JP2687579B2 - Liquefaction control pile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used for constructing a structure on the ground where liquefaction may occur, and for seismic reinforcement of an existing structure. The present invention relates to a liquefaction prevention pile for suppressing liquefaction due to external force and for suppressing lateral flow and slip of the ground.

[Conventional technology]

As a liquefaction prevention means currently in use, the ground compaction method and the crushed stone drain method, which have been widely used in the past, have been used (Japanese Patent Laid-Open No. 56-1
No. 00919 method, see Japanese Utility Model Laid-Open No. 56-116434), and is applied to the ground where liquefaction is expected to occur. Further, a pressure-resistant resin pipe provided with a filter on the peripheral surface of the pipe has been conventionally used for the purpose of collecting and draining pore water in the ground and as a countermeasure against liquefaction. Also, in recent years, for the purpose of draining excess pore water in the ground in the event of an earthquake, etc., a large number of holes are drilled in piles made of steel pipes, etc., and a filter with water permeability is installed in the holes to prevent the ingress of sediment. In addition to the drainage effect, it is expected that the strength and rigidity of the pile will be high. Hollow perforated pile (JP-A-61-146
No. 910), porous concrete pile (Japanese Patent Laid-Open No. Sho 6-66).
1-83711) and the like have been developed. In addition,
A steel sheet pile with a vertical pipe for drainage attached (JP-A-62-14631)
(See No. 5 publication).

[Problems to be solved by the invention]

The ground compaction method is difficult in terms of cost when the ground that has the risk of liquefaction is alternating with the soft ground, and the crushed stone drain method impairs the drainage effect due to clogging, etc. There is no guarantee.

Further, the hollow perforated pile disclosed in JP-A-61-146910 and the JP-A-6-146910.
In the porous concrete pile of 1-83711, the load-carrying capacity of the pile body as a structure is reduced due to the holes for drainage.

Since the pressure-resistant resin pipe having small holes in the pipe body has low strength and rigidity, it is hardly expected to resist lateral flow of the ground or slip due to an earthquake.

In addition, the steel sheet pile of Japanese Patent Laid-Open No. 62-146315 additionally provided with a vertical pipe for drainage only drains water from the lower end to the upper end of the vertical pipe, and drainage function over the entire thickness of the ground that may cause liquefaction. There is no question about the drainage effect as a liquefaction countermeasure.

Furthermore, any of the above technologies that expected drainage effect,
Since it does not pay attention to the direction of the applied load, it does not exhibit reasonable sectional performance in terms of the function as a pile, making it an uneconomical product.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems in the prior art as described above.

[Means for solving the problem]

The liquefaction-preventing pile that is the subject of the present invention is provided with a filter for preventing the intrusion of many openings and earth and sand in the axial direction of the pile, that is, in the thickness direction of the ground where liquefaction may occur, or The drainage member having a large number of openings and a filter for preventing intrusion of earth and sand is provided on the outer peripheral surface of the pile body in one or more rows. The term "pile" as used herein is not limited to foundation piles, but includes ground reinforcement materials that resist lateral flow and circular slip of the ground.

Further, the opening of the pile body or the drainage member in the liquefaction suppressing pile of the present invention may have any shape such as a circular hole or a slit, but the area of the opening is a predetermined ratio with respect to the surface area of the drainage member. ing. In the present invention, regarding this aperture ratio, the aperture ratio in the load acting direction (the load acting direction means the direction in which a large load, which is predominant among the external forces acting on the pile main body, acts in comparison with other directions). The opening ratio is significantly reduced so that the opening ratio is different between the load acting direction side and the direction orthogonal to the load acting direction, or the drainage member is used in the load acting direction to increase the rigidity in the load acting direction.

As a method of making the opening ratio different when the openings are provided in the pile main body, a method of changing the size of the holes or slits of the opening, a method of changing the number of the holes or slits of the opening, etc. in the both directions. (Including 0) may be considered.

The filter for preventing the inflow of sediment is preferably made of synthetic fiber or synthetic resin, such as nylon, polyethylene monofilament, polyester or other warp knitted fabric, polypropylene, polyester fiber or other non-woven fabric, etc. Can be used. Further, a filter may be formed by combining synthetic fibers or synthetic resins, or combining or overlapping synthetic fibers and a synthetic resin. For example, on one or both sides of a synthetic fiber filter made of thin warp knitted fabric or non-woven fabric, a synthetic resin filter that is thicker than this synthetic fiber filter and has a larger mesh, or a synthetic resin filter that is thicker than the synthetic fiber filter and larger than that mesh. It is also possible to use a filter in which synthetic resin nets (filters) having a large number of small holes are stacked and reinforced.

