JP2010090588A - Pile hole excavating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pile hole excavating method for excavating a pile hole in a short time without needing a large-scale facility for press-fitting a pipe. <P>SOLUTION: The pile hole excavating method for rotationally driving and lowering a rod 24 of an excavator 2 to excavate the pile hole 10 for a cast-in-place pile with a bit 25 provided at the lower end of the rod 24, is characterized by inserting a hole wall protective pipe 11 with a diameter smaller than the hole diameter of the pile hole 10 down to a predetermined depth in the pile hole 10 in association with the descent of the bit 25 in the excavator 2. In this pile hole excavating method, the excavation of the pile hole 10 and protection of a pile wall can be simultaneously executed to permit the excavation of the pile hole 10 in a short period of time. Further, the hole wall protective pipe 11 in this pile hole excavating method can be inserted into the pile hole 10 without being press-fitted because its diameter is smaller than the hole diameter of the pile hole 10. The large-scale facility for press-fitting is thereby dispensed with to miniaturize an excavating apparatus 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pile hole excavation method used for excavation of a pile hole for cast-in-place piles.

  When excavating the pile holes of cast-in-place piles, especially in places close to existing structures such as railroad tracks and places where the ground is soft, the hole walls are protected so that the hole walls near the ground surface do not collapse. . For example, in the method for creating a cast-in-place pile described in Patent Document 1, after performing a pre-digging in the ground, a cylindrical casing is built in the pile hole to prevent the hole wall from collapsing during excavation. We are trying to protect. As a method of erection of such a casing, for example, a method of press-fitting a tubular casing into the ground, or a method of assembling a casing along a hole wall by connecting a plurality of arc-shaped liner plates in a hole by an operator It has been known.

JP 2005-273411 A

  However, the above-mentioned conventional cast-in-place pile construction method has the following problems. That is, in order to press-fit a casing having a size corresponding to the hole diameter into the ground, a relatively large facility is required, and it is difficult to use it in a space-constrained place such as a place close to the track. Moreover, in the method of assembling the casing in the hole by the worker, it is necessary to carry out in a short time at night when the train is not operating, and there is a problem that the construction period becomes long when it is installed deeply.

  The present invention has been made in view of the above-described circumstances, and provides a pile hole excavation method that can eliminate a large facility for press-fitting a pipe and can excavate a pile hole in a shorter period of time. For the purpose.

  In order to achieve the above object, the present invention relates to a pile hole excavation method in which a rod of an excavator is rotated and lowered, and a pile hole for a cast-in-place pile is excavated by a bit provided at a lower end of the rod. According to the descent of the bit in the machine, a hole wall protective tube having a diameter smaller than the hole diameter of the pile hole is inserted to a predetermined depth in the pile hole.

  According to this pile hole excavation method, the rod of the excavator is driven to rotate and lowered so that the hole wall is protected by inserting the hole wall protection tube while excavating the pile hole with the bit at the lower end of the rod. Can do. As a result, the excavation of the pile hole and the protection of the hole wall can be performed at the same time, so that the excavation of the pile hole can be performed in a shorter period of time. Moreover, the hole wall protective pipe in this pile hole excavation method is smaller than the hole diameter of the pile hole, and is inserted into the pile hole instead of being press-fitted. This eliminates the need for large-scale equipment for press-fitting the hole wall protective tube, so that the construction equipment can be downsized.

  The hole wall protective tube is preferably formed by connecting a plurality of wall bodies. In this way, the hole wall protection tube can be assembled from a plurality of wall bodies, thereby saving space in the hole wall protection tube during transportation and storage compared to the case of using a ready-made hole wall protection tube. Is planned.

  Further, the excavator has a gate-shaped fixed portion arranged so as to straddle the pile hole, and a movable portion that moves up and down along the fixed portion and that fixes the upper end of the rod. After excavating with a bit while lowering, after excavating for a predetermined distance, release the fixation between the rod and the movable part, raise the movable part, and then between the rod and the movable part released from the fixation A new rod is added and excavation proceeds by lowering the movable part again. When the movable part is raised, a plurality of wall bodies are connected so as to surround the rod fixed to the movable part. After forming the hole wall protection tube, suspending the hole wall protection tube on the movable part and lowering the movable part, the hole wall protection pipe is inserted into the pile hole in accordance with the descent of the bit, and then the inserted hole Suspended by moving parts while the wall protection tube is suspended by other suspension After releasing the movable part and raising the movable part, a hole wall protection tube is formed to surround the newly added rod, and the hole wall protection pipe is suspended from the movable part to protect the already inserted hole wall. It is preferable that after being connected to the pipe side, the suspension by another hanging tool is released, and the hole wall protection pipe is inserted again into the pile hole as the bit descends.

