JP2005016231A - Liquefaction countermeasure construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquefaction countermeasure construction method capable of being costlessly executed, preventing pore water pressure of the ground in the central part of a fill from rising and also securely preventing settlement of the fill. <P>SOLUTION: In the liquefaction countermeasure construction method in a fill structure 1 for a railway/road, a shearing deformation restriction wall 2 is executed from the toe of slope of the fill structure toward the ground G, and drain pipe 5 or the like is provided so that the pipe slants from the toe of slope of the fill structure 1 to the ground G toward the substantially central part of the structure 1. In the vicinity of the shearing deformation restriction wall 2, a plurality of beam sections 4 or the like are formed along the depth direction of the shearing deformation restriction wall 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquefaction countermeasure method in a banking structure for railways and roads.
[0002]
[Prior art]
Measures for liquefaction during earthquakes in existing embankment structures include, for example, compaction methods that increase the density by compacting the ground, solidification methods such as chemical injection methods and infiltration solidification methods, gravel columns, drain pipes, etc. Steel sheet pile construction method that suppresses deformation and flow of liquefied ground by installing and closing the structure with a drainage construction method (drain construction method), steel sheet pile wall, etc. Etc. have already been proposed.
[0003]
In addition, these methods have been improved from the past, and as a method of preventing the deformation of the embankment in combination with the ground restraint effect, the excess pore water pressure generated around the embankment and in the ground at the bottom of the earthquake is dissipated. It is known to place a liquefaction suppression sheet pile having a function from the embankment slope or near the bottom of the slope toward the ground (see Patent Document 1).
Specifically, as the liquefaction suppression sheet pile having the above drainage function, a large number of openings are formed in a predetermined section of the steel pipe, and a filter for preventing the inflow of earth and sand is provided in these openings, and the inside of the steel pipe is a drainage space. Drainage members along the longitudinal direction of the steel pipe, drainage members with many openings with filters, and drainage along the longitudinal direction of the plate-like sheet pile with joints at both ends Examples include a member, and a member for drainage and a sheet pile provided with a large number of openings with filters.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-106216
[Problems to be solved by the invention]
However, liquefaction countermeasures such as the above-mentioned compaction method, solidification method, drainage method, steel sheet pile method, etc. are different from existing tanks and buildings, especially in existing linear structures such as roads and railways. The distance that requires countermeasures against disinfection is very large, and it is difficult to implement with the above-mentioned construction method from the viewpoint of countermeasure costs.
Moreover, in patent document 1, the water in the ground which arises at the time of an earthquake is drained with the liquefaction suppression sheet pile which provided the drainage function, and the liquefaction suppression sheet pile is provided substantially perpendicularly in the ground from the embankment of the embankment. Therefore, the water in the ground immediately below the bottom of the embankment is drained, but the water in the ground at the center of the embankment is difficult to drain. Therefore, during the earthquake, the pore water pressure in the ground is different between the Hoshijiri and the center of the embankment, and the pore water pressure in the ground in the center of the embankment increases, so the ground in the center of the embankment is locally weakened. Therefore, the settlement of the embankment will occur.
[0006]
The present invention has been made in view of the above circumstances, and provides a liquefaction countermeasure construction method that can be constructed at low cost, and that prevents increase in the pore water pressure of the ground in the center of the embankment and can reliably prevent settlement of the embankment. It is an issue.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the invention of claim 1 is a liquefaction countermeasure construction method in a banking / road embankment structure 1 as shown in FIGS. 1 (a) and 1 (b), for example.
Construction of the shear deformation restraint wall 2 from the bottom of the embankment structure toward the ground G,
The drainage pipes 5,... Are provided so as to incline toward the approximate center of the embankment structure in the ground from the bottom of the embankment structure.
[0008]
According to the first aspect of the present invention, the shear deformation restraining wall is constructed from the slope bottom portion of the embankment structure into the ground, and is inclined from the slope bottom portion into the ground toward the approximate center of the embankment structure. Since the drainage pipe is provided, the shear deformation restraint wall restrains the shear deformation of the ground just below the bottom of the embankment structure, and the ground that liquefies by restraining the shear deformation has a pore water pressure due to the drainage effect of the drain pipe. Rise is suppressed.
Further, in the present invention, since the drain pipe is provided in the ground so as to be inclined toward the approximate center of the embankment structure from the slope bottom portion, the ground immediately below the slope bottom portion as compared with the conventional case. In addition, the water in the ground in the center of the embankment structure can be drained, and can be drained evenly over a wide area in the ground. Therefore, the local weakening of the ground in the center of the embankment structure can be prevented, and therefore the settlement of the embankment structure at the time of an earthquake can be prevented more reliably.
Moreover, it can be implemented with a relatively small machine and can be applied to an existing embankment structure with no site margin. Furthermore, even in the embankment structure that requires a liquefaction countermeasure such as a railway or a road, the liquefaction countermeasure can be performed at a low cost according to the importance of the embankment structure.
[0009]
The invention of claim 2 is, for example, in the liquefaction countermeasure method according to claim 1 as shown in FIGS.
A plurality of beam portions 4,... Are provided in the vicinity of the shear deformation restraining wall along the depth direction of the shear deformation restraining wall.
[0010]
According to the second aspect of the present invention, since the plurality of beam portions are provided in the vicinity of the shear deformation restraining wall along the depth direction of the shear deformation restraining wall, the restraining effect of the shear deformation restraining wall is further increased by these beam portions. It can also be done easily.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 (a) is a front sectional view of an embankment structure subjected to the liquefaction countermeasure method according to the present invention, and FIG. 1 (b) is an upper sectional view of the embankment structure (note that FIG. 1 (b) ), The symbol A represents the slope of the embankment structure).
