JP2016011492A - Pile investigation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pile investigation method that allows a pile to be investigated readily from inside a building, without demolition work.SOLUTION: When investigating a pile body 12 buried in ground 20 underneath a pressure-resistant slab 11 of an existing building 10, a small-diameter hole 11a is drilled through the pressure-resistant slab, and the ground 20 is excavated in a vertical direction by water jet, using a rod 3 inserted into the small-diameter hole 11a. When the ground 20 is highly viscous, the ground 20 between the rod 3 and the pile body 12 is excavated in a horizontal direction by water jet using the rod 3 inserted into the ground 20, to discharge excavated soil and form a space 23 for investigating the pile body 12. Then, the pile body 12 is investigated using a photographing device 8 and a displacement meter fitted on the rod 3.

Description

  The present invention relates to a pile survey method for investigating a pile body.

  When constructing a new building by rebuilding an existing building, the piles of the existing building are investigated and used for the new building if possible.

  As a method for investigating a pile body, for example, Non-Patent Document 1 describes a method in which excavation is performed from a site on the outer periphery of a building to expose the pile body. Patent Document 1 describes a method of excavating the ground from a site on the outer periphery of a building toward a pile head and performing a contact test on the pile body.

  On the other hand, Non-Patent Document 2 describes a method for conducting a pile survey from the inside of an existing building by dismantling a pressure-resistant plate near the pile, excavating the ground, and performing a pile survey with the exposed pile head. . Patent Document 2 describes that as a method for inspecting the damage state of a pile foundation during an earthquake, the hollow pile foundation immediately below is inspected through an inspection hole provided in advance in a footing or the like.

  Non-Patent Document 3 describes a method of conducting a pile survey in a state where a pile body is exposed after dismantling of an existing building.

JP 2007-271587 JP-A-8-302722 Masaaki Kakurai: Background of the idea of using existing piles and investigation contents and techniques for reuse, foundation work, pp.17-22, February 2011 Makoto Kakeya, Akira Miyata: Survey of existing piles during dismantling of ground structures in urban areas, Abstracts of Annual Conference of Architectural Institute of Japan, Structure 1, pp.469-470, August 2013 Masafumi Edera: Administrative response in reuse of existing foundations, Foundation works, pp.10-16, February 2011

  When the investigation is performed from the outer periphery of the building as in Non-Patent Document 1 and Patent Document 1, a wide open space for arranging heavy machinery for excavation around the building is necessary. However, it is difficult to secure open spaces in urban buildings. There is also a problem that only piles located on the outer periphery of the building can be investigated.

  In the methods of Non-Patent Document 2 and Patent Document 2, since the pile body can be investigated from the inside of the building, the above problem does not occur. However, the method of Non-Patent Document 2 requires the dismantling work of the pressure plate near the pile, and it is necessary to dismantle at least 2m square in order to secure the space for the investigator to pass through during the pile investigation. It is. In order to secure this size in the situation where a building is used, the construction method is limited in terms of noise and vibration. For example, a method of making holes by core boring and disassembling the pressure-resistant plate little by little is preferable because noise and vibration are small, but on the other hand, a construction period and cost are required. In addition, since a large amount of concrete cylinders cut out by core boring are generated, the storage space must be secured. Moreover, the method of patent document 2 has the problem that it can apply only to the investigation of a hollow pile foundation, and it is necessary to provide an inspection hole beforehand at the time of construction of a building.

  When reconstruction of an existing building is a premise, as in Non-Patent Document 3, an investigation is often performed after the existing building is dismantled. After demolition of the building, it is in an optimal state for investigating pile bodies. However, when existing buildings are demolished, the design of new buildings after rebuilding has already been completed. When using a pile body of an existing building for a new building, the pile body is designed with reference to the design document of the existing building, so redesign if the result of the pile survey is different from the design document It is necessary, and the rebuilding schedule will be greatly extended. In some cases, rebuilding itself may have to be canceled, but rebuilding cannot be canceled because the existing building has already been demolished.