  According to such a configuration, excavation by the bit is performed by repeating the work of lowering the movable part after adding the rod and adding the hole wall protection pipe between the raised movable part and the bit. It is possible to realize the insertion of the hole wall protection pipe into the pile hole in accordance with. Moreover, since the movable part should just be the structure which has a movable distance for predetermined distance, compared with the case where a boring machine etc. are utilized, it can aim at the height reduction of an excavator, and is a place with a height restriction. Even if it exists, this invention can be applied suitably.

  In addition, it is preferable to extend the hole wall protective tube by connecting a plurality of wall bodies to the upper end of the already formed hole wall protective tube during the lowering of the movable part. By extending the hole wall protection pipe while the movable part is descending, that is, while the bit is being excavated, it is possible to excavate the pile hole and insert the hole wall protection pipe in a shorter period of time.

  The bit is a rotating body that expands in the radial direction with the central axis of the rod as the center of rotation, and its outer peripheral part enters the inside, and can be reduced in diameter so as to be smaller than the inner diameter of the hole wall protective tube. When lifting and collecting, it is preferable to make the outer periphery of the bit smaller than the inner diameter of the hole wall protective tube. Thus, when the bit is lifted and collected, the bit is easily collected while maintaining the hole wall protective tube inserted into the pile hole by making the outer periphery of the bit smaller than the inner diameter of the hole wall protective tube. be able to.

  According to the present invention, a large facility for press-fitting a pipe is not required, and a pile hole can be excavated in a shorter period of time.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a plan view for explaining a pile hole excavation method according to the present embodiment, and FIG. 2 is a side sectional view for explaining the pile hole excavation method according to the present embodiment.

  As shown in FIGS. 1 and 2, the pile hole excavation method according to the present embodiment is used for excavation of a pile hole 10 for a concrete pile foundation by a cast-in-place pile method. The site where the pile hole 10 according to the present embodiment is formed is located in the vicinity of the railway track T, which is an existing structure, and its formation is in the vicinity of the ground surface, which is a soft formation that requires protection of the hole wall during excavation. It is divided into the A layer and the deep B layer, which is a solid formation. Further, the pile hole 10 is composed of a preceding digging hole 10A, an intermediate pile hole 10B, and a deep pile hole 10C that are continuous in the vertical direction, and in that order, the preceding digging hole 10A, the intermediate pile hole 10B, and the deep pile hole 10C. It is formed so that the hole diameter becomes small. The preceding digging hole 10A and the intermediate pile hole 10B are formed in the A layer, and the deep pile hole 10C is formed in the B layer.

  The excavator 1 used in this pile hole excavation method includes an excavator 2 installed on the pile hole 10, a mud supply pipe 3 for supplying mud water from a mud tank (not shown) into the pile hole 10, and a pile hole 10 is provided with a mud drain pipe 4 for sucking out mud and sand excavated from 10. Further, the excavator 1 includes a pump unit 5 that sends excavated sediment and mud water to a mud tank through a mud drain pipe 4, and a temporary receiving beam (other hanging tool) 6 for temporarily receiving a hole wall protective pipe 11 to be described later. And.

  The excavator 2 has a gate-shaped fixing portion 20 including two column portions 20a installed on the ground and a connecting portion 20b that connects the tip portions of the column portions 20a. An operation panel 21 for operating the excavator 2 is provided at the base of the one column portion 20a. A beam-shaped movable portion 22 extending in the horizontal direction is stretched between the two column portions 20a in the fixed portion 20. At both ends of the movable portion 22, a drive portion 22a that moves along the two column portions 20a is provided, and the movable portion 22 moves up and down by the cooperation of these drive portions 22a.

