JP4809741B2 - manhole - Google Patents

Description

  The present invention relates to a manhole provided in the ground for the purpose of inspecting and maintaining a water and sewer pipe buried in the ground, and more specifically, the manhole is lifted by a ground liquefaction phenomenon caused by an earthquake or the like. It is related with the manhole provided with the drain part for preventing.

FIG. 7 shows an example of a manhole provided in the ground for the purpose of inspecting and maintaining a water and sewage pipe buried in the ground.
In general, such a conventional manhole is dug from the ground to a necessary depth, and a basic crushed stone layer 23 made of crushed stone is provided at the bottom. A concrete foundation bottom 24 is provided on the foundation crushed stone layer 23. One or more cylindrical manhole blocks 22 that are precast concrete products are stacked on the foundation bottom plate 24, the height is adjusted as necessary, and the uppermost manhole block 22 is stacked. To construct. The upper end opening of the manhole housing 21 is set to the height of the ground GL, and the upper end opening can be opened and closed by fitting the lid 28 into the lid frame 29 provided in the upper end opening. Further, the base bottom plate 24 in the manhole housing 21 is provided with a bottom plate 25 with a water channel groove called invert, and an inflow pipe and an outflow pipe are formed on the wall surface of the manhole housing 21 so that water flows through the water channel groove of the invert 25. Connect pipes such as 31. Thereafter, the dug portion is backfilled and the manhole housing 21 is buried in the ground. In the example of FIG. 7, the inflow pipe is in front of the cross section and is not shown.

  In such a manhole, when the underground ground has been liquefied due to the occurrence of an earthquake, it has been regarded as a problem that the manhole housing 21 including the foundation bottom 24 is lifted from the ground due to an increase in the groundwater pressure. . For this reason, as shown in FIG. 7, it has been proposed to bury a drainage portion 26 that reaches the ground GL from the ground in the vicinity of the base bottom 24 of the manhole housing 21. Alternatively, it has also been proposed to form a backfill layer that reaches the ground surface GL made of gravel material around the manhole housing 21. By these measures, the groundwater pressure generated in the ground near the bottom of the manhole housing 21 due to the liquefaction phenomenon of the ground that occurs in the event of an earthquake is released to the ground through the drainage part 26 or the backfill layer, and the manhole It is intended to prevent lifting.

  However, in the drainage part 26 and the backfill layer of gravel material as shown in FIG. 7, groundwater always exists to the same level as the groundwater level GWL in the ground. For this reason, there is a problem that the resistance for releasing the water pressure when a liquefaction phenomenon due to an earthquake occurs is large, and it is impossible to expect a drainage action that can effectively prevent the manhole from rising.

  As means for solving this problem, as disclosed in JP-A-8-92984, JP-A-8-165665, and JP-A-8-165667, the basics of the manhole housing 21 are passed through a drain pipe or a backfill layer. It has also been proposed to allow water drawn from the vicinity of the bottom plate 24 to flow into the manhole housing 21 instead of onto the ground GL. This reduces drainage resistance when draining water when liquefaction occurs, and reduces the buoyancy applied to the manhole housing from the surrounding ground by allowing water to flow into the manhole housing. This is to prevent lifting.

  However, when these drainage parts are provided outside the manhole housing or a backfill layer made of gravel material is provided around the manhole housing, the surroundings of the manhole housing must be dug when constructing the existing manhole. To that end, crushing of the pavement layer, vertical hole excavation using heavy machinery, etc. are required, and thereafter, processes such as backfilling and re-paving are required.

  In addition, in the ground liquefaction phenomenon caused by an earthquake, groundwater liquefies including earth and sand, which may clog the drainage layer and the backfill layer made of gravel material. Therefore, as shown in Japanese Patent Laid-Open No. 8-92984, it is necessary to attach a filter or the like to the inlet side connected to the manhole housing of the drainage portion. However, even if this filter is provided on the inlet side connected to the manhole housing of the drainage portion, it results in clogging of water at the filter portion, and an effective drainage effect cannot be achieved.

JP-A-8-92984 JP-A-8-165665 JP-A-8-165666 JP-A-8-165667

  In view of the problem of the above-described conventional manhole, in particular, lifting prevention technology due to the liquefaction phenomenon of the ground due to an earthquake, the present invention can be easily applied to an existing manhole, and clogging is possible without using a filter or the like. The purpose is to make it possible to install a drainage portion that does not occur, thereby easily and reliably preventing the manhole from rising due to the liquefaction phenomenon of the ground due to an earthquake.

