JP2018185150A - Geological exploration device for pit face front - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of geological exploration by ensuring geological exploration even in poor grounds where hole walls tend to collapse, and further minimizing the influence on tunnel excavation work and simplifying measurement work.SOLUTION: The geological exploration device includes: a pipe 4 to be inserted into a hole 3 installed in a ground in front of a pit face; a plurality of vibration receivers 5, 5... for measuring elastic waves arranged in the pipe 4 at predetermined intervals along the axial direction; and a current electrode 6 and a potential electrode 7 for measuring the specific resistance of the ground in the vicinity of the hole wall of the hole 3 installed on the outer peripheral surface on a distal end side of the pipe 4. The plurality of receivers 5, 5... are integrated by a connecting member 11 connecting adjacent ones of the receivers 5, 5 and a distal end thereof is fixed via a cuttable member 12 to a distal end inside the pipe 4.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a geological exploration device for exploring the geology ahead of a face when excavating a tunnel or the like.

  In tunnel excavation, there is an increasing need for ground surveys in front of the face from the viewpoint of preventing troubles such as face collapse disasters and evaluating the validity of the support pattern during tunnel excavation in advance.

  As one of the geological exploration methods in front of the face that is performed from inside the tunnel tunnel, a drilling jumbo is used to form a hole in front of the face and the velocity logging technique is used to measure the velocity of elastic waves propagating in the ground. Has been established.

  The velocity logging can be classified into several types according to the relationship between the vibration generating position and the vibration receiving position, and the downhole method is most widely used (Patent Document 1 below). As shown in FIG. 6, the downhole method described in Patent Document 1 below includes placing a geophone 51 in a hole 50 drilled with a hydraulic jumbo or the like and hitting the face S with a hammer 52. This is a technique for measuring the velocity of elastic waves when vibrating.

JP-A-11-182171

  However, in the conventional downhole method described in Patent Document 1, when the geophone 51 is inserted into the perforation 50, the geophone 51 is directly attached by being attached to an insertion assisting vinyl chloride pipe 53 or a steel wire. Therefore, in a bad ground where the hole wall tends to collapse, the geophone 51 cannot be inserted due to the collapsed hole wall or the like, and the geophone 51 is sandwiched between collapsed rocks and restrained in the perforation 50. The problem of becoming uncollectable often occurred.

  In addition, in order to attempt to collect the geophone 51 from the borehole 50 where the hole wall has collapsed, if work is performed near the entrance of the borehole 50, the time taken to occupy the face for geological exploration becomes longer. There was a problem that greatly affected the excavation work.

  Further, considering the risk when the hole wall collapses and the geophone 51 cannot be recovered from within the perforation 50, the number of geophones 51 inserted into the perforation 50 is 3 as shown in FIG. Although measures were taken to limit the number to a small number, it is necessary to repeat the data acquisition by moving the geophone 51 in the perforation 50 because the number of data that can be acquired by one vibration is small. There was a problem that the number of measurements increased. For example, in the velocity logging described in Patent Document 1 shown in FIG. 6, three geophones 51, 51, 51 are arranged at an interval of 1 m, and elastic waves at these three points are measured by one excitation. Thereafter, the operation of drawing out the PVC pipe by 2 m and vibrating it in the same manner to measure the elastic wave is repeated until the geophone 51 reaches the entrance of the perforation 50. Therefore, in order to measure the perforation 50 having a length of 30 m, it is necessary to repeat the measurement work 15 times. Thus, when repeatedly acquiring data by changing the measurement point, the hit data at the face is different each time, and there is a problem that the accuracy and reliability of the measured data is reduced.

  Furthermore, in the method described in Patent Document 1, specific information, which is often used as an index for evaluation of natural ground, cannot be obtained because the obtained information is only the velocity of elastic waves.

