JPH03279516A - Laying for underground buried pipe - Google Patents

Abstract

PURPOSE:To prevent the adhering and escaping of earth and sand at the time of sheet pile pulling-out to stabilize the buried condition of a pipe by arranging scrapers at given intervals on the inner sides of sheet piles placed on both the sides of an excavated groove. CONSTITUTION:Scrapers 31 and 32 are arranged on the inner side surfaces of sheet piles 2 on a foundation floor 1 constructed on the original ground, and soil 4 is covered on the foundation floor to laid a pipe 5. Moreover back filling is made with the soil 4, and the sheet piles 2 are pulled out one by one in order after an excavated groove 6 is back filled. At that time, earth and sand intruded in the recessed parts of the sheet piles 2 are scraped off with the buried scrapers 31 and 32 to prevent the adhering and escaping of earth and sand. Thus the stability of the buried condition of the pipe 5 can be obtained.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a method for laying underground pipes.

<Prior Art> When installing underground pipes, a trench is excavated, the pipe is placed in the excavated trench, and then the excavated trench is backfilled. In this case, when the trench is deep or the ground is soft, sheet piles are driven on both sides of the trench, the earth and sand between the sheet piles is dug out, the trench is excavated, and the earth retention is secured. The pipes were installed and backfilled with earth and sand, and after this backfilling, the sheet piles were pulled out.

According to this sheet pile construction method, voids are generated at the site where the sheet piles have been pulled out, and backfilling earth and sand flows into these voids. Conventionally, in order to prevent abnormal deformation of the pipe, based on the premise that the flow of this backfilling earth and sand loosens or washes away the earth and sand directly under the pipe, lowering the bearing angle of the pipe and causing abnormal deformation of the pipe. It is known to surround the backfilling earth and sand directly under the pipe together with a sheet to prevent the earth and sand from flowing directly under the pipe.

<Problem to be Solved> However, the present inventor installed a strain gauge at the center of the side surface of the pipe, and based on the above-mentioned known example, surrounded the pipe with a sheet along with backfill earth and sand directly under the pipe, and used the sheet pile method. When conducting pipe installation experiments, it was found that it was often impossible to prevent the flattening of the pipe due to sheet pile removal, and the flattening of the buried pipe when the sheet pile was pulled out caused backfilling of earth and sand directly under the buried pipe. I learned that this is not caused only by loosening or washing away.

Strain in a buried pipe due to earth pressure is a superposition of strain due to vertical earth pressure acting on the top of the pipe and strain due to horizontal soil pressure acting on the side of the pipe. In this case, the horizontal earth shoal occurs as a result of the vertical earth pressure P8 acting on the side of the pipe preventing the earth and sand from spreading laterally at Poisson's ratio μ. The concentrated earth pressure Px approximated by this horizontal earthen can be expressed as PxoCμP8 .

Deformation of a buried pipe due to earth pressure can be approximately considered to be due to concentrated earth pressure py in the vertical direction acting on the top of the pipe and concentrated earth pressure Px in the horizontal direction acting on the side surface of the pipe. 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 equation for the deflection U (deflection at a position separated by an angle ζ from the point of load application) is as follows. Yes, the solution is U=PR'PR'',PR'EI7r 4
Since EIζSinζ−unitζ−■EI, the strain ε 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 is given by:

As is clear from the 0th equation, flattening of the tube also occurs due to a decrease in the horizontal upper pressure Px. Also, as is clear from equation 0, this Px is the vertical earth pressure P2 acting on the side of the pipe.
decreases due to a decrease in

However, in the above-mentioned pipe installation experiment, the present inventors observed that a considerable amount of earth and sand adhered to the sheet piles and escaped when the sheet piles were pulled out. It is unavoidable that the voids left by the extraction will become larger. Therefore, if the void in the sheet pile remains becomes large, the soil adjacent to the void will flow, the compaction of the soil will loosen, the density will decrease, and the vertical earth pressure Pg acting on the pipe side will decrease. Therefore, the concentrated earth pressure Px acting on the side surface of the pipe decreases, causing flattening of the pipe.

The present inventors have confirmed from the above-mentioned pipe installation experiment that the adhesion and escape of earth and sand during sheet pile pulling is also one of the causes of flattening of the pipe when sheet piles are pulled out.

Based on this knowledge, an object of the present invention is to prevent soil from adhering to and escaping when the sheet pile is pulled out, and to guarantee the stability of the buried state of the pipe in a method for laying underground pipes using the sheet pile method. .

Means for Solving the Problems> The method for installing an underground pipe according to the present invention includes the steps of: retaining earth using sheet piles, placing the pipe in an excavated trench, and backfilling the trench;
Then, in the pipe installation method in which the sheet pile is pulled out, when backfilling the trench, a scraper is buried to scrape off the adhered soil from the sheet pile surface.

