JP2007321482A - Liquefaction prevention method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquefaction preventive construction method capable of preventing the situation of dropping the ground in the sea or the water, by preventing liquefaction of the ground in a vicinal area of a quay. <P>SOLUTION: This liquefaction preventive construction method comprises a plurality of first improved bodies 2 extending in the direction orthogonal to the quay 1, and a second improved body 3 for connecting the mutual adjacent first improved bodies 2. A water permeable member 9 is vertically arranged in an area 8 surrounded by the first improved bodies 2 and the second improved body 3 (a well Wi). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for preventing liquefaction of the ground in a quay such as a coast or a river shore or in the vicinity thereof.

FIG. 7 shows a cross section of the ground in the quay of the shore (or river shore, etc.) and in the vicinity thereof.
In FIG. 7, if the quay 1 is not supported in the horizontal direction by a tie rod or the like (not shown), the ground in the region above the natural slip line SLN in the quay 1 and the vicinity thereof (the ground in the region indicated by symbol α in FIG. 7). However, as indicated by the arrow S, there is a risk of falling (collapse) to the sea 10 or the river side (the sea side in FIG. 7).
Further, when the ground G in the quay 1 portion is liquefied, the ground G in the region above the slip line SLL of the liquefied ground G in FIG. 7 falls to the sea 10 side.

If the ground G in the region α or the ground G in the region above the sliding line SLL falls to the sea 10 side, there is a concern about a great adverse effect on the ship 20 anchored to the quay 1 and a large amount of earth and sand is generated. Since it flows out into the sea 10 or underwater, it must be dredged.
In particular, if the ground G in the region above the sliding line SLL of the liquefied ground G falls to the sea 10 side, a larger amount than the ground G in the region α above the natural sliding line SLN falls. Since the earth and sand fall, the damage to the ship 20 is great, and the labor for dredging work becomes large.

As another conventional technique, for example, there is a technique for preventing liquefaction of sandy ground by forming a ground improvement body in a lattice shape and limiting the ratio between the width dimension and the height direction dimension of the lattice. (See Patent Document 1)
However, the conventional technique limits the dimensional ratio of the width and height of the lattice to keep the maximum excess pore water pressure ratio within a desired range, and prevents liquefaction at the quay or the vicinity thereof as described above. Is not directly involved.
Japanese Patent No. 2568115

  The present invention has been proposed in view of the above-mentioned problems of the prior art, and prevents liquefaction of the ground in the quay and its nearby region, thereby preventing the ground from falling into the sea or water. The purpose is to provide a liquefaction prevention method that can be used.

In the liquefaction prevention method of the present invention, a plurality of parallel-walled first improved bodies (2) extending in a direction perpendicular to the quay (1: sea, river, lake, other quay) are created in parallel. The first improvement body (2) is formed below the liquefaction depth (or below the sliding line SLN or SLL), and connects the adjacent first improvement bodies (2) to each other. The second improvement body (3) is formed in a region near the end of the first improvement body (2) on the side remote from the quay (1) and the first improvement body (3) is formed. A member (9: drain material) extending in a direction orthogonal to the improved body (2) and having water permeability in the region (8) surrounded by the first improved body (2) and the second improved body (3) , Water drain pipes, sand columns, etc.) are arranged in the vertical direction (providing the well Wi) (Claim 1: FIGS. 1, 4, and 5).
Here, SLN represents a natural slip line, and SLL represents a liquefied ground slip line.

  In the present invention, a member (9: drain material, drain pipe, sand column, etc.) having water permeability in the region (8) surrounded by the first improvement body (2) and the second improvement body (3). It is preferable to arrange and communicate the water-permeable member (9) to the area outside the quay (1) (the sea 10, rivers, lakes, etc.) (FIGS. 1, 4, and 5).

  In the present invention, a third improvement body (4) is formed in a region near the end of the first improvement body (2) on the quay (1) side, and the third improvement body (4) The first improvement bodies (2) extending in the direction orthogonal to the improvement body (2) and adjacent to each other are preferably connected in a region near the end on the quay (1) side (Claim 2: FIG. 1). ).