  In order to achieve the above-described object, in the present invention, the drainage portion 6 leading to the ground below the foundation bottom base 4 of the manhole housing 1 is provided in the wall portion of the manhole housing 1 so that it can be easily applied to an existing manhole. In addition, it is possible to release the water pressure immediately below the foundation bottom 4 which is most effective in preventing the manhole housing 1 from being lifted. In addition, the basic crushed stone layer 3 under the basic bottom plate 4 can be used as a filter.

That is, the manhole according to the present invention is provided with a pedestal plate 12 under the invert 5 that forms the bottom plate of the manhole, and under the pedestal plate 12, a water reservoir portion 14 that communicates with the ground under the base bottom plate 4 is formed. By standing the inner cylinder 15 on the plate 12, a drainage portion 6 is formed in the inner cylinder 15 or between the inner cylinder 15 and the concrete casing 1, and the lower end of the drainage portion 6 is connected to the base plate 12. The upper water drainage portion 6 is disposed in the manhole housing 1 while being communicated with the lower water reservoir portion 14 .
For example, the drainage portions 6 are provided on both sides of the step 7 provided on the wall portion of the manhole housing 1.

In such a manhole according to the present invention, a pedestal plate 12 is provided in advance under the invert 5 that forms the bottom plate of the manhole, and a water reservoir portion 14 is formed under the pedestal plate 12 so as to communicate with the ground below the base bottom plate 4. Since the drainage portion 6 is provided by standing the inner cylinder 15 on the pedestal plate 12 , even in an existing manhole, a person enters the manhole housing 1 and stands the inner cylinder 15 on the pedestal plate 15. Thus, the drainage part 6 can be installed. Therefore, excavation around the manhole housing 1 is not required, and it can be easily installed in an existing manhole. Of course, it can also be installed in a new manhole.

  Furthermore, when the ground liquefaction phenomenon occurs due to the earthquake, the ground water under the foundation bottom 4 that has the greatest influence on the manhole lift can be drawn into the manhole housing 1 through the drainage 6. Can be effectively prevented. Further, the uppermost layer of the ground leading to the drainage section 6 is usually the basic crushed stone layer 3, and therefore groundwater flows into the drainage section 6 through the basic crushed stone layer 3. At this time, the basic crushed stone layer 3 functions as a filter, and only the water can be extracted from the ground by the drainage portion 6. Thereby, inflow of the earth and sand to the drainage part 6 can be prevented, and it can prevent that the piping connected to the drainage part 6 and a manhole is clogged with earth and sand.

Further, draining unit 6 is provided by erecting the inner cylinder 15 to the base plate 12 because, it is possible to easily secure a space for the working person enters into the manhole skeleton 1, the existing manhole It is easy to install the water draining part 6 in the water.

  As described above, in the manhole according to the present invention, the drainage portion 6 can be installed regardless of whether the manhole is existing or newly installed. And when the liquefaction phenomenon of the ground due to the earthquake occurs, the water of the ground under the foundation bottom 4 that has the greatest influence on the lift of the manhole is drawn into the manhole housing 1 through the drainage part 6, so The lower water pressure can be reduced, and the manhole can be effectively prevented from rising.

In the present invention, the drainage portion 6 leading to the ground below the foundation bottom 4 of the manhole housing 1 is erected in the manhole housing 1 so that it can be easily constructed in an existing manhole and the manhole housing 1 The water immediately below the foundation bottom 4 that is most effective in preventing the lifting of water can be removed without clogging.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

1 is a longitudinal side view showing a manhole according to the first embodiment of the present invention, FIG. 2 is a sectional view taken along line AA ′, and FIG. 3 is a longitudinal front view thereof.
A manhole digs up a shaft from the ground to a necessary depth into the ground, and a basic crushed stone layer 3 made of crushed stone is provided at the bottom. On this basic crushed stone layer 3, a precast foundation bottom board 4 molded in advance at a factory is installed, or concrete is cast on site to provide the foundation bottom board 4. On top of this foundation base 4, stack one or more cylindrical manhole blocks 2, which are precast products, and adjust the height as necessary, then stack the uppermost manhole blocks 2 to construct the manhole housing 1 To do.

  The upper end opening of the manhole housing 1 is set to the height of the ground GL, and the upper end opening can be opened and closed by fitting the lid 8 into the lid frame 9 provided in the upper end opening. Further, the foundation bottom plate 4 in the manhole housing 1 is provided with a bottom plate with a water channel groove called invert, and an inflow pipe 10 (see FIG. 1) is formed on the wall surface of the manhole housing 1 so that water flows into the water channel of the invert 5. ) And the outflow pipe 11 are connected. Thereafter, the dug out portion is backfilled and the manhole housing 1 is buried in the ground. Steps 7 are provided on the inner wall surface of the manhole housing 1 at appropriate intervals in the vertical direction so that a person can step up and down the manhole.