  Therefore, the main problem of the present invention is to make sure that geological exploration can be carried out even in bad ground where the hole wall tends to collapse, minimize the influence on tunnel excavation work, simplify the measurement work, and It is to provide a geological exploration device in front of the face with improved accuracy.

  In order to solve the above-mentioned problems, the present invention according to claim 1 is provided with a pipe inserted into a drill hole provided in a natural ground in front of a face, and a predetermined interval along the axial direction inside the pipe. In addition, a plurality of geophones for measuring elastic waves, a current electrode and a potential for measuring the specific resistance of the natural ground around the hole wall in the perforation, provided on the outer peripheral surface on the tip side of the pipe There is provided a geological exploration device in front of a face characterized by comprising an electrode.

  According to the first aspect of the present invention, a plurality of geophones for measuring elastic waves are arranged at predetermined intervals along the axial direction inside a pipe inserted into a drill hole provided in a natural ground in front of the face. Therefore, even in a bad ground where the hole wall is likely to collapse, the pipe serves as a support for inserting the geophone and a casing, so that geological exploration can be carried out reliably.

  In addition, since the geophone is protected by a pipe, the geophone is not recovered by being caught between rock pieces even if the hole wall collapses, and the geophone can be reliably collected. At this time, it takes only a short time to collect the geophone. For this reason, a geophone can be installed over the entire length of the perforation, and elastic waves at all points can be measured with a single vibration. Thus, since the work related to geological exploration can be simplified, the time for occupying the face for the geological exploration can be shortened, and the influence on the excavation work of the tunnel can be minimized. Further, since it is not necessary to acquire repeated data, the measurement work can be simplified and the investigation accuracy can be improved.

  Furthermore, in the geological exploration device according to the present invention, the current electrode and the potential electrode for measuring the resistivity of the natural ground are provided on the outer peripheral surface on the tip side of the pipe. The specific resistance of the mountain can be measured. This makes it possible to comprehensively evaluate the geology in front of the face together with the result of velocity logging by the geophone, and improve the accuracy of geological exploration.

  According to a second aspect of the present invention, there is provided the geological exploration device in front of the face according to the first aspect, wherein the pipe is made of resin and a plurality of pipes divided by a predetermined length are connected by a connector. Provided.

  In the invention according to the second aspect, by using a pipe formed by connecting a plurality of pipes divided by a predetermined length made of resin, the pipe insertion work and the drawing work become easy. The time required for exploration can be further reduced.

  According to a third aspect of the present invention, the plurality of geophones are integrated by a connecting member that couples the neighboring geophones, and a tip portion is interposed through a member that can be cut to a tip inside the pipe. A geological exploration device in front of the face according to any one of claims 1 and 2 is provided.

  The invention described in claim 3 is a means for allowing only the internal geophone to be recovered when the hole wall collapses and the pipe cannot be pulled out, and is integrated by the connecting member. The tip portions of the plurality of geophones are fixed to the tip inside the pipe via a member that can be cut. As a result, even when the hole wall collapses and the pipe cannot be pulled out, by forcibly pulling the vibration receiving device integrated by the connecting member inside the pipe, the cuttable member is cut, and the vibration receiving device and The pipe is released and the geophone can be recovered. In this way, even if the hole wall collapses and the pipe cannot be pulled out, only the expensive geophone can be recovered, so the economic burden can be reduced.

  According to a fourth aspect of the present invention, in the current electrode and the potential electrode, a contact portion with a natural mountain is formed in a brush shape in which a large number of fine-line electrodes protrude. A geological exploration device in front of the face is provided.

  In the invention of claim 4, the current electrode and the potential electrode are in close contact with the uneven hole wall so that the specific resistance of the ground can be measured with high accuracy. The contact portion with the natural ground is formed in a brush shape in which a large number of fine-line electrodes protrude.

  According to a fifth aspect of the present invention, there is provided the geological exploration device in front of the face according to any one of the first to fourth aspects, wherein the lead wires extending from the current electrode and the potential electrode are wired inside the pipe. .

