JPH03239885A - Reinstallation method of buried pipe - Google Patents

Abstract

PURPOSE:To suppress the cross-directional flattening of a pipe by backfilling earth and sand just under the pipe in an excavated channel and up to the channel middle position higher than the pipe top on both sides of the pipe followed by tamping, further backfilling a compressive back fill from just above of the pipe to the middle position, and then backfilling from the back middle position to the original ground. CONSTITUTION:Grounding a1 is carried out on the channel bottom part of an excavated channel 1, a plastic pipe 2 is disposed on the grounding a1, and the part a1, a2 up to the pipe top height on both sides of the pipe 2 is backfilled with earth and sand and tamped. Then, a compressive backfill (b) such as foamed styrene is placed on the pipe 2, and both the sides are backfilled with earth and sand a3, a3 and tamped. After the tamping of the earth and sand a3, a3 on both sides of the backfill (b), backfilling with the generated earth (original earth) a4 is conducted up to the height of the original ground. Consequently, the stability of the pipe to ring pressure load can be increased, and the safety of an underground buried pipe and a deep buried pipe can be ensured in a place having strict load conditions.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a method for backfilling a buried pipe.

<Conventional technology> When burying sewage pipes, agricultural water pipes, gas pipes, etc. underground, a trench is excavated and a foundation is constructed at the bottom of the excavated trench.
The pipe is installed on top of this pipe base, and then backfilled with earth and sand (backfilling is performed while compacting the earth and sand). In this case, the width of the excavated trench is made slightly wider than the width of the pipe so that the pipe can be easily joined and compacted during backfilling.

Figure 3 shows the buried state of the pipe, and the distortion of the buried pipe due to the tonosho is the superposition of the strain due to the vertical earth pressure acting on the top surface of the pipe and the strain due to the horizontal soil pressure acting on the side surface of the pipe. In this case, the horizontal earth pressure is generated as a result of the vertical earth pressure Pt acting on the side of the pipe preventing the earth and sand from spreading laterally at Poisson's ratio μ. Concentrated earth pressure Px, which approximates this horizontal earth pressure, can be expressed as PXOCμri.

By the way, the deformation of buried pipes due to earth pressure is approximately due to concentrated earth pressure py in the vertical direction acting on the top of the pipe and concentrated upper pressure Px in the horizontal direction acting on the sides of the pipe. It can be considered as a thing. Therefore, when a radial load P is applied to a point on the circumference of a circular beam with radius R1 and cross-sectional bending stiffness EI, the deflection U (the load application points are separated by an angle ζ, and the solution is PR' PH1 , PR'"" EI7r4EIζSinζ-C (5ζ-■EI) Therefore, the inventors of the present invention find that at the center of the pipe side surface under the action of the concentrated earth pressure py in the vertical direction and the concentrated earth pressure Px in the horizontal direction, A plastic pipe with a strain gauge attached to the center of the pipe side was buried in an excavated trench using the conventional method described above, and the strain ε at the center of the pipe side was measured. In the conventional backfilling method, a phenomenon of settling of the backfilling soil at the opening in the pipe was observed in the early stage of backfilling, and under such conditions, the pipe side shown in Figure 3 The vertical pressure Py of The objectivity of the results is confirmed.

In this way, if the pipe is buried in a state where it is flattened in the horizontal direction, the cross section of the pipe is likely to be bent and deformed by the subsequent load, making it difficult to manage in locations with severe load conditions such as aircraft loads and truck loads. It is dangerous to install or bury deeply (more than 10 meters in soil).

The purpose of the present invention is to reduce the strain acting on the top surface of the tube in relation to the strain acting on the side surface of the tube, thereby reducing the tensile strain on the side surface of the tube, that is, flattening the tube in the lateral direction. It is an object of the present invention to provide a method for backburying a buried pipe by which the pipe can be buried in a state where the pipe is sufficiently suppressed.

<Means for Solving the Problems> The method for backfilling a buried pipe according to the present invention includes backfilling and compacting with earth and sand immediately below the pipe in an excavated trench and up to the middle of the trench which is higher than the top of the pipe when the pipe circumference is open. This configuration is characterized in that most of the area from directly above the pipe to the intermediate position is backfilled with a compressible backfilling material, and then the area from the intermediate position to the original ground is backfilled. .

<Function> Since a compressible backfill material such as styrene foam or urethane foam is buried above the pipe, the above-mentioned py can be made small in relation to Px, and in the fourth equation, Py
The state in which the tensile strain ε on the tube side surface is reduced due to the decrease in
In other words, the tube can be buried in a state where lateral flattening of the tube is reduced.

<Explanation of Examples> Hereinafter, the present invention will be explained in detail with reference to the drawings.

In FIG. 1, reference numeral 1 indicates an excavated groove, the depth of which is 1.3 to 4 times the diameter of the buried pipe, and the depth is set according to load conditions such as truck load.

