JP2007218072A - Manhole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manhole capable of being easily constructed in an existing manhole, enabling the installation of a drain pipe prevented from being clogged without using a filter or the like, and hence easily securely preventing the manhole from floating by the liquefaction of the ground due to earthquake. <P>SOLUTION: A cylindrical manhole skeleton 1 is provided on a foundation bottom board 4 provided underground and is embedded underground and its opening is opened to the ground surface GL in the manhole. The drain pipe 6 which passes through the foundation bottom board 4 and leads to the ground under it is raised in the cylindrical manhole skeleton 1, and the upper end of the drain pipe 6 is arranged in the manhole skeleton 1. Concretely the lower end of the drain pipe 6 passes through the foundation bottom board 4 and a water storage part 14 in a seating plate 12 provided on it and leads to the ground under it. The height of the upper end opening of the drain pipe 6 is adjustable and the height of the upper end opening of the drain pipe 6 is more than an underground water level GWL. <P>COPYRIGHT: (C)2007,JPO&INPIT

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. The present invention relates to a manhole equipped with a water drain pipe for preventing the above.

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.
FIG. 7 shows a conventional manhole example. 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 at 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 an invert. 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. . Therefore, as shown in FIG. 7, it has been proposed to bury a drain pipe 26 reaching 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. With 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 pipe 26 or the backfill layer. It is intended to prevent lifting.

  However, in the drainage pipe 26 and the gravel backfill layer 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 a drainage action that can effectively prevent the manhole from rising up cannot be expected.

  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 suppresses the buoyancy applied to the manhole housing from the surrounding ground by allowing water to flow into the manhole housing. It is intended to prevent the lifting.

  However, when these drainage pipes 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 pipe and the backfill layer made of gravel material. Therefore, as shown in Japanese Patent Application 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 drain pipe. However, even if this filter is provided on the inlet side of the drainage pipe connected to the manhole housing, the filter is clogged with water, 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 drain pipe that does not occur, thereby easily and reliably preventing the manhole from rising due to the liquefaction of the ground due to an earthquake.

  In order to achieve the above-mentioned object, in the present invention, the drainage pipe 6 that leads to the ground below the foundation bottom 4 of the manhole housing 1 can be easily installed in the existing manhole by standing in the manhole housing 1. At the same time, it was 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 up. 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 includes a cylindrical manhole housing 1 provided on the foundation base 4 provided in the ground, and embeds these in the ground and opens the opening to the ground GL. The drain pipe 6 leading to the ground below the foundation bottom 4 is erected in a cylindrical manhole casing 1 and the upper end of the drain pipe 6 is arranged in the manhole casing 1.
More specifically, the lower end of the drain pipe 6 communicates with the foundation bottom through the foundation bottom 4 and the water reservoir 14 in the base plate 12 provided thereon. Alternatively, the lower end of the drain pipe 6 passes through the foundation bottom 4 and reaches the underlying crushed stone layer 3.

  In such a manhole according to the present invention, the drain pipe 6 leading to the ground below the foundation bottom 4 of the manhole housing 1 is erected in the manhole housing 1, so that even in the existing manhole, a person can The drain pipe 6 can be installed by working inside. 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 effect on the manhole lift can be drawn into the manhole housing 1 through the drainage pipe 6. Can be effectively prevented. Further, the uppermost layer of the ground leading to the drainage pipe 6 is usually the basic crushed stone layer 3, and therefore groundwater flows into the drainage pipe 6 through the basic crushed stone layer 3. At this time, the basic crushed stone layer 3 functions as a filter, and only water can be extracted from the ground with a drain pipe 6. Thereby, the inflow of earth and sand to the drain pipe 6 can be prevented, and the pipe connected to the drain pipe 6 and the manhole can be prevented from being clogged with earth and sand.

  In addition, the height of the upper end opening of the drain pipe 6 can be adjusted, and the height of the upper end opening of the drain pipe 6 is equal to or higher than the groundwater level GWL, so that the ground liquefaction phenomenon caused by the earthquake does not occur. In this state, the water level in the water drain pipe 6 can be made lower than the height of the upper end opening. Thereby, in the normal state, inflow of groundwater into the manhole housing 1 can be prevented. Moreover, by adjusting the height of the upper end opening of the drain pipe 6, the height of the drain pipe 6 can be adjusted at any time according to the groundwater level at the site.

  As described above, in the manhole according to the present invention, the drainage pipe 6 can be installed regardless of existing or new installation. And when the liquefaction phenomenon of the ground due to the earthquake occurs, the water of the ground below the foundation bottom 4 that has the greatest influence on the manhole lift is drawn into the manhole housing 1 through the drain pipe 6 so that the manhole lifts up. It can be effectively prevented.

In the present invention, the drainage pipe 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. For example, the inflow pipe 10 and the outflow pipe 11 are constructed by a propulsion method using the manhole as an arrival shaft and a transmission shaft. Thereafter, the dug out portion is backfilled and the manhole housing 1 is buried in the ground.

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, a drain pipe 6 that leads to the ground below the foundation bottom 4 of the manhole housing 1 is erected in the manhole housing 1. In the illustrated example, as shown in FIG. 2, four drainage pipes 6 are erected, but the number of the drainage pipes 6 can be appropriately changed depending on the size of the manhole housing 1 or the like. The lower end of the drainage pipe 6 is erected by being fitted into a pedestal plate 12 described below, and also communicates with the basic crushed stone layer 3 below the base bottom 4 through a water reservoir 14 described below. Moreover, the height of the upper end opening of the drain pipe 6 can be adjusted by the adjusting unit 7, and the height of the upper end opening of the drain pipe 6 is set to be higher according to the groundwater level GWL. .

