JP2018044399A - Trial excavation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform trial excavation work efficiently without damaging an object installed underground.SOLUTION: A guard pipe 3g having a cylindrical form that surrounds a part of a tip of a bit 3b is provided on an outer periphery of the bit 3b at a tip of a trial excavation rod 3 constituting a trial excavation drill 1. A tip of the guard pipe 3g is located closer to a ground than the tip of the bit 3b. The tip of the guard pipe 3g comes in contact with an object installed underground at a time of excavation, but the tip of the bit 3b does not contact the object installed underground directly. The configuration enables trial excavation work to be performed efficiently without damaging the object installed underground.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a trial digging apparatus, for example, a technique for preventing damage to underground buried objects.

  If underground objects such as communication lines, power lines, water pipes or gas pipes and their protective pipes are expected to exist in the ground subject to excavation work, test the ground prior to excavation work. A so-called trial drilling operation is being carried out. In this trial excavation work, an operator performs excavation manually using a scoop or the like, and visually confirms the type, size, buried position (planar position and depth), standard and structure of the underground buried object.

  In addition, about the technique regarding trial digging, it is described in, for example, Patent Document 1, in order to excavate the natural ground without damaging the underground buried object, non-contact excavation means for excavating the natural ground, and excavation An excavation apparatus including a suction conveyance unit that sucks and conveys earth and sand is disclosed.

JP 2006-193912 A

  By the way, when the ground to be excavated is a normal soil layer, trial excavation work by manual excavation is possible, but the excavation target is a strongly consolidated layer or a composite layer of consolidated layer and normal soil, etc. In the case of a hard soil layer, since the work load becomes large when the manual excavation is adopted, it is necessary to use a mechanical excavator such as an electric pick or a breaker.

  However, when using a mechanical excavator, there is a risk of serious damage to the underground objects. Therefore, it is necessary to carefully proceed with the excavation work so as not to damage the underground objects. It is an obstacle. For this reason, in the trial excavation work, how to carry out the work efficiently without damaging the underground buried object is an important issue.

  The present invention has been made from the above-described technical background, and an object thereof is to provide a technique capable of efficiently performing work without damaging underground buried objects in trial digging work. With the goal.

  In order to solve the above-mentioned problem, the trial digging apparatus according to the first aspect of the present invention includes a trial digging rod and drive means for rotationally driving the trial digging rod, and the trial digging rod is connected to the drive means. A drive shaft that is connected and serves as the center of rotation drive, a drilling member that is attached to the tip of the drive shaft and drills the object to be drilled, and a state in which the outer periphery of the drive shaft swivels in the same direction behind the drilling member And a state where the tip end portion is located closer to the excavation target side than the tip end portion of the excavation member and the rear end portion is located so that the whole or part of the spiral blade is exposed. A surrounding member formed in a cylindrical shape so as to surround the whole or a part of the excavating member, and allowing the surrounding member to rotate along the rotation direction of the drive shaft, and the surrounding member Is the axis of the drive shaft A support member for supporting the enclosing member in a state in which the engaged to the drive shaft so as to allow to move along a direction, characterized in that it comprises a.

  According to a second aspect of the present invention, there is provided a test mine apparatus according to the first aspect of the invention, wherein the air is connected to the test digging rod and supplies air to the air circulation hole of the test digging rod that is rotationally driven. A supply portion, the air circulation hole provided in communication with the drive shaft and the excavation member, and an opening at the tip surface of the excavation member in communication with the air circulation hole, and connected to the drive shaft. And an air injection port for injecting the air supplied from the air supply unit through the air circulation hole from the tip surface of the excavation member.

  According to a third aspect of the present invention, there is provided a test drilling apparatus according to the second aspect of the present invention, wherein the first air injection blows air toward the front face facing the front end surface of the excavation member as the air injection port. One or both of an opening and a second air injection opening that blows air toward the inner peripheral wall of the surrounding member is provided.

  According to a fourth aspect of the present invention, in the invention according to the second or third aspect, the drive means is a pneumatic motor.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to implement | achieve an operation | work efficiently, without damaging an underground buried object in a trial digging operation.