Alternatively, in the present invention, the third improvement body (5, 6, 7) is formed in the region near the end of the first improvement body (2) on the quay (1) side, and the third improvement body (5 , 6, 7) may not be connected to the first improvement body (2) (Claim 3: FIG. 4, FIG. 5, FIG. 6).
In this case, you may comprise the 3rd improvement body (5) in the shape of the continuous wall extended in the direction orthogonal to the 1st improvement body (2) (refer FIG. 4).
Or you may comprise a 3rd improvement body (6) in pile shape (refer FIG. 5).

  Here, the said 3rd improvement body (7) is inclined and arrange | positioned with respect to the direction orthogonal to a 1st improvement body (2), and is near the quay (1) of a 3rd improvement body (7). The side end is preferably close to the first improvement (2) (Claim 4: FIG. 5).

According to the present invention having the above-described configuration, a member (9: drain material, water) having water permeability in the region (8) surrounded by the first improvement body (2) and the second improvement body (3). Since the pipe (sand pipe, etc.) is arranged in the vertical direction and the water-permeable member (9) communicates with the ground side to form a well (Wi), the water-permeable member (9 ) Or the well (Wi) constitutes an escape route for excess pore water pressure in the region (8), so that even if an earthquake or the like occurs, the excess pore water pressure in the region (8) is released to the ground side.
Therefore, the excess pore water pressure does not increase. And since excess pore water pressure does not rise, the liquefaction of the said area | region (8) is prevented.

Further, in the present invention, a member having water permeability in the region (8) surrounded by the first improved body (2) and the second improved body (3) (9: drain material, drain pipe, sand column, etc.) Are arranged in a horizontal direction, and the member (9) having water permeability is communicated with a region outside the quay (1) (10: sea, river, lake, etc.), and the member (9) having water permeability is If an escape path for excess pore water pressure in the region (8) is configured, even if an earthquake or the like occurs, the excess pore water pressure in the region (8) is transferred to the outside of the quay (1) via the water-permeable member (9). (10: sea, rivers, lakes, etc.)
Therefore, an increase in excess pore water pressure is reliably prevented, and liquefaction of the region (8) is prevented (because the excess pore water pressure does not increase).

  According to the present invention, the first improved body (2) is formed below the liquefaction depth (or down below the slip line SLN or SLL), so the vicinity of the first improved body (2). Even if the ground is liquefied, the surrounding ground is supported by the frictional force in the shear direction between the non-liquefied ground (the ground below the liquefaction depth) and the first improvement body (2). I can do it.

Moreover, since the adjacent 1st improvement body (2) is connected by the 2nd improvement body (3), the ground of the area | region where liquefaction prevention is not performed liquefies, earth pressure and water pressure Even if it acts on the first improvement body (2), the relative positional relationship between the adjacent first improvement bodies (2) does not change, and it becomes more easily affected by earth pressure and water pressure ( (See FIG. 3).
In addition, although the earth pressure and water pressure when the ground of the area | region where liquefaction prevention is not given are liquefied act on the 2nd improvement body (3), the 2nd improvement body (3) is the 1st improvement body. It is connected to the improvement body (2), and the first improvement body (2) is adjusted to the earth pressure and the water pressure by the frictional force in the shear direction with the ground that is not liquefied (the ground below the liquefaction depth). Can resist.

  Furthermore, according to the present invention, the third improvement body (4, 5, 6, 7) is formed in the region near the end of the first improvement body (2) on the quay (1) side. The ground in the region (8) surrounded by the improvement body (1), the second improvement body (3), and the third improvement body (4, 5, 6, 7) is a natural slip line (SLN: If you try to move to the area outside the quay (1) (10: sea, rivers, lakes, etc.) along the quay (1) (see Fig. 6 and Fig. 2), Blocked by the improvements (4, 5, 6, 7).

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, a first embodiment will be described with reference to FIGS.
Here, in the illustrated embodiment, the liquefaction prevention method is applied to a region near the quay on the coast. However, the berth includes not only the coast but also the river and lake shore.

Here, FIG. 1 has shown the state which looked at the construction site of 1st Embodiment from upper direction, and FIG. 2 has shown the XX cross section of FIG.
FIG. 3 shows a situation in which the possibility of realization is very small when the adjacent first improvement body is not connected by the second improvement body.

