JP2007197989A - Structure for preventing lift of manhole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple low-cost structure for preventing the lift of a manhole which dispenses with large-scale work, can also be easily applied to an existing manhole, and can surely prevent the manhole from being lifted due to a ground liquefaction phenomenon during an earthquake. <P>SOLUTION: In this structure for preventing the lift of the manhole 1, a manhole body 2 is buried like an erected pile so as to be used, for example, for detecting a sewerage pipe 5 as a buried pipeline, and connected to the sewerage pipe 5. A plurality of through-holes 11 which make an underground 10 side communicate with the side 200 of the manhole body 2 are formed at circumferential intervals in the side wall 2a of the manhole body 2; and a grouting material is solidified by being injected into the underground 10 side from the inside 200 of the manhole 2 via the through-holes 11, so that a ground improving structure 13 can be provided on the outer periphery of the side wall 2a of the manhole body 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a manhole levitation preventing structure for preventing a manhole buried underground from floating due to a ground liquefaction phenomenon during an earthquake.

Liquefaction of the ground may occur during an earthquake, and this phenomenon has caused manholes in underground structures to rise to the surface. The cause of the rise is that the apparent specific gravity of the manhole is small. Hereinafter, the mechanism of the liquefaction phenomenon of the ground and the lift of the manhole will be described in detail.
In general, the manhole 51 as shown in FIG. 3 may be embedded in the sand ground 52. In this case, the sand ground 52 is made up of countless sand grains 53, but there is a gap between the sand grains 53 and the sand grains 53. When water is present and filled in the gap portion, the water is referred to as pore water 54. The pressure of the pore water 54 is called the pore water pressure, but is usually a hydrostatic pressure. In such a case, when an earthquake occurs, as shown in FIG. 4, the sand water 53 tends to enter the gap, and the pore water pressure increases. This increase in pore water pressure is called excess pore water pressure. When excess pore water pressure is generated and the pore water pressure becomes greater than the force (effective stress) that presses the sand particles 53 together, the sand particles 53 are disconnected from each other, and the water 54 It will be in the state where the sand grain 53 drifts inside. This is the ground liquefaction phenomenon. At this time, an underground structure having a small specific gravity, such as the assembly manhole 51, is lifted, and a structure having a large specific gravity sinks into the liquefied ground. Then, after a while, the liquefaction phenomenon, as shown in FIG. 5, sand grains 53 having a specific gravity larger than that of water 54 sinks with time, and the sand ground 52 is reconstructed.
It is generally said that the liquefaction phenomenon occurs under the condition that the groundwater level of the ground is high and there is a seismic motion with a seismic intensity of about 5 in a loose sandy ground. Since the Niigata Chuetsu Earthquake was exactly this situation, many manholes emerged.

Conventionally, as a means to prevent the manhole from rising due to the ground liquefaction phenomenon during an earthquake, the manhole bottom plate is widened to increase the apparent specific gravity, or the side of the manhole is surrounded by crushed stone or gravel material A method (see, for example, Patent Document 1) is provided.
In such a technique, a backfill material layer made of gravel material is provided around the side wall of the manhole, and permeable pavement is performed so as to be continuous with the backfill material layer around the manhole surface side opening, The manhole is prevented from rising during an earthquake.

JP-A-8-165666

However, among the above-described conventional techniques, in the method of widening the bottom plate of the manhole, it is difficult to significantly increase the apparent specific gravity of the manhole with respect to the liquefied ground, so the manhole in the ground liquefaction phenomenon during an earthquake Could not be sufficiently prevented.
Of the conventional techniques described above, in the method of surrounding the manhole side with gravel, etc., the manhole is buried and compacted so as to surround a backfill material made of gravel. Since the permeable pavement is performed around the opening on the front side, the entire apparatus is large, requiring a large-scale construction, resulting in a high construction cost and a long construction period.

  The present invention has been made in view of such circumstances, and its purpose is a low-cost structure that does not require a large-scale construction with a very simple structure, and can be easily applied to an existing manhole. It is an object of the present invention to provide a manhole rising prevention structure that can reliably prevent the manhole from rising due to ground liquefaction during an earthquake.

  In order to solve the above-described problems of the prior art, the present invention provides a manhole levitation preventing structure in which a manhole body is embedded in a standing pile shape and used for inspection of an embedded pipeline and connected to the embedded pipeline. A plurality of through holes communicating with the underground side and the inside of the manhole body are formed at intervals in the circumferential direction in the wall portion of the manhole body, and a grout injection material is formed from the inside of the manhole body through the through holes. A ground improvement structure is provided on the outer periphery of the wall portion of the manhole body by being injected into the underground side and solidified.

  In the present invention, it is preferable that the manhole body and the ground improvement structure are integrated.