  In the invention of claim 5, the lead wire connected to the current electrode and the potential electrode is wired inside the pipe so that the lead wire is not disconnected when the pipe is inserted or pulled out. .

  As described in detail above, according to the present invention, geological exploration can be reliably performed even on bad ground where the hole wall tends to collapse, the influence on tunnel excavation work can be minimized, measurement work can be simplified, and geological exploration can be performed. Accuracy can be improved.

It is sectional drawing which shows the concept of the geological exploration using the geological exploration apparatus 1 which concerns on this invention. 3 is a cross-sectional view of a perforation 3. FIG. (A) is sectional drawing of the pipe 4, (B) is the BB line arrow directional view. 4 is an enlarged cross-sectional view of a tip portion of a pipe 4. 4 is an enlarged cross-sectional view of the vicinity of electrodes 6 and 7 of a pipe 4. FIG. It is sectional drawing which shows the conventional velocity logging (downhole method).

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

  As shown in FIG. 1, a geological exploration device 1 according to the present invention includes a pipe 4 inserted into a drill hole 3 formed in a natural mountain in front of a face S from a tunnel space by a drilling machine 2, A plurality of geophones 5, 5,... For measuring elastic waves, which are arranged at predetermined intervals along the axial direction, and the perforations 3 provided on the outer peripheral surface on the tip side of the pipe 4. Current electrodes 6 and 6 and potential electrodes 7 and 7 for measuring the resistivity of the natural ground around the inner hole wall are provided.

  The drilling machine 2 includes a drifter mounted on a guide cell so as to be able to move forward and backward with respect to a travelable carriage, and a drilling rod connected to the drifter via a shank rod and having a drilling bit at the tip. It is a heavy machine for drilling such as drill jumbo.

  The perforation 3 is a drilling hole formed substantially horizontally from the face S to the front by the perforator 2, and has a length (depth) of several m to several tens m, preferably about 30 to 50 m. Is preferred. As this drilling 3, it is possible to use a hole subjected to drilling logging for evaluating the geology in front of the face from data such as drilling speed and impact pressure during drilling by the drilling machine 2.

  The pipe 4 inserted into the perforation 3 is made of a resin such as vinyl chloride, polyethylene, or acrylic, and a plurality of pipes 4a, 4a,... Divided by a predetermined length are connectors 8 as shown in FIG. It is preferable to be configured to be connected. The outer diameter of the pipe 4 may be any size as long as it can be inserted into the perforation 3, but is preferably 90% or less, particularly about 50 to 80% of the diameter of the perforation 3. The pipe 4 has an inner diameter of at least 35 mm, preferably 40 to 50 mm, in view of disposing the geophone 5 inside. Accordingly, the diameter of the perforations 3 is larger than this, and should be 40 mm or more, preferably about 50 to 100 mm.

  The length L per one of the divided pipes 4a is 1 to 3 m, preferably about 2 m. A plurality of these are inserted into the perforation 3 while being connected, and formed into a predetermined length (the length of the perforation 3).

  In order to connect the two divided pipes 4a and 4a, as shown in FIG. 3, both ends of each pipe 4a are cut in advance with female threads, and both ends of the connector 8 are cut off with male threads. The pipes 4a and 4a can be formed by screwing one end. That is, after the connector 8 is screwed to the rear end of one pipe 4a to an intermediate position in the axial direction, the front end of the other pipe 4a is screwed to the rear end of the connector 8, and the divided pipe 4a 4a are sequentially connected.

  The connector 8 is a circular tube made of a resin or the like, and an external thread that can be screwed into an internal thread of the pipe 4a is cut on the outer surface. When the female thread portion of the pipe 4a is screwed to both ends of the connector 8, the two divided pipes 4a and 4a are connected. The connector 8 has one end side in the one pipe 4a and the other end side protruding from the one pipe 4a, and one end side is fixed to the one pipe 4a by an adhesive or the like, and the protruding portion The other pipe 4a may be screwed into the projecting portion of the male screw.

