Face ahead exploration method

Abstract

To provide a face ahead exploration method capable of carrying out a plurality of face ahead explorations in a series of operations.SOLUTION: In a face ahead exploration method for exploring characteristics of the natural ground ahead of a tunnel face 2, a drilling machine 1 equipped with a communication space leading to a hole bottom 3 drills ahead from the tunnel face 2, and an exploration process ahead of the face is carried out using the communication space (A rock powder sampling process for sampling rock powder drilled at the hole bottom 3, an elastic wave exploration process for analyzing elastic waves emitted by a tip bit 11 of the drilling machine 1, a core sampling process for sampling rock cores, a wellhead pressure measurement process for measuring wellhead pressure from the hole bottom 3, a horizontal load test process in the hole to determine the deformation coefficient of the natural ground, a hole observation process for photographing the inside of the hole, etc.).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for investigating the nature of the natural ground ahead of a tunnel face. [Background technology]

[0002] When excavating mountain tunnels in natural ground with complex geology, a survey is conducted ahead of the tunnel face to grasp the geological conditions ahead of the tunnel face as the excavation proceeds. For example, a drilling machine such as a jumbo drill or hydraulic hammer is used to survey the characteristics of the natural ground ahead of the tunnel face from machine data (drilling energy) during drilling (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-125296 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when excavating mountain tunnels, in addition to "A. Drilling logging: determining the hardness of the ground based on the drilling energy," surveys ahead of the face as shown in B to G below are also carried out as necessary. "B. Rock powder collection: Rock powder (chestnut powder) from the drilled hole is collected and used as a sample for investigating the heavy metal content." "C. Elastic wave exploration: The position of reflectors such as fault fracture zones is estimated by analyzing the elastic waves emitted by the tip of the drill bit." "D. Core collection: Collect rock cores and conduct uniaxial compressive strength test specimens and heavy metal content surveys." "E. Measuring the water pressure: Insert a packer and measure the water pressure." "F. Horizontal loading test in a borehole: A packer is used to deform the inside of the borehole, and the deformation coefficient of the ground is calculated." "G. Borehole observation: Insert a borehole camera into the hole to grasp the weathering and alteration of the ground, the frequency of cracks, the stability of the ground, the state of spring water, etc."

[0005] When multiple of the A to G ahead of the face surveys were carried out, it was necessary to carry out each operation separately using different procedures. "B. Rock powder collection" could have been carried out at the same time as "A. Well drilling logging", but because the sample passes outside the pipe and reaches the hole mouth, it contains materials other than the rock powder drilled at the tip, making it impossible to obtain an accurate sample. When "C. Elastic wave exploration" is carried out simultaneously with "A. Hole-drilling logging", it is necessary to prepare a special rod with a built-in elastic wave receiver. "D. Core sampling" requires re-drilling with a special bit. For "E. Water Seepage Pressure Measurement" and "F. In-hole Horizontal Load Test", it is necessary to insert a packer or the like after removing all of the drilling machine's bits and rods. "G. Borehole Observation" requires the insertion of a camera after all of the drilling machine's bits and rods have been removed.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a method for detecting ahead of a tunnel face that can solve the above-mentioned problems and perform multiple detections ahead of a tunnel face in a series of operations. [Means for solving the problem]

[0007] The method for investigating the characteristics of the ground ahead of the tunnel face of the present invention is a method for investigating the characteristics of the ground ahead of the tunnel face, characterized in that a hole is drilled forward from the tunnel face using a drilling machine equipped with a communicating space leading to the bottom of the hole, and a process of investigating ahead of the face is carried out using the communicating space. Furthermore, in the face-front exploration method of the present invention, the drilling machine may be provided with the communicating space as an outlet for rock powder drilled at the bottom of the hole, and a rock powder collection process for collecting the rock powder discharged from the communicating space may be carried out as the face-front exploration process. Furthermore, in the face-ahead exploration method of the present invention, an elastic wave exploration process may be carried out as the face-ahead exploration process, in which elastic waves emitted by the tip bit of the drilling machine are analyzed using a pilot sensor installed near the tip bit of the drilling machine through the communicating space and a receiver installed in a measurement hole drilled in a direction intersecting the tunnel axis. Furthermore, in the face-ahead exploration method of the present invention, the drilling machine may be provided with the communicating space as an outlet for rock powder drilled at the bottom of the hole, and a core sampling process may be carried out as the face-ahead exploration process in which a rock core is sampled through the communicating space using a core sampler installed on the tip bit of the drilling machine. Furthermore, in the face-front exploration method of the present invention, a water well pressure measurement process for measuring the water well pressure from the bottom of the hole using a packer section installed in the gap between the bottom of the hole and the tip bit of the drilling machine through the communicating space may be carried out as the face-front exploration process. Furthermore, in the face-ahead exploration method of the present invention, an in-hole horizontal load test process for determining the deformation coefficient of the ground may be carried out as the face-ahead exploration process using a packer section installed in the gap between the bottom of the hole and the tip bit of the drilling machine through the communicating space. Furthermore, in the face-ahead exploration method of the present invention, a hole-hole observation process of photographing the inside of the hole using a hole-hole camera installed through the communicating space in the gap between the bottom of the hole and the tip bit of the drilling machine may be carried out as the face-ahead exploration process. Effect of the Invention

