JPH01125413A - Steel sheet pile for preventing liquefaction - Google Patents

Abstract

PURPOSE:To prevent the liquefaction of embedded sand by a method in which a perforated plate and a filter are attached to a steel sheet pile for protecting buried pipes in such a way as to discharge excess void water to be generated when earthquake occurs. CONSTITUTION:Two rows of steel sheet piles 10 are erectly set on the natural ground 1 to form a sheathing pile walls, and the ground between them is excavated. A pipe 2 is set in the trench and embedding sand 3 is placed on it to protection. Perforated plates 11 are set between the flanges 10a of the sheet piles 10 and filters 13 are packed into the aperture between the piles 10 and the plates 11. When earthquake occurs, excess void water generated is discharged to dissipate excess void water pressure in the ground 1, thereby preventing the liquefaction of the embedded sand 3.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to buried pipes such as gas pipes, water pipes, and electric pipes buried underground, underground structures such as culverts, as well as sea walls, quay walls, earth retaining walls, etc. This invention relates to liquefaction-preventing steel sheet piles used to prevent damage caused by liquefaction of sheet pile structures during earthquakes.

[Conventional technology and problems]

As mentioned above, since there are a wide variety of light applications, conventional techniques and problems related to buried pipes will be explained below.

Conventionally, when constructing buried pipes, etc., as shown in Fig. 5, the original ground 1 is excavated widely, the buried pipes 2, etc. are laid, and then the buried pipes 2, etc. are protected with backfilling sand 3, etc.; As shown in Fig. 6, a retaining sheet pile wall is formed with two rows of steel sheet piles 5,
Excavate between 5 steel sheet piles, lay underground pipes 2, etc., and backfill with sand 3.
Methods of protection are being adopted.

However, with the above conventional burial method, when an earthquake occurs, the backfilling sand
may liquefy, and in some cases, the original ground 1 itself may also liquefy)
, the strength of the backfilling sand 3 decreases, creating a situation where the buried pipes, etc., exist in a liquid with a specific gravity that is a mixture of water and sand, and the buried objects float or sink depending on their weight. As a result, damage may occur due to deformation or breakage of buried pipes, etc.

The purpose of the steel sheet pile for liquefaction prevention of this invention is to solve the above-mentioned problems, and by using it for laying buried pipes, etc., it is possible to eliminate excess waste generated in backfilling sand and the original ground during earthquakes. Drains pore water from the steel sheet pile position to prevent liquefaction,
This is to prevent damage to buried pipes, etc.

Conventional seismic reinforcement methods to prevent liquefaction include a method in which gravel columns are driven into the ground where liquefaction is expected, and the excess pore water pressure that occurs during an earthquake is dissipated within the gravel columns. Such gravel columns are described in Japanese Patent Application Laid-Open No. 56-100919 and Japanese Patent Application Laid-open No. 56-11.
It is described in Publication No. 6434, etc.

In addition, a liquefaction prevention method using concrete piles or porous concrete piles with many small holes was developed in Japanese Patent Application Laid-Open No. 61-83.
It is disclosed in Japanese Patent Application Laid-open No. 712, Japanese Patent Application Laid-Open No. 146910/1982, Japanese Patent Application Laid-open No. 1.69520/1984, and the like.

[Means for Solving the Problems] An overview of the present invention will be described below using reference numerals in the drawings corresponding to the embodiments.

The steel sheet pile 10 for preventing liquefaction of the present invention is provided with a perforated plate 11 and a filter between the flanges 10b, so that the steel sheet pile 10
Excess pore water generated in the ground where the concrete is cast is drained through the gap formed between the steel sheet pile 10 and the perforated plate 11, and excess pore water pressure in the ground is dissipated to prevent liquefaction.

The perforated plate 11 has a width between the flanges 10b of the steel sheet pile 10, and has a large number of small holes 12 at required intervals in a long and narrow steel plate extending in the longitudinal direction.
A drainage channel in the longitudinal direction of the steel sheet pile 10 is formed by attaching both sides between the flanges 10b of the steel sheet pile 10 by welding or the like.

As a filter, a wire mesh 1 is placed in the small hole 12 part of the perforated plate 11.
4 (preferably something that does not rust), attach a synthetic resin filter, etc., or attach a perforated plate 11 and a steel sheet pile 10.
Filling the gap between the web 10b and the web 10b with a synthetic resin filter material 13 (in this case, a filter is formed not only in the small holes 12 but also inside the holes) to prevent the intrusion of foreign substances. To prevent. These wire mesh 14, synthetic resin filter material 13, etc. may be used in combination, or each may be used alone.

Further, the perforated plate 11 may be installed over the entire length of the steel sheet pile 10, or may be installed up to a predetermined depth depending on the ground condition.

[For production]

When the steel sheet pile 10 for preventing liquefaction of the present invention is used, for example, as an earth retaining wall for laying buried pipes 2, etc. described in the section of the prior art, by providing the perforated plate 11 and the filter, the steel sheet pile 10 It is possible to forcibly drain the original ground 1 when placing the pipe, and also to drain excess pore water generated during an earthquake in the backfill sand 3 used for burying the buried pipe 2, etc. . Therefore, while the original ground 1 is compacted, liquefaction of the backfill sand 3 is suppressed.

