JP3525294B2 - Non-average force countermeasure structure for buried pipe - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Inside the retaining wall, soft ground where ground strength cannot be expected, ground that may liquefy due to an earthquake, pipes that are buried in places where uneven earth pressure may act on pipes on sloping ground, etc. The present invention relates to a non-average force countermeasure structure for buried pipes to ensure the safety of pipelines.

[0002]

2. Description of the Related Art In a bent portion of a pipe line which is constructed under normal burial conditions, as shown in FIG. It is general that the concrete block 2 is placed on the ground and the thrust force W is resisted by the passive earth pressure R on the back surface as shown in FIG.

By the way, when the earth pressure to oppose the thrust force W cannot be expected, for example, as shown in FIG.
When the thrust force W due to the internal pressure acts in the direction of the slope 3a in the curved pipe 1 buried near the slope 3a, the thrust protection structure of the pipeline is as shown in FIGS. 13 and 14. With the structure, as shown in FIG. 15, since the passive earth pressure R of the slope 3, which is the back surface, cannot be expected sufficiently, there is a risk that the curved pipe 1 may move with a small thrust force and the slope 3a may collapse in some cases. Accompany.

Therefore, in order to ensure the safety of the pipeline without considering the passive earth pressure, the weight of the concrete block 2 must be increased as shown in FIG. For this reason, a much larger block is required as compared with the case where it is installed in normal ground.

Further, when the pipe line has a high internal pressure, the thrust force also becomes large. Therefore, as shown in FIG. 16, the curved pipe 1 and the straight pipes 10 and 10 extending before and after the curved pipe 1 have a considerable length, for example, several meters. It is necessary to wrap it in concrete for over 10 to 10 m, and a plurality of joint parts may be engulfed although not shown. As a result, the joint portion 1a is also entangled with concrete, and in the case of a seismic structure pipeline, the flexibility of expansion and contraction of the joint portion, which is a feature thereof, is impaired.

Further, in the soft ground area, since uneven settlement occurs before and after the concrete structure, a large amount of cost is required for large-scale ground improvement work and derivative measures such as using flexible pipes. .

In addition, there is a risk that a large phase difference will occur between the underground structure and the ground during an earthquake, excessive stress will be generated in the pipe of the structure wrinkle, and the joint will slip out. Furthermore, when the ground behind the concrete block liquefies during an earthquake,
There is a danger that the block will move due to the thrust force due to 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 so as to bear thrust force by resistance force. However, there is a problem that installation of the pile requires a large cost and stress concentrates on a part of the curved pipe that is in contact with the PC pile.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and has the possibility of liquefying in the vicinity of the slope of the embankment, inside the retaining wall, soft ground where the earth bearing capacity cannot be expected, or due to an earthquake. Regarding pipelines buried in places where soil pressure may act on the ground or on sloping ground, protection measures against non-uniform force of the buried pipes were taken as an issue to ensure the safety of the pipelines. It is a thing.

[0010]

In order to solve the above-mentioned problems, the structure for preventing a non-uniform force of a buried pipe according to claim 1 extends from the curvature center side of the buried curved pipe to the curved pipe bottom portion, the fold Succoth covers the outside of the tube to the center of curvature side, songs
A strong geosynthetic is laid in a direction opposite to the thrust force applied to the pipe and is embedded in the ground together with the curved pipe. It is designed to be supported by resistance.

Therefore, since the thrust force of the curved pipe is supported by the strong pulling resistance force of the geosynthetics in the ground from the center of curvature side, even if no passive earth pressure can be expected on the back side, it is easy. The configuration ensures protection against non-uniform forces.

The pull-out resistance in the above claim 1 is obtained by embedding strong geosynthetics in the ground to exert the pull-out resistance due to friction, and when the strong geosynthetic is buried underground. When wrapping a foundation material such as buried soil to exert resistance against a large non-uniform force due to its own weight and the load of backfill soil above that, further, in the underground of strong geosynthetics There is a case where the buried portion is connected to an anchor or a pile to effectively utilize the strength of the ground portion to secure a large resistance force.