  This invention is made in view of the above-mentioned problem, and it aims at providing the pile investigation method which can carry out a pile investigation easily from the inside of a building, without performing demolition construction.

  The present invention for solving the above-mentioned problems is a pile investigation method for investigating a pile body embedded in the ground under a pressure plate, the step of forming a hole in the pressure plate, and passing through the hole Excavating the ground in the vertical direction using a rod; excavating the ground between the rod and the pile in the horizontal direction using a rod inserted into the ground from the hole; excavating; Discharging the ground, forming a survey space for the pile body, and investigating the pile body using a survey device attached to a rod inserted into the survey space from the hole And a pile survey method characterized by comprising:

  According to the pile investigation method of the present invention, the pile body can be easily investigated by the work inside the building, the open space around the building does not have to be wide, and only the pile body on the outer periphery of the building can be investigated. In addition, it is possible to work in a narrow space on the pressure plate, and the holes can be small in diameter, and the work of dismantling the pressure plate is unnecessary. In addition, since the survey can be conducted without demolishing the existing building, the pile survey results can be reflected when designing a new building, and the pile is investigated after the existing building is demolished. As in the case, redesign is not required depending on the state of the pile. In addition, it is possible to cancel rebuilding before demolishing existing buildings based on the survey results of piles.

It is preferable that the vertical and horizontal excavation of the ground is performed by a water jet.
Thereby, excavation of the ground can be suitably performed using the rod passed through the hole of the pressure plate.

After excavating the ground in the vertical direction, it is desirable to eject the solidified material from the rod inserted into the ground through the hole to the ground in the vicinity of the pile body including between the rod and the pile body. Moreover, when excavating the ground in the horizontal direction, it is desirable to discharge a thickener from the rod to the ground between the rod and the pile body.
Thereby, the strength of the ground is increased even when the space for investigating the pile body is formed, the space holding capacity is ensured, and the groundwater can be prevented from flowing into the space. Moreover, by excavating soil in this range, it can be easily discharged by using a thickener to muddy the part of the portion where the solidifying material is ejected.

It is desirable to arrange a pressure device on the pressure plate so as to cover the position of the hole and pressurize the inside of the pressure device.
Thereby, it can prevent that groundwater etc. overflow from a hole during work.

The survey device is a photographing device, and it is desirable to photograph the pile body with the photographing device when investigating the pile body. In addition, it is desirable that the investigation device is a non-contact displacement meter, and the distance from the displacement meter to the surface of the pile body is measured by the displacement meter during the investigation of the pile body.
As a pile survey, a visual survey is performed using still images and videos obtained from a camera attached to the rod, or a detailed survey of the shape of the pile body is performed using a non-contact displacement meter mounted on the rod. It is possible.

  According to the present invention, it is possible to provide a pile survey method capable of easily performing a pile survey from the inside of a building without performing demolition work.

The figure which shows the existing building 10 Flow chart showing the procedure of the pile survey method The figure which shows formation of the small diameter hole 11a, and the excavation of the ground 20 in the vertical direction Diagram showing ground improvement The figure which shows mudification of the ground 20 The figure which shows formation of space 23 for investigation The figure which shows the pile investigation with photographing device 8 The figure which shows the backfill of the space 23 for investigation, and the hole filling of the small diameter hole 11a Diagram showing ground improvement The figure which shows formation of space 23 for investigation

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

(1. Existing building 10)
Drawing 1 is a figure showing a part of existing building 10 used as the object of the pile investigation method concerning the embodiment of the present invention. The existing building 10 supports an upper pile cap 13 with a pile body 12 embedded in the ground 20, and a pressure plate 11, a slab 14, and the like are provided on the side. The pressure plate 11 is made of reinforced concrete, and the pile body 12 is provided at a planar position corresponding to the pile cap 13.

  The pile investigation method of this embodiment is to investigate the pile body 12 by work in the work space 15 on the pressure plate 11 without dismantling the existing building 10.

(2. Pile survey method)
Next, the procedure of the pile investigation method of this embodiment will be described. FIG. 2 is a flowchart showing the procedure of the pile survey method. In the present embodiment, it is assumed that information such as the soil quality and groundwater level of the ground 20 is obtained in advance by a preliminary survey, a design book of an existing building, or the like.