  As shown in FIG. 4, a conical nose 9 having a base end portion having substantially the same outer diameter as that of the pipe 4 and a tapered shape toward the tip is attached to the tip of the pipe 4. Yes. The nose 9 is formed of a solid member made of resin or the like. In order to connect the nose 9 to the tip of the pipe 4, an annular or columnar connecting portion 9a protruding rearward is provided at the rear end of the nose 9, and a male screw is cut on the outer periphery of the connecting portion 9a. This can be done by screwing the portion 9a into a female screw cut at the tip of the pipe 4.

  A screw hole 9b is provided along the axial direction in the central part of the rear of the nose 9, and a hook or hook portion is provided in the screw hole 9b. The stopper 10 is screwed together. As will be described in detail later, the tip of the geophone 5 is fixed to the latch 10 via a severable member 12.

  The geophones 5, 5... Are arranged inside the pipe 4 at predetermined intervals along the axial direction, and receive the elastic waves transmitted through the natural ground when the face S is hit with a hammer.

  The geophones 5, 5... Are arranged over almost the entire length of the perforation 3 (pipe 4). The arrangement interval of the geophones 5, 5.

  The plurality of geophones 5, 5... Are integrated by a connecting member 11 that couples the neighboring geophones 5, 5. The connecting member 11 is composed of a tube made of resin or the like, and lead wires connected to the geophone 5 are wired inside. As shown in FIG. 2, the lead wires extending from the geophones 5, 5... Extend from the rear end of the connecting member 11 to the outside and are connected to a recording device (not shown).

  The geophones 5, 5... Integrated by the connecting member 11 are fixed to the hooking tool 10 provided at the tip of the pipe 4 through a member 12 that can be cut. Since the geophones 5, 5... Are fixed to the tip of the pipe 4 through the severable member 12, by inserting and removing the pipe 4 with respect to the perforation 3, the geophones 5, 5,. It will be inserted and removed.

  The geophone 5 is not fixed to the pipe 4 except that its tip is fixed to the pipe 4 via the severable member 12. For this reason, the geophone 5 can freely move along the inner periphery of the pipe 4 by the rotation of the pipe 4, and the geophone 5 is moved by gravity according to the rotation angle at which the pipe 4 is installed in the perforation 3. It is naturally arranged at the lower end of the inner periphery. For this reason, it becomes easy to receive the elastic wave from the hole wall of the lower end part in the perforation 3 which the outer surface of the pipe 4 contacts.

  The severable member 12 refers to the connecting member that is not cut when the pipe 4 is inserted into and removed from the perforation 3 but cannot be pulled out from the perforation 3 due to collapse of the hole wall or the like. The cutable member 12 is cut by the pulling force when only the geophones 5, 5,. As the severable member 12, it is preferable to use a wire or a chain having a predetermined tensile stress.

  The current electrode 6 and the potential electrode 7 are electrodes for measuring the specific resistance of the natural ground around the hole wall in the perforation 3 provided on the outer peripheral surface on the tip side of the pipe 4. 6 is used for resistivity logging to measure and analyze the potential difference between the potential electrodes 7 and 7 by passing a current through the formation between the six electrodes.

  As shown in FIG. 3, the current electrode 6 and the potential electrode 7 are arranged at approximately equal intervals along the axial direction in a predetermined section on the tip side of the pipe 4 at two locations. Specifically, in the predetermined section, current electrodes 6 are respectively disposed at the front and rear end portions of the pipe 4 in the axial direction, and potential electrodes 7 are respectively disposed at two positions with a predetermined interval therebetween. .