〔Example〕

Next, the illustrated embodiment will be described.

FIG. 2 shows an example of the steel sheet pile 5 of the present invention, in which a perforated plate 11 having a large number of small holes 12 is attached to the steel sheet pile 10 so as to connect the flanges 10b. A filter made of wire mesh 14 is attached to each small hole 12 to prevent ground particles and backfill sand particles from entering the drainage area surrounded by the steel sheet pile 10 body and the perforated plate 11.

These small holes 12 and filters are provided along the entire length of the steel sheet pile 10 when the original ground 1 is likely to liquefy due to an earthquake, and to that depth when only the liquefaction of the backfill sand 3 is targeted. It will be done. In the figure, 10c is a joint portion of the steel sheet pile 10, and 15 is a welded portion of the perforated plate 11.

The embodiment shown in FIG. 1 is different from the embodiment shown in FIG. 2 described above,
Rather than attaching a filter to the small holes 12 of the perforated board 11, the drainage area surrounded by the steel sheet pile 10 body and the perforated board 11 is filled with filter material 13 to prevent the intrusion of ground particles and backfill sand particles. The walls were made of sheet piles. In the figure,
As shown by the arrow, in the sheet pile wall using the steel sheet pile 10 of the present invention, water in the ground can be drained from both sides of the sheet pile wall. If you want to further improve drainage capacity, use steel sheet pile 1.
A hole is also made in the web 10a portion of the filter hole 13.
Alternatively, the wire mesh 14 shown in FIG. 2 may be used.

FIGS. 3 and 4 show the steel sheet pile 10 of the present invention in a buried pipe 2.
This shows an example of how it is used for laying.
This will be explained in comparison with the conventional example shown in FIGS. 5 and 6 described above.

In the case of the embodiment shown in FIG. 3, excess pore water generated and accumulated in the backfill sand 3 during an earthquake is drained from the drainage area of the steel sheet pile 10, so that excess pore water pressure is sufficiently suppressed. , the backfill sand 3 maintains its original strength as sand, but in the conventional construction method shown in Figures 5 and 6, the pore water in the backfill sand 3 is not drained, so excess pore water pressure accumulates, causing the backfill to deteriorate. The sand 3 becomes liquefied, and the buried pipe 2 is deformed as a whole, and its joints, fixing parts, etc. are damaged.

The embodiment shown in FIG. 4 further enhances the drainage effect, in which crushed stone 16 is laid down before the buried pipe 2 is laid, and a filter 17 for preventing clogging is installed on top of the crushed stone 16. In the liquefaction countermeasure shown in FIG. 3, it is possible to increase the distance between the sheet pile walls to around 3 to 5 m, and in the case of FIG. 4, it is possible to further increase the distance between the sheet pile walls. Moreover, the crushed stones 16 in the embodiment shown in FIG. 4 may be wrapped and installed in a mesh-like filter material at a pitch of 3 to 5 m or less, like sleepers on a railway roadbed.

As mentioned above, by using the steel sheet pile 10 of the present invention, in the event of an earthquake, it is possible not only to prevent damage caused by liquefaction of so-called lifelines such as gas, water, and electricity, but also to prevent secondary disasters.
Disaster restoration of other structures can also be carried out promptly.

〔Effect of the invention〕

The steel sheet pile of this invention is capable of forcibly draining pore water in the original ground when the steel sheet pile is placed by using perforated plates and filters provided between the flanges, and also allows for forced drainage of pore water in the original ground when the steel sheet pile is placed. of water can be drained during an earthquake.

Therefore, it is possible to improve the bearing capacity of the original ground and effectively prevent a decrease in strength during an earthquake due to liquefaction of backfill sand, etc. Furthermore, the equipment used for constructing the steel sheet piles remains the same as before.
There is no problem in construction, and it can be applied to all conventional sheet pile structures, making it extremely practical.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing one embodiment of the steel sheet pile of the present invention, Fig. 2 is a perspective view showing another embodiment, and Fig. 3 is a vertical sectional view showing an example of use in laying underground pipes. , FIG. 4 is a vertical cross-sectional view showing another example of use in laying underground pipes, and FIGS. 5 and 6 are vertical cross-sectional views showing conventional examples. 1... Original ground, 2... Buried pipe, 3... Backfill sand,
4... Generated soil, 5... Steel sheet pile, 6... Ground surface, 7
...Groundwater table, 10...Steel sheet pile, ], Oa...
Web, 10b... flange, 10c... joint part,
11... Perforated plate, 12... Small hole, 13... Filter material, 14... Wire mesh, 15... Welder, 16...
・Crushed stone, 17...Filter Figure 6

Claims (3)

[Claims] (1) A perforated plate with a large number of small holes formed therein is joined between flanges of a steel sheet pile, a longitudinal gap is formed between the perforated plate and the web of the steel sheet pile, and at least the small holes in the perforated plate are formed. A steel sheet pile for liquefaction prevention that is characterized by having filters installed in some parts. (2) The steel sheet pile for liquefaction prevention according to claim 1, wherein the filter is a wire mesh attached to the small hole portion of the perforated plate. (3) The steel sheet pile for liquefaction prevention according to claim 1, wherein the filter is a synthetic resin filter material filled in the gap between the perforated plate and the web of the steel sheet pile.