  In this embodiment, when the groundwater level of the ground 20 is higher than the pressure plate 11 (S1; “YES”), first, as shown in FIG. 3A, the pressure device 2 is placed on the pressure plate 11 of the existing building 10. It installs (S2) and the elevator 4 for holding a cylindrical rod so that raising / lowering is possible is fixed to the pressure-resistant plate 11 (S3). 14a in FIG. 3 (a) is an opening for an investigator to enter and exit, such as a manhole.

  The pressure device 2 is disposed so as to cover a formation position of a small-diameter hole described later. The pressure device 2 can pressurize the inner space 2a of the outer shell. The outer shell is also provided with a through hole for allowing the rod to pass therethrough. The pressure device 2 is provided in order to prevent the overflow of groundwater or the like through the small-diameter hole by setting the space above the small-diameter hole to a high pressure.

  Subsequently, as shown in FIG. 3B, the pressure plate 11 is perforated to form a small diameter hole by performing water jet from the nozzle at the tip of the rod 3 held by the elevator 4 inside the pressurized pressure device 2. 11a is formed (S4). The small-diameter hole 11a is formed in a position near the pile body 12 in a plane while avoiding the reinforcing bar in the pressure plate 11. The small diameter hole 11a can also be formed by core boring. When it is unavoidable, the reinforcing bar in the pressure plate 11 may be cut.

  On the other hand, when the groundwater level of the ground 20 is equal to or lower than the pressure-resistant plate 11 (S1; “NO”), there is little risk of overflow of groundwater when the small-diameter hole 11a is formed. Accordingly, the elevator 4 is first fixed to the pressure plate 11 (S2 '), and the small diameter hole 11a can be formed using the rod held by the elevator 4 (S3') as described above.

  In the present embodiment, thereafter, the pressure device 2 is installed in the same manner as described above (S4 '). This is for preventing water from flowing back and overflowing when excavating the ground 20 described later.

  After forming the small-diameter hole 11a in the pressure plate 11 as described above, the nozzle at the tip of the rod 3 is replaced with a nozzle device for ground excavation, and the rod 3 is passed from the inside of the pressure device 2 through the small-diameter hole 11a. As shown in (c), the rod 3 is lowered while performing a water jet downward from the tip of the nozzle device of the rod 3. As a result, the ground 20 is excavated downward in the vertical direction (S5).

  In this embodiment, a plurality of rods 3 having a predetermined length including the rod 3 are prepared, and a new rod 3 is added to the upper end of the rod 3 and extended as the rod 3 descends. Although not shown in the drawing, inside these rods 3 are passed a hose for supplying water for a water jet, a hose for supplying a solidified material to be described later, and other various hoses as required.

  In the present embodiment, when the viscosity of the ground 20 such as sandy soil is low (S6; “low viscosity such as sandy soil”), as shown in FIGS. 4 (a) and 4 (b), the soil 20 is inserted into the ground 20. The rod 3 is rotated and moved up and down while a solidifying material such as cement milk is ejected laterally from a hole (not shown) provided in the nozzle device of the rod 3 (S7). 4A shows a part of the existing building 10 as in FIGS. 1 and 3, and FIG. 4B is a cross-sectional view taken along line AA in FIG. 4A. . The same applies to the subsequent drawings.

  Thereby, the solidified material is ejected to the ground 20 in the range 21 in the vicinity of the pile body 12, and the ground is improved by the solidification of the ground 20. This range 21 is centered on the position of the rod 3 and reaches the surface of the pile body 12. In addition, when the groundwater level has reached the height of the pressure plate 11, the inflow of groundwater into the range 21 is detected by a sensor (not shown) provided on the rod 3, and further when groundwater flows in. It is also possible to improve the water shielding property by ejecting the solidified material.