  The current electrode 6 and the potential electrode 7 are provided at a position where the current electrode 6 and the potential electrode 7 can come into contact with the ground on the outer peripheral surface of the pipe 4. That is, at least a part of each of the electrodes 6 and 7 is in contact with the natural ground, and is arranged in a state in which the natural ground can be energized.

  Here, the surface of the hole wall in the perforation 3 is not flat but has a lot of irregularities. Therefore, in order to make the current electrode 6 and the potential electrode 7 easily come into contact with the natural ground, the current electrode 6 and the potential electrode 7 have a brush shape in which the contact portion with the natural ground protrudes a number of thin line electrodes. Preferably formed. Thereby, adhesiveness with the hole wall which the surface has an unevenness | corrugation increases, and a measurement precision can be improved.

  The brush-like electrodes 6 and 7 preferably have a protrusion length a from the outer surface of the pipe 4 of 2 to 10 mm, and an axial width b of the pipe 4 of 1 to 5 mm. The brush-like electrodes 6 and 7 are preferably provided continuously or intermittently in the circumferential direction of the pipe 4. In the illustrated example, as shown in FIG. 3B, a plurality of brush-like electrodes 6 and 7 are intermittently arranged at predetermined intervals in the circumferential direction. As a result, regardless of the rotation angle of the pipe 4, the electrodes 6 and 7 positioned on the lower side of the pipe 4 can come into contact with the natural ground on the lower side of the perforation 3. When the electrodes 6 and 7 are intermittently arranged in the circumferential direction, the number of the electrodes 6 and 7 is preferably about 4 to 20, and is 12 in the illustrated example.

  The current electrode 6 and the potential electrode 7 are preferably arranged at equal intervals in the axial direction of the pipe 4, and the separation distance is preferably about 100 to 500 mm.

  In order to attach the current electrode 6 and the potential electrode 7 to the pipe 4, as shown in FIG. 5, an annular electrode ring 13 to which the electrodes 6 and 7 are attached at a predetermined interval along the circumferential direction of the outer surface is provided. The pipes 4b and 4b are divided at the positions where the electrodes 6 and 7 are disposed, and the pipes 4b and 4b are connected by a connector 14. In order to assemble the electrode ring 13 into the pipe 4, the connector 14 is screwed into the rear end of one pipe 4 b, the electrode ring 13 is inserted into the connector 14, and the front end of the other pipe 4 b is screwed into the connector 14. In addition, the electrode ring 13 is pressed and fixed between the ends of both pipes 4b and 4b.

  Further, as shown in FIG. 4, the current electrode 6 provided at the front end portion of the pipe 4 has an electrode ring 13 to which a plurality of current electrodes 6, 6... Are attached at predetermined intervals along the circumferential direction of the outer surface. , Between the nose 9 and the front end of the pipe 4.

  The lead wires connected to the electrodes 6 and 7 of the electrode ring 13 are preferably bundled together and wired so as to extend to the inner surface side of the electrode ring 13. Also, the connector 14 is provided with a slit 14a extending in the axial direction from the other edge to the axial center, and when the electrode ring 13 is inserted into the connector 14, the lead wire of the electrode ring 13 is It is preferable that the lead wire is wired inside the pipe 4 by engaging with the slit 14 a of the connector 14.

  The electrode ring 13 may be formed integrally with the connector 14 at an intermediate portion in the axial direction of the connector 14 instead of being formed separately from the connector 14.

  Alternatively, the electrodes 6 and 7 may be disposed directly on the pipe 4 without using the electrode ring 13.

  As shown in FIG. 2, the lead wire 15 extending from the current electrode 6 and the potential electrode 7 is wired inside the pipe 4, extends from the rear end of the pipe 4 to the outside, and is connected to a recording device (not shown). Has been.

  In order to perform geological exploration by the geological exploration apparatus 1 having the above-described configuration, after the drill 3 is formed in the ground in front of the face S from the tunnel space by the drill 2, the geophone 5 is inserted into the drill 3. The pipe 4 provided with the current electrode 6 and the potential electrode 7 is inserted. In order to insert the pipe 4, the pipes 4 a, 4 a... Divided into a predetermined length are sequentially connected by the connector 8 and the geophone 5 is sequentially connected.

