JP3147793U - Wall prevention structure for manholes during an earthquake - Google Patents

Abstract

A manhole structure is provided for preventing the surrounding ground of a sewer manhole from liquefying and rising when an earthquake occurs. After excavation is completed, the base chestnut 5 is spread and the bottom plate 3 of the factory product is installed. A straight wall pipe 1c is placed on this and a sewer pipe 6 is attached at a predetermined position, and then a cast-in-place concrete bottom slab 4 is placed, and a sewage channel 7 is provided on the top of the bottom slab. At the stage of assembling up to the uppermost straight wall pipe 1c, the periphery of the manhole straight wall pipe is backfilled while being sufficiently compacted. A hollow concrete cylindrical pipe 8 is placed on the straight wall pipe 1c, and the pipes are connected to each other by a connecting plate 9b. Further, the manhole inclined wall tube 1b and the manhole cover receiving frame 1a are assembled. After that, the manhole cover tube 1 is filled back with sufficient tightening on the upper surface of the circular projecting portion of the hollow concrete cylindrical tube 8, and the soil 12 is applied. Complete it. [Selection] Figure 1

Description

  The present invention relates to a manhole structure for preventing the surrounding ground of a sewer manhole from becoming liquefied and rising during an earthquake.

Sewer manholes are frequently raised due to liquefaction during earthquakes, causing problems such as the fact that the water in the pipes can no longer flow and the roads are raised. This is because when the ground around the manhole is a fine sand layer and the groundwater level is high, the ground liquefies due to a strong earthquake and a large buoyancy acts on the manhole.
Possible countermeasures include increasing the weight of the manhole and anchoring it to the non-liquefied layer with a steel rod, but there is still room for study in terms of structure, workability, safety, etc. .

As a method for preventing the manhole from rising, 1) the ground around the manhole is backed up with crushed stones that are difficult to liquefy, 2) a steel rod is attached to the manhole, and the non-liquefied layer is anchored, and 3) the manhole is heavy. There are ways to do this. In the new manhole construction work, the work to prevent lifting is added, which increases the amount of work on the road, necessitates long-term traffic regulation, and a rational method that can further reduce the time is desired.
In order to solve this problem, when assembling the manhole member of the factory product on-site, a member for increasing the weight of the manhole is prepared, and the construction can be completed in a short time by performing a series of assembly operations.

Means to solve

  In the case of a new manhole, each part of the factory product is usually brought to the site, and after completion of excavation, the bottom plate, straight wall pipe, slant wall pipe and lid receiving frame are assembled. In the assembly process, a hollow concrete cylindrical pipe having a short outer diameter of 1.2 to 1.8 times and an inner diameter of the same diameter as the straight wall pipe is formed at the top of the straight wall pipe. Is formed into a circular protrusion, and the lifting of the manhole is suppressed by the weight of the cylindrical tube and the weight of the backfill and pavement on the upper surface of the protrusion. As a result, a manhole having a lifting prevention structure can be completed in substantially the same process as normal manhole construction.

Effect of device

  According to the present invention, in the case of a new manhole, it is possible to install a manhole having a lifting prevention structure in almost the same process as normal construction. A hollow concrete cylindrical tube with an outer diameter 1.2-1.8 times larger than that of a straight-walled tube built into the top of the straight-walled tube forms a circular protrusion on the outer periphery of the manhole, and is applied to its own weight and the upper surface of the protrusion Prevents the manhole from rising due to the weight of the backfill soil.

Each part of the factory product is brought into the field, and after excavation is completed, the bottom plate and straight wall pipe are assembled, and the work is performed while the backfill soil around the manhole is fully compacted. Next, a hollow concrete cylindrical tube, a slanted wall tube, and a manhole cover receiving frame that form the protrusions are assembled and constructed in sequence, and then, the upper surface of the hollow concrete cylindrical tube is sufficiently compacted to construct backfill soil and pavement.

Embodiments will be described with reference to the accompanying drawings.
FIG. I [A] shows a longitudinal cross-sectional view of the newly installed manhole. After excavation, the foundation chestnut 5 is spread and the bottom plate 3 of the factory product is installed. A straight wall pipe 1c is placed on this and a sewer pipe 6 is attached at a predetermined position, and then a cast-in-place concrete bottom slab 4 is placed, and a sewage channel 7 is provided on the top of the bottom slab. At the stage of assembling up to the uppermost straight wall pipe 1c, the periphery of the manhole straight wall pipe is backfilled while being sufficiently compacted.
A hollow concrete cylindrical pipe 8 is placed on the straight wall pipe 1 c and the pipes are connected to each other by a connecting plate 9. Further, the manhole inclined wall tube 1b and the manhole cover receiving frame 1a are assembled. After that, the backfilling soil 12 is applied to the upper surface of the circular projecting portion of the hollow concrete cylindrical tube 8 while being sufficiently tightened, and the pavement 10 is performed thereon. Complete.

[A] is a manhole longitudinal sectional view taken along the line II of FIG. 2, and [B] is a soil column diagram around the manhole. Is a cross-sectional view of the manhole taken along line II-II shown in FIG. [A] is an enlarged cross-sectional view showing a coupled state of a straight wall pipe, a hollow concrete cylindrical pipe and a slant wall pipe, and [B] is an enlarged front view of the inner wall side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Manhole cover frame 1b Slanted wall pipe 1c Straight wall pipe 2 Manhole cover 3 Bottom plate 4 Cast-in-place concrete bottom plate 5 Foundation chestnut stone 6 Sewer pipe 7 Sewer channel 8 Hollow concrete cylindrical tube 9a Bolt 9b Joint plate 9c Nut 10a Pavement 10b Liquefaction Formation 11 Groundwater level 12 Backfill soil

Claims (2)

  At the top of the manhole straight wall pipe, there is a short hollow concrete cylindrical pipe whose inner wall diameter is the same as that of the manhole straight wall pipe and whose outer wall diameter is 1.2-1.8 times the outer diameter of the manhole straight wall pipe. A manhole lift prevention structure, characterized in that a protrusion is formed on the outside of the manhole straight wall tube, and the upper surface of the protrusion is backfilled with crushed stone and paved.   2. The manhole lifting prevention structure according to claim 1, wherein the inner wall of the short hollow concrete cylindrical tube and the inner wall of the lower straight wall tube are joined by a connecting plate.

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