JP2020007817A - Method of forming underground space and repair of underground buried objects - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming an underground space capable of easily forming an underground space for investigation and repair of an underground buried object. SOLUTION: A step of improving the ground of the ground 1 under the slab 7 by using a rod passed through the slab 7 to form a ground improvement body 25 around a foundation pile 3 and a hole 27 for a person to enter the slab. Investigation and repair of foundation pile 3 by the process of forming in 7 and the process of excavating the ground 1 under the slab 7 through the hole 27 to form the underground space 29 whose side surface is surrounded by the ground improvement body 25. The underground space 29 for performing the above is formed. [Selection diagram] Fig. 1

Description

  The present invention relates to a method for forming an underground space and a method for repairing an underground buried object using the underground space.

  After a major earthquake, the foundations of existing buildings may be investigated or repaired. For example, in Patent Literature 1, after an investigation space is formed on the side of a foundation pile of an existing building, a rod is inserted into the investigation space from a hole in the slab, and a camera or the like attached to the tip of the investigation pile is used to form the foundation pile. It states that a survey will be conducted.

  In addition, Non-Patent Document 1 describes a method of constructing a retaining wall around an existing building, excavating the ground below the building from the side of the building, and then performing soundness determination of the foundation pile and repairing the foundation pile. Have been. At the time of repair of foundation piles, after temporarily receiving the load of the building with steel pipe piles and jacks, repair work of foundation piles will be performed.

  In addition, when constructing a new building by rebuilding an existing building, the foundation of the existing building may be surveyed and, if possible, used for the new building. For example, Non-Patent Document 2 describes a method of dismantling a pit slab, excavating the ground, exposing a pile head of a foundation pile, and conducting a pile survey in parallel with the ground demolition work of an existing building.

Patent No. 6286296

Shiranohama Shozo: Damage to buildings and repair cases in the Great East Japan Earthquake: Apartment houses in the Tohoku region, Basic Engineering, pp.63-66, May 2014 Makoto Kakeya, Akira Miyata: Investigation of existing piles during demolition of aboveground structures in urban areas, Summary of academic lectures of the Architectural Institute of Japan, Structure 1, pp.469-470, August 2013

  In the investigation method of Patent Document 1, although an investigation can be performed by an investigation device such as a camera using an investigation space, it is difficult to conduct an investigation by directly looking at a foundation pile. In addition, a separate process is required to repair the foundation pile.

  In Non-patent Documents 1 and 2, the ground is excavated to form an underground space where people can enter around the foundation pile, so that the foundation pile is directly visually inspected using this underground space, and the foundation pile is repaired. You can do.

  However, the method of Non-Patent Document 1 requires extensive preparations such as installation of a retaining wall around an existing building and driving of a steel pipe pile for temporary load reception. Furthermore, in order to investigate and repair the foundation pile near the center of the building, it is necessary to excavate the ground extensively from the side of the building.

  On the other hand, the method of Non-Patent Document 2 dismantles a slab of a building and excavates the ground from inside the building, and omits a mountain retaining wall. There is a danger of the ground breaking.

  The present invention has been made in view of the above-described problems, and has as its object to provide a method of forming an underground space capable of easily forming an underground space for investigating and repairing an underground buried object.

  A first invention for achieving the above-mentioned object is to improve the ground of the ground below the slab using a rod passed through the slab, and to improve the ground around an underground buried object on the ground below the slab. The step of forming a body (a), the step of forming a hole for a person to enter in the slab (b), and the excavation of the lower part of the slab through the hole, the side surface of the ground improvement body And (c) forming an underground space in which the underground object is exposed while being surrounded by the underground space.

  In the present invention, the ground improvement body is formed in the ground below the slab, and the side surface forms an underground space surrounded by the ground improvement body, so that the underground space in which lateral pressure from the surrounding ground is supported by the ground improvement body is formed. Obtained easily. Therefore, installation of the retaining wall can be omitted, and the ground around the underground space does not collapse even if the excavation depth is large.

  In the present invention, ground improvement is performed by a rod passed through the slab, and excavation under the slab and access to an underground space can be made through holes provided in the slab so that a person can pass through. Therefore, without dismantling the slab over a wide area, it is possible to form an underground space where people can enter and to investigate and repair underground buried objects from the inside of the building, even if it is an underground object near the center of the building. Investigation and repair can be easily performed. By utilizing the underground space, it is possible to directly inspect the underground buried objects, and since the excavation area can be limited, steel pipe piles and jacks for temporary load receiving are not required at the time of repair.