  A long protective tube suspension 23 for hanging the hole wall protective tube 11 is attached to the lower part of the movable portion 22 near both ends. These protective tube hanging parts 23 are configured to be detachable from the movable part 22. Moreover, the protection tube suspending portion 23 is configured to be able to attach a suspension wire 26 for suspending the hole wall protection tube 11 in the pile hole 10.

  The hole wall protection pipe 11 is a circular pipe-shaped member having an outer diameter smaller than the hole diameter of the intermediate pile hole 10B in the pile hole 10, and is disposed along the hole wall of the intermediate pile hole 10B of the pile hole 10 during excavation. Prevents the collapse of the hole wall. The distance between the hole wall protective tube 11 and the hole wall of the intermediate pile hole 10B is particularly preferably in the range of 5 cm to 10 cm. When this interval is 5 cm or less, there is a high possibility that the hole wall protection tube 11 will not easily enter the intermediate pile hole 10B due to the formation error of the intermediate pile hole 10B. Sometimes the pore walls are more likely to collapse.

  Further, the hole wall protection tube 11 is formed by connecting a plurality of tube segments 12 divided in the central axis C direction (vertical direction). Each of the plurality of tube segments 12 is formed by annularly connecting steel liner plates (wall bodies) 13 divided in the circumferential direction. The length of the hole wall protection tube 11 can be changed by changing the number of tube segments 12 connected in the direction of the central axis C.

  In the center of the movable portion 22, a rod tube connecting portion 22b to which an upper end of a rod tube (rod) 24 extending in the vertical direction is connected is provided. The rod tube 24 has flange portions at both ends, and a plurality of rod tubes 24 having the same length are connected via the flange portion. These rod pipes 24 are connected so as to extend from the rod pipe connecting portion 22b toward the pile hole 10, and a wing bit for excavating the ground is provided at the lower end of the rod pipe 24 positioned at the lowest position. 25 is fixed. Further, the rod tube connecting portion 22b is provided with a motor for rotating the connected rod tube 24 in the circumferential direction.

  The wing bit 25 is an umbrella-shaped member that expands in the radial direction with the central axis of the rod tube 24 as the center of rotation, and is configured as a rotating body that rotates in the circumferential direction as the rod tube 24 is driven to rotate by a motor. The wing bit 25 has a shaft portion 25b protruding upward from the center thereof, and the lower end of the rod tube 24 is connected to the shaft portion 25b. Further, the outer periphery 25a of the wing bit 25 is configured to be retracted inward, and the diameter of the wing bit 25 is smaller than the inner diameter of the hole wall protective tube 11 by the outer periphery 25a entering inside. Diameter.

  The mud drain pipe 4 for sucking excavated earth and sand and mud is connected to the upper part of the rod pipe connecting part 22b. The inside of the mud drain pipe 4 and the inside of the rod pipe 24 are communicated via a rod pipe connecting portion 22b. In addition, a suction port 25c is provided in the shaft portion 25b of the wing bit 25 to which the rod pipe 24 is connected, for sucking and discharging the earth and mud excavated by the wing bit 25 to the ground.

  Next, a pile hole excavation method for excavating a pile hole of a cast-in-place pile using the excavator 1 described above will be described in detail with reference to the drawings.

  3 is a side sectional view showing a state of preceding digging, FIG. 4 is a side sectional view showing a state where the excavator shown in FIG. 1 is installed, and FIG. 5 is a rod tube connected to the movable part shown in FIG. Side surface sectional drawing which shows a state, FIG. 6: is side surface sectional drawing which shows the state which assembled the hole wall protective tube. 7 is a side cross-sectional view showing a state in which the hole wall protective tube shown in FIG. 6 is inserted into a previously dug hole, and FIG. 8 is a front cross-sectional view showing a state in which the hole wall protective tube is temporarily received. 9 is a side cross-sectional view showing a state where a rod pipe is added, FIG. 10 is a side cross-sectional view showing a state where a hole wall protection pipe is inserted to a required depth, and FIG. 11 is a state where excavation of a pile hole is finished. It is side surface sectional drawing shown.

