JPH05106216A - Counterplan construction for liquifaction for filling - Google Patents

Abstract

PURPOSE:To prevent filling from being transformed, with ground constraining effect, by avoiding excessive void-water-pressure to be generated in liquified soil at the time of earthquake without interrupting underground water flowing under the filling, in the case of setting the filling on the liquified soil. CONSTITUTION:In place of a normal sheathing sheet pile in a wall construction type, a liquifaction suppressing sheet pile 3a with drain function is set near the toe of the slope of filling 1. The head sections of the respective liquifaction suppressing sheet piles 3a are connected to each other with coping concrete 6, and both sides with the filling 1 placed between them are connected to each other with a tie rod 7. Besides, at the drain positions of the upper sections of the liquifaction suppressing sheet piles 3a, crushed stone mats 8 are arranged by backfilling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquefaction prevention structure for embankment using a liquefaction prevention pile or a liquefaction prevention sheet pile having a drainage function.

[0002]

2. Description of the Related Art As a liquefaction countermeasure structure which has been conventionally studied, a wall structure method and a discrete pile arrangement are applied to an embankment structure on a ground where liquefaction may occur (hereinafter, simply referred to as liquefaction ground). Method, compaction method, drainage method. These features are described below.

(1) Wall structure method As shown in FIG. 11, the wall structure method uses a tie rod 20 by forming a wall structure made of steel sheet piles 21 or steel pipe sheet piles (not shown) on both sides of the embankment 1. The heads of the wall structure are connected at a predetermined pitch. In soft ground that does not liquefy, deformation of the embankment 1 (general term for subsidence, slope slippage, and lateral flow of the ground under the embankment) during earthquakes can be prevented, and rapid construction is possible.

In the application to the embankment on the liquefied ground,
When the width of the embankment cross section is narrow, even if the ground around the embankment 1 is liquefied, the ground restraint effect due to the strength and rigidity of this method is exerted, and the excessive pore water pressure below the embankment 1 is exerted. It is possible to suppress the rise and the decrease in the strength of the ground, and to suppress the deformation of the embankment 1.

(2) Pile Discrete Arrangement Method As shown in FIG. 12, the pile pile arrangement method is to lay piles 22 on both sides of the embankment 1 in a staggered manner with a center interval 2D (D: pile diameter). ..

In this method, the heads of the piles 22 extending in the extension direction of the embankment 1 are connected to each other by a cap concrete or concrete foundation 6 made of reinforced concrete, and the tie rods 20 are used to connect the piles 22 on both sides of the embankment 1 at a predetermined pitch. is doing.

This method also has the same advantages as the sheet pile wall structure method in soft ground that does not liquefy, and since the piles 22 are arranged in a discrete manner, the flow of groundwater is not interrupted.

(3) Ground Compaction Method As shown in FIG. 13, the ground compaction method is a method of compacting both sides of the embankment 1 on the liquefied ground 4 (sand compaction pile method, etc.). Depending on the size of the cross section, as shown in FIG. 14, there is also a method of using the pressing embankment 24 together. In the figure, 13 indicates a ground compacting work such as a sand pile.

This method suppresses the rise of excess pore water pressure in the compacted ground by the compaction effect and suppresses the deformation of the embankment by the ground constraining effect even under the seismic force such that the surrounding ground is liquefied. You can Moreover, in this method, since the sand material is used and the liquefied ground 4 itself is compacted, the flow of groundwater under the embankment 1 is not interrupted.

(4) Drainage system As shown in FIG. 15, the drainage system is provided on both sides of the embankment 1 for the purpose of suppressing an increase in excess pore water pressure in the liquefied ground 4 during an earthquake when crushed stone drain or resin is used. Drainage materials such as drains 2
5 is provided in a columnar shape.