[0008] According to the present invention, it is possible to carry out a plurality of ahead-of-face surveys in a single operation without withdrawing the drilling machine. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional view illustrating a hole-drilling process in an embodiment of a method for detecting ahead of a face according to the present invention. [Diagram 2] FIG. 11 is a cross-sectional view illustrating the elastic wave exploration process. [Diagram 3]FIG. 4 is a cross-sectional view illustrating a core sampling process. [Figure 4] FIG. 2 is a cross-sectional view illustrating the spring water pressure measurement process and the borehole horizontal loading test process. [Diagram 5] FIG. 11 is a cross-sectional view illustrating the hole observation process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Next, a mode for carrying out the present invention (hereinafter simply referred to as an "embodiment") will be specifically described with reference to the drawings. 1, in the method for prospecting ahead of the tunnel face of this embodiment, a drilling machine 1 equipped with a hollow rod 10 is used to drill a hole forward from the tunnel face 2 (drilling process). The hollow portion of the hollow rod 10 is provided for the purpose of supplying air and water to the hole bottom 3 and discharging rock powder generated at the hole bottom 3. An opening 11a is formed in the center of the tip bit 11 of the drilling machine 1, which communicates with the hollow portion of the hollow rod 10 and reaches the hole bottom 3. The opening 11a of the tip bit 11 and the hollow portion of the hollow rod 10 function as a communicating space from the tunnel face 2 to the hole bottom 3.

[0011] The drilling machine 1 uses, for example, a reverse circulation hammer system (hereinafter referred to as RC hammer). The RC hammer is a drilling device that uses a tip impact method. The RC hammer includes a hollow rod 10 with a tip bit 11 connected to the tip, and a boring machine (not shown) that holds the hollow rod 10 and applies rotational force and propulsive force. The RC hammer moves a piston 13 back and forth by supplying air from the outer periphery (the gap between the hollow rod 10 and the outer periphery rod 12) of a double tube rod consisting of the hollow rod 10 and the outer periphery rod 12, thereby generating an impact on the tip bit 11 at the tip. In the RC hammer, the rock powder drilled is discharged to the outside through a communication space (the opening 11a of the tip bit 11, the hollow part of the hollow rod 10).

[0012] "A. Drilling logging" calculates the drilling energy based on the drilling data from the drilling machine 1 during the drilling process, and uses this to grasp the hardness of the ground. When the drilling machine 1 is an RC hammer, the energy index value calculated by air supply pressure x number of blows / drilling speed can be considered as the drilling energy. The restitution coefficient of the RC hammer (the ratio of the rebound speed to the impact speed of the piston 13) increases in proportion to the strength of the rock, and the impact frequency of the piston 13 changes according to the strength (restitution coefficient) of the rock. An increase in air supply pressure increases the energy per blow and the impact frequency.

[0013] In "B. Rock Powder Collection" (rock powder collection process), the rock powder drilled is discharged to the outside through the communicating space (opening 11a of the tip bit 11, hollow part of the hollow rod 10). The discharged rock powder does not contain anything other than the rock powder drilled at the tip. Therefore, the discharged rock powder becomes an accurate sample, and the heavy metal content, etc. can be accurately evaluated.

[0014] "C. Elastic wave exploration" (elastic wave exploration process) is carried out by stopping the drilling work once a predetermined distance has been reached in the drilling process, and using a pilot sensor 20 and a receiver 21. Referring to Fig. 2, the pilot sensor 20 is installed in a position close to the piston 13 through the hollow part of the hollow rod 10. The receiver 21 is installed in a measurement hole 22 that is drilled from inside the tunnel towards the natural ground in a direction that intersects with the tunnel axis.