(A) is the whole block diagram of an example of the trial digging apparatus concerning one embodiment of the present invention, (b) is a schematic sectional view along the axial direction of the trial digging rod which constitutes the trial digging equipment of Drawing 1 (a), (C) is a general | schematic expanded sectional view of the front-end | tip part of the rod for trial digging of FIG.1 (b). (A) is a side view of a tip portion of a test digging rod constituting the trial digging device of FIG. 1, (b) is a side view showing a part of the tip of the digging rod shown in FIG. FIG. 3 is a side view of a guard pipe and a guard pipe support member of the test excavation rod in FIG. FIG. 2A is a side view of the tip portion of the prospecting rod when FIG. 2A is viewed from below, and FIG. 3B is a side view of the tip portion of the prospecting rod of FIG. FIG. 4C is a plan view of a guard pipe support member of the test rod of FIG. 3A, and FIG. 3D is a side view of the guard pipe and guard pipe support member of the test rod of FIG. . FIG. 2A is an enlarged side view of the main part of the test rod shown in FIG. 2A, with the tip portion enlarged and the guard pipe broken, and FIG. 4B shows the tip portion of the test rod shown in FIG. FIG. 4C is a plan view seen from the right side, FIG. 4C is an enlarged side view of the main part shown by magnifying the tip of the test rod of FIG. 3A and breaking the guard pipe, and FIG. It is the top view which looked at the front-end | tip part of the rod for trial digging from the right side. (A) is a schematic cross-sectional view of the main part of the trial digging apparatus during excavation of the ground, (b) is an enlarged cross-sectional view of the main part of the trial digging apparatus of FIG. 5 (a), and (c) is a state in contact with the underground buried object. FIG. 4D is a schematic cross-sectional view of the main part of the trial drill, and FIG. 4D is a schematic cross-sectional view of the main part of the test drill when the trial drill is extracted from the ground.

  Hereinafter, an embodiment as an example of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  First, a configuration example of a trial drilling apparatus according to the present embodiment will be described with reference to FIGS. FIG. 1A is an overall configuration diagram of an example of a trial digging apparatus according to the present embodiment, and FIG. 1B is a schematic cross-sectional view along the axial direction of a trial digging rod that constitutes the trial digging apparatus of FIG. FIG. 1 (c) is a schematic enlarged cross-sectional view of the tip of the test digging rod in FIG. 1 (b), FIG. 2 (a) is a side view of the tip of the test digging rod constituting the test digging device in FIG. 2 (b) is a side view showing a part of the tip of the test rod shown in FIG. 2 (a), and FIG. 2 (c) is a guard pipe and a guard pipe support member of the test rod shown in FIG. 2 (a). 3 (a) is a side view of the tip of the test digging rod when FIG. 2 (a) is viewed from below, and FIG. 3 (b) is the same as the tip of the digging rod of FIG. 3 (a). FIG. 3C is a plan view of the guard pipe support member of the test digging rod shown in FIG. 3A, and FIG. 3D is a side view of the test digging rod shown in FIG. 3A. guard 4A is a side view of the guard pipe support member, FIG. 4A is an enlarged side view of the main part shown by enlarging the tip portion of the test digging rod in FIG. 2A and breaking the guard pipe, and FIG. 4A is a plan view of the tip of the test digging rod shown in FIG. 4A viewed from the right side, and FIG. 4C is an enlarged view of the tip of the digging rod shown in FIG. FIG. 4D is a plan view of the tip of the test digging rod shown in FIG. 4C viewed from the right side.

  The drill 1 for trial drilling of this Embodiment shown to Fig.1 (a) is the information (a kind, a magnitude | size, a plane position, depth, for example) of the underground burial buried in the ground prior to the excavation construction of the ground. , Standard and structure etc.) is a small test digging apparatus used for manual excavation of the ground to test it. The digging machine main body 2, the test digging rod 3, the swivel (air supply unit) 4, It has.

  The trial digger main body 2 incorporates a motor (driving means) for rotationally driving the trial digging rod 3. The motor in the trial digger main body 2 is constituted by, for example, a pneumatic motor that is driven by compressed air. However, the motor of the trial digger main body 2 is not limited to the pneumatic motor, and can be variously changed. For example, a hydraulic or electric motor may be used.