When the above-mentioned pull-out resistance is to be exerted by encapsulating a foundation material such as buried soil in a tough underground buried part of geosynthetics, crushed stone should be used as the foundation material and the backfill material above. This can suppress an increase in excess pore water pressure that causes liquefaction.

The non-average force countermeasure structure for the buried pipe according to claim 2 is
Extending from the ground side of the straight pipe buried along the contour line of the slope to the bottom of the straight pipe, covering the outside of the straight pipe and returning to the ground side, strong geosynthetics are laid and arranged, and the straight pipe is The earth pressure applied in the direction perpendicular to the pipe axis is supported by the pulling resistance force of the tough geosynthetics in the ground.

The structure for preventing the non-uniform force of the buried pipe according to claim 2 is for the non-uniform force of a straight pipe, and the buried pipe laid along the contour line of the slope has an eccentric earth pressure in the direction perpendicular to the pipe axis. However, due to this soil pressure, geosynthetics laid toward the natural ground exert the same pull-out resistance as in claim 1, or crushed stone is used for the foundation material and the backfill material in the upper part. By doing so, it is possible to suppress an increase in excess pore water pressure that causes liquefaction.

Here, the tough geosynthetics have the physical properties of high strength, low elongation, small creep deformation, excellent impact resistance during construction, and high friction resistance with soil,
It refers to 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 obtained by combining aramid fiber with high-density polyethylene resin or polyester fiber.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the non-averaged force countermeasure structure for a buried pipe of the present invention will be described. FIG. 1 is a plan view in which a structure for preventing uneven force of a buried pipe is applied to a curved pipe, FIG.
2 is a sectional view taken along the line AA of FIG.

In FIG. 1, the curved pipe 1 extends from the side of the center of curvature 1b to the bottom 1c of the curved pipe, is expanded to the top 1f of the pipe along the outer surface 1d of the curved pipe 1, and again to the side of the center of curvature 1b. It is covered with the folded and strong Geosynthetics 4.

The geosynthetics 4 has a net shape as shown in the drawing, and is expanded into the ground to form the curved pipe 1
In addition, it is buried in the ground, and the pulling-out resistance forces r ... R working in the ground along the geosynthetics 4 are combined so as to be a resistance force R opposed to the thrust force w.

Further, the geosynthetics 4 are formed in a strip shape and are arranged so as to be in a direction perpendicular to the tube axis 1e of the curved tube 1, and the portions 4a where the strip nets 4 overlap with each other are a connecting member ( (Not shown).

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

Next, a method of constructing the structure for preventing the non-uniform force of the buried pipe according to the embodiment will be described. First, the ground 5 is excavated to the depth at which the curved pipe 1 is laid, and as shown in FIG. 3, the geosynthetics 4 are laid from the curvature center 1b side of the conduit toward the radially outer side.

The curved pipe 1 is installed on the curved pipe 1, and the geosynthetics 4 outside the curved pipe 1 is tucked up to the top 1f of the curved pipe 1. Next, as shown in FIG. 4, the curved pipe 1 is backfilled to the top 1f, and the geosynthetics 4 tucked up on the backfilled 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 to backfill the excavation trench. Therefore, the buried curved pipe 1 is
c, from the pipe top 1f to the center of curvature side 1b, the geosynthetics 4 extend in the state of being buried in the ground, and the pull-out resistance r ... r generated along the geosynthetics 4
Serves as a resistance R, R against the thrust force W and protects the curved pipe 1.

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

In the above embodiment, the case where the geosynthetics 4 is laid in a U shape is shown.
As shown in Fig. 3, the open side of the geosynthetics 4 is laid so as to be closed by the extension 4b.
The thrust force W also depends on the mass G of the backfill soil 6a surrounded by
May be opposed to.

Furthermore, 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 filled above the curved pipe 1. The mass of the backfill soil 6a may be directly added to the curved pipe 1 in addition to the drag force R of the geosynthetics 4 due to the pulling resistance force r to oppose the thrust force.

In this case, if crushed stones are used for the backfill soil 6a surrounded by the geosynthetics 4 and the backfill soil 6 on the upper side, an increase in excess pore water pressure that causes liquefaction is suppressed and prompt dissipation is promoted. As a result, it exerts a very large effect in suppressing the movement of the curved pipe.