  In the present embodiment, before the ground 20 in the above-described range 21 is solidified, as shown in FIGS. 5A and 5B, the rod 3 is moved up and down and a necessary range is rotated and provided in the nozzle device. From the hole (not shown), a thickener is discharged to the side to the range 22 between the rod 3 and the pile body 12 as needed (S8). At the same time, a water jet is performed laterally from another hole (not shown) provided in the nozzle device, and the above-described range 22 is excavated in the horizontal direction (S9).

  Thereby, the range 22 between the rod 3 and the pile body 12 in the above-described range 21 becomes mud, and the excavated soil in this range 22 is discharged, so that the pile as shown in FIGS. 6 (a) and 6 (b). An investigation space 23 for the pile body 12 is formed on the side of the body 12 (S10). There are various methods for discharging the excavated soil. For example, after the rod 3 is pulled up and collected, the hose is passed through the small-diameter hole 11a, and the excavated soil can be sucked up from the hose using a pump.

  On the other hand, when the viscosity of the ground 20 such as the viscous soil is high (S6; “high viscosity such as the viscous soil”), the above ground improvement (S7) and the discharge of the thickener (S8) are omitted, and the above directly. The ground 20 in the range 22 can be excavated in the horizontal direction in the same manner as described above (S9). By expelling the excavated soil, a survey space 23 is formed on the side of the pile body 12 (S10).

  After forming the investigation space 23 as described above, as shown in FIGS. 7A and 7B, the photographing device 8 such as a camera is attached to the rod 3, and the rod 3 is attached to the investigation space from the small diameter hole 11a. The surface of the pile body 12 is photographed as a still image or a moving image by the photographing device 8 while being moved up and down and rotated. From this image, visual inspections such as cracks and construction defects can be performed.

  Further, the imaging device 8 is replaced with a non-contact displacement meter such as a laser displacement meter, and the distance from the displacement meter to the surface of the pile body 12 is measured while the rod 3 is moved up and down and rotated in the same investigation space 23. Thereby, the shape, position, etc. of the pile body 12 such as the pile diameter and the pile core position are measured in detail. Thus, the pile body 12 is investigated (S11).

  After completion of the pile survey, as shown in FIGS. 8A and 8B, the pressure device 2, the rod 3, the elevator 4, etc. are removed, the survey space 23 is backfilled with the backfill 24, and the pressure plate 11 The small-diameter hole 11a is filled with a hole filling material 25 such as mortar or concrete (S12). For the backfill soil 24, for example, the excavated soil discharged earlier is used. Thereby, it can return to the state before pile investigation easily. In addition, the inside of the pressure apparatus 2 is returned to normal pressure at an appropriate stage in which there is no risk of overflow of groundwater or the like in the procedure described above. Alternatively, it can be removed at that stage.

  Depending on the existing building 10, for example, when the diameter of the pile body 12 is small, the planar distance between the small diameter hole 11a of the pressure plate 11 and the pile body 12 may be inevitably increased.

  At this time, when the solidifying material such as cement milk is ejected in S7, in addition to the ejection of the solidifying material as described in FIGS. 4A and 4B, FIGS. 9A and 9B are performed. As shown in FIG. 5, it is preferable to eject a solidified material such as cement milk at a high pressure from the hole provided in the nozzle device toward the side pile body 12.

  Accordingly, the region 21a around the rod 3 where the solidified material is ejected by the method described with reference to FIGS. 4A and 4B and the rod 3 from which the solidified material is ejected by the above-described method is directed to the pile body 12. Ground improvement can be made in both radial ranges 21b.

  Thereafter, the procedure is the same as described above. That is, by discharging the thickener (S8) and horizontal digging with a water jet (S9) to the range between the rod 3 and the pile body 12 and discharging the mud-like excavated soil, FIG. As shown to a) and (b), the space 23 for investigation can be formed in the side of the pile body 12 (S10).