  When the insertion of the pipe 4 is completed, the face S is struck, the propagation speed of elastic waves is measured by the geophones 5, 5..., And then the ground between the current electrodes 6 and 6 is pulled out while the pipe 4 is pulled out. A specific current is obtained by passing a current through the mountain and measuring a potential difference between the potential electrodes 7 and 7.

  When measuring the propagation speed of the elastic wave, in the geological exploration device 1, a plurality of geophones 5 are arranged at a predetermined interval over the entire length of the perforation 3. The elastic wave can be measured over the entire area. For this reason, the work of velocity logging can be simplified, and since the vibration data is equal, the accuracy and reliability of the measurement data can be improved.

  The specific resistance contains almost no information on the cracks in the natural ground, and the elastic wave has a feature that the influence of the cracks in the natural ground is large. Therefore, from the equation that coefficient K = elastic wave propagation speed / specific resistance, You can get information on mountain cracks.

  In addition to the geological exploration (elastic wave velocity, specific resistance) by the geological exploration device 1, the drilling 3 is used to directly investigate the borehole logging and the geology ahead of the face with an endoscope. By doing this, it becomes possible to comprehensively evaluate the geology ahead of the face.

  In the geological exploration device 1, the geophone 5 is provided in the pipe 4, so that the pipe 4 serves as an insertion aid even in a bad ground where the hole wall tends to collapse. Even if the hole wall collapses with the pipe 4 inserted, the pipe 4 serves as a casing and protects the geophones 5, 5,. It can be carried out.

  Further, when the hole wall collapses and the pipe 4 cannot be pulled out, the member 12 that can be cut at the tip is cut by strongly pulling the geophones 5, 5... Integrated by the connecting member 11. Since the connection with the pipe 4 is released, the expensive geophones 5, 5... Can be recovered while leaving the pipe 4 in the perforation 3. Therefore, the economic burden can be reduced.

  Furthermore, in the geological exploration apparatus 1, the geological exploration work can be simplified as described above, and the geophone 5 can be easily recovered even when the hole wall collapses. The impact on the tunnel excavation work is minimized.

  DESCRIPTION OF SYMBOLS 1 ... Geological exploration device, 2 ... Drilling machine, 3 ... Drilling, 4 ... Pipe, 5 ... Vibration receiving device, 6 ... Current electrode, 7 ... Potential electrode, 8 ... Connector, 9 ... Nose, 10 ... Stopper, 11 ... Connecting member, 12 ... Cutable member, 13 ... Electrode ring, 14 ... Connector, 15 ... Lead wire

Claims (5)

  A pipe to be inserted into a perforation provided in a natural ground in front of the face, a plurality of geophones for measuring elastic waves disposed in the pipe at predetermined intervals along the axial direction; A geological exploration device in front of a face, comprising a current electrode and a potential electrode provided on an outer peripheral surface on a tip end side of a pipe for measuring a specific resistance of a natural ground around a hole wall in the perforation.   The geological exploration device in front of the face according to claim 1, wherein the pipe is made of resin, and a plurality of pipes divided by a predetermined length are connected by a connector.   The plurality of geophones are integrated by a connecting member that couples adjacent geophones, and a tip portion is fixed to a tip inside the pipe via a severable member. The geological exploration device in front of the face according to any one of the above.   The geological exploration apparatus in front of the face according to any one of claims 1 to 3, wherein the current electrode and the potential electrode are formed in a brush shape in which a contact portion with a natural mountain protrudes a number of thin wire electrodes.   The geological exploration device in front of the face according to any one of claims 1 to 4, wherein a lead wire extending from the current electrode and the potential electrode is wired inside the pipe.

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