JP2014005597A - Floatation prevention pile for underground structure and floatation prevention method for underground structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the floatation prevention pile of an underground structure and the floatation prevention method of an underground structure capable of reducing a workload in the case of installing a floating prevention pile, and preventing the floatation of the underground structure by reducing a floating force corresponding to the underground structure while making the pull-out resistance force of the floatation prevention pile remain when a liquefaction phenomenon occurs.SOLUTION: In a floatation prevention pile 12 of an underground structure 1 including a hollow pipe material 2 fixed to the bottom of the underground structure 1 and a penetration section 22 formed in at least the top end side of the hollow pipe material 2, the hollow pipe material 2 is formed with at least water permeable holes 17 configured to penetrate the inside and outside of the hollow pipe material at a position below the bottom of the structure 1 in a state that the hollow pipe material 2 is fixed to the bottom of the underground structure 1.

Description

The present invention relates to a floating prevention pile for an underground structure and a floating prevention method for the underground structure.
As used herein, “underground structure” refers to manholes in sewers, sewage dredges, underground ditches that protect underground facilities equipment and cables in power and communications, buried conduits under the road surface in waterworks and gas pipes, and A box or the like that protects the accessory device is generically named.

  Subsurface structures such as manholes in sewers have a low specific gravity because they are hollow inside. For this reason, when the surrounding ground is a sand layer and the groundwater level is high, the surrounding ground is liquefied at the time of an earthquake, resulting in a buoyancy exceeding its own weight, and the underground structure is raised above the ground.

  In order to prevent such a phenomenon, various countermeasures have been studied (for example, refer to Patent Documents 1 to 3).

  Patent Document 1 uses a peripheral shelf portion of an inverted portion of an existing manhole, provides a hollow pipe that penetrates the shelf portion and has a lower end reaching a natural ground, and has an upper end equal to or higher than the groundwater level. It describes a method for seismic reinforcement of existing manholes in which moisture is filtered and released by a hollow pipe.

  Patent Document 2 includes a step of drilling through a bottom plate of an existing manhole and drilling to a non-liquefiable layer, a step of inserting a stay anchor having a plurality of expandable resistance members at the lower end into the drilled hole, The step of expanding the resistance member by applying an impact to the resistance member, causing the resistance member to enter the bottom wall or side wall of the hole, the step of filling the drilled hole with cement, and the upper end of the stay anchor A method for preventing the rising and sinking of an existing manhole including a process of fixing to the bottom plate of the manhole is described.

  Patent Document 3 includes a step of staking inverted concrete placed at the bottom of the manhole, a step of drilling from the bottom of the manhole to the non-liquefied layer, and inserting an anchor tensile material into the drilled hole, Injecting the grout to fix the tip of the anchor tensile material to the non-liquefied layer, and disposing the pressure receiving plate at the bottom of the manhole so that the upper end of the anchor tensile material protrudes from the opening provided in the center. And a method of fixing the upper end of the anchor tensile member to the pressure receiving plate, a step of covering the upper end of the anchor tensile member with a cap, and a step of placing invert concrete at the bottom of the manhole. Have been described.

JP 2007-23603 A JP 2011-99217 A Japanese Patent No. 4325995

  However, although the contents described in Patent Document 1 are intended to dissipate groundwater with a hollow pipe, they are intended to prevent the manhole from rising only by reducing the buoyancy caused by the dissipation, and have no pull-out resistance against the ground. Therefore, depending on the degree of buoyancy exerted on the manhole, the effect of preventing the manhole from rising may not function sufficiently.

  The contents described in Patent Documents 2 and 3 require deep drilling up to the non-liquefied layer, and further require work such as injecting a grout material up to the deepest part of the hole, which is problematic in workability. In addition, since the main body of the manhole is integrally fixed to the non-liquefiable layer with an anchor, when ground subsidence occurs due to liquefaction, a force acts on the joint between the bottom plate of the manhole and the anchor, and the joint is destroyed. There is a fear.

  The present invention has been made in consideration of the above-mentioned problems of the prior art, and reduces the work load when installing the anti-floating pile, and reduces the buoyancy against the underground structure when liquefaction occurs. It is another object of the present invention to provide a floating prevention pile for an underground structure and a floating prevention method for the underground structure that can prevent the floating of the underground structure by leaving the pulling resistance of the floating prevention pile.