In FIG. 1, a plurality of first improvement bodies 2 extending in a direction perpendicular to the quay 1 (the direction of arrow H in FIG. 1) are formed.
The vicinity of both ends in the longitudinal direction (arrow H direction) in the first improved body 2 is connected to the adjacent improved body 2 by a plurality of second improved bodies 3 and a plurality of third improved bodies 4. The 2nd improvement body 3 and the 3rd improvement body 4 are extended in the direction (arrow S direction in FIG. 1) parallel to the quay 1.

The second improved body 3 is connected to the first improved body 2 in the vicinity of the end of the first improved body 2 on the side away from the quay 1. On the other hand, the third improved body 4 is connected to the first improved body 2 in the vicinity of the end portion of the first improved body 2 on the side close to the quay 1.
Here, the second improved body and the third improved body 4 can have the same structure.

As shown in FIG. 2, the first improved body 2 is formed in the ground G to the lower side of the slip line (slid line of the liquefied ground) SLL or the slide line (natural slip line) SLN. Yes. In other words, the 1st improvement body 2 is created below the liquefaction depth.
Since it is constructed below the liquefaction depth, even if the surrounding ground is liquefied, the first improvement body 2 is able to remove the surrounding ground G by the frictional force in the shearing direction with the ground G that is not liquefied. I can support it.

Returning to FIG. 1, as described above, the adjacent first improved bodies 2 are connected by the second improved body 3 and the third improved body 4 in the vicinity of both ends in the arrow H direction.
Here, when the adjacent first improvement bodies 2 are not connected to each other by the second improvement body 3 and the third improvement body 4, the possibility of occurrence of a situation as shown in FIG. Exists.

That is, when the ground G in the region where the liquefaction prevention method is not applied is liquefied and the earth pressure and water pressure in the ground G act as indicated by the arrow P, as shown in FIG. There is a possibility that the improved body 2 moves as shown by the arrow W in FIG. 3 and moves to the position shown by the reference numeral 2w.
And if the 1st improvement body 2 moves to the position shown by the code | symbol 2w in FIG. 3, it will become further susceptible to the influence of the earth pressure shown by the arrow P, and a water pressure.

On the other hand, if the first improvement bodies 2 are connected to each other by at least the second improvement body 3 (may be connected by the third improvement body 4), the position indicated by reference numeral 2w in FIG. It is prevented that the 1st improvement body 2 moves.
In addition, since the several 2nd improvement body 3 and the 3rd improvement body 4 should just connect adjacent 1st improvement body 2 mutually, unlike the 1st improvement body 2, rather than liquefaction depth. It does not have to be built down.

A region 8 surrounded by the first improvement body 2, the second improvement body 3, and the third improvement body 4 includes a water-permeable member (drain material, drain pipe, sand column, etc .: First embodiment. Then, a drain pipe) 9 is arranged in the horizontal direction, and the member (drain pipe) 9 having water permeability is connected to a drain port 9a on the sea 10 side.
In the region 8, the drain pipe 9 is arranged in the vertical direction to form the well Wi.

The drain pipe extending in the vertical direction, that is, the well Wi constitutes an escape path for allowing excess pore water pressure in the region 8 to escape to the ground side. At the same time, the drain pipe 9 extending in the horizontal direction is buried in order to serve as an escape route for allowing excess pore water pressure in the region 8 to escape to the sea 10 side.
As a result, even if a large earthquake occurs, excess pore water pressure in the region 8 surrounded by the first improvement body 2, the second improvement body 3, and the third improvement body 4 is perpendicular to the well Wi. The air is released to the ground side, and is also released to the sea 10 side via a drain pipe 9 extending in the horizontal direction. Therefore, the excess pore water pressure in the region 8 does not increase, and the ground G does not liquefy.
That is, the drain pipe (well Wi) that extends in the vertical direction and the drain pipe 9 that extends in the horizontal direction disposed in the region 8 cause excess pore water pressure in the ground G in the region 8 to be on the ground side or the sea 10 side. Therefore, the excess pore water pressure is prevented from rising and the ground G is liquefied.

  Here, although the ground G does not liquefy in the region 8, the soil G in the region 8 moves to the sea 20 side (left side in FIG. 1) along the natural slip line SLN (see FIGS. 7 and 2). There is a fear of doing. However, the third improved body 4 prevents the soil G in the region 8 from moving to the sea 10 side.

