JPH1121870A - Liquefaction countermeasure method for underground structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the settlement or floating of an underground structure even when the ground is liquefied by driving a steel sheet pile to a non-liquefied layer depth or more, and welding a reinforcement in a side wall constituting the underground structure with the steel sheet pile. SOLUTION: Existing steel sheet piles 12 are driven to a ground 11 deeper than a non-liquefied layer 13 to perform the sheathing, and the ground 11 nipped by the steel sheet piles 12 is excavated to the depth of the bottom plate of an underground structure to be buried. After the excavation, square timbers 14 for forming a drain groove 17 are arranged along the back surfaces of the steel sheet piles 12 so that the lower ends are vertically pierced in the same depth as the bottom plate of the structure. The reinforcements in the side walls of the arranged structure are welded to the inner surfaces of the steel sheet piles 12, concrete 16 is placed to form the structure. Thereafter, the square timbers 14 are pulled out before the concrete is perfectly hardened to form the drain groove 17, a filter 18 is set on the upper end, and the upper part of the structure is back filled. Thus, settlement or floating of the structure is suppressed by the frictional resistance between the steel sheet piles 12 and the non-liquefied layer 13, and liquefaction of the ground 11 can be reduced by the formation of the drain groove 17.

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 underground reinforced concrete structures such as roads, railways, and common trenches.

[0002]

2. Description of the Related Art Soil liquefaction occurs when a saturated sandy soil loses shear strength due to a sharp rise in pore water pressure due to an earthquake or the like, causing destruction of the soil structure. When liquefaction occurs, the underground structure is lifted by its buoyancy, and eventually becomes unusable. For the purpose of suppressing and escaping the rise of pore water pressure that causes liquefaction and reducing the liquefaction of the ground, a liquefaction countermeasure method for underground structures using steel sheet piles for earth retaining has been proposed, for example, in Japanese Unexamined Patent Publication No. -127045
No. has been proposed.

[0003] In this construction method for liquefaction of underground structures using steel sheet piles for soil retaining, as shown in FIG. 4, an existing steel sheet pile 2 penetrates into the ground 1 until it reaches the water-impermeable layer 3, thereby retaining the soil. ,
After excavating between the steel sheet piles 2 to the bottom plate of the underground structure A, an artificial drain material 4 made of, for example, plastic having a drainage function is installed on the back surface of the steel sheet pile 2. In this method, for example, a fluidized soil 5 obtained by kneading soil, cement, and water is backfilled with the sheet pile 2.

[0004]

However, in the liquefaction countermeasure method proposed in the above-mentioned Japanese Patent Application Laid-Open No. 7-127045, installation of a drain material on the back of a steel sheet pile and a gap between an underground structure and the steel sheet pile are required. Special on-site construction such as ground improvement to backfill fluidized soil is required, which causes cost increase. In addition, although the liquefaction countermeasure method can reduce liquefaction, it cannot completely prevent liquefaction. Therefore, even if the above-described liquefaction countermeasure method is implemented, if the ground is still liquefied, there is a problem that settlement and lifting of the underground structure cannot be suppressed.

The present invention has been made in view of the above-mentioned conventional problems, and does not require any special on-site construction, and furthermore, after implementing a liquefaction countermeasure method, the ground is temporarily liquefied. Even in such a case, it is an object of the present invention to provide a liquefaction countermeasure method for an underground structure capable of suppressing settlement and lifting of the underground structure.

[0006]

In order to achieve the above object, according to the present invention, a steel sheet pile is driven into a non-liquefied layer and a steel sheet pile is welded to a reinforcing bar in a side wall constituting an underground structure. You are going to. And, in this way, after implementing the liquefaction countermeasure method, even if the ground liquefies, the sinking and lifting of the underground structure due to the frictional resistance between the steel sheet pile and the non-liquefied layer is ensured Can be suppressed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the liquefaction countermeasures method for underground structures according to the present invention, a steel sheet pile is driven to a depth below a non-liquefied layer, and then excavation is performed between steel sheet piles to a bottom plate position of an underground structure to be buried. Then, after welding the reinforcing bars in the side walls constituting the underground structure to the steel sheet piles, concrete is poured into the excavated portion between the steel sheet piles and backfilled. After excavation, before welding the reinforcing bars in the side walls that make up the underground structure to the steel sheet pile, place a square bar vertically on the back of the steel sheet pile that has been driven into the non-liquefaction layer and deepen the concrete. After the installation, before the concrete is completely hardened, the square bar is pulled out to form a drain groove.

In the liquefaction countermeasure method of the underground structure according to the present invention, the steel sheet pile is driven to a depth below the non-liquefied layer and the reinforcing steel in the side wall constituting the underground structure is welded to the steel sheet pile. Even if the soil liquefaction method of the present invention is implemented after the liquefaction countermeasure method of the underground structure of the present invention is performed, the subsidence of the underground structure due to frictional resistance between the steel sheet pile and the non-liquefied layer can be suppressed from rising. .