In the step (a), the ground improvement body is formed into a tubular shape by the rods passed through a plurality of locations of the slab, and in the step (c), the ground inside the ground improvement body is excavated. desirable.
If the soil improvement body is formed in a cylindrical shape, the formation area of the soil improvement body can be minimized to reduce material costs, and at the same time, the ground inside the soil improvement body is excavated to easily form an underground space. Can be.

  A second invention is a method of repairing an underground buried object, wherein a person enters the underground space formed by the underground space forming method of the first invention to repair the underground buried object.

  ADVANTAGE OF THE INVENTION According to this invention, the formation method of the underground space which can easily form the underground space for investigation and repair of an underground buried object can be provided.

The figure which shows the underground space 29. The figure which shows the underground space 29. The figure which shows the formation method of the underground space 29. The figure which shows the formation method of the underground space 29. The figure which shows about ground improvement. The figure which shows the formation method of the underground space 29. The figure which shows about use of the underground space 29. The figure which shows the formation method of the underground space 29. The figure which shows the formation method of the underground space 29. The figure which shows about ground improvement and formation of the underground space 29.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1. Existing building 10)
FIG. 1 is a diagram showing an underground space 29 formed by the method for forming an underground space according to the embodiment of the present invention. FIGS. 2A and 2B show horizontal cross sections taken along lines AA and BB in FIG. 1, respectively.

  The underground space 29 is provided around the foundation pile 3 (underground buried object) of the existing building 10. The underground space 29 is a space whose side surface is surrounded by the side wall portion 25a of the ground improvement body 25 and whose bottom surface is surrounded by the bottom plate portion 25b of the ground improvement body 25.

  A footing 6 is provided on the head of the foundation pile 3. The pillar 5 is provided on the footing 6, and a slab 7 and a foundation beam 8 on the lower surface thereof are provided beside the footing 6. An upper slab 9 supported by columns 5 and the like is provided on the slab 7. These are mainly formed by reinforced concrete.

  In FIG. 1, reference numeral 27 denotes a hole for a person to enter, and reference numeral 30 denotes a hole filling material 30 in which the small-diameter hole of the slab 7 is filled, which will be described later.

(2. Method of forming underground space 29)
Next, a method of forming the underground space 29 of the present embodiment will be described. In the present embodiment, first, as shown in FIG. 3A, a small-diameter hole 15 is formed in the slab 7 of the existing building 10. The small diameter hole 15 can be formed by core boring or the like.

  FIG. 3B is a diagram showing a plane on the slab 7. In the present embodiment, the small-diameter holes 15 are formed at a plurality of locations around the foundation pile 3, for example, three or four locations (four locations in the example in the drawing). The small diameter hole 15 is formed in the slab 7 avoiding the positions of the footing 6 and the foundation beam 8 where the reinforcing bars are dense.

  Thereafter, as shown in FIGS. 4A and 4B, the rod 21 is inserted into the ground 1 below the slab 7 through each small-diameter hole 15, and the ground 1 below the slab 7 is Improve the ground by high-pressure injection stirring method.

  In the high-pressure injection stirring method, the rod 21 is slowly rotated and pulled up while a solidified material mainly composed of cement is injected into the ground 1 on the side of the rod 21. The ground 1 is cut by the ejection of the solidified material, and at the same time, the soil and the solidified material are mixed and agitated. The strength of the improved body can be adjusted by the amount of cement, and the mixing may be insufficient depending on the ground. Therefore, the vertical movement of the rod 21 can be repeated. A small construction machine 17 can be used for the high-pressure injection stirring method, and construction is possible even when the work space 11 on the slab 7 is narrow. There is also an advantage that various shapes of improved bodies can be easily formed by controlling the direction of ejection and the ejection pressure of the solidified material.

  Here, at the time of construction of the bottom plate portion 25b of the ground improvement body 25 shown in FIG. 4A, the ejection direction and ejection distance (ejection pressure) of the solidified material are controlled as exemplified by the arrow in FIG. The ground improvement range from each rod 21 reaches the outer peripheral surface of the foundation pile 3 and the ground improvement range from the adjacent rods 21 overlaps. Thus, the entire area around the foundation pile 3 is improved to form the plate-like bottom plate portion 25b.