  As shown in FIG. 3, in the pile hole excavation method in the present embodiment, first, excavation by a hydraulic excavator or human power is performed on the ground forming the pile hole 10 for cast-in-place piles. In the preceding digging, the preceding digging hole 10A having a hole diameter larger than the diameter of the wing bit 25 in the non-reduced state and having a depth into which the entire wing bit 25 enters is formed.

  Thereafter, a cylindrical guide pipe 15 is provided along the hole wall of the preceding digging hole 10A. For example, the guide pipe 15 may be configured by connecting a plurality of liner plates, or may be configured by inserting a ready-made guide pipe. At this time, in order to improve the stability of the guide pipe 15 against horizontal earth pressure or the like, mortar or the like is backed up between the hole wall of the preceding digging hole 10 </ b> A and the guide pipe 14.

  Next, as shown in FIG. 4, after a plurality of support blocks 16 are installed on the bottom surface of the preceding digging hole 10 </ b> A, the wing bits 25 are arranged on the support blocks 16 so that the shaft portion 25 b faces upward. . Thereafter, the excavator 2 having the gate-shaped fixing portion 20 is installed so as to straddle the preceding digging hole 10A. Moreover, supply of muddy water is started into the preceding digging hole 10A from the muddy water pipe 3 arranged in the preceding digging hole 10A.

  Next, as shown in FIG. 5, the movable part 22 of the excavator 2 is raised, and in this state, the upper end of the rod pipe 24 is connected to the rod pipe connecting part 22b. Thereafter, as shown in FIG. 6, the movable portion 22 is lowered to an appropriate height, and the lower end of the rod tube 24 and the shaft portion 25 b of the wing bit 25 are connected.

  Subsequently, the movable part 22 is raised, and the two protective tube suspension parts 23 are respectively attached below the vicinity of both sides of the movable part 22. Then, a plurality of liner plates 13 are connected in an annular shape so as to surround the rod tube 24 in a state of being suspended by the protective tube suspending portion 23, and the tube segment 12 is formed from the outside. Here, a semi-columnar fall prevention frame (not shown) that prevents the operator who connects the liner plate 13 from the outside from falling into the preceding digging hole 10 </ b> A is suspended to the left and right of the connecting portion 20 b of the fixed portion 20. Lower. Such a fall prevention frame is provided with an arcuate guide frame along the inner surface of the tube segment 12 to be formed. The operator connects the plurality of liner plates 13 while being guided by the guide frame, and forms a pipe segment 12 having an outer diameter smaller than the diameter of the wing bit 25 in a non-reduced state, that is, the diameter of the intermediate pile hole 10 to be inserted. . Thereafter, the hole wall protective tube 11 having a length corresponding to the length of the rod tube 24 is formed by the three-stage tube segments 12 connected in the vertical direction. As described above, the hole wall protection tube 11 can be assembled from the liner plate 13 so that the space of the hole wall protection tube 11 during transportation and storage can be reduced compared to the case of using a ready-made hole wall protection tube. Is achieved.

  Next, as shown in FIG. 7, excavation of the intermediate pile hole 10 </ b> B is started from the bottom surface of the preceding excavation hole 10 </ b> A by lowering the movable portion 22 while rotating the wing bit 25 by the motor. At this time, the hole wall protection tube 11 is inserted into the preceding digging hole 10A in accordance with the lowering of the movable portion 22, that is, the lowering of the wing bit 25.

  In addition, at the start of excavation, the pump unit 5 is operated, and the excavated soil and mud are sucked from the suction port 25c of the wing bit 25. The earth and sand sucked into the suction port 25c is discharged to the ground mud tank through the rod pipe 24 and the drain mud pipe 4. Further, at the start of excavation, a pipe (not shown) is inserted between the hole wall of the intermediate pile hole 10B excavated by the wing bit 25 and the hole wall protective pipe 11 inserted into the intermediate pile hole 10B, and the fluidity is passed through the pipe. Pour the filler with. This filler makes it difficult for the hole wall of the intermediate pile hole 10B to collapse, and the hole wall is more reliably protected. As such a filler, one that cures over time is used, and one that has sufficient fluidity during construction and that cures after construction is selected.

