JP5096206B2 - Manhole levitation prevention device - Google Patents

Description

  The present invention relates to a manhole floating prevention apparatus. More specifically, the present invention relates to a technique for preventing manholes from rising and protruding to the ground during an earthquake.

  There is a problem that a manhole standing on the road bed and having a top iron cover on the road surface protrudes on the road surface in the event of an earthquake, and hinders the operation of emergency vehicles and the like. It is very important for earthquake countermeasures to take measures to prevent such manholes from protruding to the ground.

  The mechanism by which the manhole is pushed up and projected to the ground during an earthquake is not always clear, but the ground is fluidized during an earthquake and pushed up by the increase in the pore water pressure of the groundwater acting on the lower surface of the manhole and the buoyancy of the manhole It is estimated that. Therefore, as a countermeasure, it is considered that the manhole can be prevented from being pushed up by reducing the fluctuation of groundwater around the manhole and the increase in water pressure.

    The design which copes with the influence on sewer facilities by liquefaction is calculated | required (for example, refer nonpatent literature 1).

  Ground liquefaction is caused by the fact that loose saturated sandy ground with a high groundwater level is subjected to rapid repeated loads due to earthquakes, etc., resulting in an increase in pore water pressure between sand particles and a sharp decrease in shear resistance. It is a phenomenon that behaves like When liquefaction occurs, sand and water fountains are generated, and the ground is compressed and sinks.Piles and buried pipes in the ground are moved by the ground movement due to lateral flow near the inclined ground and the revetment. There is a risk of serious damage.

  In addition, the Tokachi-oki earthquake (2003) and the Niigata Chuetsu earthquake (2004) caused liquefaction of backfill soil on the ground where there was no risk of liquefaction in the surrounding area, causing serious damage to the pipeline facilities. did. The characteristics of the damage were mostly subsidence of the excavated part of the pipeline constructed by excavation and floating of the pipeline. Especially in the Niigata Chuetsu Earthquake, over 1,400 manholes occurred.

  Due to the liquefaction of sand in the backfill material, pipes and manholes rise due to the landfill of the backfill due to mountain sand in the manhole, causing subsidence during the earthquake, causing volume shrinkage of the backfill material and excessive pore water pressure. The backfill soil that is generated and liquefied violently wraps around the lower side of manholes and underground pipes, and pushes the manholes and underground pipes upward.

  Based on this concept, there is a technique for ejecting water around the manhole into the inner cavity of the manhole as a technique for preventing the fluctuation of the groundwater around the manhole and the local increase in water pressure. (For example, refer to Patent Document 1).

  In this technology, a drain pipe is provided around the manhole, the lower end is opened below the groundwater level, the upper end is opened above the groundwater level surface and below the ground surface, and an excess pore water inlet is provided in the manhole. . This technology is prone to mud clogging and malfunction, and there is a problem of whether a sufficient water passage can be secured or whether a sufficient pressure relief effect can be expected at the time of an earthquake in which normal operation is most necessary.

  In addition, there is a technique in which a drain pipe that extends downward through the manhole base bottom plate in the manhole and rises above the groundwater level in the manhole is provided (for example, see Patent Document 2).

  This technique is intended to eliminate the drawback of clogging the drainage pipe provided outside the manhole or the backfill layer made of gravel material. However, since the underwater opening is only the pipe end opening, and the cross-sectional area is small and the inflow resistance is large, a good operation may be hindered.

As a liquefaction countermeasure method for the surrounding ground, the above Non-Patent Document 1
a) Compaction, replacement and solidification below groundwater level.

  b) Backfilling the excavated section with high-permeability crushed stones and the like to above the groundwater level to suppress the generation of excess pore water during an earthquake.

  c) Fix piles and anchors to the support layer to resist lifting.

d) For example, an underground pile made of crushed stone drain is constructed, and the pore water is drained above the ground water level or in the manhole to dissipate excess pore water pressure.
The construction method is raised.
JP-A-8-92984 JP 2007-218072 A Japan Water Works Association: Seismic Guidelines and Explanations for Sewerage Facilities-2006 Edition-

  In view of the above-described situation, the present inventors have conducted experiments and researched, and as a result, have developed a technology that effectively suppresses an increase in water pressure during an earthquake around a manhole.

  An object of the present invention is to provide an effective device for reducing the rise of water pressure around a manhole during an earthquake and preventing the manhole from rising based on the facts confirmed by such experiments.