  In addition, an air supply unit 2S is mechanically connected to the trial digger body 2. The air supply unit 2 </ b> S is mechanically connected to a motor in the trial digger main body 2 and mechanically connected to a compressor 6 for supplying compressed air via a distribution device 5. As a result, the compressed air sent from the compressor 6 via the distribution device 5 is supplied to the motor in the drilling machine main body 2 through the adjustment valve 2Sv and the pipe 2St of the air supply unit 2S in this order. . The adjustment valve 2Sv of the air supply unit 2S is a valve that adjusts the flow rate and pressure of the compressed air supplied to the motor of the trial digger main body 2, and is configured by, for example, a ball valve. The distribution device 5 is a device for supplying the compressed air sent from the compressor 6 separately to the motor of the trial digger main body 2 and the trial digging rod 3.

  Further, a pair of gripping portions 2g are provided on both side surfaces (both side surfaces along the paper surface) of the trial digger main body 2. The pair of gripping portions 2g are formed in a frame shape, for example, so that the operator can hold the trial drill 1 by hand. Although not particularly limited, the total length in the axial direction of the trial drill 1 is, for example, 1117 mm, and the total length in the axial direction of the trial drill body 2 is, for example, 275 mm.

  The digging rod 3 is a digging steel rod for digging a ground to be excavated, and includes a drive shaft 3s, a bit (digging member) 3b, an air circulation hole 3h, a guard pipe (going member) 3g, And a guard pipe support member (support member) 3U.

  As shown in FIGS. 1 (a) and 1 (b), the drive shaft 3s is a steel rod portion that serves as a center for rotational driving of the trial digging rod 3 and transmits a rotational force to the bit 3b at the tip of the trial digging rod 3. It is mechanically connected to the rotating shaft of the motor in the trial digger main body 2 in a detachable state.

  As shown in FIGS. 1 to 3A and 3B, a spiral blade 3r is formed integrally with the drive shaft 3s between the bit 3b and the guard tube support member 3U on the outer periphery of the drive shaft 3s. Yes. The spiral blade 3r is formed in a spiral shape in a state of turning in the same direction in order to send earth and sand excavated by the trial drill 1 to the outside of the excavation hole. The spiral blade 3r may be provided over the entire length of the drive shaft 3s.

  Further, as shown in FIGS. 1B, 2B, 3A, and 3B, a pair of support pillars 3p are provided behind the region where the spiral blade 3r is disposed on the outer periphery of the drive shaft 3s. Is formed integrally with the drive shaft 3s. The support column 3p is a portion for engaging the guard tube support member 3U with the drive shaft 3s, and is formed in a state of protruding in the radial direction of the drive shaft 3s from the outer periphery of the drive shaft 3s. This will be described later.

  Further, as shown in FIG. 2 and FIG. 3B, a spacing holding portion 3k is formed integrally with the drive shaft 3s on the outer periphery of the drive shaft 3s before and after the support column 3p. The spacing holding portion 3k is a member that regulates the spacing between the inner wall of the guard tube support member 3U and the outer periphery of the drive shaft 3s, and has a predetermined length in the radial direction of the drive shaft 3s from the outer periphery of the drive shaft 3s. It is formed in a state where it protrudes. By providing the interval holding portion 3k, the interval between the drive shaft 3s, the guard pipe support member 3U, and the guard pipe 3g can be kept constant during the rotation of the drive shaft 3s. It can be further stabilized.

  As shown in FIGS. 1 (b), 1 (c), 2 (b), 3 (b), and 4, the bit 3b is detachably attached to the tip of the drive shaft 3s. Has been. The bit 3b is a member for excavating the ground, and a cemented carbide chip is provided at the tip thereof. However, the bit 3b may be configured by directly forming (heat treatment hardening) the tip of the drive shaft 3s.

  As shown in FIGS. 1B and 1C, the driving shaft 3s and the central shaft portion of the bit 3b are formed with air circulation holes 3h communicating along the axial direction thereof. The air circulation hole 3h is a hole that guides the compressed air supplied from the compressor 6 through the air injection port 3i to the air injection ports 3ja and 3jb on the tip surface of the bit 3b.

  As shown in FIG. 1B, the air injection port 3i is an injection hole for sending the compressed air supplied from the compressor 6 through the distribution device 5 and the swivel 4 to the air circulation hole 3h. The end side surface is opened in communication with the air circulation hole 3h.