[0009] Further, when a drainage channel is formed on the back surface of the steel sheet pile, the rise in pore water pressure due to an earthquake or the like can be suppressed and can be dissipated, so that liquefaction of the ground can be reduced. In addition, when the drainage grooves are formed, if the filters for preventing inflow of earth and sand are installed at the upper and lower ends of the drainage grooves, clogging of the drainage grooves can be prevented.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an underground structure liquefaction countermeasure method according to the present invention; FIG. FIG.
(A) to (e) are diagrams for explaining the method for countermeasures against liquefaction of underground structures according to the present invention in order, FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG.

1 to 3, reference numeral 11 denotes a ground.
A ready-made steel sheet pile 12 is driven into the ground 11 at a predetermined interval deeper than the non-liquefied layer 13 to perform earth retaining [FIG.
(A)]. Even if the ground 11 is liquefied, the driving depth of the steel sheet pile 12 and the non-liquefied layer 1
This is a depth at which the underground structure A can withstand its buoyancy due to the frictional resistance with No. 3 and can suppress sinking and lifting.

The ground 11 sandwiched between the driven steel sheet piles 12 is excavated to a required depth (see FIG. 1B). Here, the required depth refers to the position of the bottom plate of the underground structure A to be buried. After excavation, along the rear surface of the steel sheet pile 12, that is, along the inner surface of the steel sheet pile 12 exposed by the excavation, as shown in FIG. A square member 14 for forming a drain groove is disposed so as to penetrate in the direction [see FIG. 1 (c)]. At this time, a filter 15 for preventing intrusion of earth and sand
It is desirable to set up.

Next, after welding the reinforcing bar a in the side wall constituting the underground structure A disposed at the excavated place and the inner surface of the exposed steel sheet pile 12, concrete 16 is poured between the steel sheet piles 12. An underground structure A is formed (see FIG. 1D). After the concrete 16 has been cast, for example, one day has passed, and before the concrete 16 is completely hardened, the aforementioned square member 14 is pulled out to form a drain groove 17. Then, after installing, for example, a filter 18 at the upper end of the drain groove 17, the upper part of the underground structure A is backfilled (see FIG. 1 (e)). In addition, 1
Reference numeral 9 denotes a backfilling unit.

When the liquefaction countermeasure method of the underground structure according to the present invention described above is implemented, the steel sheet pile 12 is driven into the non-liquefied layer 13 and deeper, and the underground structure A is formed. Since the reinforcing bars a in the side walls are welded to the steel sheet pile 12, even if the ground 11 is liquefied, the subsidence structure A is effectively settled and lifted by frictional resistance between the steel sheet pile 12 and the non-liquefied layer 13. Can be suppressed.

Further, by forming a drain groove 17 on the back surface of the steel sheet pile 12, a rise in pore water pressure due to an earthquake or the like can be suppressed and dissipated, so that liquefaction of the ground 11 can be effectively reduced. be able to.

In the above-described embodiment, the drain groove 17 is formed on the back surface of the steel sheet pile 12, that is, the one corresponding to the second aspect of the present invention. Uplift of the underground structure A due to liquefaction of 11 can be effectively prevented. This is the invention corresponding to claim 1.

[0017]

As described above, according to the liquefaction countermeasures method for underground structures of the present invention, the ground liquefies after the liquefaction countermeasures method for underground structures of the present invention is implemented. Even in this case, the settlement and lifting of the underground structure can be effectively suppressed by the frictional resistance between the steel sheet pile and the non-liquefied layer. Also,
When the drainage groove is formed on the back of the steel sheet pile, the liquefaction of the ground can be effectively reduced more economically as compared with the conventional method.

[Brief description of the drawings]

1 (a) to 1 (e) are diagrams for explaining a method of countermeasure against liquefaction of an underground structure according to the present invention in order.

FIG. 2 is a sectional view taken along line AA of FIG. 1 (e).

FIG. 3 is a detailed view of a portion B in FIG. 1 (e).

FIG. 4 is an explanatory view of a conventional underground structure liquefaction countermeasure method.

[Explanation of symbols]

 A Underground Structure a Reinforcement 11 Ground 12 Steel Sheet Pile 13 Non-liquefied Layer 14 Square Timber 16 Concrete 17 Drainage 19 Backfill

Claims (2)

[Claims] After driving a steel sheet pile to a depth below a non-liquefied layer, excavation is performed between steel sheet piles to a position of a bottom plate of an underground structure to be buried, and then a reinforcing bar in a side wall constituting the underground structure is removed. A liquefaction countermeasure method for underground structures, characterized in that concrete is cast in the excavated area between steel sheet piles and then backfilled after welding to steel sheet piles. 2. After excavating between the steel sheet piles, before welding the reinforcing steel in the side wall constituting the underground structure to the steel sheet piles, a square bar is vertically applied to the back of the steel sheet piles driven into the non-liquefied layer. 2. The underground structure liquefaction countermeasure method according to claim 1, wherein, after the concrete is poured, the square bar is pulled out to form a drain ditch before the concrete is completely hardened.