As described above, the manhole levitation prevention structure according to the present invention is a manhole levitation prevention structure in which a manhole body is embedded in a standing pile shape to be used for inspection of an embedded pipeline and connected to the embedded pipeline. A plurality of through holes communicating with the underground side and the inside of the manhole body are formed in the wall portion of the manhole body at intervals in the circumferential direction, and a grout injection material is formed from the inside of the manhole body through the through hole. By injecting into the ground side and solidifying, the ground improvement structure is provided on the outer periphery of the wall of the manhole body, so it is extremely simple and low cost and does not require large-scale construction. This prevents the occurrence of ground liquefaction due to an earthquake and reliably prevents the manhole from rising during an earthquake.
In addition, since the anti-floating structure of the present invention does not need to dig up a paved road around the manhole installation site, it is not necessary to stop the vehicle, and can be easily applied to existing manholes.

  Further, in the present invention, when the manhole body and the ground improvement structure are integrated, the apparent specific gravity of the manhole with respect to the liquefied ground can be greatly increased, and the manhole can be further lifted during an earthquake. This can be prevented more reliably.

Hereinafter, the present invention will be described in detail based on illustrated embodiments.
1 and 2 are manholes to which the structure for preventing floating according to the embodiment of the present invention is applied. FIG. 1 is a longitudinal sectional view of a state before the ground improvement structure is provided, and FIG. 2 (A) is the ground improvement structure. FIG. 2B is a longitudinal sectional view of the plane after the body is provided.

  In FIG. 1, 1 is a manhole, 2 is a manhole body which is a concrete part of the manhole 1, and this manhole body 2 is made of, for example, a cylindrical precast concrete block so as to be used for inspection of a buried pipe which will be described later. It is configured by stacking. A bottom plate 3 is provided at the bottom of the manhole body 2, and an invert block 4 is provided on the bottom plate 3. The invert block 4 is formed with an invert 4a, and a sewer pipe 5 is connected to both ends of the invert 4a so as to circulate drainage through the interior 200 of the manhole body 2.

The manhole body 2 includes a cylindrical upper block 7 in which one or more cylindrical body blocks 6 are stacked (one in this example), and one side thereof is inclined in a tapered shape on the body block 6. It is formed by stacking. Further, a ring-shaped opening block 8 is placed on the upper part of the upper block 7, and an upper lid (not shown) is fitted and disposed in the upper end opening of the opening block 8. The body block 6, the upper block 7, and the opening block 8 form a side wall (wall portion) 2 a.
The manhole body 2 configured in this manner is embedded in a standing pile shape in the ground 10 so that the upper surface of the upper lid is at the same height as the ground surface 9, and the sewer pipe 5 is connected thereto.

A plurality of (four in this embodiment) through-holes 11 communicating with the inside 200 of the manhole body 2 and the underground 10 are perforated at equal intervals in the circumferential direction on the side wall 2a of the installation location of the upper block 7. Has been formed. These through-holes 11 are used when a ground improvement structure described later is provided, and can be arbitrarily selected depending on the vertical length of the manhole body 2, the situation of the ground, and the size of the ground improvement structure described later. Any number of places can be provided.
Therefore, for example, when the length from the through hole 11 of the upper block 7 to the bottom plate 3 below is 1 m or more, the similar through holes 12 are equally spaced in the circumferential direction on the side wall 2a of the installation location of the body block 6. A set of four holes are drilled.

As shown in FIGS. 2A and 2B, a ground improvement structure 13 is provided on the entire periphery of the outer periphery of the side wall 2 a of the manhole body 2 in the embodiment of the present invention. The ground improvement structure 13 is formed by solidifying a grout injection material (cement-based material or the like) injected into the underground 10 by a method described later. The ground improvement structure 13 of the present embodiment has a diameter that is approximately twice the diameter of the manhole body 2 and a height from the vicinity of the upper end of the upper block 7 to the vicinity of the lower end of the trunk block 6 (near the upper surface of the bottom plate 3). It is formed in a cylindrical shape.
As described above, in the embodiment of the present invention, since the ground improvement structure 13 is provided around the side wall 2a of the manhole body 2, there is pore water between the sand grains and the buried portion of the manhole 1. Even in the ground 10 of the sand ground, the ground is improved by filling the gap between the sand grains with the grout injection material, eliminating the cause of the ground liquefaction phenomenon due to the earthquake, It has a structure that can prevent lifting.

For this reason, in the through hole 11 of the upper block 7 and the through hole 12 of the trunk block 6, the tip of the grout hose 14 extends from the inside 200 of the manhole body 2 to the ground 10 side as shown in FIG. 1. It is inserted and arranged over a certain length. This grout hose 14 is a conveying means used for supplying grout injection material, and its base end is connected to a pump 15 installed on the ground surface 9, and through these grout hose 14 and pump 15. A grout injection material is pumped from an injection material supply source (not shown).
The pump 15 is electrically connected to a flow rate measuring device, an injection pressure gauge, etc. (not shown) in order to control and adjust the supply amount of the grout injection material, the injection pressure, and the like.