The present invention has been made to solve the above problems, and is characterized by taking the following technical means. That is, the present invention includes a penetrating pipe penetrating the side wall of the manhole, a flexible pipe body having water permeability connected to the outside of the manhole of the penetrating pipe, and disposed inside the manhole of the penetrating pipe. A manhole inner tube having an opening position higher than the natural water level in the ground, and the flexible tube having water permeability includes a cylindrical filter provided in a spiral skeleton rib, and the skeleton. A manhole levitation comprising a plastic screw tube fitted to the outer diameter of the rib and a tube end cover, the tube end cover having a film body that is broken by pressure on the cover surface. Prevention device.

  The apparatus of the present invention can be provided with a large number of through pipes that penetrate the side wall of the manhole. The shape of the through tube is preferably a shape that minimizes the flow resistance.

  In addition, the water-permeable flexible tube disposed outside the manhole can be freely disposed in any length, in any arrangement, in any depth, etc., and can have a large water-permeable opening area. .

In the present invention, the flexible tubular body having water permeability is composed of a cylindrical filter provided in a spiral skeleton rib, a plastic screw tube fitted to the outer diameter of the skeleton rib, and a tube end lid. , tube end lid film body to break by pressing the lid surface (e.g., slit rubber elastic body or the like) Ru member der equipped with.

Cylindrical filter is a polypropylene cylindrical filter, excellent water permeability high strength, water flows from the cylinder entire surface prevents the inflow of sediment. In addition, since the handling weight is light and it is excellent in flexibility, it is possible to connect the pipes to any length, shape, and location according to the actual situation by using various connecting parts.

  The plastic screw tube is a thin-walled tube having an internal thread-like inner groove that is externally fitted to a spiral skeleton rib, and is provided at a connection portion of a cylindrical filter or a portion to be protected.

  According to the present invention, a flexible tubular body having a large water-permeable opening area can be freely disposed in the ground, and a water-permeable flexible tube can be used for groundwater around a manhole when the pore water pressure increases during an earthquake. It leads to the manhole through the body and prevents its pressure rise, reduces the force by which the bottom plate of the manhole is pushed up from below, and reduces the buoyancy due to the weight of groundwater flowing into the manhole as the pore water pressure increases. Projecting to the ground can be prevented.

  Accordingly, it is possible to effectively prevent road traffic troubles and the like in the event of an earthquake.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a manhole showing an embodiment of the present invention, and FIG. 2 is a plan view thereof. 1 and 2 show a manhole embedded in the ground, but the surrounding ground and earth and sand are not shown.

  The manhole 10 includes an upper end lid portion 11, an inclined cylindrical casing 12, a cylindrical casing 13, and a bottom plate 14. A through pipe 21 is provided in the housing 13 through the wall.

  The through pipe 21 includes a seal member 30 formed of a water expansion rubber ring or the like in a manhole wall penetration portion and an expansion mortar 31 that holds the seal member 30 and is held so as not to leak water from the penetration portion.

  A flexible tube 22 having water permeability is connected to the outside of the manhole of the through tube 21. The flexible tube 22 is provided with an outer cylinder 23 at a joint or a portion requiring protection, and a lid 24 is provided at an end of the flexible tube 22. When the mandrel is laid, the lid 24 is buried until it reaches the depth position of the bottom plate 14, and the effect of contributing to the reduction in the interstitial water pressure at the lowermost manhole is enhanced. The tube body 22 is made of a material having water permeability such as a cylindrical filter.

  An inner tube 25 is connected to the inside of the manhole of the through tube 21. The inner tube 25 may be a flexible plastic hose or the like, and is attached to the inner wall surface of the manhole 10 with a fixture 32. The upper end opening 26 of the inner pipe 25 is cut and adjusted in length so as to open at a position slightly higher than the groundwater level surface 60 around the manhole 10.

  The manhole levitation preventing device 20 of the present invention is composed of these pipes, and the inside of the pipes is filled with ground water in normal times. As shown in FIG. 2, a plurality of manhole floating prevention devices 20 are provided in one manhole 10 and can be arranged so as not to interfere with the underground pipe 50. In addition, when a plurality of tubes are installed, if they interfere with the underground pipe 50, the flexible pipe 22 is used, so that the underground pipe 50 is arranged to be avoided as shown in FIG. Can do.

