a surface connecting the lower end portion A of the revetment 1 and the ground surface B located near the side surface 2a opposite to the revetment 1 in the structure 2.
It is not limited to this. The slip surface S is a boundary surface between a portion where the lateral flow is expected to occur in the liquefied layer G1 due to the earthquake and a portion where the lateral flow does not flow, and the depth of the lower end of the revetment 1 and the revetment of the structure 2 are provided. Distance from 1, other,
What is necessary is just to set suitably according to the conditions of the ground G in which the structure 2 is constructed.

Further, in the above-described embodiment, the construction in which the lateral lateral flow prevention method according to the present invention is applied to the pile-type foundation 3 has been described. However, it goes without saying that the form of the foundation is not limited. Etc. can be applied to other structures. In addition, regarding the liquefaction countermeasure method used,
For example, the sand compaction method, the gravel drain method, the cement solidification method, and the like can be applied effectively if the ground improvement can be performed. It may be improved.

[0020]

As described above, according to the method for preventing lateral flow of the ground according to the first aspect, in order to prevent the lateral flow accompanying the liquefaction of the ground due to an earthquake or the like, the ground surface is prevented from slipping to the slip surface in the ground. It is configured to improve the ground. According to the method for preventing lateral flow of the ground according to claim 2, the slip surface is a surface that connects the position of the structure located near the revetment on the opposite side to the revetment and the lower end of the revetment. The configuration is as follows. In this way, even when the ground on the revetment side liquefies due to liquefaction due to the earthquake and lateral displacement occurs, the slip surface can be discontinued and the foundation can be prevented from being damaged, Seismic resistance can be greatly improved.
At this time, since the ground improvement does not need to be performed for the entire liquefied layer, the construction period and cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a sectional elevational view showing an example of a structure to which a lateral lateral flow prevention method according to the present invention is applied.

FIG. 2 is a sectional elevational view showing another example of a structure to which the lateral lateral flow prevention method according to the present invention is applied.

FIG. 3 is a vertical sectional view showing a state in which a structure subjected to a conventional liquefaction countermeasure is damaged by an earthquake.

[Explanation of symbols]

 1 revetment 2 structure G ground S slip surface L, L 'range

Claims (2)

[Claims] 1. A method for preventing lateral flow of a ground, comprising improving the ground to a slip surface in the ground in order to prevent lateral flow accompanying liquefaction of the ground due to an earthquake or the like. 2. The method according to claim 1, wherein the slip surface is formed by connecting a ground surface of a structure located in the vicinity of the revetment with a ground surface opposite to the revetment and a lower end of the revetment. Ground side flow prevention method characterized by a tied surface.