  Subsequently, as shown in FIGS. 1 and 8, after the hole wall protection tube 11 is inserted, the two temporary receiving beams 6 are stretched over the hole of the preceding digging hole 10A. The two temporary receiving beams 6 are disposed substantially parallel to the connecting portion 20b of the fixed portion 20 and temporarily receive the suspended hole wall protection tube 11 in the preceding digging hole 10A. In this state, the suspension of the hole wall protection tube 11 by the protection tube suspension 23 is released. Further, the rotation of the wing bit 25 and the muddy water supply / drainage are stopped, and the rod tube 24 is released from being fixed at the rod tube connecting portion 22b.

  Next, as shown in FIG. 9, the movable part 22 is raised, and the upper end of the new rod pipe 24 is connected to the rod pipe connecting part 22b in the movable part 22 in the raised state. Thereafter, the movable portion 22 is lowered to an appropriate height, and the lower end of the new rod tube 24 connected to the rod tube connecting portion 22b and the upper end of the rod tube 24 connected to the shaft portion 25b of the wing bit 25 are connected. Thus, a new rod tube 24 is added between the wing bit 25 and the movable portion 22.

  Thereafter, in the protective tube suspending portion 23 in the movable portion 22, the tube segment 12 is formed from the plurality of liner plates 13 so as to surround the new rod tube 24, and a length corresponding to a predetermined length of the new rod tube 24 is formed. A new hole wall protection tube 11 having a thickness is formed from three stages of tube segments 12.

  Then, the movable part 22 is connected by connecting the lower end of the new hole wall protective pipe 11 suspended by the protective pipe hanging part 23 and the upper end of the hole wall protective pipe 11 already inserted in the pile hole 10. And a new hole wall protection tube 11 is added between the hole wall protection tube 11 already inserted. Thereafter, the suspended hole wall protection tube 11 inserted by the temporary support beam 6 is released. In this way, a new rod tube 24 and a new hole wall protection tube 11 are added between the movable portion 22 and the wing bit 25. By rotating the wing bit 25 and lowering the movable part 22 in this state, the wing bit 25 is pushed deeper by the length of the added new rod pipe 24, and excavation of the intermediate pile hole 10B proceeds. . Then, in accordance with the lowering of the wing bit 25, the two hole wall protection tubes 11 connected in the vertical direction are inserted into the intermediate pile hole 10B.

  Thereafter, as shown in FIG. 10, the excavation by the wing bit 25 and the insertion operation of the hole wall protection tube 11 are repeated to the vicinity of the depth of the lower end of the predetermined A layer. Then, in a state where the movable portion 22 is lowered, the hole protection tube 11 in the pile hole 10 is suspended by the temporary receiving beam 6 and the suspension of the hole protection tube 11 by the protection tube suspension 23 is released. Thereafter, the protective tube hanging part 23 is removed from the movable part 22 and fixed to the ground. Then, the protection tube suspension 23 fixed to the ground and the hole wall protection tube 11 in the pile hole 10 are connected by the suspension wire 26, and the suspension of the hole wall protection tube 11 by the temporary support beam 6 is released.

  Thereafter, in the raised movable portion 22, only the new rod tube 24 is added without adding the hole wall protection tube 11, the movable portion 22 is lowered, and the intermediate pile hole 10B is excavated to the lower end of the A layer. At the same time, a plurality of hole wall protective pipes 11 that are vertically connected so as to cover the entire hole wall of the intermediate pile hole 10B are inserted.

  Next, as shown in FIG. 11, after the excavation of the intermediate pile hole 10 </ b> B is finished, the outer peripheral portion 25 a of the wing bit 25 is drawn inward to reduce the diameter of the wing bit 25. In this state, the deep pile hole 10C of the B layer is excavated, and the pile hole 10 is excavated to a depth necessary for forming a concrete pile foundation.