  As shown in FIGS. 1C, 4B, and 4D, the air injection ports 3ja and 3jb are supplied through the air circulation hole 3h in order to blow off the earth and sand excavated by the drill 1 for trial digging. This is an injection hole for injecting compressed air from the distal end surface of the bit 3b to the excavation site, and is opened at the distal end surface of the bit 3b in a state communicating with the air circulation hole 3h.

  Of the air injection ports 3ja and 3jb, the air injection port (first air injection port) 3ja is formed so as to blow compressed air toward the front face facing the front end surface of the bit 3b. On the other hand, the air injection port (second air injection port) 3jb is formed so as to blow compressed air obliquely toward the inner peripheral wall side of the guard pipe 3g. By providing the two types of air injection ports 3ja and 3jb in this way, the earth and sand excavated by the trial drill 1 can be blown off more satisfactorily, so that the ground can be excavated well. However, a structure in which only one of the air injection ports 3ja and 3jb may be provided.

  As shown in FIGS. 1 to 4, for example, a steel guard tube 3g formed in a cylindrical shape so as to surround a part of the outer periphery of the tip of the bit 3b is provided on the outer periphery of the bit 3b. Yes. By providing the guard pipe 3g on the outer periphery of the bit 3b in this way, the excavation location by the bit 3b can be defined in the range in the guard pipe 3g, so that the ground can be excavated well in a stable state. . Although not particularly limited, the inner diameter of the guard tube 3g is, for example, 54.5 mm, and the total axial length of the guard tube 3g is, for example, 25 mm.

  The guard pipe 3g is provided such that the tip of the guard pipe 3g is located on the ground side with respect to the tip of the bit 3b. That is, the tip of the bit 3b does not protrude from the tip of the guard tube 3g. Thereby, in the excavation work, the bit 3b having the cemented carbide chip can be prevented from coming into contact with the underground buried object, so that the work can be efficiently performed without damaging the underground buried object. . Therefore, excavation work can be performed safely and smoothly. The tip of the guard tube 3g is preferably heat treated to prevent deformation.

  As shown in FIGS. 1A and 1B to FIG. 3, the guard pipe 3g is supported by a guard pipe support member 3U. The tip ends of two steel support rods 3Us and 3Us of the guard tube support member 3U are joined to the outer peripheral side surface of the guard tube 3g. The rear ends of the two support rods 3Us and 3Us are joined to the outer periphery of the support tube 3Ut1 on the front end side of the pair of steel support tubes 3Ut1 and 3Ut2 of the guard tube support member 3U.

  Therefore, in the present embodiment, the guard tube 3g surrounds a part of the tip of the bit 3b, and only the support rod 3Us is provided between the support cylinder 3Ut1 from the rear of the bit 3b. The plurality of spiral blades 3r between the support cylinder 3U1 are not surrounded by the guard tube 3g and are exposed (exposed). That is, in the present embodiment, the excavated earth and sand are sufficiently discharged to the outside behind the guard pipe 3g so that the gap between the guard pipe 3g and the spiral blade 3r is not blocked by the excavated earth and sand generated in the trial excavation work. In this configuration, a sufficiently wide opening is provided. For this reason, at the time of the trial digging operation using the trial digging drill 1, the excavated earth and sand can be sufficiently discharged to the outside, and the blockage by the excavated earth and sand can be prevented, so that the excavation performance can be improved. Note that the above configuration is the best from the viewpoint of improving excavability, but instead of the configuration, for example, the entire axial direction of the bit 3b may be surrounded by the guard pipe 3g. In addition, if it is within a range where clogging due to excavated soil or the like does not occur, a part of the plurality of spiral blades 3r behind the bit 3b is surrounded by the guard pipe 3g, and a part of the plurality of spiral blades 3r is surrounded. An exposed configuration can also be used.

  The pair of support cylinders 3Ut1 and 3Ut2 are arranged side by side on both sides of the pair of support columns 3p of the drive shaft 3s. The two support cylinders 3Ut1 and 3Ut2 are formed in a cylindrical shape so as to surround the outer periphery of the drive shaft 3s, and are fixed by steel bolts and nuts 3Un while sandwiching a pair of support pillars 3p. The guard tube support member 3U allows the guard tube 3g to rotate along the rotational direction of the drive shaft 3s and allows the guard tube 3g to move along the axial direction of the drive shaft 3s. In addition, it is installed in a state of being engaged with the drive shaft 3s.