  As explained above, according to the pile survey method of this embodiment, the pile body 12 can be easily surveyed by the work inside the building, the open space around the building does not have to be wide, and only the pile body on the outer periphery of the building can be investigated. There is no such thing. Further, the work in a narrow space on the platen 11 is possible, and it is only necessary to open the small-diameter hole 11a. Furthermore, since the survey can be conducted without dismantling the existing building 10, the survey result of the pile body 12 can be reflected when designing a new building in the case of rebuilding, and the pile body after dismantling of the existing building at the time of rebuilding. As in the case of investigating, the redesign is not required depending on the state of the pile body 12. Moreover, it is also possible to cancel rebuilding before the dismantling of the existing building 10 according to the survey result of the pile body 12.

  Further, in the present embodiment, excavation of the ground 20 is performed with a water jet, so that excavation of the ground 20 can be suitably performed using the rod 3 passed through the small diameter hole 11a.

  Furthermore, when the above ground improvement is performed, the strength of the ground is increased even when the investigation space 23 of the pile body 12 is formed, the space holding capacity is secured, and the groundwater level reaches the position of the pressure plate 11. If it is, groundwater can be prevented from flowing into the investigation space 23. In this embodiment, the level of viscosity is determined from information obtained in advance. For example, when the rod 20 is pulled up after the ground 20 is excavated in the vertical direction by a water jet in S5, the surrounding ground 20 is If it collapses, it can be determined that the viscosity is low.

  Further, in the present embodiment, the excavated soil in this range can be sucked up by a pump or the like and easily discharged by using a thickener to muddy the part of the portion where the solidifying material is ejected.

  Furthermore, in this embodiment, the pressure device 2 provided so as to cover the position of the small-diameter hole 11a can prevent groundwater, water from a water jet or the like from overflowing from the small-diameter hole 11a during work. However, the pressure device 2 can be omitted if there is no concern about these overflows.

  Moreover, in this embodiment, a pile investigation can be performed suitably by using the imaging device 8 attached to the rod 3 or a non-contact type displacement meter. However, the pile investigation is not limited to this, and various pile investigations can be performed by attaching various investigation devices to the rod 3. For example, it is possible to investigate pile body elastic wave velocity and reinforcing bar arrangement.

  In this embodiment, the example of the pile survey of the existing building 10 is shown. However, the target of the pile survey is not limited to this. For example, for a new building, the construction of the pile foundation is finished and the superstructure is constructed. It is also possible to investigate the pile body in the state where it is, and to investigate earthquake resistance. It is also possible to investigate piles when there is concern about pile damage after an earthquake.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

2; Pressure device 3; Rod 4; Elevator 5; Nozzle device 8; Imaging device 10; Existing building 11; Pressure-resistant plate 11; Small-diameter hole 12; Pile 13; Pile cap 14; Ground 23; Survey space 24; Backfill 25; Hole filling material

Claims (7)

A pile survey method for investigating pile bodies buried in the ground under pressure-resistant plates,
Forming a hole in the pressure plate,
Using the rod passed through the hole, excavating the ground in the vertical direction;
Using the rod inserted into the ground from the hole, excavating the ground between the rod and the pile body in a horizontal direction;
Discharging the excavated ground and forming a survey space for the pile body;
Using the investigation device attached to the rod inserted into the investigation space from the hole, the step of investigating the pile body,
A pile survey method characterized by comprising:   The pile investigation method according to claim 1, wherein excavation of the ground in the vertical direction and the horizontal direction is performed by a water jet.   After excavating the ground in the vertical direction, the solidified material is ejected from the rod inserted into the ground through the hole to the ground in the vicinity of the pile body including between the rod and the pile body. The pile investigation method according to claim 1 or claim 2 to be performed.   The pile investigation method according to claim 3, wherein when excavating the ground in a horizontal direction, a thickener is discharged from the rod to the ground between the rod and the pile body.   The pile investigation method according to any one of claims 1 to 4, wherein a pressure device is disposed on the pressure plate so as to cover the position of the hole and pressurizes the inside of the pressure device.   The pile investigation method according to any one of claims 1 to 5, wherein the investigation device is a photographing device, and the pile body is photographed by the photographing device when the pile body is examined. The survey device is a non-contact displacement meter, and the distance from the displacement meter to the surface of the pile body is measured by the displacement meter when the pile body is surveyed. The pile survey method according to claim 6.

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