  In order to achieve the above object, in the present invention, a floating prevention pile of an underground structure comprising a hollow pipe member fixed to a bottom portion of an underground structure, and an intrusion portion formed at least on a distal end side of the hollow pipe member. In the hollow pipe material, in a state where the hollow pipe material is fixed to the bottom portion of the underground structure, at least a plurality of positions penetrating the inside and outside of the hollow pipe material at a position lower than the bottom portion of the underground structure. Provided is an anti-floating pile for an underground structure characterized by providing a water permeable hole.

  Preferably, the penetration portion includes a spiral blade formed on the outer periphery of the hollow pipe material.

  Further, in the present invention, a penetration step of penetrating the levitation prevention pile into the bottom portion of the underground structure, a penetration step of penetrating into the ground by the levitation prevention pile, a bottom portion of the underground structure and the levitation prevention pile, A penetration step formed on at least the tip side of the anti-floating pile is arranged in the liquefied layer among the liquefied layer and the non-liquefied layer forming the ground. It also provides a method for preventing the rise of underground structures.

  According to the present invention, when the ground is liquefied, pore water (groundwater) flows into the inside of the hollow pipe material from the water permeable holes provided in the hollow pipe material, and the inside of the underground structure and the ground via the hollow pipe. Since the water pressure is excessively discharged, the water pressure of excess pore water is reduced, and a dissipating effect can be obtained. That is, the buoyancy with respect to the underground structure due to the liquefaction of the ground can be reduced. In addition, since the degree of liquefaction of the ground around the anti-floating pile can be reduced, the pull-out resistance of the anti-floating pile to the ground can be maintained according to the decrease in excess pore water pressure, and the floating of the underground structure It can be prevented more reliably. In other words, when the intrusion part formed in the levitation prevention pile remains in the liquefied layer of the ground, the penetration depth of the levitation prevention pile can be shallow to maintain the pulling resistance of the levitation prevention pile to the ground. The work load when installing prevention piles can be reduced.

It is the schematic sectional drawing which looked at the levitation prevention pile of the underground structure concerning the present invention from the side. It is the schematic sectional drawing which looked at the levitation prevention pile of the underground structure concerning the present invention from the front. It is the partial schematic of the vicinity which formed the water-permeable hole of the levitation prevention pile of the underground structure which concerns on this invention.

  The underground structure 1 according to the present embodiment is configured as a sewer manhole, and the overall shape thereof is a substantially cylindrical shape, and at least a space that allows an operator to pass through is secured inside. Actually, the operator moves up and down in the underground structure 1 using a plurality of steps 11 arranged on the inner wall of the underground structure 1.

  The underground structure 1 is formed by connecting a cylindrical straight wall body 5 and a plurality of slant wall bodies 6 with inclined peripheral walls in the axial direction. The lower end of the underground structure 1 is connected to the bottom plate 4. Blocked. Further, when the underground structure 1 is buried in the ground, a crushed stone foundation material 10 is laid in advance under the bottom plate 4. A receiving frame 8 is installed on the upper portion of the underground structure 1 through the bulk adjusting unit 7 so as to match the ground surface. Here, the bulk adjusting unit 7 includes a bulk adjusting piece (not shown) screwed to a bolt standing on the upper surface of the underground structure 1, and a plurality of adjustment rings (illustrated) placed on the upper surface of the underground structure 1. The installation height of the receiving frame 8 is adjusted by a bulk adjustment piece or an adjustment ring. The receiving frame 8 is formed with an opening 3 exposed to the ground surface, and the opening 3 is covered with a lid 9 that can be opened and closed.

  An inflow side and an outflow side pipe 14 are arranged on the lower side surface of the underground structure 1. On the bottom 4 provided at the lower end of the underground structure 1, an invert 15 having a groove 16 communicating with the inflow side and outflow side pipes 14 is provided as an integral or separate body with the bottom plate 4.

  The levitation prevention pile 12 extends from the underground structure 1 to the ground through the bottom while being fixed to the bottom (invert 15 and bottom plate 4) of the underground structure 1. That is, one end of the anti-floating pile 12 is in the underground structure 1 and the other end is arranged in the ground. Further, the levitation prevention pile 12 is fixed to the bottom of the underground structure 1. This fixing method includes a method of attaching fins to the outer periphery of the levitation prevention pile 12 and fixing the fins via the fins. The number of the levitation prevention piles 12 can be set as appropriate depending on the size of the underground structure 1, the penetration direction of the levitation prevention pile depending on the installation environment, the required pulling resistance force, and the like.