In this method, when the embankment width and height are small,
Even if the surrounding ground of the embankment 1 is liquefied, the drainage effect of the drainage material 25 suppresses an increase in excess pore water pressure of the surrounding ground,
It is possible to suppress the sand flow and to suppress the deterioration of the ground strength and the deformation of the embankment 1. Moreover, this method does not interrupt the flow of groundwater.

[0012]

The liquefaction countermeasure structure of the embankment structure on the liquefaction ground described above has the following problems.

(1) Wall structure method As the embankment cross-section width (particularly the slope) widens, the ground restraint effect due to the strength and rigidity of the wall structures provided on both sides of the embankment decreases and the wall structure is surrounded by the wall structure. Even in the ground, excess pore water pressure rises, the wall becomes streamlined, and sand is seen along the wall, resulting in large deformation of the embankment.

Since the water pressure (1-K ₀ ) Δu [K ₀ : initial earth pressure coefficient, Δu: excess pore water pressure] acting on the wall structure when the excess pore water pressure rises also increases, the excess pore water pressure rises. Compared with the case where it is not done, it is necessary to further increase the strength and rigidity of the wall structure, which is uneconomical.

Furthermore, since the wall structure blocks the flow of groundwater, the groundwater environment changes.

(2) Discrete pile arrangement method During an earthquake, the ground strength is reduced due to an increase in excess pore water pressure in the ground on the bottom of the bottom of the embankment method, and the sand breaks out between the piles, causing deformation of the embankment. This method is not suitable for embankments on liquefied ground.

(3) Ground compaction method When this method is applied to an existing embankment, regardless of the cross-sectional width of the embankment, the soil must be formed outside the bottom of the embankment method and the soil must be compacted on both sides of the embankment. The width between the ground becomes wider and the same tendency as the wall structure is seen. For this reason, it becomes necessary to use it together with the press embankment (Fig. 14), which is uneconomical.

In addition, regardless of whether the embankment is new or existing, excess shear water pressure generated in the liquefied ground is transmitted to the compaction ground, so that the shear strength of the compaction ground near the boundary surface is reduced. Since the extent of the decrease is unknown, it is necessary to allow some room for the compaction width. As a result, the economy is impaired and the construction period is extended.

(4) Drainage system In this system, the region where the drainage effect is expected at the time of an earthquake is about 1 m from the drainage position, and therefore the suppression region of ground strength reduction due to the suppression of excess pore water pressure is not so wide as about 1 m. In addition, since the drainage material itself uses crushed stone drain, resin drain, etc., the shear strength is smaller than when steel drainage material is applied. Therefore, the construction width is wider than that in the case where the steel drainage material is applied, and as a result, the economical efficiency is impaired and the construction period is extended.

The present invention is intended to solve the above-mentioned problems in the prior art. That is, when a large-scale embankment is installed on the liquefied ground, the groundwater flowing under the embankment is not blocked, and the excessive pore water pressure generated around the embankment and inside the ground under the earthquake is dissipated to restrain the ground. The purpose is to prevent the deformation of the embankment in combination with the effect and to improve the workability and economic efficiency of the liquefaction countermeasure structure.

[0021]

The outline of the present invention will be described below with reference to the reference numerals in the drawings corresponding to the embodiments.

The liquefaction countermeasure structure of the embankment according to the present invention is a liquefaction prevention pile 2 or a wall-shaped liquefaction prevention pile 2 arranged in rows near the slope or slope of the embankment, which has both water permeability and drainage. By installing the deterrent sheet pile 3, the flow of groundwater in the liquefied ground 4 and the non-liquefied ground 5 under the embankment 1 is not blocked, and the excess pore water pressure in the liquefied ground 4 that occurs during an earthquake rises. It suppresses sand blast along the liquefaction prevention pile 2 and the liquefaction prevention sheet pile 3 and prevents deformation of the embankment due to its strength and rigidity.