  In this first embodiment, a pedestal plate 12 is provided on the foundation bottom plate 4, the drainage pipe 6 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 example shown in the figure, four holes are provided in advance so as to fit the lower end of the drain pipe 6.

  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, the manhole block 2 is stacked on the foundation bottom board 4. Also, before and after this, a base plate 12 is placed on the central portion of the foundation bottom 4 and a drain pipe 6 is erected and fixed thereto. 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 drain pipe 6 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 drain pipe 6 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 hole, the drain pipe 6 is inserted into the base plate 12 from the invert 5 side. The depth of insertion of the drain pipe 6 is such that its lower end is flush with the lower surface of the pedestal plate 12, and the gap between the holes is filled with mortar and clogged.

  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. A drain pipe 6 is erected and fixed to the invert 5 and the base plate 12. On the other hand, when constructing the invert 5 by placing concrete on site, after placing and fixing the drain pipe 6 on the pedestal plate 12, the concrete is cast at the bottom of the manhole block 2. Invert 5 is reconstructed.

  In this manhole, groundwater enters the drainage pipe 6 from the basic crushed stone layer 3 through the water reservoir 14 during normal times, and the drainage pipe 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 foundation bottom 4 from the foundation crushed layer 3 through the water reservoir 14 enters the drainage pipe 6. The groundwater flows into the manhole housing 1 from the drain pipe 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. Water that has flowed into the manhole housing 1 through the drain pipe 6 is drained from an outflow tube 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 drain pipe 6 from here. Therefore, the basic crushed stone layer 3 serves as a filter, and the earth and sand are removed from the groundwater. Filter, and only the groundwater flows into the drain pipe 6. For this reason, a lot of earth and sand does not flow into the drainage pipe 3, and it is possible to prevent the drainage pipe 3 from being clogged or clogging the pipe 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.

  This second embodiment is different from the first embodiment described above in that no pedestal plate is used and no hole is provided in the foundation bottom 4, and the drainage pipe 6 penetrates the foundation bottom 4 of the manhole housing 1. Is erected in the manhole housing 1. The lower end of the drainage pipe 6 penetrates the foundation bottom 4 and reaches the underlying crushed stone layer 3. That is, in this second embodiment, there is no water reservoir, and groundwater flows directly into the drainage pipe 6 through the basic crushed stone layer 3.

  For example, in the case of constructing the foundation floor 4 by placing concrete on the site in a new manhole, the drainage pipe 6 is erected and fixed on the foundation crushed stone layer 3, and the part that becomes the foundation floor 4 in this state A formwork is assembled around the base, and ready-mixed concrete is placed there, and this is cured to form the foundation bottom 4. Thereafter, the manhole block 2 is stacked, and concrete is placed on the bottom of the manhole block 2 to form the invert 5, and the shape of the upper surface thereof is adjusted.

  Further, for example, when constructing an existing manhole, a concrete drilling machine is used to make a hole through which the drain pipe 6 passes from the invert 5 provided at the bottom of the concrete frame 1 to the foundation bottom 4, and the drain pipe 6 is provided in this hole. After that, raw mortar or the like is filled between the hole and the drain pipe 6 to be cured, and then clogged.

  In this manhole, groundwater enters the drainage pipe 6 through the basic crushed stone layer 3 during normal times, and the drainage pipe 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 groundwater increases, the groundwater under the manhole foundation bottom 4 flows into the drainage pipe 6 through the foundation crushed stone layer 3, Groundwater flows from the drain pipe 6 into the manhole housing 1. As a result, the rapid increase in the groundwater pressure below the manhole foundation floor 4 is suppressed, and the manhole foundation floor 4 is restrained 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.

In addition, the water flowing into the manhole housing 1 through the drain pipe 6 is drained by the outflow pipe 11, and the ground crushed stone layer 3 serves as a filter when the ground water flows into the drain pipe 6. This is the same as in the first embodiment.
However, since the area where the groundwater flows into the drainage pipe 6 through the basic crushed stone layer 3 is limited to the total inner cross-sectional area of the drainage pipe 6, the drainage efficiency is slightly inferior to that of the first embodiment described above. In order to solve this, measures such as slightly increasing the diameter of the drain pipe 6 are necessary.

It is a vertical side view which shows the manhole which is one Example of this invention. It is a cross-sectional top view which shows the manhole which is the same Example. 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. It is a cross-sectional top view which shows the manhole which is the same Example. 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 layer 4 Foundation bottom 6 Drain pipe 12 Pedestal board 14 Water reservoir GL Ground GWL Groundwater level

Claims (6)

In the manhole in which a cylindrical manhole housing (1) is provided on the foundation floor (4) provided in the ground and these are embedded in the ground and the opening is opened in the ground (GL), the foundation floor ( 4) The drainage pipe (6) leading to the ground below is erected in the cylindrical manhole casing (1), and the upper end of the drainage pipe (6) is placed in the manhole casing (1). Characteristic manhole. The lower end of the drain pipe (6) communicates with the ground below it through a water reservoir (14) in a base bottom plate (4) and a base plate (12) provided thereon. The listed manhole. The manhole according to claim 1, characterized in that the lower end of the drain pipe (6) passes through the foundation bottom (4) and reaches the ground below it. The manhole according to any one of claims 1 to 3, wherein the uppermost layer of the ground leading to the drain pipe (6) is a basic crushed stone layer (3). The manhole according to any one of claims 1 to 4, wherein the height of the upper end opening of the drain pipe (6) is adjustable. The manhole according to any one of claims 1 to 5, wherein a height of an upper end opening of the drain pipe (6) is set to be equal to or higher than a groundwater level (GWL).

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