The above is the same as the conventional example described above with reference to FIG. However, in recent manhole installation work, a steel blade for press-fitting propulsion is provided at the lower end of the cylindrical manhole block 2, and the manhole block 2 is propelled while being pressed into the ground. A shaft propulsion method is also performed in which the earth and sand inside is discharged onto the ground, thereby building the manhole housing 1 in the ground.
However, it goes without saying that the present invention can be applied to manholes constructed by any method other than the method exemplified here.

Further, in the present invention, the drainage portion 6 that leads to the ground below the foundation bottom 4 of the manhole housing 1 is provided on the wall portion of the manhole housing 1. In this first embodiment , two inner cylinders 15 are erected on both sides of the step 7 provided on the inner wall surface of the manhole housing 1, and the inside of the inner cylinder 15 serves as a drainage portion 6. The inner cylinder 15 is made of a metal such as stainless steel or a synthetic resin such as vinyl chloride. Its shape is a cylindrical shape having a partial cylindrical surface having the same diameter as the inner wall surface of the manhole housing 1, and is attached symmetrically to both sides of step 7 with the partial cylindrical surface fixed to the inner wall surface of the manhole housing 1. Step 7 is installed between the inner cylinders 15 on both sides. The lower end of the inner cylinder 15 penetrates the invert 5, and the drainage portion 6 communicates with the basic crushed stone layer 3 below the foundation bottom 4 through a water reservoir portion 14 of the base plate 12 described below. Further, the height of the upper end of the inner cylinder 15 is provided so as to be higher than the groundwater level GWL, and a normal step 7 is used.

A pedestal plate 12 is provided on the base bottom plate 4, the inner cylinder 15 is erected on the pedestal plate 12, and the invert 5 is constructed thereon. The base plate 12 is a bottomless precast concrete member in which a cup is turned upside down, and a cross-shaped rib 13 for reinforcement is provided on the lower surface thereof. In the illustrated example, four holes for fitting the lower end of the inner cylinder 15 are provided in advance.

  Moreover, the foundation bottom board 4 provided between the foundation crushed stone layer 3 and the said base board 12 is a ring-shaped thing, and the center part is vacant. As a result, a water reservoir 14 is formed between the foundation base 4 and the lower side of the pedestal plate 12 for storing groundwater. The foundation bottom 4 may be either precast or may be molded by concrete placement on site.

For example, in the case of constructing a precast foundation bottom 4 in a new manhole, the foundation bottom 4 is installed horizontally on the foundation crushed stone layer 3. Then, manhole blocks 2 are stacked on the foundation bottom 4 to construct a manhole housing 1. Also, before and after this, a base plate 12 is placed on the center portion on the foundation bottom board 4, and an inner cylinder 15 is erected on this, and this is fixed to the inner wall surface of the manhole housing 1. Step 7 is also provided on the inner wall surface of the manhole housing 1. Further, ready-mixed concrete is cast on the bottommost part of the manhole block 2, the invert 5 is molded, and the shape of the upper surface thereof is adjusted. The base plate 12 and the inner cylinder 15 are completely fixed when the invert 5 is driven.

On the other hand, when the invert 5 is made of precast, a hole through which the inner cylinder 15 passes is provided in accordance with the base plate 12. After installing the invert 5 by aligning the positions of the base plate 12 and the holes, the inner cylinder 15 is inserted into the base plate 12 from the invert 5 side. The insertion depth of the inner cylinder 15 is set so that the lower end thereof is flush with the lower surface of the pedestal plate 12, and the gap between the holes is filled with mortar for clogging.

For example, when constructing in an existing manhole, after crushing the existing invert, a concrete drilling machine is used, and a hole having a diameter about half the diameter of the foundation bottom base 4 is formed in the center of the foundation bottom base 4. When the pedestal plate 12 is placed thereon and the precast invert 5 is used, it is placed on the pedestal plate 12 in the same manner as the above-described new construction. An inner cylinder 15 is erected on the invert 5 and the base plate 12, and is fixed to the inner wall surface of the concrete frame 1. On the other hand, when constructing the invert 5 by placing concrete on site, after placing and fixing the inner cylinder 15 on the pedestal plate 12, the concrete is cast on the bottommost part of the manhole block 2. Invert 5 is reconstructed.