  Even when the guard tube 3g moves rearward in the axial direction, the tip of the bit 3b is set so as not to protrude from the tip of the guard tube 3g. Although not particularly limited, the length from the front end of the guard tube 3g to the rear end of the support tube 3Ut2 is, for example, 322 mm, and the length from the front end of the guard tube 3g to the rear end of the support tube 3Ut1 is For example, 247 mm.

  As shown in FIGS. 1A and 1B, a swivel 4 is mechanically connected to the position of the air inlet 3i on the outer periphery of the drive shaft 3s of the test digging rod 3 in a detachable state. The swivel 4 is a member that continuously supplies compressed air into the air circulation hole 3h of the rotating test digging rod 3, and is mechanically connected to the air circulation hole 3h in the digging rod 3. And mechanically connected to a compressor 6 for supplying compressed air via a distributor 5. Thereby, the compressed air sent from the compressor 6 through the distribution device 5 is supplied to the air circulation hole 3h in the test rod 3 through the adjustment valve 4v of the swivel 4, the pipe 4t, and the connection portion 4j in this order. It is like that.

  The adjustment valve 4v of the swivel 4 is a valve that adjusts the flow rate and pressure of the compressed air supplied into the air circulation hole 3h of the trial digging rod 3, and is configured by, for example, a ball valve. Further, a groove (not shown) is formed in the inner peripheral wall of the connection portion 4j of the swivel 4 so as to make one round along the inner peripheral direction. The groove on the inner peripheral wall of the swivel 4 communicates with the pipe 4t of the swivel 4 and also communicates with the air inlet 3i of the drive shaft 3s. Thereby, even if the test rod 3 is rotating, the compressed air supplied from the compressor 6 can be supplied through the swivel 4 into the air flow hole 3 h of the test rod 3.

  Next, the effect | action of the drill 1 for trial drilling of this Embodiment is demonstrated with reference to Fig.5 (a)-(d). In FIG. 5, for the sake of easy understanding, the drawing is simplified, such as omitting the spiral blade 3 r, and the dimensions and shape are exaggerated. Moreover, the code | symbol G has shown the ground and the code | symbol UB has shown underground piping (an example of an underground buried object).

  FIG. 5A is a schematic cross-sectional view of a main part of the trial drill during excavation of the ground, and FIG. 5B is an enlarged cross-sectional view of a main part of the trial drill in FIG. First, as shown by an arrow R1 in FIG. 5 (a), the operator holds the gripping part 2g of the trial drill 1 shown in FIG. Then, after rotating the test digging rod 3 around the drive shaft 3s, the tip of the digging rod 3 (the bit 3b and the guard pipe 3g) is pressed against the ground G as shown by the arrow P1, and the ground G is excavated. To do. At this time, the earth and sand excavated by the trial digging rod 3 is carried out of the excavation hole H by the action of the spiral blade 3 r by the rotation of the trial digging rod 3.

  At this time, as shown in FIG. 5 (a), when the tip of the test digging rod 3 is pressed toward the ground G, the support column 3p of the drive shaft 3s of the test digging rod 3 is connected to the guard pipe support member 3U. As a result of increasing the frictional force at the contact portion between the support column 3p and the support cylinder 3Ut1 by being pressed against the support cylinder 3Ut1 on the distal end side, as shown by an arrow R2 in FIG. The guard tube 3g supported by the shaft also continuously or intermittently follows the rotation of the drive shaft 3s. The ground G can be excavated stably and satisfactorily by the rotation of the guard pipe 3g.

  Further, at this time, as shown in FIG. 5 (b), the compressed air supplied from the compressor 6 (see FIG. 1) to the air circulation hole 3h of the prospecting rod 3 is used as the air at the tip of the bit 3b of the prospecting rod 3. It sprays to the ground G side from the injection ports 3ja and 3jb. Thereby, since the earth and sand etc. which were excavated with the rod 3 for trial digging can be blown off favorably, the ground G can be excavated favorably. Moreover, an environmental load etc. can be suppressed by using an air pressure.

