JP2005248496A - Method for uplift preventive manhole in liquefaction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for uplift preventive a manhole in the liquefaction of a ground due to an earthquake. <P>SOLUTION: The method for uplift preventive manhole contains a process in which invert concrete placed on the bottom section of the manhole is chipped, a process, in which a section from the bottom section of the manhole to a non-liquefied layer is drilled, and a process in which an anchor tendon is inserted into a drilled hole, a grout is injected and the front end of the anchor tendon is fixed on the non-liquefied layer. The method further contains a process in which a pressure-support plate is arranged on the bottom of the manhole so that the upper end of the anchor tendon is projected from an opening section formed at a center, a process in which the upper end of the anchor tendon is fixed onto the pressure-support plate, a process, in which the upper end of the anchor tendon is covered with a cap. and a process in which invert concrete is placed on the bottom section of the manhole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for preventing the manhole from rising due to liquefaction of the ground during an earthquake.

  Since the 1995 Hyogoken-Nanbu Earthquake, efforts to make sewers seismic resistant have been rapidly demanded. Under such circumstances, seismic joints installed at joints between manholes and pipes, and seismic culverts with pipe / pipe joints having expansion / contraction flexibility have been developed by sewage material manufacturers.

On the other hand, the manhole has the following characteristics.
(1) A manhole is a light-weight structure with a space inside, and is easily lifted when lift pressure acts on the bottom.
(2) Since the member cross section of the manhole itself is small, it is difficult to connect the member to the manhole even if a lifting prevention member is installed in the manhole.
(3) In a highly rigid member such as a pile, the behavior of the pile during an earthquake is easily transmitted to the manhole, so the behavior of the pile during the earthquake may act on the manhole as a load.
(4) In general, there are many other buried objects around the manhole, and when the area for countermeasures to lift extends to parts other than the manhole installation area, other buried objects are moved or protected. Is required.
(5) The existing manhole is installed in an existing urban area and the construction environment is narrow, so it is difficult to construct with a large machine.
(6) In the method involving re-excavation around the existing manhole, the construction period becomes longer, and there is a concern about the influence on the surrounding environment due to the excavation.
(7) If the manhole itself is increased in weight to prevent lifting, an excessive load may be applied to the ground.

  Regarding the lift of manholes due to the liquefaction of the ground at the time of an earthquake, the present situation is that no effective countermeasures have been taken yet because the manholes have the above-mentioned characteristics. On the other hand, if a manhole rises during an earthquake, it will cause problems such as hindering the passage of emergency vehicles in firefighting activities, medical activities, relief activities, etc. It is an urgent issue.

  Therefore, an object of the present invention is to provide a method for preventing a manhole from rising due to liquefaction of the ground during an earthquake.

  The method for preventing the manhole from rising due to liquefaction according to claim 1 of the present invention includes a step of hanging invert concrete placed at the bottom of the manhole, a step of drilling from the bottom of the manhole to the non-liquefied layer, Inserting an anchor tensile material into the drilled hole, injecting grout and fixing the tip of the anchor tensile material to the non-liquefied layer, and an upper end of the anchor tensile material from an opening provided in the center Projecting the pressure plate at the bottom of the manhole, fixing the upper end of the anchor tension member to the pressure plate, covering the upper end of the anchor tension member with a cap, and And a step of placing invert concrete on the bottom of the manhole.

  The method for preventing the manhole from rising due to liquefaction according to claim 2 is the method according to claim 1, wherein the pressure receiving plate disperses the lifting pressure uniformly over substantially the entire bottom of the manhole. It is characterized in that it is shaped so as to have a diameter slightly smaller than the inner diameter.

  The method for preventing the manhole from rising due to liquefaction according to claim 3 of the present invention is the method of claim 2, wherein the region between the side wall of the manhole and the outer periphery of the pressure receiving plate, and the cap and the invert concrete An elastic body is disposed in the area between them.

  According to the present invention, a manhole can be prevented from being lifted without using a large machine, without affecting other buried objects, surrounding ground, structures and the like, and without re-excavating. Moreover, in the method of this invention, since it resists only uplift pressure, an excessive load is not given to the ground. In the method of the present invention, unlike a rigid member such as a pile, the behavior of the anchor tension member does not excessively affect the manhole during an earthquake. Further, by increasing the area of the pressure receiving plate, it is possible to prevent the punching shear failure at the bottom of the manhole. Furthermore, in the method of the present invention, an elastic body (rubber tube) is arranged in a region between the side wall of the manhole and the outer periphery of the pressure plate and a region between the cap and the inverted concrete, thereby fixing an anchor at the time of an earthquake. Damage to the head and the side wall of the manhole can be prevented.

  Next, an example of an existing sewer manhole will be described in detail with reference to the drawings (mainly FIG. 3), with reference to the drawings (mainly FIG. 3). FIG. 3A is a view showing a manhole before performing the lifting prevention method. First, prior to construction, the sewage flowing into the existing manhole is stopped, and the invert concrete placed at the bottom of the manhole is hung (FIG. 3B).