The mesh spacing or gap of the filter, such as warp knitted fabric or non-woven fabric, may cause the filter to be clogged with soil, taking into account the soil particle size distribution of the ground (usually sand ground) to be liquefied. It is better to set it not to. This mesh interval or gap, in the ground that may be liquefied, the particle size of the soil is particularly large, it is possible to set as large as about 1-3 mm in the ground that is relatively uniformly distributed, Such a ground is small, and it is preferable that the ground is set to be considerably smaller than about 1 to 3 mm in a general ground which may be liquefied.

The permeability of the filter in liquefaction countermeasures depends on the ground where the liquefaction-preventing pile is installed, but is generally 10 ^-2 cm / sec to 10 ^-1.
It is preferably about cm / sec or more.

Needless to say, the filter is attached to the opening of the pile body or the drainage member, and any attachment method may be used, and when the liquefaction suppressing pile of the present invention is installed in the ground, the filter is damaged. Anything that does not need to be done.

In addition, the cross-sectional shape (for example, circular, rectangular, triangular, U-shaped, U-shaped, etc.) and material (steel material, aluminum material, synthetic resin, etc.) of the drainage member are not particularly limited, and the liquefaction prevention of the present invention It does not matter if the pile is installed in the ground without damage.

The pile body is generally made of steel, but may be made of another metal, a synthetic resin, or another material as long as it has a necessary strength as a seismic reinforcing means of the pile or the ground.

[Action]

Excessive pore water generated in the ground due to an earthquake, etc. enters through the openings of the pile body or drainage member and is drained through the pile body or the gap between the pile body and drainage member, causing liquefaction of the soil around the pile. Be deterred. At this time, infiltration of sediment is blocked by the filter at the opening.

When providing holes, etc., as openings in the pile body, by reducing or eliminating the opening ratio (the area ratio that means the total area of openings such as holes to the pile surface) in the part that acts in the load acting direction, The reduction of the section modulus can be suppressed, and the reduction of the strength and rigidity of the pile can be reduced.

Even when the drainage member is attached to the pile body, by attaching it to the portion corresponding to the load acting direction, the section modulus of the pile can be increased, and its strength and rigidity are improved.

With the drainage effect described above (the effect of suppressing the liquefaction of the soil around the pile),
Combined with the effect of improving the cross-sectional performance as a pile, horizontal resistance as a pile is expected against external forces during earthquakes, etc., and it is possible to restrain the ground near the pile and resist lateral flow and slip of the ground. .

〔Example〕

 Next, the illustrated embodiment will be described.

1 (a) to (c) show a first embodiment of the present invention, in which a hole 2 having a small diameter is provided in the center of the side surface 1a of the liquefaction prevention pile A on the load acting direction side, and the orthogonal Side 1b on the direction side
A hole 3 having a large diameter is provided in the. For example, the opening ratio of the side surface 1a on the load acting direction side is about 5%, the opening ratio of the side surface 1b on the orthogonal direction side is about 10% or more, and the overall opening ratio is 5%.
The pore size is changed so that it becomes ~ 20%. The holes 2 and 3 serving as openings are provided with the above-mentioned filter 4 for preventing the inflow of earth and sand.

FIGS. 2 (a) to (c) show a second embodiment of the present invention, in which the hole 2 of the side surface 1a on the load acting direction side of the liquefaction prevention pile A and the side surface 1b on the orthogonal direction side thereof are formed. The hole 3 has the same diameter, and the numbers of the holes 2 and 3 are changed. The aperture ratio is the same as in the case of the first embodiment.

FIGS. 3 (a) to 3 (c) show a third embodiment of the present invention, in which a hole is not provided on the side surface 1a of the liquefaction prevention pile A on the load acting direction side.

4 (a) and 4 (b) show a fourth embodiment of the present invention, in which the pile main body 11 of the liquefaction-preventing pile B has no holes,
A drainage member 15 including a channel steel 13 having a hole 12 and a filter 14 is attached to the center of the side surface in the load acting direction by welding or the like. Holes of the same shape are provided so that the aperture ratio is about 10 to 20% of the surface of the channel steel.

FIGS. 5 (a) and 5 (b) show a fifth embodiment of the present invention, in the case where the load acting directions are two directions (that is, when there are two directions in which an outstandingly large load acts). The drainage member 15 is provided in the longitudinal center of the side face in that direction.