  In this manhole, groundwater enters the drainage part 6 from the basic crushed stone layer 3 through the water reservoir 14 during normal times, and the drainage part 6 contains water at the same height as the groundwater level GWL. When a large earthquake occurs from this state and the ground liquefies and the pressure of the groundwater increases, the groundwater under the manhole base bottom 4 from the foundation crushed stone layer 3 through the water reservoir 14 flows into the drainage section 6. The groundwater flows into the manhole housing 1 from the drainage portion 6. Therefore, a rapid increase in the groundwater pressure under the manhole foundation bottom 4 is suppressed, and the manhole foundation bottom 4 is pressed from above by the gravity of the groundwater flowing into the manhole housing 1. Thereby, it is prevented that the foundation bottom board 4 is pushed up from the bottom by a groundwater pressure, and the manhole housing 1 does not float up.

  In particular, in this manhole, since the ground water directly under the foundation bottom 4 that determines the rising of the manhole can be drawn into the manhole housing 1, the lifting of the manhole housing 1 can be effectively prevented. The water that has flowed into the manhole housing 1 through the drainage section 6 is drained from an outflow pipe 11 connected near the bottom of the manhole housing 1. In addition, when underground ground fluidizes due to liquefaction, groundwater often contains a lot of earth and sand. In such a case, the groundwater flows into the water reservoir 14 through the basic crushed stone layer 3, and the groundwater flows into the drainage portion 6 from here, so the basic crushed stone layer 3 serves as a filter, and the earth and sand are removed from the groundwater. Filtration is performed, and only groundwater flows into the drainage section 6. For this reason, a lot of earth and sand does not flow into the drainage part 3, and it is possible to prevent the drainage part 3 from being clogged, or to prevent clogging of the piping due to accumulation of earth and sand in the manhole housing 1.

4 is a longitudinal side view showing a manhole according to a second embodiment of the present invention, FIG. 5 is a sectional view taken along line BB ′, and FIG. 6 is a longitudinal front view thereof.
The basic structure of the manhole in the second embodiment is the same as that of the first embodiment described above, and the same parts are indicated by the same reference numerals. Description of these parts is omitted.

  The second embodiment is different from the first embodiment described above in that a cylindrical inner cylinder 15 is provided inside the manhole casing 1 and the space between the manhole casing 1 and the inner cylinder 15 is provided as a drainage portion 6. It is a point to be. The lower side of the drainage portion 6 outside the inner cylinder 15 penetrates the invert 5 and communicates with the basic crushed stone layer 3 below the base bottom plate 4 through a water reservoir portion 14 of the base plate 12 described below.

  In this manhole, groundwater enters the drainage section 6 through the basic crushed stone layer 3 during normal times, and the drainage section 6 contains water at the same height as the groundwater level GWL. When a large earthquake occurs from this state and the ground liquefies, and the pressure of the groundwater increases, the groundwater under the foundation bottom 4 of the manhole flows into the drainage part 6 through the foundation crushed stone layer 3, Groundwater flows from the drainage section 6 into the manhole housing 1. As a result, the rapid increase in the groundwater pressure under the manhole foundation floor 4 is suppressed, and the manhole foundation floor 4 is suppressed from above by the groundwater flowing into the manhole chassis 1 so that the manhole chassis 1 does not rise. Is the same as in the first embodiment described above.

It is a vertical side view which shows the manhole which is one Example of this invention. FIG. 2 is a cross-sectional view taken along line A-A ′ of FIG. 1. It is a vertical front view which shows the manhole which is the same Example. It is a vertical side view which shows the manhole which is the other Example of this invention. FIG. 2 is a sectional view taken along line B-B ′ of FIG. 1. It is a vertical front view which shows the manhole which is the same Example. It is a vertical front view which shows the prior art example of a manhole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Manhole frame 3 Foundation crushed stone layer 4 Base bottom 6 Drainage part 12 Base plate 14 Reservoir part GL Ground GWL Groundwater level

Claims (2)

In the manhole in which the cylindrical manhole housing (1) is provided on the foundation bottom plate (4) provided in the ground and these are buried in the ground and the opening is opened to the ground (GL), the bottom plate of the manhole A base plate (12) is provided under the invert (5) forming the base plate, and a water reservoir (14) leading to the ground under the base bottom plate (4) is formed under the base plate (12), and the base plate By erecting the inner cylinder (15) on (12), a drainage part (6) is formed inside the inner cylinder (15) or between the inner cylinder (15) and the concrete casing (1). The lower end of the drainage part (6) is connected to the water reservoir (14) under the base plate (12), and the upper end of the drainage part (6) is arranged in the manhole housing (1). Manhole to do. 2. The manhole according to claim 1, wherein the drainage part (6) is provided on both sides of the step (7) provided on the wall part of the manhole housing (1).

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