JPH08170349A - Manhole - Google Patents

Abstract

PURPOSE: To prevent the generation of floating up resultant from a ground fluidization phenomenon mainly during seismic time. CONSTITUTION: A manhole comprises a water flow hole 10 which is penetrated through a peripheral wall of a manhole main body 1 buried underground so as to let outside water in. A check valve is installed to the water flow hole 10 where the check valve is designed so as to pass water only from outside the peripheral wall of the manhole main body 1 Geotextiles 14 are buried so as to surround backfilled earth and sand 11 around the manhole main body 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manhole which is prevented from rising mainly due to the fluidization phenomenon of the ground during an earthquake.

[0002]

2. Description of the Related Art In a conventional manhole, a water pipe connecting block for connecting a water pipe such as a sewer pipe is arranged at the bottom, and a cylindrical body block constituting a body is formed on it.
The manhole main body, which is formed by stacking in a single-stage or multiple-stage arrangement and stacking the upper end block that constitutes the upper opening at the uppermost part, is buried in the ground. Although many of these blocks are made of precast concrete, they may be manufactured locally.

[0003]

It is generally known that the ground liquefaction phenomenon occurs during an earthquake, and the conventional manhole described above sometimes rises due to this liquefaction phenomenon. The reason for this levitation is that when the manhole body is buried, the shearing force of the earth and sand backfilled around it is not reversed due to the seismic wave of the earthquake.

When the manhole floats in this way, not only is the drainage slope of the sewer pipe impaired, but
There was a problem that the function of the pipeline was lost when the ascent was extremely high.

The present invention has been made in view of such problems of the prior art.
The purpose was to provide a manhole that will prevent lifting even in the event of an earthquake.

[0006]

The features of the present invention for solving the above-mentioned conventional problems and achieving the intended purpose are as follows.
The manhole body is buried in the ground, and has a water hole for inflowing outside water penetrating inward and outward in the peripheral wall of the manhole body, and a geotextile is buried in an arrangement surrounding the manhole body. In addition, it is more preferable to embed the geotextile at the boundary between the inner surface of the excavation hole and the backfilling earth when burying the manhole body, and to surround the whole backfilling earth with the geotextile. It is more preferable to provide a check valve that allows water to pass through only from the outside of the peripheral wall of the main body.

[0007]

As described above, the reason why the manhole floats up during an earthquake is that the ground is liquefied and the ground around the manhole flows, and in the present invention, the external water flowing into the main body of the manhole flows through the manhole. By providing holes, the outside water, which is the surplus water in the soil, is taken into the manhole through the water passage holes to lower the water content of the surrounding ground and prevent the flow, and even when liquefaction occurs, it surrounds the surroundings. The presence of geotextile prevents the escape of sediment and prevents fluidization,
The permeability of geotextiles can dissipate excess pore water pressure, which prevents manholes from floating.

Further, a geotextile is buried at the boundary between the inner surface of the excavation hole and the backfilled earth when the manhole body is buried,
By surrounding the whole backfilled soil with the geotextile, it is possible to prevent fluidization by limiting the range of backfilled soil that is unstable with respect to the surrounding stable ground.

Furthermore, by providing a check valve in the water passage for the inflow of outside water to allow water to pass through only from the outside of the peripheral wall of the manhole body, it is possible to prevent the inside water from penetrating into the surrounding ground when the water in the manhole increases. It

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

In the figure, reference numeral 1 is a manhole body constructed by stacking precast concrete blocks. This manhole body 1 has a bottomed cylindrical water pipe connecting block 3 installed on the foundation concrete 2 at the lowest part.
The water pipes 4 and 4 are connected to the left and right.

A tubular body block 5 is piled up on the water pipe connecting block 3, and a cylindrical upper end block 6 having one side inclined in a tapered shape is piled up on it. A ring-shaped opening block 7 is fitted into the upper end opening of the manhole 6, and a manhole body 1 is constructed by fitting an upper lid 8 to the opening block 7. The upper surface of the upper lid 8 has substantially the same height as the ground surface 9. It is buried in the ground so that it becomes small.

Each of the blocks 3, 5 and 6 other than the opening block 7 has a large number of water holes 10, 10 ...
... are penetrated through inside and outside. It is preferable to provide the water passage holes in a range that occupies 3 to 10% of the peripheral wall surface of each block, and if it is less than 3%, the intended purpose cannot be achieved.
If it is 0% or more, the manhole strength is lowered, so that it is necessary to increase the thickness of the peripheral wall, which is not preferable.