  Then, after the excavation of the pile hole 10 is completed, the wing bit 25 and the plurality of rod pipes 24 which are reduced in diameter to be smaller than the hole diameter of the hole wall protection pipe 11 are collected on the ground. Specifically, the movable portion 22 is first raised, and the rod tube 24 below the uppermost rod tube 24 connected to the rod tube connecting portion 22b is lifted by a crane or the like (that is, the wing bit 25 and the uppermost rod tube 24). In the state where all the rod tubes 24 connected to the wing bit 25 except the upper rod tube 24 are lifted), the uppermost rod tube 24 is removed from the lower rod tube 24 and the rod tube connecting portion 22b. Thereafter, the movable portion 22 is lowered to connect the upper end of the rod tube 24 that is newly at the uppermost position to the rod tube connecting portion 22b. And after canceling | hanging the lifting state by a crane etc., the movable part 22 is raised. Thereafter, the rod pipe 24 just below the newly placed uppermost rod pipe 24 is lifted again by a crane or the like, and the uppermost rod pipe 24 is removed from the lower rod pipe 24 and the rod pipe connecting portion 22b. Then, the movable portion 22 is lowered and the upper end of the rod tube 24 which is newly at the uppermost position is connected to the rod tube connecting portion 22b, and the movable portion 22 is raised.

  As described above, the plurality of rod tubes 24 are sequentially collected through the hole wall protective tube 11 and finally the wing bit 25 is collected. As described above, when the wing bit 25 is lifted and collected, the outer peripheral portion 25a of the wing bit 25 is made smaller than the inner diameter of the hole wall protective tube 11, thereby maintaining the hole wall protective tube 11 inserted into the pile hole 10. Thus, the wing bit 25 can be easily recovered.

  And after collection | recovery of the wing bit 25, a concrete pile foundation is shape | molded by performing concrete placement by the conventional method with respect to the pile hole 10 in which the hole wall protection tube 11 was inserted.

  As described above, in the pile hole excavation method according to this embodiment, the hole wall can be protected by inserting the hole wall protection tube 11 while excavating the pile hole 10 with the wing bit 25. As a result, since excavation of the pile hole 10 and protection of the hole wall can be performed simultaneously, the excavation of the pile hole 10 can be performed in a shorter period of time.

  Moreover, the hole wall protective tube 11 in this pile hole excavation method is smaller in diameter than the intermediate pile hole 10B that needs to be protected, and is inserted into the intermediate pile hole 10B instead of being press-fitted. This eliminates the need for a large facility for press-fitting the hole wall protective tube 11, so that the excavator 1 can be downsized.

  Further, in this pile hole excavation method, the rod tube 24 is added and the hole wall protection tube 11 is added between the raised movable portion 22 and the wing bit 25, and then the movable portion 22 is lowered. By repeating the above, it is possible to realize the insertion of the hole wall protective tube 11 into the pile hole 10 in accordance with the excavation by the wing bit 25. Further, the excavator 2 only needs to have a configuration in which the movable portion 22 has a movable distance corresponding to the length of the predetermined rod tube 24. Therefore, the excavator 2 can be reduced in height as compared with the case of using a boring machine or the like. Therefore, the present invention can be suitably applied even in places where the height is limited.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said embodiment. For example, in the above-described embodiment, the hole wall protection tube 11 is formed only in a state where the movable portion 22 is raised. However, the hole wall protection tube 11 is inserted while the movable portion 22 is lowered, that is, during the excavation of the intermediate pile hole 10B by the wing bit 25. A mode in which a plurality of liner plates 13 are connected to a hole wall protection tube 11 on the way to form a tube segment 12 and the hole wall protection tube 11 is extended may be employed. According to such an aspect, excavation of the pile hole 10 and insertion of the hole wall protective tube 11 can be performed in a shorter period of time. In this case, the protection tube suspending portion 23 is attached not to the upper end of the hole wall protection tube 11 but to the inside or the outside to suspend the hole wall protection tube 11.

  In the above embodiment, the excavated earth and sand and mud are sucked from the suction port 25c of the wing bit 25 and discharged to the ground, but mud and the like are supplied from the wing bit 25 into the pile hole 10 through the rod tube 24. Further, the excavated earth and sand may be discharged from the hole of the pile hole 10 by the rising water flow.

  Moreover, the hole wall protection pipe 11 may be formed not from three-stage pipe segments but from two-stage or four-stage or more pipe segments, or by connecting one-stage pipe segments, that is, liner plates 13 in an annular shape. It may be formed. Further, instead of the steel liner plate 13, a hole wall protective tube may be formed of a wall body made of FRP (Fiber Reinforced Plastics) or the like.