  Next, a drilling machine for installing the anchor is arranged on the ground, and drilling is performed from the bottom of the manhole to the non-liquefied layer using the drilling machine (FIG. 3 (c)). A grout is injected into the hole (FIG. 3 (d), the anchor tension member 10 is inserted into the hole (FIG. 3 (e)), and the tip of the anchor member 10 is inserted into the non-liquefied layer into which the grout is injected. (Fig. 3 (f)) As the anchor tension member 10, a PC steel wire is preferably used.

Next, the pressure receiving plate 12 is disposed at the bottom of the manhole. The pressure receiving plate 12 is for uniformly dispersing the lifting pressure over almost the entire manhole bottom. Therefore, the pressure receiving plate 12 is formed to have a larger diameter, in other words, a diameter (D _P ) slightly smaller than the inner diameter (D _M ) of the bottom surface of the manhole (FIG. 2 (c). )reference). The pressure receiving plate 12 serves to prevent the punching shear failure of the concrete at the bottom of the manhole when the anchor tension member 10 resists the lifting pressure. Moreover, since the opening part 12a for letting the upper end of the anchor tension | tensile_strength material 10 pass is provided in the center of the pressure receiving board 12 (refer FIG.2 (b)), when the pressure receiving board 12 is arrange | positioned at the bottom part of a manhole, it will open. The upper end of the anchor tension member 10 protrudes from the portion 12a.

  A male screw portion 10 a is provided at the upper end of the anchor tension member 10, and the nut 14 is screwed into the male screw portion 10 a protruding from the opening 12 a of the pressure receiving plate 12, so that the upper end of the anchor tension member 10 has a manhole. Fixed to the bottom. The upper end of the anchor tension member 10 and the nut 14 are protected by disposing the cap 16 in the center of the pressure receiving plate 12 so as to cover the upper end of the anchor tension member 10 and the nut 14. The cap 16 is fixed to the pressure receiving plate 12 by appropriate means (welding, adhesive, etc.). In order to enhance the corrosion prevention effect, it is preferable to apply an epoxy resin to the upper ends of the pressure receiving plate 12 and the anchor tension member 10.

  Finally, after placing invert concrete at the bottom of the manhole and passing sewage, the operation is completed (see FIG. 3 (h)).

  Since the cap 16 is fixed to the pressure receiving plate 12 as described above, when the pressure receiving plate 12 vibrates in the horizontal direction during an earthquake, the pressure receiving body 12 itself collides with the side wall of the manhole, or the cap 16 Since the manhole, the cap 16 and the like may be damaged by colliding with the invert concrete, the manhole, the cap 16 and the like may be damaged in the region between the manhole side wall and the outer periphery of the pressure receiving plate 12 and the region between the cap 16 and the invert concrete. The elastic body 18 is preferably disposed. The elastic body 18 is preferably formed of a rubber tube.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say, it is something.

  For example, in the above embodiment, the existing sewer manhole has been described as an example. However, the method of the present invention may be applied to other manholes other than the sewer manhole, and the method of the present invention may be applied to a new manhole. May be.

It is the schematic which showed the state which gave the lifting prevention method of this invention to the manhole. 2A is an enlarged view of the bottom portion of the manhole in FIG. 1, FIG. 2B is an enlarged view of the portion 2b in FIG. 2A, and FIG. 2C is a line 2c in FIG. 2A. FIG. 2C is a view taken along -2c (invert concrete not shown in order to clearly show the head of the anchor tension member). It is the schematic which showed the series of processes of the lifting prevention method of this invention.

Explanation of symbols

10 Anchor tension material 12 Pressure receiving plate 14 Nut 16 Cap 18 Elastic body (rubber tube)

Claims (3)

A method for preventing the manhole from rising due to liquefaction,
A process of hanging the inverted concrete placed at the bottom of the manhole,
Drilling from the bottom of the manhole to the non-liquefiable layer;
Inserting an anchor tensile material into the drilled hole, injecting grout, and fixing the tip of the anchor tensile material to the non-liquefiable layer; and
A step of arranging a pressure receiving plate at the bottom of the manhole so that the upper end of the anchor tension member protrudes from an opening provided in the center;
Fixing the upper end of the anchor tension member to the pressure receiving plate;
Covering the upper end of the anchor tension member with a cap;
Placing invert concrete at the bottom of the manhole;
A method comprising the steps of: 2. The pressure receiving plate according to claim 1, wherein the pressure receiving plate is shaped to have a diameter slightly smaller than the inner diameter of the bottom surface of the manhole in order to uniformly distribute the lifting pressure over substantially the entire bottom of the manhole. The method described. The method according to claim 2, wherein an elastic body is disposed in a region between the side wall of the manhole and the outer periphery of the pressure receiving plate and a region between the cap and invert concrete.

Images