A check valve 12 that is closed by water pressure inside the manhole body 1 is provided at the opening inside the manhole body 1 in each of the water holes 10, 10 ...
Water is prevented from flowing from the inside to the outer farts.

Further, a filter 13 is installed in each of the water passage holes 10, 10 ... To prevent the earth and sand outside the peripheral wall from flowing together with water.

Around the manhole body 1, a geotextile 14 is buried in a manner that it surrounds the backfilled earth / sand 11 when the manhole body 1 is buried. Geotextile is a water-permeable synthetic resin plate material that is generally used in the embankment reinforcement method for civil engineering, and specifically, the following conditions can be used.

Specific Example A B Element Material Nylon Polyethylene Unit Weight g / m ² 500 410 Thickness (mm) 1.0 1.8 Unit (mm) Vertical 0.30 Vertical 1.6 Horizontal 0.35 Horizontal 1. 5 Longitudinal tensile strength kgf / cm ² 430 360 If the geotextile 14 has a large mesh, it is not preferable because the fine sand part in the soil also flows together with the water flowing through the geotextile. The length is preferably in the range of 0.1 to 2.0 mm both vertically and horizontally, and 2.0 mm
With the above, preferable fluidization prevention cannot be achieved. The geotextile used in the present invention may be a synthetic resin fiber woven in a lattice or a non-woven fabric.

Geotextile 14 and manhole body 1
It is necessary to keep the distance from the surrounding wall of 60c to keep the backfilled earth and sand sufficiently compacted.
m or more is preferable.

In the manhole constructed as described above, the water in the ground including the backfilled sand 11 around the manhole body 1 passes through the water holes 111, 11 ...
Since the water flows in, a water level gradient shown by a temporary line a in FIG. 1 is formed, and the ground around the manhole body 1 is compacted.
Therefore, even if the soil pore water pressure increases due to the vibration during the earthquake, liquefaction does not easily occur around the manhole body 1,
Even if liquefaction occurs, the earth and sand surrounded by the geotextile 14 are prevented from flowing, and the interaction of these prevents the manhole body 1 from rising.

The buried position of the geotextile 14 is
As shown in FIG. 1, the manhole body 1 has a burial hole 15 for burial.
Although it may be in the middle of the backfill earth 11 inside, as shown in FIG. 4, it is installed along the inner surface of the excavation hole 15 for burying, the inside is filled with the backfill earth 11 and the whole backfill earth 11 is wrapped. By doing so, fluidization can be prevented by limiting the entire backfill portion that is unstable with respect to the surrounding stable ground.

Further, in the above-mentioned embodiment, the check valve 12 is provided in the water passage hole 10. However, it is not always necessary depending on the manhole conditions, for example, the water level in the inside does not rise so much, and the check valve 12 is not necessary. The filter 13 in the water hole 10 is
It is not always necessary when the water passage hole 10 is small or depending on the backfilling state. Further, in the above-mentioned embodiment, the manhole body is constructed by stacking the precast concrete blocks, but it may be a precast product integrally formed as a whole, or may be one formed by casting other parts of the precast product. .

[0022]

As described above, the manhole of the present invention is
By providing water holes for the inflow of outside water on the peripheral wall of the manhole body and embedding the geotextile around the backfill soil around the manhole body, liquefaction of the surrounding ground is less likely to occur during an earthquake. ,
Even if the liquefaction occurs, the fluidization of the surrounding ground is prevented and the floating of the manhole body is prevented.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an example of implementation of a manhole according to the present invention.

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

FIG. 3 is an enlarged cross-sectional view of a water passage hole portion of the above.

FIG. 4 is a vertical sectional view showing another embodiment of the manhole according to the present invention.

[Explanation of symbols]

 a Water level gradient 1 Manhole body 2 Foundation concrete 3 Block for connecting water pipe 4 Water pipe 5 Body block 6 Upper end block 7 Opening block 8 Top lid 9 Ground surface 10 Water hole 11 Backfill soil 12 Check valve 13 Filter 14 Geotextile 15 Drilling hole

Claims (3)

[Claims] 1. A peripheral wall of a manhole body buried in the ground is provided with a water hole for inflowing outside water penetrating inward and outward, and a geotextile is buried in an arrangement surrounding the backfilled earth and sand around the manhole body. It's a manhole. 2. The manhole according to claim 1, wherein a geotextile is buried at a boundary between the inner surface of the excavation hole and the backfilling earth when the manhole body is buried, and the whole backfilling earth is surrounded by the geotextile. 3. A check valve for letting water pass only from outside the peripheral wall of the manhole body, in the water passage for inflowing outside water.
Or the manhole described in 2.