The liquefaction countermeasure method according to the present invention will be described with reference to FIGS. 1 (a) and 1 (b).
The liquefaction countermeasure method of the present invention is suitably applied to an existing linear embankment structure for railways and roads. First, for such a embankment structure 1, the ground from the bottom of the method A shear deformation restraining wall 2 is continuously placed in G along the longitudinal direction of the embankment structure 1.
[0012]
As the shear deformation restraining wall 2, for example, a steel sheet pile type continuous underground wall formed by continuously engaging steel sheet piles such as sheet piles, and a steel pipe sheet pile are similarly engaged with each other and continuously driven. Steel pipe sheet pile type continuous underground wall, and continuous underground wall (SMW wall) formed by mixing and stirring soil and cementitious suspension. These shear deformation restraining walls 2 are appropriately changed according to the degree of allowable deformation of the ground G.
[0013]
Then, the head portions of the shear deformation restraining walls 2 and 2 facing each other with the embankment structure 1 interposed therebetween are connected by a tie rod 3.
Further, a plurality of beam portions 4,... Are provided along the depth direction of the shear deformation restraint wall 2 at predetermined intervals on the inside and outside of the shear deformation restraint wall 2, respectively. As the beam portion 4, for example, a steel underground beam can be used.
[0014]
Further, a plurality of drain pipes 5,... Are provided on the ground G from the slope of the embankment structure 1 so as to incline toward the approximate center of the embankment structure 1. The plurality of drain pipes 5,... Are arranged along the longitudinal direction of the embankment structure 1 so as to be staggered with respect to the embankment structure 1. At this time, the drain pipes 5,... Are located in the shallow part of the ground G, and the shear restraint deformation wall 2 is located further deeper than the drain pipes 5,.
The drain pipe 5 can be an existing pipe having a large water permeability, in which a large number of openings with filters that allow the water in the ground G to permeate and prevent intrusion of earth and sand are formed. For the filter, for example, a nonwoven fabric or the like is preferably used.
[0015]
As described above, according to the liquefaction countermeasure method of the embodiment of the present invention, the shear deformation restraining wall 2 is constructed from the butt portion of the embankment structure 1 toward the ground G, and the embankment is embedded in the ground G from the butt portion. Since the drain pipes 5 are provided so as to incline toward the substantial center of the structure 1, the shear deformation restraining wall 2 restrains the shear deformation of the ground G immediately below the slope of the embankment structure 1, and the shear deformation is prevented. The ground G that is liquefied by restraining is prevented from increasing the pore water pressure due to the drainage effect of the drain pipes 5.
Further, since the drain pipes 5,... Are provided so as to be inclined toward the center from the method bottom of the embankment structure 1, compared to the conventional case, the drain pipes 5,. It can be drained. Therefore, the local weakening of the ground G in the center of the embankment structure 1 can be prevented, and therefore the settlement of the embankment structure 1 during an earthquake can be more reliably prevented.
Moreover, it can enforce with a comparatively small machine and it becomes possible to apply also to the existing embankment structure 1 without site margin. Furthermore, even in the embankment structure 1 having a long distance requiring countermeasures against liquefaction, such as railways and roads, the shear deformation restraining wall 2 is connected to the above-mentioned steel sheet pile type continuous land according to the importance of the embankment structure 1. By appropriately changing to an intermediate wall, steel pipe sheet pile type continuous underground wall, SMW wall, etc., liquefaction measures can be taken at low cost.
Further, since a plurality of beam portions 4,... Are provided in the vicinity of the shear deformation restraining wall 2, the restraining effect of the shear deformation restraining wall 2 can be further increased by these beam portions 4,. Can be done.
[0016]
In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, it can change suitably.
For example, in order to increase the restraining effect of the shear deformation restraining wall 2, the number of beam portions 4,... May be increased, or the spacing between the beam portions 4 may be arranged more closely, and the arrangement method may be changed as appropriate. Is possible.
Further, the number of drain pipes 5 may be increased, or the intervals between the drain pipes 5 may be arranged more closely.
[0017]
【The invention's effect】
According to the first aspect of the present invention, the shear deformation restraining wall restrains the shear deformation of the ground immediately below the bottom of the embankment structure and restrains the shear deformation to increase the pore water pressure generated in the ground. It can be suppressed by the drainage effect. Moreover, compared with the past, it can drain equally over the wide area in the ground. Therefore, it is possible to prevent local softening of the ground below the center of the embankment structure, and more reliably prevent settlement of the embankment structure during an earthquake.
Moreover, it becomes possible to apply also to the existing embankment structure without site margin. Furthermore, liquefaction measures can be taken at low cost according to the importance of the embankment structure.
[0018]
According to the invention of claim 2, the effect similar to that of claim 1 can be obtained, and the restraining effect of the shear deformation restraining wall can be further increased by the beam portion. Easy to do.
[Brief description of the drawings]
FIG. 1A is a front sectional view of a banking structure subjected to a liquefaction countermeasure method according to the present invention, and FIG. 1B is a top sectional view of the banking structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Embankment structure 2 Shear deformation restraint wall 4 Beam part 5 Drain pipe G Ground

Claims (2)

A liquefaction countermeasure method for embankment structures for railways and roads,
Install a shear deformation restraint wall from the bottom of the embankment structure toward the ground,
A liquefaction countermeasure construction method characterized in that a drain pipe is provided in the ground from the bottom of the embankment structure so as to incline toward the approximate center of the embankment structure. The liquefaction countermeasure method according to claim 1, wherein a plurality of beam portions are provided in the vicinity of the shear deformation restraining wall along the depth direction of the shear deformation restraining wall.

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