[0015] The pilot sensor 20 is a sensor that receives bit vibration transmitted from the tip bit 11. The pilot sensor 20 can be installed in a position close to the piston 13 through the hollow part of the hollow rod 10, so that it can receive bit vibration generated from the tip bit 11 during drilling in a state close to actual vibration. The pilot sensor 20 can be a three-component accelerometer that is generally used in elastic wave exploration, but a one-component accelerometer may also be used.

[0016] The receiver 21 receives the bit vibrations that have traveled through the natural ground from the position of the tip bit 11, which is the vibration source. The receiver 21 can be a three-component accelerometer that is generally used in elastic wave exploration.

[0017] After the pilot sensor 20 and the receiver 21 are installed, the drilling operation of the drilling machine 1 is started, and the bit vibration generated from the tip bit 11 is continuously received by the pilot sensor 20 and the receiver 21.

[0018] The information on the bit vibration received by the pilot sensor 20 and the receiver 21 is analyzed by a data processing device 23 such as a personal computer. This makes it possible to calculate the elastic wave velocity of the natural ground ahead of the tunnel in the range from the position of the tip bit 11 to the tunnel face 2, and to estimate the position of a reflection surface such as a fault fracture zone.

[0019] "D. Core Sampling" (core sampling process) is performed using a rock core sampling system 4. As shown in Fig. 3(a), the rock core sampling system 4 includes a core sampler 40 and a recovery tool 46. In the sampling process, when the hole has been drilled a predetermined distance in the hole drilling process, the drilling work is temporarily stopped and the core sampler 40 is pumped through the hollow part of the hollow rod 10 by water pressure (or air pressure) and placed in the opening 11a of the tip bit 11 as shown in Fig. 3(b).

[0020] The core sampler 40 comprises a cylindrical sampling portion 41 for sampling rock cores, and a cylindrical fixing portion 42 for mounting the sampling portion 41 in the opening 11a of the tip bit 11. The sampling portion 41 is a tubular body, and is mounted in the opening 11a of the tip bit 11 so that one open end faces the hole bottom 3. The sampling portion 41 and the fixing portion 42 are connected via a spring 43.

[0021] The fixed part 42 includes a stopper 44. The stopper 44 is hinged and configured to be displaceable (movable) between a protruding state protruding from the circumferential surface of the fixed part 42 and a stored state housed within the fixed part 42 and retracted from the circumferential surface. The stopper 44 is biased in a direction protruding from the circumferential surface of the fixed part 42 by a spring (not shown), and engages with the connecting part of the hollow rod 10 as an engaged part, thereby fixing the fixed part 42 to the communication space. By fixing the fixed part 42, the collection part 41 is installed at a predetermined position of the opening 11a of the tip bit 11. A spear 45 is provided on the rear end side of the fixed part 42, and by pulling the spear 45 rearward, the stopper 44 is displaced to a stored state retracted from the circumferential surface.

[0022] After the core sampler 40 is installed, the drilling operation of the drilling machine 1 is started. The core sampler 40 is installed in the discharge path of the rock powder, so that a rock core (or a natural ground sample close to the rock core) is collected by the collection unit 41. Note that, since the discharge path of the air discharged together with the rock powder is blocked by the core sampler 40, the air is discharged through the outside of the outer circumferential rod 12.

[0023] After a rock core of a predetermined length has been collected in the collection section 41, the drilling operation of the drilling machine 1 is stopped, and the core sampler 40 is collected by the collection tool 46. With a cable 47 connected to its rear end, the collection tool 46 is pumped by water pressure (or air pressure) through the hollow part of the hollow rod 10 to the position of the core sampler 40. The collection tool 46 is equipped with a latch mechanism 48, and the latch mechanism 48 engages with the spear 45 of the core sampler 40 by the pumping. In this state, by pulling the cable 47, the stopper 44 is put into a housed state, and the core sampler 40 connected to the collection tool 46 is collected.

[0024] The pilot sensor 20 may be provided on the core sampler 40, and "C. Elastic wave exploration" and "D. Core sampling" may be performed simultaneously. In this case, the work of installing the pilot sensor 20 and the work of installing the core sampler 40 can be performed in the same task, further improving work efficiency.

[0025] "E. Spring water pressure measurement" (spring water pressure measurement process) and "F. In-hole horizontal load test" (in-hole horizontal load test process) are carried out after the hole has been drilled a specified distance in the hole drilling process, at which point the drilling work is stopped. Then, as shown in Figure 4(a), the drilling machine 1 is pulled out a specified distance to ensure a gap between the hole bottom 3 and the tip bit 11. "E. Spring water pressure measurement" and "F. In-hole horizontal load test" should be carried out after "D. Core sampling".