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

To carry out the present invention, sheet piles are driven into the original ground, earth and sand between the sheet piles is dug out, trenches are excavated, and a foundation floor is constructed using concrete, chestnut stone, or the like. Afterwards, as shown in Fig. 1, a scraper 3 is placed on the foundation floor 1 in contact with the inner surface of the sheet pile 2, soil 4 is spread on top of it, a pipe 5 is placed, and the material is filled with ±4. I'll bring it back. Backfilling of soil 4 is as follows:
A scraper 32 can also be placed in the middle of the backfill layer, which is used to compact the backfill layer to a predetermined thickness using a tamper or the like.

FIG. 2 shows a cross section taken along the line ■-■ in FIG. U-shaped steel sheet piles are used for the sheet piles 2, and are engaged in alternately convex and concave directions. The scraper 31 uses a large number of divided pieces, and the head of each piece is housed in the four parts of the sheet pile. Z-shaped steel sheet piles shown in FIG. 3 can also be used for the sheet piles.

After backfilling the excavation 7116, the sheet piles will be pulled out one by one. In this case, since the heads of the scrapers 31 and 32 are housed in the recesses of the sheet pile 2, the earth and sand that have bitten into the recesses of the sheet pile 2 can be scraped off by the scrapers 31 and 32 and remain in the soil.

That is, in FIG. 1, below the scraper 31, soil that has bitten into the recessed portion of the sheet pile 2 can be scraped off by the scraper 31, and the soil can be scraped off by the scraper 31.
Between the scraper 1 and the scraper 32, the scraper 32 can scrape off the earth and sand that has dug into the recessed part of the sheet pile 2, and the earth and sand that have dug into any part can remain in the soil.

In the above, it is necessary to firmly fix the scrapers 31 and 32 against the soil scraping force, and the length y of the rear end of the scraper is determined by the penetration depth of the sheet pile, the height of the earth cover, It may be determined according to the soil quality, etc.

As the material of the scraper, any suitable material can be used as long as it has a specified rigidity or strength and can be molded into a specified shape.For example, synthetic resin such as hard thermoplastic resin or thermosetting resin can be used. , a single plate of ceramic, concrete, metal, etc., a reinforcing material such as a metal plate embedded in a synthetic resin material, or Figure 4A (plan view) and Figure 4B (side view)
It is possible to use a material with reinforcing ribs 30 molded as shown in FIG.

Scraper 31. (32), a continuous type as shown in Fig. 5, or a divided piece in male and female stages as shown in Fig. 6A and Fig. 6B (each cross-sectional view of Fig. 6A). It is also possible to use a device that locks with a surface, etc.
With these scrapers, the earth cover holding area is large for pulling out sheet piles one by one, so y is
can be almost equivalent to

Further, in the case of a continuous type, those shown in FIG. 7A or FIG. 7B can be interlocked with each other and stacked, which is convenient for transportation, storage, etc.

In the above, among the soil that digs into the recesses of the sheet pile when the sheet pile is driven, the soil above the base bed can be easily removed when trenching and excavating, and the backfilling soil in the trench usually contains sand. Since sand is rarely attached to the sheet piles, it is usually sufficient to use a scraper to scrape off only the soil that has dug into the recesses of the sheet piles at the thickened portions of the sheet piles. It is only necessary to provide it directly above. However, depending on the soil quality, soil conditions, etc., the soil may dig firmly into the recesses of the sheet pile above the rooting part, and it will be necessary to scrape it off. It is also necessary to arrange cylindrical scrapers at predetermined vertical intervals in the return section.

<Effects of the Invention> The method for laying underground pipes according to the present invention is as described above, and when laying underground pipes by the sheet pile method,
The soil adhering to the sheet piles is scraped off with a scraper, and the adhering soil remains in the soil when the sheet piles are pulled out. Even in soils that tend to adhere to the sheet piles, the voids left by the sheet piles can be made sufficiently small. The flow of soil into the void can be stopped unevenly, and the decrease in the vertical earth pressure acting on the side of the pipe, and therefore the reduction in the horizontal soil pressure acting on the side of the pipe, can be well prevented. Deformation of the pipe due to unbalance with horizontal earth pressure on the sides can be eliminated, and the buried pipe can be held stably.

[Brief explanation of drawings]

FIG. 1 is an explanatory view of one embodiment of the present invention, showing the state before the sheet pile is pulled out. Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, Fig. 3 is an explanatory diagram showing the side tilting of the sheet pile used in the present invention, Fig. 4A, Fig. 5, Fig. 6A, Fig. 7A. 7B is an explanatory plan view showing the side tilting of the scraper used in the present invention, FIG. 4B is a side view of FIG. 4A, and FIG. 6B is a cross-sectional explanation of each of FIG. 6A. It is a diagram. 1... Base floor, 2... Sheet pile, 31.32... Scraper 41.・Backfill soil, 5...pipe, 6...excavation trench.

Claims (1)

[Claims] In a pipe installation method in which earth retaining is performed using sheet piles, a pipe is placed in an excavated trench, the trench is backfilled, and the sheet piles are then pulled out. An underground pipe installation method characterized by burying a scraper for scraping off soil.