Therefore, in the present invention, as the pile constituting the liquefaction prevention pile 2, for example, a liquefaction prevention pile having a perforated portion in which a large number of small holes 11 are formed in a portion located in the liquefaction ground 4 of the pile body. 2a, or a liquefaction prevention pile 2b having a longitudinal hollow portion and a drainage member 13 having a large number of small holes 11 formed in a portion located in the liquefaction ground 4 is used.

In the case of the liquefaction-preventing sheet pile 3, for at least a part of the sheet piles constituting the wall-shaped structure, for example, a liquefaction-preventing sheet pile 3a in the form of a steel pipe sheet pile formed by perforating the entire sheet pile main body, or A plate-shaped liquefaction prevention sheet pile 3b having a drainage member 13 similar to the liquefaction prevention pile 2b is used.

In addition, liquefaction prevention piles 2a or 2 during an earthquake
b. As a measure for draining underground water flowing into the liquefaction prevention sheet piles 3a or 3b, a crushed stone mat in the embankment extension direction from the periphery of the liquefaction prevention pile or the head of the liquefaction prevention sheet pile to a position higher than the groundwater level 8, or a crushed stone mat 8 and a blind underdrain 9 may be provided.

[0026]

[Function] This structure is designed to properly install liquefaction prevention piles or liquefaction prevention sheet piles with high strength and rigidity up to the non-liquefaction ground below the liquefaction ground in the most liquified area of the embankment, so It is possible to suppress an increase in excess pore water pressure around the liquefaction-preventing pile or the liquefaction-preventing sheet pile to prevent the ground strength from lowering, and to suppress the deformation of the embankment due to the ground restraining effect as the pile or the sheet pile.

Furthermore, the drainage function of the liquefaction prevention pile or the liquefaction prevention sheet pile prevents the formation of streamlines on the same surface and prevents sand blow.

In this structure, the liquefaction-preventing piles that are discretely arranged or the liquefaction-preventing sheet piles that are arranged like walls are made to have water permeability so that the groundwater environment can be controlled without interrupting the flow of underground water. maintain.

[0029]

EXAMPLES Next, the illustrated examples will be described.

FIG. 1 shows an embodiment in which a liquefaction prevention pile 3a having a drainage function and water permeability is used as a countermeasure against liquefaction of the embankment.

That is, in place of the ordinary retaining sheet pile in the wall structure system, a liquefaction inhibiting sheet pile 3a (see FIG. 4) provided with a large number of openings and filters in a predetermined section of a steel pipe sheet pile is used. Liquefaction-preventing sheet piles 3a in the embankment extension direction are connected by head concrete or concrete foundation 6 at the head of 3a, and tie rods 7 connect liquefaction-prevention sheet piles 3a in the direction perpendicular to the embankment extension. A crushed stone mat 8 is provided by backfilling at the drainage position above the liquefaction prevention sheet pile 3a.

In this embodiment, due to the drainage effect of the liquefaction prevention sheet pile 3a, an increase in excess pore water pressure generated in the liquefaction ground sheet 4 during an earthquake is suppressed near the liquefaction prevention sheet pile 3a, and It is possible to prevent the strength from decreasing. Further, by inserting the liquefaction-preventing sheet pile 3a having strength and rigidity as a sheet pile up to the non-liquefying soil 5 below the liquefying soil 4, a ground restraining effect can be exhibited and deformation of the soil can be suppressed. ..

In the design of the self-supporting sheet pile, when the embankment 1 can be stabilized only by the liquefaction-preventing sheet pile 3a, the tie rod 7 and the like can be omitted.

Instead of the liquefaction-preventing sheet pile 3a, as shown in FIG.
A plate-like liquefaction prevention sheet pile 3b as shown in FIG. 6 or liquefaction prevention piles 2a, 2b as shown in FIGS. 2 and 3 may be used. In the case of the liquefaction prevention piles 2a and 2b, by placing them at an appropriate pile pitch, the sand between the liquefaction prevention piles forms a kind of wall structure, and the same effect as the liquefaction prevention pile 3a. Indicates.