[0026] The packer part 50, which is made of a rubber tube or the like, is installed in the gap between the bottom of the hole 3 and the tip bit 11 through the communication space (the opening 11a of the tip bit 11, the hollow part of the hollow rod 10). The packer part 50 is passed through the communication space in a contracted state. The packer part 50 may be pumped by water pressure (or air pressure), or may be inserted using the connected first pipe communication pipe 51 and second pipe communication pipe 52. If there is a step in the communication space, it is advisable to form a tapered part 53 on the tip side of the packer part 50 to overcome the step. If a tapered surface is formed at the step in the communication space, the tapered part 53 can be omitted.

[0027] One end of the first pipe communication pipe 51 communicates with the inside of the packer section 50, and the other end located on the tunnel face 2 side is connected to a pump 55 via a measuring device 54. One end of the second pipe communication pipe 52 communicates with the gap between the hole bottom 3 and the tip bit 11, and the other end located on the tunnel face 2 side is connected to a water pressure gauge 56.

[0028] In "E. Measuring the spring water pressure," water is injected from the pump 55 into the packer section 50 through the first pipe connecting pipe 51, causing the packer section 50 to expand as shown in FIG. 4(b). The gap between the bottom of the hole 3 and the tip bit 11 is sealed off by the packer section 50, and the spring water pressure is measured by the water pressure gauge 56. By removing the water pressure gauge 56, the water is discharged through the second pipe connecting pipe 52, making it possible to measure the amount of spring water.

[0029] In "F. In-hole horizontal load test", water is further injected from pump 55 into packer section 50 through first pipe connecting pipe 51 to apply pressure to the hole wall. The pressure and the amount of deformation of the ground are measured by measuring instrument 54 to obtain the deformation coefficient of the ground.

[0030] As shown in Figure 5, in "G. Borehole observation", a borehole camera 60 is pumped through the hollow part of the hollow rod 10 by water pressure (or air pressure) and installed at the opening 11a of the tip bit 11. The borehole camera 60 can be installed after "E. Spring water pressure measurement" and "F. Borehole horizontal loading test" are completed and the contracted packer section 50 is pulled out. In this case, "E. Spring water pressure measurement", "F. Borehole horizontal loading test" and "G. Borehole observation" can be performed in a single operation.

[0031] With the in-hole camera 60 installed in the opening 11a of the tip bit 11, the drilling machine 1 is pulled out while the in-hole camera 60 takes pictures of the inside of the hole. This allows the image of the inside of the hole taken by the in-hole camera 60 to be observed on a monitor 61 installed on the tunnel face 2 side. Fig. 5 shows an example in which the in-hole camera 60 and the monitor 61 are connected by a cable 62, but the connection may be wireless. The in-hole camera 60 can also be equipped with a recording function.

[0032] As described above, this embodiment is a method for investigating the properties of the ground ahead of the tunnel face 2, in which a drilling machine 1 equipped with a communicating space leading to the hole bottom 3 is used to drill a hole ahead of the tunnel face 2, and the communicating space is used to carry out the investigation process ahead of the face. With this configuration, the exploration ahead of the face can be carried out in a series of operations without pulling out the drilling machine 1. Since there is no need to pull out the drilling machine 1, there is little possibility that the hole wall will collapse. Since there is no need to insert equipment into the open hole after the drilling machine 1 is pulled out for a new exploration ahead of the face, there is little risk that the equipment will get caught on the hole wall.

[0033] In addition, in this embodiment, the drilling machine 1 has a communicating space as an outlet for rock powder drilled at the hole bottom 3, and a rock powder collection process for collecting rock powder discharged from the communicating space is carried out as a face front exploration process. With this configuration, rock powder collection can be performed in a series of operations with high precision in the collection position of the rock powder (chunks) without pulling out the drilling machine 1.

[0034] In addition, in this embodiment, an elastic wave exploration process is carried out as a front-of-face exploration process, in which elastic waves emitted by the tip bit of the drilling machine 1 are analyzed using a pilot sensor 20 installed near the tip bit 11 of the drilling machine 1 through the communicating space and a receiver 21 installed in a measurement hole 22 drilled in a direction intersecting the tunnel axis. With this configuration, seismic exploration can be carried out in a series of operations without pulling out the drilling machine 1.