  Further, the connection of the tube segment 12 and the liner plate 13 is not limited to the bolt tightening, but by a one-touch mechanism using a U-shaped connection fitting, clip, magnet, etc. sandwiching the flange portions formed at the edges of the liner plate 13. It may be performed, and may be performed by welding or an adhesive.

  Further, instead of the hollow rod tube 24, a rod-shaped rod may be used. In this case, it is necessary to provide a separate facility for discharging earth and sand.

It is a top view for demonstrating the pile hole excavation method which concerns on this embodiment. It is side surface sectional drawing for demonstrating the pile hole excavation method which concerns on this embodiment. It is side surface sectional drawing which shows the state of preceding digging. It is side surface sectional drawing which shows the state which installed the excavator shown in FIG. It is side surface sectional drawing which shows the state which connected the rod pipe | tube to the movable part shown in FIG. It is side surface sectional drawing which shows the state which assembled the hole wall protective tube. It is side surface sectional drawing which shows the state inserted in the hole dug the hole wall protective tube shown in FIG. It is front sectional drawing which shows the state which received the hole wall protective tube temporarily. It is side surface sectional drawing which shows the state which added the rod pipe | tube. It is side surface sectional drawing which shows the state which inserted the hole wall protective tube to the required depth. It is side surface sectional drawing which shows the state which excavation of the pile hole was complete | finished.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Excavator, 2 ... Excavator, 6 ... Temporary receiving beam (other suspension tool), 10 ... Pile hole, 10A ... Pre-drilling hole, 10B ... Intermediate pile hole, 10C ... Deep pile hole, 11 ... Hole wall protection Pipes, 12 ... pipe segments, 13 ... liner plates (walls), 20 ... fixed parts, 22 ... movable parts, 23 ... protective pipe hanging parts, 24 ... rod pipes (rods), 25 ... wing bits, 25a ... outer circumferences Part, T ... orbit.

Claims (5)

In the pile hole excavation method of excavating a pile hole for cast-in-place piles with a bit provided at the lower end of the rod while rotating and driving the rod of the excavator,
A pile hole excavation method characterized by inserting a hole wall protection pipe having a diameter smaller than the hole diameter of the pile hole to a predetermined depth in the pile hole in accordance with the descent of the bit in the excavator.   The pile hole excavation method according to claim 1, wherein the hole wall protection pipe is formed by connecting a plurality of wall bodies. The excavator has a gate-shaped fixed portion disposed so as to straddle the pile hole, and a movable portion that moves up and down along the fixed portion and to which the upper end of the rod is fixed,
Excavation by the bit while lowering the movable part, and after completion of excavation for a predetermined distance, the fixation between the rod and the movable part was released, and after the movable part was raised, the fixation was released A new rod is added between the rod and the movable part, and the excavation is advanced by lowering the movable part again.
In the state where the movable part is raised, the hole wall protection pipe is formed by connecting the plurality of wall bodies so as to surround the rod fixed to the movable part, and the hole wall protection pipe is connected to the movable part. The hole wall protective tube is inserted into the pile hole in accordance with the lowering of the bit by suspending the movable portion and the movable portion is lowered, and then the inserted hole wall protective tube is suspended by another hanging tool. In the lowered state, the suspension by the movable part is released, and after the movable part is raised, the hole wall protective tube is formed so as to surround the newly added rod, and the hole wall protective tube is After hanging on the movable part and connected to the already inserted hole wall protection tube side, the suspension by the other hanging tool is released, and the hole into the pile hole again as the bit descends The pile drilling according to claim 2, wherein the insertion of the wall protection pipe is advanced. Method.   4. The pile hole excavation according to claim 3, wherein the plurality of wall bodies are connected to upper ends of the already formed hole wall protection pipes to extend the hole wall protection pipes during the lowering of the movable part. Method. The bit is a rotating body that expands in the radial direction with the central axis of the rod as a rotation center, and the outer peripheral portion of the bit enters the inside, and can be reduced in diameter so as to be smaller than the inner diameter of the hole wall protective tube,
The pile hole excavation method according to any one of claims 1 to 4, wherein when the bit is lifted and collected, an outer peripheral portion of the bit is made smaller than an inner diameter of the hole wall protective tube.

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