2 and 3 show examples of the liquefaction-preventing pile used in the present invention, and FIGS. 4, 5 and 6 show examples of the liquefaction-preventing sheet pile used in the present invention.

The liquefaction prevention pile 2a in FIG. 2 has a large number of openings 11 formed over a predetermined section of the steel pipe, that is, the thickness of the liquefaction ground, and a filter 12 for preventing the inflow of earth and sand into the openings 11. Is provided and the inside of the steel pipe is used as a drainage space (see Japanese Patent Laid-Open No. 61-146910).

The liquefaction prevention pile 2b of FIG. 3 is provided with a drainage member 13 at a predetermined section in the longitudinal direction of the outer surface of the steel pipe, and a large number of openings 11 in the drainage member 13 and intrusion of soil from the ground through the openings 11. A filter 12 for preventing the above is provided.

The liquefaction-preventing sheet pile 3a in FIG. 4 is a male / female joint 1
A large number of openings 1 in a predetermined section of a steel pipe sheet pile having 4 and 15
1 is formed, and a filter 12 for preventing the intrusion of earth and sand is provided in the opening 11 so that the inside of the steel pipe serves as a drainage space (see JP-A-1-226920, etc.).

The liquefaction-preventing sheet pile 3b shown in FIGS. 5 and 6 is a sheet-like sheet pile having joints 16 at both ends, and a drainage member 13 provided at a predetermined section along the longitudinal direction. A large number of openings 11 and openings 1 on the anti-oxidation sheet pile 3b.
Filter 1 to prevent infiltration of soil from the ground 1
2 is provided (see Japanese Patent Application Laid-Open No. 1-125413, etc.).

The above are examples of the liquefaction prevention pile and the liquefaction prevention sheet pile, respectively. As the liquefaction prevention pile and the liquefaction prevention sheet pile used in the present invention, the function of the pile or the sheet pile and the function of the pile sheet pile at the time of earthquake are used. Any form may be used as long as it has a drainage function for dissipating excess pore water pressure generated in the ground.

7 to 10 show examples of installation of the crushed stone mat 8 for drainage used in the present invention.

The crushed stone mat 8 for drainage is continuously constructed along the embankment extension direction from the periphery of the head of the liquefaction prevention pile 2 or the liquefaction prevention sheet pile to a position higher than the groundwater level.

The crushed stone mat 8 may be provided with a blind underdrain 9 or the like for further smoothing the drainage. FIG. 10 shows a case where the blind underdrain 9 is provided on both sides of the liquefaction prevention pile 2 as shown in FIG. FIG. 9 shows a case where it is provided on one side. Blind culvert 9
Is a vinyl chloride pipe, a reinforced concrete pipe, a ceramic pipe, or the like as long as it can ensure the water permeability when the underground water is drained.

Although the crushed stone mat 8 is usually connected to a general drainage channel, the drainage channel is not provided and underground water is stored in the crushed stone mat 8 and the stored underground water is discharged to the ground after an earthquake. There is also a method of draining by infiltration.

[0045]

EFFECTS OF THE INVENTION The liquefaction countermeasure structure of the embankment of the present invention is a liquefaction having drainage and water permeability near the embankment slope or the bottom of the embankment that is most likely to be liquefied during an earthquake and has strength and rigidity as a pile or sheet pile. Suppression piles or liquefaction prevention sheet piles are properly installed inside the non-liquefied ground below the liquefied ground. As a result, the following effects are obtained.

By securing a drainage route for underground water that occurs during an earthquake, it is possible to suppress an increase in excess pore water pressure and prevent a decrease in ground strength.

By sufficiently embedding a liquefaction-preventing pile or a liquefaction-preventing sheet pile having strength and rigidity into the liquefaction ground, a ground restraining effect is exhibited.