  The flexible tubular body 22 outside the manhole is simply hanging up and down in FIGS. 1 and 2, but this is only an example, and it may be arranged in any configuration in the ground. . Further, the tube end cover 24 is provided so that earth and sand do not easily enter the flexible tube 22, but may be configured to open when the pore water pressure increases.

  FIG. 3 shows an example of the structure of the flexible tube 22.

  The flexible tubular body 22 has a spiral skeleton rib 41 on the outer periphery, a cylindrical filter 42 attached to the inside thereof, and the cylindrical filter 42 is strongly bonded to the inner surface of the skeleton rib 41 using a nonwoven fabric 43. It is. For example, a flexible tube 22 having an inner diameter of 50 to 200 mmφ is used.

  FIG. 3 is a schematic partial cross-sectional view of the flexible tubular body 22, in which the upper part shows the outer shape, the middle part shows the inside of the tubular body by cutting and removing the filter 42, and the lower part Shows the inside of the nonwoven fabric 43 cut and removed, and the attached state of the tube end lid 24. The skeleton rib 41 is formed by molding a strong flexible material such as a long polypropylene resin material into a spiral shape, and has a size capable of withstanding earth pressure. Due to this spiral structure, the flexible tubular body 22 maintains a cylindrical shape and is given flexibility in the longitudinal direction.

  The filter 42 has a water permeability and is a film body that does not allow sand or gravel to pass through. For example, a high-strength polypropylene filter is disposed in a spiral shape and attached to the inside of the skeleton rib.

  The nonwoven fabric 43 is to fix the seam 44 of the filter 42 to the inner surface of the skeleton rib 41 by pressing.

  The lower end of the flexible tube 22 is closed with a tube end cover 24 so that earth and sand do not enter the flexible tube 22. The lid 24 is made of plastic or rubber. As shown in the bottom view of the tube end cover 24 in FIG. 4, for example, when a cross-shaped weakening or notch is provided in the center of the cover 24 and a large impact pressure or the like is generated on the lower surface of the tube end cover 24 It is preferable that the weakened portion or the notch 27 is opened and the lid 24 is opened.

  Further, as shown in FIG. 1, by using the cylindrical body 23 provided with a spiral inner surface groove fitted on the spiral skeleton rib 41, the flexible tubular body 22 can be easily coupled or a necessary portion can be protected. can do.

  A flexible tubular body is obtained by using a Y-shaped joint, a T-shaped joint, or a cross joint having a spiral rib similar to the skeleton rib 41 and connecting the flexible tubular body 22 to the flexible tubular body 22 by a cylindrical body 23. The branch pipe and the collecting pipe can be easily formed.

  Since the manhole levitation prevention device of the present invention is configured as described above, the groundwater is normally filled with water, and in the event of an earthquake, the groundwater enters the pipe through a large inflow area through the filter of the tube body 22, and the manhole. Erupts inside. Therefore, an increase in the water pressure around the manhole is suppressed, and the floating property of the manhole is reduced, so that the manhole can be effectively prevented from protruding to the ground.

It is the side view which showed the partial cross section of the manhole which shows the apparatus of an Example. It is a top view of FIG. It is explanatory drawing of the Example of a flexible tube. It is a bottom view of the lid | cover of a flexible tubular body lower end.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Manhole 11 Upper end cover part 12 Inclined cylinder housing 13 Cylindrical housing 14 Bottom plate 20 Levitation prevention device 21 Through tube 22 Flexible tube 23 Outer tube 24 Tube end cover 25 Inner tube 26 Opening 27 Weaker or cut 30 Sealing material 31 Resin-based mortar 32 Mounting material 41 Skeletal rib 42 Tubular filter 43 Non-woven fabric 44 Seam 50 Underground pipe 60 Groundwater level surface

Claims (2)

A penetrating pipe penetrating the side wall of the manhole, a flexible tubular body connected to the outside of the manhole of the penetrating pipe and having water permeability, connected to the inside of the manhole of the penetrating pipe, An inner pipe having an opening position higher than the natural water level, and the flexible tubular body having water permeability is fitted to a cylindrical filter provided in a spiral skeleton rib and an outer diameter of the skeleton rib. An apparatus for preventing a manhole from rising , comprising: a plastic screw tube; and a tube end cover, wherein the tube end cover is a member having a film body that is broken by pressure on a cover surface . 2. The apparatus according to claim 1, wherein the inner tube connected to the inside of the manhole has flexibility and can be freely cut to adjust its length .

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