  The levitation prevention pile 12 is formed of a hollow pipe material 2, and a penetration portion 22 is formed on the distal end side of the hollow pipe material 2. In the present embodiment, the penetration portion 22 is composed of the hollow pipe material 2 and the spiral blade 13 formed on the outer periphery thereof. In addition, if the penetration part 22 is a shape in which the penetration efficiency at the time of penetrating into the ground by the levitation prevention pile 12 is good and can hold the pulling-out resistance force of the levitation prevention pile to the ground, a spiral blade is used. It is not limited and can be applied. For example, it is also conceivable to form the hollow pipe member 2 at the front end side in the form of a solid rod and to provide a spiral blade on the outer periphery. In this case, the diameter of the spiral blade is made larger than the diameter of the hollow pipe member 2, the diameter of the spiral blade is gradually increased from the tip side upward in the longitudinal direction, It can be set as appropriate, for example, by providing a spiral blade by extending not only to this part but also to the part of the hollow pipe member 2 located on the upper side. Further, instead of the spiral blades, a plurality of flat plates obtained by halving donut-shaped flat plates can be provided on the outer periphery of the hollow pipe member 2 at an interval to form a pseudo spiral blade. . By doing in this way, when attaching a flat plate to a hollow pipe by welding etc., there exists an advantage that it is easy to manufacture. In this embodiment, the end of the hollow pipe member 2 in the underground structure 1 is opened, and the end on the underground side is closed. By including the spiral blades 13 in the penetrating portion 22, when the anti-floating pile 12 is rotated and dug into the ground, the penetration efficiency is improved, and the anti-floating pile 12 is easily installed. After the anti-floating pile 12 is installed, the pull-out resistance force of the anti-floating pile 12 can be maintained. The spiral blade 13 may be provided on a part of the distal end side of the hollow pipe material 2 or may be provided from a part of the longitudinal direction to the entire region. The levitation prevention pile 12 may be made of cast iron including the spiral blades 13 or may be made of steel, but by making it cast (made of cast iron, cast steel, etc.), the hollow pipe material 2 and the spiral There is an advantage that the blades 13 can be manufactured integrally.

  In a state where the levitation prevention pile 12 is fixed to the bottom of the underground structure 1, a plurality of water permeable holes 17 are formed in a portion below the bottom of the underground structure 1. This water permeable hole 17 penetrates the inside and outside of the hollow pipe material 2 forming the levitation preventing pile 12. By providing this water permeable hole 17, when the ground is liquefied, pore water (groundwater) flows into the levitation prevention pile 12 (hollow pipe material 2) from the water permeable hole 17, thereby reducing the water pressure of excess pore water. And a dissipating effect can be obtained. That is, the buoyancy with respect to the underground structure 1 can be reduced. Moreover, since the degree of liquefaction of the ground can be reduced by escaping the pore water into the underground structure 1, the pull-out resistance force of the levitation prevention pile 12 can be maintained in accordance with the decrease in the excess pore water pressure. The floating of the underground structure 1 can be prevented more reliably. By preventing the underground structure 1 from rising, damage to the bottom (invert 15 and bottom plate 4) of the underground structure 1 can also be prevented. That is, since the penetration portion 22 on the tip side of the levitation prevention pile 12 does not reach the non-liquefaction layer 19, when liquefaction occurs, the bottom portion of the underground structure 1 and the levitation prevention pile 12 are fixed to the fixed portion. It is difficult to apply force, and damage to the bottom of the underground structure 1 can be prevented. The size, shape, number, and arrangement of the water permeable holes 17 can be appropriately set according to the strength of the levitation preventing pile 12 and the water permeable effect. In the present embodiment, as shown in FIG. 1, the water permeable holes 17 are provided in the portion of the hollow pipe material 2 above the penetrating portion 22, but the water permeable holes 17 may also be provided in the portion of the penetrating portion 22. it can. In this case, the effect of dissipating pore water can be better exhibited.

  As shown in FIG. 3, the water permeable sheet 20 may be affixed to the inner surface of the position where the water permeable holes 17 of the ascent prevention pile 12 are formed. The water permeable sheet 20 here passes only moisture and does not allow gravel or sand to pass through. Further, the water-permeable sheet 20 may be filled with a filler 21 having good water permeability. By providing such a water-permeable sheet 20 and the filler 21, clogging due to earth and sand in the anti-floating pile 12 can be prevented.

