JP2002276853A - Uneven force countermeasure structure for buried pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide thrust protection of a bent pipe part during loading of internal pressure in regard to a pipe line buried in poor ground such as near a face of a slope of banking or an interior of a retaining wall where sufficient yield strength can not be expected, or ground with a possibility of liquefaction following an earthquake. SOLUTION: Strong geosynthetics 4 extended from a curvature center 1b side of a buried pipe 1 to a bent pipe bottom, covering an outer side 1d of the bent pipe 1 and folded back to the curvature center 1b side are laid and buried in the ground with the bent pipe 1. Thrust force W acting on the bent pipe 1 is supported by subterranean pulling resistance R of the strong geosynthetics 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an embankment near a slope,
For pipelines buried in the inside of retaining walls, soft ground where ground strength is not expected, ground that may be liquefied due to earthquake, places where there is a possibility that uneven earth pressure may act on pipes on sloping ground, The present invention relates to a structure for countermeasures against non-average force of buried pipes to secure pipe safety.

[0002]

2. Description of the Related Art As shown in FIG. 13, around a bent portion of a pipe constructed under a normal embedding condition, the pipe is not moved by a thrust force acting on the bent portion when an internal pressure is applied. In general, a concrete block 2 is cast on the rear surface, and as shown in FIG.

When the earth pressure to be opposed to the thrust force W cannot be expected, for example, as shown in FIG.
When the thrust force W due to the internal pressure acts on the curved pipe 1 buried in the vicinity of the slope 3a or the like in the direction of the slope 3a, the thrust protection structure of the pipeline is as shown in FIGS. With this structure, as shown in FIG. 15, since the passive earth pressure R on the slope 3 serving as the rear face cannot be expected sufficiently, there is a danger that the curved pipe 1 moves with a small thrust force and the slope 3a may collapse in some cases. Accompany.

[0004] Therefore, in order to ensure the safety of the pipeline without taking into account the passive earth pressure, the weight of the concrete block 2 must be increased as shown in FIG. For this reason, much larger blocks are required as compared with a case where a normal ground is provided.

[0005] Further, when the internal pressure of the pipe is high, the thrust force also increases. Therefore, as shown in FIG. And more than ten meters from concrete, and a plurality of joints may be involved, though not shown. As a result, the joint 1a is also involved in the concrete, and in the case of an earthquake-resistant pipe, the elasticity of the joint, which is a feature thereof, is impaired.

Further, in a soft ground area, uneven settlement occurs before and after a concrete structure, so that large-scale ground improvement works and secondary measures such as the use of flexible pipes require a large amount of cost. .

[0007] In addition, during an earthquake, a large phase difference occurs between the underground structure and the ground, and there is a danger that excessive stress will be generated in the tube of the structure and that the joint will come off. Furthermore, when the ground behind the concrete block liquefies during the earthquake,
There is a danger that the block will move due to the thrust force caused by the internal pressure, causing serious damage.

As a means for avoiding such a danger, it is conceivable to drive a PC pile or the like from the center of curvature of the curved pipe to the outside and bear a thrust force with a resistive force. However, there is a problem that installation of the pile requires a large cost and stress is concentrated on a part of the curved pipe in contact with the PC pile.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and there is a possibility of liquefaction due to the vicinity of a slope of an embankment, the inside of a retaining wall, soft ground where ground strength cannot be expected, or an earthquake. For pipes buried in the ground or on sloping lands where there is a possibility of uneven pressure on the pipes, measures were taken to protect the pipes against uneven force in order to ensure pipe safety. Things.

[0010]

According to a first aspect of the present invention, there is provided a buried pipe having a structure for preventing non-average force, wherein the buried pipe extends from the center of curvature of the buried pipe to the bottom of the bent pipe. The outer surface of the pipe is folded back toward the center of curvature, and a strong geosynthetics is laid and laid and buried in the ground together with the curved pipe, and the thrust force applied to the curved pipe is reduced by the strong geosynthetics. It is designed to be supported by pull-out resistance underground.

Therefore, since the thrust force of the curved pipe is supported by the strong geosynthetics pull-out resistance from the center of the curvature, even if passive earth pressure cannot be expected on the back side, it is simple. The configuration ensures protection against uneven forces.

The pull-out resistance according to the first aspect of the present invention can be applied to a case where a strong geosynthetics is buried in the ground to exert a pull-out resistance due to friction, and a case where the strong geosynthetics is buried in the ground. When wrapping a foundation material such as buried soil, and exerting resistance against a large non-average force with the weight of the part and the load of the backfill soil above it, furthermore, underground of strong geosynthetics In some cases, the buried part is connected to anchors and piles to effectively use the strength of the ground part to secure a large resistance.

In the case where the above-mentioned pull-out resistance is exhibited by wrapping a foundation material such as buried soil in a tough geosynthetic underground part, crushed stone is used for the foundation material and the upper backfill material. Thereby, the rise of the excess pore water pressure which causes liquefaction can be suppressed.