  On the other hand, at the time of constructing the side wall portion 25a of the ground improvement body 25 shown in FIG. 4B, the ejection direction and the ejection distance (ejection pressure) of the solidified material are controlled as illustrated by arrows in FIG. The ground improvement range from the rod 21 does not reach the outer peripheral surface of the foundation pile 3, and the ground improvement ranges from the adjacent rods 21 overlap to form the cylindrical side wall portion 25 a around the foundation pile 3. To

  In the present embodiment, after forming the bottomed cylindrical ground improvement body 25 around the foundation pile 3 on the ground 1 below the slab 7 in this way, as shown in FIG. 7 is formed. The hole 27 is formed at a position inside the side wall portion 25 a of the ground improvement body 25. After the construction of the ground improvement body 25 is completed, the small-diameter hole 15 is filled with a hole filling material 30 such as grout or concrete.

  By excavating the ground 1 below the slab 7 inside the ground improvement body 25 through the hole 27, an underground space 29 whose side and bottom are surrounded by the ground improvement body 25 is formed as shown in FIG. . Excavation of the ground 1 is performed manually, for example, to a predetermined depth, and then performed using both human power and heavy equipment.

(3. Use of underground space 29)
As shown in FIG. 1, the outer peripheral surface of the foundation pile 3 is exposed in the underground space 29. The underground space 29 is used as a work space for investigating and repairing the foundation pile 3 when there is a concern that the foundation pile 3 may be damaged by an earthquake. After forming the underground space 29, the worker enters the underground space 29 from the hole 27 and performs the inspection and repair of the foundation pile 3 as shown in FIG.

  The investigation of the foundation pile 3 can be performed by directly viewing the foundation pile 3 or by using various investigation devices. However, the method for investigating the foundation pile 3 is not limited to this.

  The repair of the foundation pile 3 is performed according to the result of the investigation on the foundation pile 3 and the like. Repair refers to the overall work to maintain or improve the performance and function of the object. The repair method for the foundation pile 3 includes, for example, filling of the foundation pile 3 with cracks, and additional concrete around the foundation pile 3. , And steel plate winding reinforcement in which a steel plate is wound around the foundation pile 3 via a mortar, but is not limited thereto.

  FIG. 7B shows an example of steel plate winding reinforcement, in which a steel plate 31 is wound around the foundation pile 3. In the present embodiment, since a person enters the underground space 29 to repair the foundation pile 3, various means can be adopted for repairing the foundation pile 3, and it can be visually confirmed whether the repair work is being performed as designed. .

  When the investigation and repair of the foundation pile 3 are completed, the underground space 29 is backfilled with soil or fluidized soil, and the holes 27 of the slab 7 are filled with hole filling materials such as grout or concrete. Thereby, it is possible to easily return to the state before the formation of the underground space 29.

  As described above, according to the present embodiment, the ground improvement body 25 is formed in the ground 1 below the slab 7, and the underground space 29 whose side surface is surrounded by the ground improvement body 25 is formed. The underground space 29 in which the lateral pressure from the surrounding ground 1 is supported by 25 is easily obtained. Therefore, the installation of the retaining wall can be omitted, and the ground around the underground space 29 does not collapse even if the excavation depth is large. Further, the underground space 29 of the present embodiment is also surrounded by the ground improvement body 25 on the bottom surface, so that the groundwater is not affected even on the site where the groundwater level is high or the site where the confined groundwater exists, and the watertightness is secured. Eliminating the need for drainage equipment.

  In this embodiment, ground improvement is performed by the rod 21 passed through the slab 7, and excavation under the slab 7 and access to the underground space 29 can be performed from the holes 27 provided in the slab 7 so that a person passing through the slab 7 can pass through. Therefore, without dismantling the slab 7 over a wide area, the formation of the underground space 29 where people can enter and the investigation and repair of the foundation pile 3 can be performed from the inside of the building. Inspection and repair can be carried out easily. By using the underground space 29, it is possible to directly inspect the foundation pile 3 by visual observation, and since the excavation range can be limited, steel pipe piles and jacks for temporary load receiving become unnecessary at the time of repair.

  Further, in the present embodiment, the ground improvement body 25 is formed in a bottomed cylindrical shape having a cylindrical side wall portion 25a and a plate-like bottom plate portion 25b, so that the formation range of the ground improvement body 25 is minimized. The material cost can be reduced, and the underground space 29 can be easily formed by excavating the ground 1 inside the ground improvement body 25. Although the side wall portion 25a of the present embodiment is cylindrical, it may be formed, for example, in a rectangular tube shape.