In the floating prevention structure of the embodiment of the present invention, first, the ground at the installation location is excavated from the ground surface 9 to a predetermined depth to form a buried hole, the bottom plate 3 is installed on the bottom surface of the buried hole, and the invert Stack block 4. Then, the body block 6 in which the through hole 12 is formed is placed on the upper surface of the bottom plate 3, and the upper block 7 in which the through hole 11 is formed is placed on the upper end of the body block 6. The manhole body 2 is assembled by placing and stacking the opening block 8 and is embedded from the ground surface 9 into the underground 10 like a standing pile, while being connected to the sewer pipe 5.
Next, as shown in FIG. 1, the grout hose 14 connected to the pump 15 is put into the inside 200 of the manhole body 2, and the tip of the hose extends over a certain length from the through hole 11 of the upper block 7 toward the ground 10. Push in. In this state, the pump 15 pumps the grout injection material from an injection material supply source (not shown), and injects the grout injection material from the tip of the grout hose 14 to the underground 10 side with a predetermined supply amount and pressure. If this injection operation is performed in all the through holes 11 and the grout injection material is solidified, the ground improvement structure 13 is provided along the entire circumference of the side wall 2a of the manhole body 2, and a structure for preventing the manhole 1 from floating is obtained. (See FIG. 2). In addition, when the length of the trunk | drum block 6 is large and the height of the manhole main body 2 is high, it is good to perform the same injection | pouring operation | work also from the through-hole 12 of the trunk | drum block 6. FIG.

  When the anti-floating structure according to the embodiment of the present invention is applied to the existing manhole 1, a plurality of through holes 11 (including the through holes 12) are drilled at predetermined locations on the side wall 2a of the manhole body 2 at the site. Then, by using the grout hose 14 and the pump 15 and injecting the grout injection material into the underground 10 side by the same injection operation, the ground improvement structure 13 is made to surround the entire circumference of the side wall 2a of the manhole body 2. It will be provided along.

  In the levitation prevention structure of the embodiment of the present invention, by injecting from the inside 200 of the manhole body 2 to the underground 10 side through the through holes 11 and 12 formed in the side wall 2a of the manhole body 2, and solidifying, Since the ground improvement structure 13 having a certain size is provided along the entire outer periphery of the side wall 2a of the manhole body 2, even if the periphery of the manhole 1 is sand ground, the presence of the ground improvement structure 13 causes an earthquake. It is possible to prevent the occurrence of liquefaction of the ground due to an earthquake because there is no gap that sometimes causes excess pore water pressure in the underground 10, and as a result, it is possible to reliably prevent the manhole 1 from being lifted during an earthquake Can do.

In addition, the floating prevention structure according to the embodiment of the present invention may be provided with the ground improvement structure 13 by drilling a plurality of through holes 11 and 12 in the side wall 2a of the manhole body 2 in the interior 200 of the manhole body 2. Since it is possible, it can be applied to the existing manhole 1 easily and quickly.
Accordingly, the ground improvement structure 13 can be provided without stopping the vehicle for a long period of time and digging up a paved road or the like constructed around the existing manhole 1.

While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention.
For example, in the structure for preventing levitation according to the present invention, the ground improvement structure 13 may be integrated with the outer periphery of the side wall 2 a of the manhole body 2, or may be a separate body. When integrated by filling with a grout injection material, the apparent specific gravity of the manhole 1 with respect to the liquefied ground can be significantly increased, and the manhole 1 can be prevented from rising more reliably. The ground improvement structure 13 may not be provided along the entire outer periphery of the side wall 2a of the manhole body 2 depending on the nature of the ground where the manhole 1 is installed. It suffices if the majority is surrounded by the ground improvement structure 13.

It is a manhole to which the floating prevention structure of the embodiment of the present invention is applied, and is a longitudinal sectional view showing a state before the ground improvement structure is provided. BRIEF DESCRIPTION OF THE DRAWINGS It is a manhole to which the anti-levitation structure of embodiment of this invention is applied, Comprising: (A) is plane sectional drawing which shows the state after providing a ground improvement structure, (B) is after providing a ground improvement structure. It is a longitudinal cross-sectional view which shows the state. It is a longitudinal cross-sectional view which shows the manhole embed | buried under the sand ground. It is a longitudinal cross-sectional view which shows the state in which the liquefaction phenomenon of the ground has arisen in the manhole embed | buried in the sand ground. It is a longitudinal cross-sectional view which shows the state after the ground liquefaction phenomenon arises in the manhole embed | buried in the sand ground.

Explanation of symbols

1 Manhole 2 Manhole body 2a Side wall (wall)
3 Bottom plate 4 Invert block 4a Invert 5 Sewer pipe 6 Trunk block 7 Upper block 8 Opening block 9 Ground surface 10 Underground 11, 12 Through hole 13 Ground improvement structure 14 Grout hose 15 Pump 200 Inside of manhole body

Claims (2)

  The manhole body is embedded in a standing pile shape to be used for inspection of buried pipes and connected to the buried pipe line. In the structure for preventing the rise of manholes, A plurality of through holes communicating with each other at intervals in the circumferential direction, and injecting a grout injection material from the inside of the manhole body to the ground side through the through holes to solidify the manhole body. A manhole levitation prevention structure characterized in that a ground improvement structure is provided on the outer periphery of the wall.   The manhole floating prevention structure according to claim 1, wherein the manhole body and the ground improvement structure are integrated.

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