According to a second aspect of the present invention, there is provided a structure for countermeasures against uneven force of a buried pipe.
The straight pipe buried along the contour line of the slope extends from the ground side to the bottom of the straight pipe, and covers the outside of the straight pipe and is turned back to the ground side, where strong geosynthetics are laid and arranged, and The uneven earth pressure in the direction perpendicular to the pipe axis applied to the pipe is supported by the pullout resistance of the tough geosynthetics underground.

The structure for preventing an uneven force of a buried pipe according to a second aspect of the present invention is for a non-average force applied to a straight pipe. However, geosynthetics laid toward the ground side can exert the same pull-out resistance as in claim 1 against this uneven earth pressure, or use crushed stone as the base material and backfill material at the top By doing so, it is possible to suppress an increase in excess pore water pressure that causes liquefaction.

Here, tough geosynthetics means physical properties such as high strength, low elongation, small creep deformation, excellent impact resistance during construction, and high frictional resistance to soil.
A net-like body formed of a fiber material having chemical properties excellent in weather resistance, chemical resistance, cold resistance, and heat resistance, for example, a fiber material in which aramid fiber is combined with high-density polyethylene resin or polyester fiber.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a structure for countermeasures against uneven force of a buried pipe according to the present invention will be described. FIG. 1 is a plan view of a case in which the structure for preventing imbalance of a buried pipe is applied to a curved pipe, and FIG.
FIG. 2 is a sectional view taken along line AA of FIG. 1.

In FIG. 1, the curved pipe 1 extends from the center of curvature 1b to the bottom 1c of the curved pipe, is developed along the outer surface 1d of the curved pipe 1 to the top 1f, and again toward the center of curvature 1b. Covered with folded strong geosynthetics 4.

The geosynthetics 4 is in the form of a net as shown in FIG.
And the underground pull-out resistances r... R acting along the geosynthetics 4 are combined to form a resistance R opposed to the thrust force w.

The geosynthetics 4 are formed in a band shape, are arranged so as to be perpendicular to the tube axis 1e of the curved tube 1, and a portion 4a where the band-shaped nets 4 overlap is connected to each other by a connecting member ( (Not shown).

Geosynthetics 4 has high strength, low elongation, low creep deformation, excellent impact resistance during construction, good physical properties of good friction with soil, weather resistance, chemical resistance, Fibers with excellent chemical resistance to cold resistance and heat resistance,
For example, a geogrid formed of a fiber material in which aramid fiber is combined with high-density polyethylene resin or polyester fiber is preferably used.

Next, a method of constructing the structure for preventing imbalance in the buried pipe according to the embodiment will be described. First, the ground 5 is excavated to a depth at which the curved pipe 1 is to be laid, and the geosynthetics 4 are laid from the curvature center 1b side of the pipe to the outside in the radial direction as shown in FIG.

The curved pipe 1 is placed on the pipe along the pipeline, and the geosynthetics 4 outside the curved pipe 1 are lifted up to the top 1f of the curved pipe 1. Next, as shown in FIG. 4, the bent pipe 1 is backfilled to the top 1f, and the geosynthetics 4 raised on the backfill soil 6 are developed and laid in the direction of the center of curvature 1b.

Then, as shown in FIG. 5, backfill soil 6 is further put on the developed geosynthetics 4, and the excavation trench is backfilled. Therefore, the buried curved pipe 1 is the pipe bottom 1
c, the pullout resistance r... r generated along the geosynthetics 4, extending from the pipe top 1 f toward the center of curvature 1 b while the geosynthetics 4 is buried underground.
Become the resistances R and R against the thrust force W to protect the curved tube 1.

Therefore, even when the outside of the curvature center 1b of the curved pipe 1 is the slope 3a of the embankment 3 and the passive earth pressure cannot be expected sufficiently, the movement of the curved pipe 1 by the thrust force W is sufficient. Is prevented.

In the above embodiment, the case where the geosynthetics 4 is laid in a U-shape has been described.
As shown in the figure, the open side of the geosynthetics 4 is laid so as to be closed by the extension 4b.
Thrust force W also depends on the mass G of the backfill soil 6a surrounded by
May be opposed.

Further, in this case, as shown in FIG. 7, the geosynthetics 4 is extended toward the top of the curved pipe 1, and the backfill soil 6a surrounded by the extension 4c is also embanked above the curved pipe 1. In this case, the mass of the backfill soil 6a may be directly applied to the curved pipe 1 to oppose the thrust force in addition to the drag R due to the underground pull-out resistance r of the geosynthetics 4.

In this case, if crushed stone is used for the backfill soil 6a surrounded by the geosynthetics 4 and the upper backfill soil 6, an increase in excess pore water pressure which causes liquefaction is suppressed, and prompt dissipation is promoted. This has a very large effect on suppressing the movement of the curved pipe.