  In the first embodiment shown in FIGS. 1 to 3, the ground G in the region where liquefaction prevention is not performed (the region on the right side of the first improvement body 2 and the second improvement body 3 in FIG. 1) is liquid. Even if the earth pressure and the water pressure act as shown by the arrow P, the earth pressure and the water pressure P are supported by the plurality of first improvement bodies 2 and the second improvement body 3 connected thereto. That is, the earth pressure and the water pressure P in the liquefied ground are supported by the shear friction between the region in the ground G that is not liquefied and the lower part of the first improved body 2.

In the region 8, the excess pore water pressure in the ground G in the region 8 is released to the ground side via the drain pipe or well Wi extending in the vertical direction, and the drain pipe 9 extending in the horizontal direction is used. Since the excess pore water pressure is released to the sea 10 side, the excess pore water pressure does not increase in the ground G in the region 8, and the ground G does not liquefy.
Further, even if the ground G in the region 8 tries to move to the sea 10 side (left side in FIG. 1) along the natural slip line SLN, the third improved body 4 prevents the ground G from moving.

  As a result, when a large earthquake occurs, the ground G in the area where the first improved body 2, the second improved body 3, and the third improved body 4 are formed may flow into the sea 10. Is prevented.

Next, the liquefaction prevention method according to the second embodiment will be described with reference to FIG.
In the first embodiment of FIGS. 1 to 3, the first improvement body 2 is prevented from moving to the position indicated by reference numeral 2 w in FIG. 3 in order to prevent the sea 10 in the first improvement body 2. Only the vicinity of the end portion on the side far from the right side (right side in FIGS. 1, 3, and 4) is connected by the second improved body 3.

  However, for the third improvement body 4 formed near the end of the first improvement body 2 on the sea 10 side (left side in FIGS. 1, 3, and 4), the ground G in the region 8 is natural. This is to prevent movement along the slip line SLN toward the sea 10 (left side in FIGS. 1 and 4). Therefore, the vicinity of the end of the first improved body 2 on the sea 10 side is not necessarily connected by the improved body.

In the second embodiment shown in FIG. 4, a third improved body formed in a continuous wall shape in the vicinity of the end of the first improved body 2 on the sea 10 side (left side in FIGS. 1, 3, and 4). 5 is not connected to the first improvement body 2.
The third improvement body 5 is such that the ground of the region 8 surrounded by the first improvement body 2 and the second improvement body 3 is indicated by an arrow Y along a natural slip line SLN (see FIG. 2). In order to prevent movement to the sea 10 side, it is constructed in the vicinity of the quay 1.

In FIG. 4, the third improvement body 5 formed in a continuous wall shape is not connected to the first improvement body 2, but in the event of an earthquake, the ground G in the region 8 extends along the natural slip line SLN. It has sufficient strength to prevent movement to the sea 10 side (left side in FIGS. 1 and 4).
As described above with reference to FIG. 1, the region 8 is configured such that the excess pore water pressure is released to the ground side by the well Wi, and the excess pore water pressure is released to the sea 10 side by the drain pipe 9. Therefore, the ground G in the region 8 is not liquefied.
In FIG. 4, the first improved body 2 is connected to the quay 1, but may be separated from the quay 1 to the right side in FIG. 4.

Further, in FIG. 4, the first improved body 2 extends rightward in FIG. 4 and is connected by a second improved body indicated by reference numeral 31, so that the improved bodies 2, 3 (31) are arranged in a lattice shape. It has been created.
In a region 81 surrounded by the second improved bodies 3 and 31 and the first improved body 2, the drain pipe 90 extends in a direction perpendicular to the drain pipe 9, and the well Wo is Is provided.

In the region 8, as described above, the excess pore water pressure is released to the ground side by the well Wi, and the excess pore water pressure is released to the sea 10 side by the drain pipe 9.
On the other hand, in the region 81, the excess pore water pressure is released to the ground side by the well Wo, and the excess pore water pressure (arrow Po1) is released to the ground adjacent to the region 81 by the drain pipe 90. As in the case of, the excessive pore water pressure does not increase in the region 81, and the liquefaction of the ground is prevented.

  Other configurations and operational effects in the second embodiment shown in FIG. 4 are the same as those in the first embodiment described with reference to FIGS.