Due to the drainage function of the liquefaction prevention pile or the liquefaction prevention sheet pile, it is possible to prevent the formation of streamlines on the surface and prevent sand from blowing.

By, it is possible to suppress the deformation of the embankment.

Due to the water permeability of the liquefaction prevention pile or the liquefaction prevention sheet pile, it is possible to maintain the groundwater environment without blocking the flow of underground water.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a liquefaction countermeasure structure for embankment of the present invention.

FIG. 2 is a perspective view showing an example of a liquefaction prevention pile used in the present invention.

FIG. 3 is a perspective view showing another example of a liquefaction prevention pile used in the present invention.

FIG. 4 is a perspective view showing an example of a liquefaction-preventing sheet pile used in the present invention.

FIG. 5 is a perspective view showing another example of a liquefaction suppressing sheet pile used in the present invention.

FIG. 6 is a perspective view showing the back side of the liquefaction suppressing sheet pile of FIG.

FIG. 7 is a vertical cross-sectional view showing an example of a crushed stone mat portion provided on the upper part of the liquefaction prevention pile.

FIG. 8 is a vertical cross-sectional view showing another example of the crushed stone mat portion provided on the upper part of the liquefaction prevention pile.

FIG. 9 is a vertical cross-sectional view showing another example of the crushed stone mat portion provided on the upper part of the liquefaction prevention pile.

FIG. 10 is a vertical cross-sectional view showing another example of the crushed stone mat portion provided on the upper portion of the liquefaction prevention pile.

FIG. 11 shows an example of a conventional wall structure method,
(a) is a horizontal sectional view and (b) is a vertical sectional view.

FIG. 12 shows an example of a conventional pile discrete arrangement method, in which (a) is a horizontal sectional view and (b) is a vertical sectional view.

FIG. 13 is a vertical sectional view showing an example of a conventional ground compaction method.

FIG. 14 is a vertical sectional view showing another example of a conventional ground compaction system.

FIG. 15 is a vertical sectional view showing an example of a conventional drainage system.

[Explanation of symbols]

1 ... Embankment, 2 ... Liquefaction prevention pile, 3 ... Liquefaction prevention sheet pile, 4
... liquefied ground, 5 ... non-liquefied ground, 6 ... hat concrete or concrete foundation, 7 ... tie rod, 8 ... crushed stone mat, 9 ... blind culvert, 11 ... opening, 12 ... filter,
13 ... Drainage member, 14 ... Male joint, 15 ... Female joint, 16
… Fittings

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Saimura 1-3-3 Otemachi, Chiyoda-ku, Tokyo Sumitomo Metal Industries, Ltd.

Claims (4)

[Claims] 1. A liquefaction-preventing sheet pile provided with a drainage function for suppressing an increase in excess pore water pressure that occurs around the embankment and in the ground on the lower surface during an earthquake is liquefied near the embankment slope or slope bottom. Liquefaction countermeasure structure for the embankment, which is characterized in that it is provided with the required length added to the layer thickness of the ground. 2. The liquefaction-preventing sheet pile has an opening for allowing underground water to pass through in a direction perpendicular to the continuous direction of the liquefaction-preventing sheet pile, and a filter for preventing permeation of sand from the opening. The liquefaction countermeasure structure for the embankment according to claim 1, wherein the structure is provided. 3. The liquefaction countermeasure structure for an embankment according to claim 1, wherein a crushed stone mat is provided continuously from the upper drainage position of the liquefaction suppressing sheet pile to a position higher than the groundwater level. 4. A liquefaction prevention pile provided with a drainage function for suppressing an increase in excess pore water pressure generated around the embankment and in the ground on the lower surface in the event of an earthquake, instead of the liquefaction prevention sheet pile, The liquefaction countermeasure structure for the embankment according to claim 1, 2 or 3, wherein the liquefaction countermeasure structure is discretely arranged in the vicinity of the slope in a length obtained by adding a required length to the layer thickness of the liquefied ground.