In FIG. 7, since the projected area of the backfill soil 6a wrapped by the geosynthetics 4 on the back side of the curved pipe 1 is larger than that of FIG. 6, the thrust resistance force particularly when the ground liquefies is reduced. Effective for increase.

Further, as shown in FIG. 8, a pile 7 may be driven into the open side of the geosynthetics 4 and the geosynthetics 4 may be engaged with the pile 7. In this case, the pile 7 provides a strong drag R with respect to the thrust force W.

Further, if there is no strong ground around the curved pipe, as shown in FIG.
, And the end of the geosynthetics 4 may be fixed to the anchor pile 7a with a connection fitting or the like.

The embodiment shown in FIG. 8 and FIG.
Even if the ground liquefies due to an earthquake or the like, the curved pipe 4 is prevented from moving from the center of curvature to the outside, so that the safety of the pipeline is improved.

Further, as shown in FIG. 10, a block material 8 formed of concrete, soil cement, EPS, or the like may be applied to the outside of the curved pipe 1, and the geosynthetics 4 may be placed thereon.

In this case, since the outside of the curved tube 1 can be formed in a square shape, a large sheet-like body 4s can be used as the geosynthetics 4 as shown in FIG.
The need for repeatedly laying a large number of strip-shaped geosynthetics 4 can be eliminated, the construction can be performed quickly and easily, and a strong thrust protection force is exhibited in combination with the weight of the formwork 8.

The above-mentioned structure for countermeasures against non-average force of buried pipes is applicable to a straight pipe portion of a pipe laid along a contour line on a slope.
With the same structure as the embodiment in the curved pipe portion, it is possible to increase the resistance against the non-average force of the pipe and increase the stability of the pipe.

That is, even when the pipeline is partially exposed from the slope as shown in FIG. 12, the resistance to the non-average force acting on the pipeline can be obtained.

[0037]

As described above, according to the present invention, the thrust protection force of the curved pipe is exerted by the pull-out resistance force of the tough geosynthetics laid on the center side of the curvature of the curved pipe, so that the curvature of the curved pipe is exerted. Reliable thrust protection can be achieved even when the embankment slope is located outside the center.

Further, in the construction, since it is only necessary to lay the strong geosynthetics in the excavation groove, the construction can be easily performed without any trouble. Further, since no concrete block is cast on the outer periphery of the curved pipe, thrust protection can be performed without impairing the expansion and contraction function even with a curved pipe joined by an earthquake-resistant joint.

[Brief description of the drawings]

FIG. 1 is a plan view showing a structure for countermeasures against uneven force of a buried pipe according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an explanatory view of a process of embedding a curved pipe, and is a cross-sectional view in a state where net-shaped geosynthetics is laid on the bottom of a digging trench.

FIG. 4 is an explanatory view of the above-described step, and is a cross-sectional view in a state where it is back-filled up to a pipe top.

FIG. 5 is an explanatory view showing a buried state.

FIG. 6 is a sectional view showing another configuration example of the embodiment.

FIG. 7 is a sectional view showing still another example of the configuration;

FIG. 8 is a sectional view showing still another example of the configuration;

FIG. 9 is a sectional view showing still another example of the configuration;

FIG. 10 is a sectional view showing still another example of the configuration;

11 is a plan view of the configuration example shown in FIG.

FIG. 12 is a cross-sectional view showing still another configuration example of the embodiment.

FIG. 13 is a plan view showing a conventional curved pipe burying structure.

FIG. 14 is a sectional view of FIG.

FIG. 15 is a sectional view of another conventional example.

FIG. 16 is a plan sectional view of another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Curved pipe 2 Concrete block 3 Embankment 3a Slope 4 Strong geosynthetics 5 Ground 6 Backfill soil

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuo Fujita 3-3-1 Nihonbashi Muromachi, Chuo-ku, Tokyo Kubota Tokyo Head Office (72) Inventor Toshinori Kawabata 3-3-1 Nihonbashi Muromachi, Chuo-ku, Tokyo No. Kubota Tokyo Head Office (72) Inventor Hiroyasu Sato 3-3-1 Nihonbashi Muromachi, Chuo-ku, Tokyo Kubota Tokyo Head Office F-term (reference) 2D046 DA17

Claims (2)

[Claims] Claims: 1. A buried curved pipe extends from the center of curvature to the bottom of the curved pipe, and covers the outside of the curved pipe and is folded back toward the center of curvature, where a strong geosynthetics is laid and arranged. A non-average force countermeasure structure for a buried pipe buried in the ground together with the pipe so that a thrust force applied to the bent pipe is supported by the pullout resistance of the strong geosynthetics in the ground. 2. A straight pipe buried along a contour line of a slope extends from a ground side to a bottom of the straight pipe, and covers the outside of the straight pipe and is turned back to the ground side to lay a strong geosynthetics. And a structure for preventing an uneven force of a buried pipe, wherein an uneven earth pressure in a direction perpendicular to a pipe axis applied to the straight pipe is supported by a pull-out resistance force of the tough geosynthetics underground.