FIG. 5 shows a modification of the second embodiment of FIG.
In the second embodiment of FIG. 4, the third improvement body 5 that is not connected to the first improvement body 2 is formed in a continuous wall shape, whereas in the modification of FIG. Instead of the improved body 5, two pile-shaped third improved bodies 6 and 6 are formed.

Even in the case where two pile-shaped third improved bodies 6 and 6 are constructed, the ground G in the region 8 is along the natural slip line SLN in the event of an earthquake, and is on the sea 10 side (left side in FIGS. 1 and 4). It has sufficient strength to prevent movement.
Other configurations and operational effects of the modification of FIG. 5 are the same as those of the second embodiment of FIG.

Next, with reference to FIG. 6, the liquefaction prevention construction method of 3rd Embodiment is demonstrated.
In the third embodiment of FIG. 6, as in the second embodiment of FIG. 4 and the modification of FIG. 5 (of the second embodiment), the first improvement body 2 on the sea 10 side (left side in FIG. 5). The third improvement body 7 in the vicinity of the end portion does not connect the vicinity of the end portion of the first improvement body 2.
Also in the third embodiment of FIG. 6, the third improved body 7 is the same as the first improved body 2 and the second improved body in the same manner as the second embodiment of FIG. 4 and its modification (FIG. 5). The ground G in the region 8 surrounded by the body 3 is formed to prevent the ground G from moving to the sea side as indicated by the arrow Y along the natural slip line SLN.

In addition to this, the third improved body 7 shown in FIG. 6 is formed as a pair of two, and they are not formed on the same line, but are arranged in a generally “C” shape. It is configured so that the one away from the sea 10 narrows.
Therefore, the third improved body 7 shown in FIG. 6 has an ocean 10 as shown by an arrow Y in the ground G that is not liquefied, as compared with the second embodiment of FIG. 4 and its modified example (FIG. 5). Good properties to prevent movement to the side.

  Other configurations and operational effects of the third embodiment shown in FIG. 6 are the same as those of the embodiments of FIGS.

The illustrated embodiment is merely an example, and does not limit the technical scope of the present invention.
For example, the third improved body 5 in the second embodiment in FIG. 4 and the third improved body 6 in the modification of the second embodiment in FIG. 5 can be combined and applied.

The top view explaining the liquefaction prevention construction method of a 1st embodiment of the present invention. XX sectional drawing of FIG. The top view explaining the state which may arise when a 1st improvement body is not connected with a 2nd improvement body. The top view explaining the liquefaction prevention construction method of 2nd Embodiment of this invention. The top view explaining the modification of a 2nd embodiment. The top view explaining the liquefaction prevention construction method of 3rd Embodiment of this invention. The aspect diagram explaining the slip when the ground near the quay is liquefied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Quay 2 ... 1st improvement body 3, 31 ... 2nd improvement body 4, 5, 6, 7 ... 3rd improvement body 8 ... With 1st improvement body A region surrounded by the second improved body and the third improved body.
9, 90 ... Permeable member / drain pipe 10 ... Sea 81 ... Area surrounded by the first improvement body and the second improvement body arranged in a lattice shape

Claims (4)

  A plurality of first improvement bodies having a continuous wall shape extending in a direction orthogonal to the quay are formed in parallel, and the first improvement bodies are formed below the liquefaction depth and are adjacent to each other. A second improvement body for connecting the two is formed, and the second improvement body is formed in a region in the vicinity of the end portion on the side separated from the quay of the first improvement body and is orthogonal to the first improvement body. A liquefaction prevention construction method characterized in that a member having water permeability is arranged in a vertical direction in a region extending to and surrounded by a first improvement body and a second improvement body.   A third improvement body is formed in a region near the end of the first improvement body on the quay side, and the third improvement body extends in a direction orthogonal to the first improvement body and is adjacent to the first improvement body. The liquefaction prevention method according to claim 1, wherein the improved bodies are connected to each other in a region near the end on the quay side.   A third improvement body is formed in a region near the end of the first improvement body on the quay side, and the third improvement body extends in a direction orthogonal to the first improvement body, The liquefaction prevention method according to claim 1, which is not connected to the improved body.   The third improvement body is disposed to be inclined with respect to a direction orthogonal to the first improvement body, and an end portion of the third improvement body close to a quay is adjacent to the first improvement body. A liquefaction prevention method of either one of 2 or 3.

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