Needless to say, in the embodiments of FIGS. 1 to 3 described above, the rigidity of the liquefaction prevention pile A with respect to the load acting direction is larger than that of the conventional liquefaction prevention pile having holes evenly formed in the pile body.

Further, in the embodiment of FIGS. 4 and 5, the pile body has no cross-section loss, and the rigidity of the liquefaction prevention pile B is improved by the effective cross-section of the drainage member.

FIG. 6 shows a specific application example of the liquefaction prevention pile of the present invention when applied to a caisson structure for a seawall or quay.

In this example, the liquefaction prevention pile A of the present invention is installed on the front surface side of the caisson 21, penetrates the mound 22 and the ground 23 under the mound 22 which may be liquefied, and reaches a good ground 24. For caisson 21, backfill 25 and backfill 26
The earth pressure acts from the above, and a force that causes a circular slip as indicated by the one-dot chain line a in the figure acts.

The load acting direction on the liquefaction prevention pile A in this case, that is, the direction in which the acting load is predominant, can be considered to be the direction toward the front of the caisson along the slip surface in the plane of FIG. 6, and the pile main body in that direction. The aperture ratio at is smaller than that in the orthogonal direction. Similarly, when the liquefaction prevention pile B of the embodiment shown in FIGS. 4 and 5 is used, a drainage member is provided in the load acting direction.

Further, in the example of FIG. 6, the liquefaction prevention pile of the present invention can be provided just below the caisson 21, and the load direction in that case is the same direction as the liquefaction prevention pile A on the front surface.

In addition to this, the liquefaction prevention pile of the present invention can be applied to the liquefaction prevention pile having a specific load acting direction due to factors such as a structure or topography.

[Advantages of the Invention] In the case of providing an opening in the pile body, in order to reduce the opening ratio on the load acting direction side of the liquefaction-preventing pile, there is less decrease in rigidity with respect to the acting load than the conventional liquefaction-preventing pile. it can.

When the drainage member is attached separately from the pile body, the drainage member is attached on the load acting direction side of the pile body, so the pile rigidity is improved.

It can be handled in the same way as conventional liquefaction prevention piles and does not require new construction equipment.

[Brief description of the drawings]

1 (a) to 1 (c) are a cross-sectional view showing a first embodiment of a liquefaction-preventing pile of the present invention, a side view on the load acting direction side and a side view on the orthogonal direction side, and FIG. 2 (a). )-(C) are respectively a transverse sectional view showing a second embodiment of the liquefaction-preventing pile of the present invention, a side view on the load acting direction side and a side view on the orthogonal direction side, and FIGS. 3 (a)-(c). Is a cross-sectional view showing a third embodiment of the liquefaction prevention pile of the present invention, a side view on the load acting direction side and a side view on the orthogonal direction side, and FIGS. 4 (a) and 4 (b).
Is a cross-sectional view and a side view showing a fourth embodiment of the liquefaction prevention pile of the present invention, and FIGS. 5 (a) and 5 (b) are transverse views showing a fifth embodiment of the liquefaction prevention pile of the present invention. FIG. 6 is a vertical cross-sectional view showing a construction example in which the liquefaction-preventing pile of the present invention is applied to liquefaction-preventing and ground-slip preventing, in plan view and side view. A, B …… Liquefaction prevention pile, 1 …… Pile body, 1a, 1b …… Side,
2,3 …… hole, 4 …… filter, 11 …… pile body, 12 ……
Hole, 13 ... Channel steel, 14 ... Filter, 15 ... Drainage member, 21 ... Caisson, 22 ... Mound, 23 ... Ground that may be liquefied, 24 ... Good ground, 25 ...... Backing material,
26 …… Backfill

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Saimura 1-3-1, Otemachi, Chiyoda-ku, Tokyo Sumitomo Metal Industries, Ltd. (56) Reference JP-A-2-96018 (JP, A) Special Features Kai 64-10819 (JP, A)

Claims (3)

(57) [Claims] 1. A liquefaction-preventing pile having a large number of openings in the pile body and a filter for preventing intrusion of earth and sand,
A liquefaction-preventing pile having different opening ratios on the load acting direction side and the orthogonal direction side of the pile body. 2. The liquefaction-preventing pile according to claim 1, wherein the pile main body is not provided with an opening on the load acting direction side. 3. A drainage member comprising a drainage member having a large number of openings and a filter for preventing intrusion of earth and sand along the longitudinal direction of the outer peripheral surface of the pile body. A liquefaction-preventing pile that is provided in the load acting direction.