[0035] In addition, in this embodiment, the drilling machine 1 is provided with a communicating space as an outlet for rock powder drilled at the hole bottom 3, and a core sampling process in which rock cores are collected through the communicating space using a core sampler 40 (collection section 41) installed on the tip bit 11 of the drilling machine 1 is carried out as a front face exploration process. With this configuration, core sampling can be carried out in a single operation without pulling out the drilling machine 1.

[0036] In addition, in this embodiment, a water well pressure measurement process is carried out as a face front exploration process, in which the water well pressure from the bottom of the hole 3 is measured using a packer section installed through a communicating space in the gap between the bottom of the hole 3 and the tip bit of the drilling machine 1. With this configuration, the wellhead pressure can be measured in a single operation without pulling out the drilling machine 1.

[0037] In addition, in this embodiment, a packer section 50 is installed through a communicating space in the gap between the bottom of the hole 3 and the tip bit 11 of the drilling machine 1, and an in-hole horizontal loading test process for determining the deformation coefficient of the ground is carried out as a face front exploration process. With this configuration, the in-hole horizontal load test can be carried out in a series of operations without pulling out the drilling machine 1.

[0038] In addition, in this embodiment, a hole observation process for photographing the inside of the hole is carried out as a face front exploration process using a hole camera 60 installed through a communicating space in the gap between the hole bottom 3 and the tip bit 11 of the drilling machine 1. With this configuration, borehole observation can be carried out in a series of operations without pulling out the drilling machine 1.

[0039] The present invention has been described above based on the embodiment. This embodiment is an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component, and that such modifications are also within the scope of the present invention. For example, AI analysis of the samples collected in "B. Rock powder collection" and AI analysis of the images taken in "G. Borehole observation" can be performed as a face-ahead exploration process. [Explanation of symbols]

[0040] 1 Drilling machine 2 Tunnel Face 3 Bottom of hole 4. Rock core sampling system 10 Hollow Rod 11 Tip Bit 11a opening 12 Outer Rod 13 Piston 20 Pilot Sensor 21 Geophone 22 Measurement hole 23 Data Processing Device 40 Core Sampler 41 Collection section 42 Fixed part 43 Spring 44 Stopper 45 Spear 46 Recovery Tool 47 Cable 48 Latch mechanism 50 Packer Division 51 1st pipe communication pipe 52 2nd pipe communication pipe 53 Tapered section 54 Measuring instruments 55 Pump 56 Water pressure gauge 60 Borehole Camera 61 Monitor 62 Cable

Claims

1. A method for investigating the nature of ground in front of a tunnel face, comprising: A drilling machine with a communicating space to the bottom of the hole is used to drill the tunnel from the tunnel face forward. A face ahead inspection method, characterized in that a face ahead inspection process is carried out using the communicating space.

2. The drilling machine has the communicating space as an outlet for rock powder drilled at the bottom of the hole, The method for prospecting ahead of the face according to claim 1, characterized in that a rock powder sampling process for sampling the rock powder discharged from the communicating space is carried out as the prospecting process ahead of the face.

3. A pilot sensor installed near a tip bit of the drilling machine through the communication space; The method for probing ahead of the tunnel face as described in claim 1, characterized in that the probing process ahead of the tunnel face is an elastic wave probing process that analyzes elastic waves emitted by the tip bit of the drilling machine using a receiver installed in a measurement hole drilled in a direction intersecting the tunnel axis.

4. The drilling machine has the communicating space as an outlet for rock powder drilled at the bottom of the hole, The method for prospecting ahead of the face as described in claim 1, characterized in that a core sampling process for sampling a rock core using a core sampler installed on the tip bit of the drilling machine through the communicating space is carried out as the prospecting process ahead of the face.

5. The method for prospecting ahead of the face as described in claim 1, characterized in that a water spring pressure measurement process for measuring the water spring pressure from the bottom of the hole using a packer section installed in the gap between the bottom of the hole and the tip bit of the drilling machine through the communicating space is carried out as the prospecting ahead of the face.

6. The method for prospecting ahead of the face as described in claim 1, characterized in that an in-hole horizontal load test process for determining the deformation coefficient of the ground is carried out as the prospecting ahead of the face using a packer section installed through the communicating space in the gap between the bottom of the hole and the tip bit of the drilling machine.

7. The method for prospecting ahead of the face as described in claim 1, characterized in that the prospecting ahead of the face includes an in-hole observation process for photographing the inside of the hole using a in-hole camera installed through the communicating space in the gap between the bottom of the hole and the tip bit of the drilling machine.

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