  In the present embodiment, the ground improvement body 25 having a shape necessary for forming the underground space 29 can be easily formed by using the high-pressure injection stirring method.

  However, the present invention is not limited to this. For example, when a thick viscous ground continues, the viscous ground plays a role of an impermeable layer, so the bottom plate portion 25b of the ground improvement body is omitted, and the bottom surface of the underground space 29 surrounded by the cylindrical side wall portion 25a. May be used as a viscous ground.

  When the ground improvement body is formed, a horizontal section is used as shown in FIG. 8B by using rods 21 passed through the small diameter holes 15 around the foundation pile 3 as shown in FIG. 8A. It is also possible to form a constant ground improvement 25 'in the vertical direction.

  After the formation of the ground improvement body 25 ', a hole 27 is formed in the slab 7 as shown in FIG. By excavating the ground improvement body 25 'below the slab 7 through the hole 27, an underground space 29 whose side and bottom are surrounded by the ground improvement body 25' can be formed as shown in FIG. 9B. In this example, the hole 27 is formed in a range overlapping with the small diameter hole 15.

  At the time of soil improvement, for example, as shown by an arrow in FIG. 10A, a solidified material is ejected from each rod 21 to a circular ground improvement area centered on the rod 21, and the ground improvement area from each rod 21 is used as a basis. The ground improvement range from the adjacent rods 21 is made to reach the outer peripheral surface of the pile 3 and overlap. When the horizontal cross section of the ground improvement body 25 'is constant in the height direction, there is no need to change the ejection pressure and the ejection direction of the solidified material during the construction of the ground improvement body 25', and control is simplified. However, there is a problem in that the amount of the solidified material increases and material costs increase, and it is necessary to excavate the solid ground improvement body 25 'when the underground space 29 is formed.

  FIG. 10B shows an example of the underground space 29 formed by excavating the ground improvement body 25 '. In the above embodiment, the plane of the underground space 29 is substantially circular, but in this example, the plane is substantially rectangular. Thus, the planar shape of the underground space 29 is not particularly limited.

  In the present embodiment, the small-diameter holes 15 through which the rods 21 pass are formed in four places of the slab 7, but the number and positions of the small-diameter holes 15 are not particularly limited, and the ground improvement body can be formed in a necessary range. I just need.

  Further, in this embodiment, an example in which the investigation and repair of the foundation pile 3 of the existing building 10 are performed is shown, but the target underground buried object is not limited to this, and for example, the foundation pile of the existing building 10 other than the foundation pile 3 is used. (For example, basic footing). By using the method of the present invention, investigation and repair of the foundation pile 3 and other foundations of the existing building 10 can be easily performed. Furthermore, the target underground buried object is not limited to the foundation of the existing building 10 and may be, for example, a buried pipe existing underground.

  Further, in this embodiment, the entire circumference of the foundation pile 3 (underground buried object) is exposed in the underground space 29, and the steel plate winding reinforcement as shown in FIG. 7B can be performed. It is not necessary to expose the entire circumference to the underground space 29, and only a part may be exposed to the underground space 29. In the case of initial investigation or minor repair, it is possible to keep the cost low by exposing partly. Become. As described above, the underground buried object in the present invention includes not only the entire plane of the underground buried object but also a part of the plane of the underground buried object.

  The preferred embodiment according to the present invention has been described with reference to the accompanying drawings, but the present invention is not limited to this example. It is obvious to those skilled in the art that various changes or modifications can be made within the scope of the technical idea disclosed in the present application, and these naturally belong to the technical scope of the present invention. I understand.

1: Ground 3: Foundation pile 7: Slab 10: Existing building 21: Rod 25, 25 ': Ground improvement 25a: Side wall 25b: Bottom plate 27: Hole 29: Underground space

Claims (3)

(A) forming a ground improvement body around an underground buried object in the ground below the slab by performing ground improvement on the ground below the slab using a rod passed through the slab;
(B) forming a hole in the slab for a person to enter;
(C) forming an underground space in which a side surface is surrounded by the ground improvement body and the underground buried object is exposed by excavating below the slab through the hole.
A method for forming an underground space, comprising: In the step (a), the ground improvement body is formed into a cylindrical shape by the rods passed through a plurality of locations of the slab,
The method for forming an underground space according to claim 1, wherein the ground inside the ground improvement body is excavated in the step (c).   A method for repairing an underground buried object, wherein a person enters the underground space formed by the underground space forming method according to claim 1 to repair the underground buried object.

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