In FIG. 7, since the projected area of the backfill soil 6a wrapped with the geosynthetics 4 on the back side of the curved pipe 1 is larger than that in FIG. 6, the thrust resistance force especially when the ground is liquefied Effective in increasing.

Alternatively, 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 locked to the pile 7. In this case, the pile 7 provides a resistance R to the strong thrust force W.

Further, when there is no strong ground around the curved pipe, the anchor pile 7a is attached to the strong ground 5a as shown in FIG.
You may drive in and fix the end part of the geosynthetics 4 to the anchor pile 7a with a connection metal fitting etc. to this.

In the embodiment shown in FIGS. 8 and 9,
Even if the ground is liquefied due to an earthquake or the like, the curved pipe 4 is prevented from moving outward from the center of curvature, so that the safety of the pipeline is enhanced.

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

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

The structure for preventing the non-uniform force of the buried pipe described above also applies to the straight pipe portion of the pipe line laid along the contour line on the sloping ground.
With a structure similar to that of the embodiment in the curved pipe section, the resistance force against the non- uniform force of the pipe line is increased or it acts in the direction orthogonal to the pipe axis.
The stability of the pipeline can be improved even with respect to uneven earth pressure .

Further, not the average forces acting on the pipe even when the pipe is partially exposed from the inclined surface as shown in FIG. 12
It can be used as a resistance force against soil pressure and eccentricity .

[0037]

As described above, according to the present invention, the thrust protection force of the curved pipe is exerted by the pulling-out resistance force of the strong geosynthetics laid on the curvature center side of the curved pipe in the ground. Even if the embankment slope is located outside the center, reliable thrust protection can be performed.

[0038] Further, at the time of construction, since it suffices to lay strong geosynthetics in the excavation trench, the construction can be carried out easily without any labor. Further, since no concrete block is placed on the outer circumference of the curved pipe, thrust protection can be performed without impairing the expansion / contraction function even for a curved pipe joined with an earthquake resistant joint.

[Brief description of drawings]

FIG. 1 is a plan view showing an anti-unequal force countermeasure structure for a buried pipe according to an embodiment of the present invention.

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

FIG. 3 is an explanatory view of a curved pipe burying step, and is a cross-sectional view of a state in which net-shaped geosynthetics are laid on the bottom of a trench.

FIG. 4 is an explanatory view of the above process, and is a cross-sectional view of a state in which the pipe top is backfilled.

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

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

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

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

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

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

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

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

FIG. 13 is a plan view showing a conventional buried structure of a bent pipe.

14 is a cross-sectional view of FIG.

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

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

[Explanation of symbols]

1 curved pipe 2 concrete blocks 3 embankments 3a slope 4 Robust geosynthetics 5 ground 6 backfill soil

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshinori Kawabata 3 1-3 Nihonbashi Muromachi, Chuo-ku, Tokyo Kubota Tokyo Head Office (72) Inventor Hiroyasu Sato 3 1-3 Nihombashi Muromachi, Chuo-ku, Tokyo No. Kubota Tokyo Head Office (56) References JP-A-54-149926 (JP, A) JP-A-9-273152 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16L 1/024 E02D 27/34 F16L 1/00

Claims (2)

(57) [Claims] 1. A stretch than the curvature center side of the buried bent tube into the bend bottom, the fold Succoth covers outside of said curved pipe to the center of curvature side, to face the thrust force applied to bend
The strong geosynthetics are laid in the direction of
A buried pipe non-uniform force countermeasure structure that is buried in the ground together with the curved pipe, and the thrust force applied to the curved pipe is supported by the pulling-out resistance force of the strong geosynthetics in the ground. 2. A tough geosynthetic structure that extends from the natural side of a straight pipe buried along a contour line of a slope to the bottom of the straight pipe, covers the outside of the straight pipe, and folds back toward the natural side to lay it. The structure for counteracting the non-uniform force of the buried pipe, in which the uneven earth pressure applied to the straight pipe in the direction perpendicular to the pipe axis is supported by the pulling-out resistance force of the strong geosynthetics in the ground.