  Next, FIG.5 (c) is a schematic principal part sectional drawing of the drill for trial digging in the state which contacted the underground embedment. In the present embodiment, the tip of the guard tube 3g of the test digging rod 3 is located in front of the tip of the bit 3b (on the ground G side). Although it contacts with underground pipe UB, the front-end | tip part of the bit 3b with a cemented carbide chip does not contact the underground pipe UB directly. Further, when the guard pipe 3g at the tip of the test digging rod 3 is in contact with the underground pipe UB during the excavation work using the trial digging drill 1, resistance is applied to the rotation of the guard pipe 3g and the rotation speed is suddenly reduced ( Since the rotation state of the guard pipe 3g clearly changes (e.g., the rotation speed is reduced), the operator can quickly and surely detect that the guard pipe 3g has contacted the underground pipe UB. . Thus, the work can be performed efficiently without damaging the underground pipe UB in the trial digging work.

  Next, FIG. 5D is a schematic cross-sectional view of the main part of the trial drill when the trial drill is extracted from the ground. In this case, when the prospecting rod 3 of the prospecting drill 1 is moved upward, the support column 3p of the drive shaft 3s of the prospecting rod 3 hits the support cylinder 3Ut2 on the rear side of the guard pipe support member 3U. 3 g can be lifted together with the test rod 3.

  The operator removes the test drill 1 from the ground G, and then directly checks the type, size, buried position (planar position and depth), standard and structure of the underground pipe UB buried in the ground. Confirm and record the information obtained for use in subsequent excavation work. Thereby, excavation work can be performed safely and smoothly.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the embodiment disclosed in this specification is an example in all respects and is limited to the disclosed technology. It is not a thing. That is, the technical scope of the present invention should not be construed restrictively based on the description in the above-described embodiment, but should be construed according to the description of the scope of claims. All modifications are included without departing from the technical scope equivalent to the described technique and the gist of the claims.

  In the embodiment, the case where the present invention is applied to the trial excavation work has been described. However, the present invention is not limited to this. For example, the present invention can also be applied to a normal excavation work for excavation.

DESCRIPTION OF SYMBOLS 1 Test drill 2 Test machine main body 2S Air supply part 2Sv Adjustment valve 2St Piping 2g Grasping part 3 Test drill rod 3s Drive shaft 3r Spiral blade 3h Air flow hole 3i Air injection port 3p Support pillar 3k Space | interval holding | maintenance part 3b Bit 3ja, 3jb Air injection port 3g Guard pipe 3U Guard pipe support member 3Us Support rod 3Ut1, 3Ut2 Support cylinder 3Un Bolt nut 4 Swivel 4v Adjustment valve 4t Piping 4j Connection 5 Distributor 6 Compressor

Claims (4)

A prospecting rod,
Drive means for rotationally driving the test rod;
With
The prospecting rod is
A drive shaft connected to the drive means and serving as the center of rotational drive;
A drilling member mounted on the tip of the drive shaft to drill a drilling target;
A spiral blade provided in a state of swirling in the same direction behind the excavation member on the outer periphery of the drive shaft;
The tip portion of the excavation member is provided in a state where the tip portion is located closer to the excavation target side and the rear end portion is located so that the whole or a part of the spiral blade is exposed. A surrounding member formed in a cylindrical shape so as to surround the whole or a part,
The surrounding member is engaged with the drive shaft so as to allow the surrounding member to rotate along the rotational direction of the drive shaft and allow the surrounding member to move along the axial direction of the drive shaft. A support member for supporting the go member in a state;
A test drilling device comprising: An air supply unit for supplying air to the air circulation hole of the test digging rod which is connected to the test digging rod and is being rotationally driven;
The air circulation hole provided in communication with the drive shaft and the excavation member;
Air that is opened at the front end surface of the excavation member in communication with the air circulation hole and is supplied through the air circulation hole from the air supply unit connected to the drive shaft is injected from the front end surface of the excavation member. An air jet,
The trial drilling device according to claim 1, further comprising:   One of the first air injection port that blows air toward the front facing the front end surface of the excavation member as the air injection port and the second air injection port that blows air toward the inner peripheral wall of the surrounding member. Or the both are provided, The trial digging apparatus of Claim 2 characterized by the above-mentioned.   4. The test drilling apparatus according to claim 2, wherein the driving means is a pneumatic motor.

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