In order to backfill the pipe according to the present invention, appropriate foundation work (a) is performed at the bottom of the trench depending on the ground conditions, burial depth, load, etc. Normally, earth and sand (for example, river sand) is spread, and this is compacted with a rammer or the like to make it flat.Next, the pipe 2, for example, a plastic pipe, is installed on this pipe base, and the pipe top height on both sides of the pipe is - Backfill the area a2.az with earth and sand,
This backfill soil is compacted.

After that, a compressible backfilling material b, such as a molded body of foamed polystyrene or foamed polyurethane, is placed on the pipe 2, and both sides of it are covered with earth and sand a3. Backfill with A3 and compact the backfill earth and sand using a tambour or the like. The height of the backfill material is usually 10 to 30 am from the top of the pipe, and the inside is approximately equal to the width of the pipe 2.

Earth and sand on both sides of backfill material A3. After compacting a3,
Backfill up to the level of the original ground with generated soil (rooftop) A4. Of this backfilling soil a4, a portion a4 that is approximately equal to the inside of the pipe 2
0 is left loose without compaction, both sides part a41
．． A4□ is preferably compacted using a rammer or the like. It is also possible to compact the entire backfill soil A4.

In the above, when using a non-formed product as the compressible backfill material, for example, when using earth and sand mixed with expanded polystyrene beads or foamed urethane beads, both sides of the area of the compressible backfill material to be backfilled are first the earth and sand A3. a
3 and compact it, then compressible backfill is used between them, and backfill is performed with a material. After that, the generated soil a is
Perform backfilling according to step 4.

FIG. 2 shows another embodiment of the present invention, in which, similarly to the embodiment shown in FIG. 1, after the foundation work a1 is constructed and the pipe 2 is installed, the earth and sand a2 are installed up to the top of the pipe. Backfill with A2, compact it, and place compressible molded backfill material directly on top of it, or after mounding earth and sand A to a thickness of 0 to 30 m,
Both sides of the backfilling material are backfilled with soil A3, which is compacted, and then backfilled with generated soil A4 up to the original ground level. Of this backfilling soil a4, a portion a4o that is approximately equal to the inside of the pipe on the pipe is left loose without being compacted, and both side portions a41. It is preferable that a41 be compacted.

In this other embodiment as well, earth and sand mixed with foamed styrene beads, foamed urethane beads, etc. can be used for the compressible backfilling material, and in this case, the soil up to the top of the pipe is filled with earth and sand
After backfilling and compacting with + a 2, earth and sand a is piled up on the pipe to a thickness of 0 to 30 cm, and earth and sand a 3. a3
Then, the space between them is backfilled with compressible backfilling material, and then backfilling with generated soil A4 is performed in the same manner as above.

In the above, it is preferable to use sand for the backfilling soil a1 to a3 and a other than the generated soil a4.

In addition, soil a, - a3 and a4. It is desirable that the compaction be carried out so that the bronchial density is 90% or more. In these soil compaction processes, the soil is compressed to a thickness of 20~
It is sufficient to compact it with a tamper etc. every 30 cm, and sieving with water is also effective.

As the compressible backfilling material, in addition to foamed polystyrene and urethane foam, any suitable molded material can be used as long as it has a low Young's modulus, low specific gravity, water resistance, and corrosion resistance. In addition to sand mixed with expanded polystyrene and expanded urethane beads, uncompacted sand, wood shavings, and small pieces of packaging material can be used as non-formed compressible backfill materials.

In Figures 1 and 2, immediately after backfilling, the density of the uncompacted soil a4Q on the pipe and the compressible backfill material is the same as that of the compacted soil a2Q on the inner side of the pipe. a3 and a
Therefore, compared to the conventional example shown in FIG.
It is possible to reduce the strain ε at the center of the tube side surface obtained by the formula. That is, horizontal flattening of the tube can be reduced.

After the above-mentioned backfilling, the surface of the backfilling site is compacted by compaction using a rammer or the like. Since pressure is hardly applied to the backfilling soil aao on the pipe, the low density state of the backfilling soil a4o on the pipe can be sufficiently maintained, and the above-mentioned effect of reducing the horizontal flattening of the pipe can be well guaranteed.

<Effects of the Invention> The method for backfilling a buried pipe according to the present invention is configured as described above, and the pipe can be buried while effectively preventing the pipe from being flattened in the horizontal direction due to tonosho. It can increase stability and guarantee the safety of underground pipes in places with severe load conditions, such as places with large load conditions such as aircraft loads and truck loads at airports, or deep buried pipes with a cover of 910 m or more. can.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory views showing an embodiment of the present invention, and FIG. 3 is an explanatory view showing the mechanical state of an underground pipe buried by a conventional method. 1...-excavation groove, 2... pipe, a2. a3...-compacted earth and sand, a4... backfill generated soil, b...-compressible backfill material.

Claims (1)

[Claims] Backfill and compact the area immediately below the pipe in the excavated trench and up to the middle position of the groove higher than the top of the pipe on both sides of the pipe, and use compressible backfill material for most of the area from just above the pipe to the intermediate position. A method for backfilling a buried pipe, characterized by backfilling, and then backfilling the area from the intermediate position to the original ground.