  In a state where the levitation prevention pile 12 is fixed to the bottom of the underground structure 1, the upper end of the levitation prevention pile 12 is arranged so as to be located above the groundwater level. The length of the levitation prevention pile 12 can be adjusted on site by appropriately connecting and connecting the hollow pipe members 2. Liquefaction of the ground occurs, and the interstitial water that has flowed in from the water permeable holes 17 flows into the underground structure 1 from the upper end of the anti-floating pile 12. This can prevent normal groundwater inflow when the groundwater level is high.

On the other hand, the penetration portion 22 formed on the tip side of the levitation prevention pile 12 is arranged in the liquefied layer 18 among the liquefied layer 18 and the non-liquefied layer 19 that form the ground.
The liquefaction of the ground occurs in the liquefied layer 18 composed of a soft sand layer in which underground water (pore water) exists in the ground, and there is a non-liquefied layer 19 below the liquefied layer 18. Yes. Here, the liquefied layer refers to the ground that is considered to be liquefiable in the state where countermeasures against liquefaction are not applied at the time of design, and is often relatively loose sandy soil. . On the other hand, the non-liquefiable layer refers to the ground where it is determined that liquefaction does not occur at the time of design, and is often a relatively tight sandy soil or viscous soil. In the present invention, since the tip of the anti-floating pile 12 exhibits the anti-floating effect of the underground structure 1 in the state where it stays in the liquefied layer 18, the penetration depth of the anti-floating pile 12 can be shallow, The work load during installation is reduced. This effect is produced in combination with the inflow of pore water through the water-permeable holes 17 described above. That is, a dissipating effect can be obtained by the water permeable holes 17, and liquefaction of the ground around the anti-floating pile 12 can be prevented. Can do. Therefore, no grout injection is required. Although it depends on the condition of the ground, it is usually necessary to excavate 20 m or more from the ground surface to reach the non-liquefied layer 19, but in this embodiment, the anti-floating pile 12 is from the lower end of the underground structure 1. There may be a case where the anchor effect can be obtained at about 3 m to 5 m.

  The floating prevention method for the underground structure 1 in the present embodiment is as follows. First, the invert 15 and the bottom slab 4 of the existing underground structure 1 buried in the ground are penetrated with a through-hole through which the anti-floating pile 12 can be inserted using a separately prepared tool, and the levitated to the through-hole. The prevention pile 12 is penetrated (penetration process). Next, the anti-floating pile 12 is rotated using an impact wrench or the like, and the spiral blades 13 are screwed into the ground to excavate the liquefied layer 18 in the ground (excavation process). Next, the bottom plate 4 of the underground structure 1 and the anti-floating pile 12 are fixed (fixing step). Thereby, the levitating prevention pile 12 can be installed with respect to the existing underground structure 1 with a simple procedure.

DESCRIPTION OF SYMBOLS 1 Underground structure 2 Hollow pipe material 3 Opening part 4 Bottom plate 5 Straight wall body 6 Slanted wall body 7 Bulk adjusting part 8 Receiving frame 9 Lid body 10 Crushed stone foundation material 11 Step 12 Lifting prevention pile 13 Spiral blade 14 Piping 15 Invert 16 Groove 17 Water permeable hole 18 Liquefaction layer 19 Non-liquefaction layer 20 Water permeable sheet 21 Filler 22 Penetration part

Claims (3)

A hollow pipe material fixed to the bottom of the underground structure;
In the anti-floating pile of the underground structure provided with an intrusion portion formed at least on the tip side of the hollow pipe material,
The hollow pipe material has a plurality of water permeable holes penetrating the inside and outside of the hollow pipe material at least at a position below the bottom of the underground structure in a state where the hollow pipe material is fixed to the bottom of the underground structure. An anti-floating pile for underground structures.   2. The underground structure floating prevention pile according to claim 1, wherein the penetration portion includes a spiral blade formed on an outer periphery of the hollow pipe member. A penetration step of penetrating the anti-floating pile at the bottom of the underground structure;
An intrusion step of penetrating into the ground with the anti-floating pile
A fixing step for fixing the bottom of the underground structure and the anti-floating pile, and the penetration formed on at least the tip side of the anti-floating pile includes a liquefied layer and a non-liquefied layer that form the ground. Of these, the underground structure floating prevention method using the underground structure floating prevention pile according to claim 1, wherein the underground structure floating prevention pile is arranged in a liquefied layer.

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