Ground survey method and device using boring drill

Abstract

To provide a ground survey method and device using a boring drill, which can quickly detect a cavity and looseness of the ground around the boring drill in a short time and in almost real time every day such as at a daily recess.SOLUTION: In a survey of a state of the ground 10 drilled with boring drills 26, hollow cylindrical sensors 30 through which discharged mud water during the drilling can flow are arranged in the inside of at least two of the plurality of hollow boring drills 26. The state of the ground 10 is surveyed by using acoustic signals directly propagated between the cylindrical sensors 30 installed in a plurality of boreholes.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a ground exploration method and apparatus using a boring drill, and particularly to a method and apparatus for quickly detecting, almost in real time, the looseness and cavities in the ground around a boring drill, which are suitable for use at the construction sites of various tunnels, on a daily basis and in a short time, and capable of preventing ground collapse, surface subsidence, etc.

Background Art

[0002] In recent years, accidents such as ground loosening and surface subsidence during the excavation of underground tunnels by shield machines have become a problem. In particular, the occurrence of loosening and cavities at great depths, which have not been anticipated much so far, cannot be detected by radar exploration from the surface, so it is necessary to investigate the front from inside the shield machine. Also, in the mountain tunnel (NATM method), which is an open excavation method using blasting or a drill machine, it is a problem to grasp the state of the ground in front of the face.

[0003] As a technique for exploring the state of the ground in front of a shield machine from inside the shield machine, there is a method of receiving the excavation vibration of the face and the seismic wave from the boring holes drilled in the segments by a receiver installed on the face or in the boring holes drilled in the segments, and investigating the reflected wave reflected by a fault or the like (FIG. 1 of Patent Document 1, FIG. 1 of Patent Document 2).

[0004] Also, a method of installing two boring holes in front of the face and grasping the elastic wave velocity of the direct wave (FIG. 1 of Non-Patent Document 1) has been proposed.

[0005] Also, a method has been proposed in which two relatively short boring holes are drilled in front of the face, a drilling vibration is generated from one boring hole, and received by a receiver installed in the other boring hole (FIG. 1 of Patent Document 3).

[0006] In addition, methods of performing boring from within the face cutter (FIG. 2 of Patent Document 4, FIG. 1 of Patent Document 5) and methods of protruding a probe rod (Patent Document 6) have also been proposed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Non-Patent Documents

[0008]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] The techniques described in Patent Documents 1 and 2 can grasp large structures such as faults located at positions away from the face. However, since the reflection waves have low accuracy, they do not have the accuracy to grasp small structures compared to faults such as ground loosening, and furthermore, it is difficult to investigate the vicinity of the face.

[0010] Moreover, the method described in Non-Patent Document 1 cannot be applied to unconsolidated ground that is not self-supporting. Furthermore, since only the elastic wave velocity can be measured, the accuracy is not sufficient to detect cavities and looseness. Additionally, since the drilling rod is removed after excavation and the hole is maintained with a gel-like filler before installing the sensor, the investigation takes time.

[0011] Moreover, the technique described in Patent Document 3 has the advantage of not taking much time for the investigation. However, since only the elastic wave velocity can be measured, the accuracy is not sufficient to detect cavities and ground looseness.

[0012] Moreover, the techniques described in Patent Documents 4 - 6 can only grasp one-dimensional information in the vicinity of the boring or exploration rod, and cannot grasp looseness or the like at locations away from the boring or exploration rod.

[0013] As described above, the conventional techniques have problems such as low accuracy, difficulty in detecting cavities and looseness, a narrow investigation range, and time-consuming investigations.

[0014] The present invention has been made to solve the above-described conventional problems, and an object thereof is to be able to quickly and almost in real time detect looseness and cavities in the ground around a boring drill using the boring drill during daily break times or the like in a short time every day.

Means for Solving the Problems

[0015] When exploring the state of the ground excavated by a boring drill, the present invention arranges a hollow cylindrical sensor through which the muddy water during excavation can pass inside at least two of a plurality of hollow boring drills, and explores the state of the ground using an acoustic signal that directly propagates between the cylindrical sensors installed in a plurality of boring holes, thereby solving the above problems.

[0016] The present invention also relates to an apparatus for exploring the state of the ground excavated by a boring drill, comprising: a hollow cylindrical sensor disposed inside at least two of a plurality of hollow boring drills and through which the muddy water during excavation can pass; and a circuit for exploring the state of the ground using an acoustic signal directly propagated between the cylindrical sensors installed in a plurality of boring holes. The present invention solves the above-mentioned problem by means of a ground exploration apparatus using a boring drill.

[0017] Here, the transmission and reception directions of the cylindrical sensor can be switched.

[0018] Further, the cylindrical sensor can be used as an acoustic sensor, and a soundproof material for preventing interference of acoustic signals can be inserted inside the sensor.

Advantages of the Invention

[0019] According to the present invention, instead of using the elastic wave velocity of the reflected wave or the direct wave, the amplitude attenuation of the direct wave is used, so that cavities and ground loosening can be reliably grasped. In addition, since measurements are made between a plurality of boring holes, the state of a wide range can be grasped. Furthermore, for example, when applied to the boring drill of a shield machine, boring, measurement, and data processing can be performed from inside the shield machine in a short time. Also, if a hollow cylindrical sensor is installed inside the hollow boring drill installed in the shield machine, excavation and investigation can be carried out, for example, during the daily break time (between two shifts). Therefore, it is possible to conduct investigations every day, plot the daily results, and generate an alarm almost in real time quickly.

Brief Description of the Drawings

[0020]

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Mode for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the contents described in the following embodiments. Further, the constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments may be combined as appropriate or selected and used as appropriate.

[0022] An embodiment of the present invention applied to the exploration of the state of the ground in front of the shield machine includes, as schematically shown in FIG. 1 (cross-sectional view) and FIG. 2 (plan view), a plurality of (three in FIG. 2) hollow boring drills 26 in front of the shield machine 20 that cuts a tunnel 12 in the ground 10. A hollow cylindrical sensor 30 disposed inside each of them, through which the muddy water during excavation can pass as shown in FIG. 3, and a signal creation / reception unit 32 for exploring the state of the ground 10 in front of the shield machine 20 by using an acoustic signal directly propagating between the cylindrical sensors 30 installed in a plurality of boring holes.

[0023] As the cylindrical sensor 30, for example, a cylindrical piezoelectric ceramic PZT manufactured by Tokin Corporation can be used.

[0024] In the figure, 22 is the cutter face of the shield machine 20, and 34 is the signal line connecting the cylindrical sensor 30 and the signal generation / reception unit 32.

[0025] The length L of the boring drill 26 can be set to, for example, about 3 m, which is the distance drilled during the period from one break time to the next (e.g., half a day).

[0026] The speed and amplitude of the acoustic signal propagating between the cylindrical sensors 30 have waveforms as shown in, for example, Fig. 4. However, if there are looseness or cavities, the arrival time will be delayed and the waveform will have a small amplitude. As can be seen from the figure, for ground deformation, the amplitude changes more sensitively than the speed calculated from the arrival time. Measure this daily to obtain Fig. 5. Calculate and plot the difference from the previous day. For example, if the amplitude becomes half (6 dB in sound pressure value), issue a warning, and if it becomes 1 / 4 (12 dB), issue an alarm. By taking the difference in amplitude illustrated by the solid line A, measurement errors and the influence of the original ground can be eliminated. In the figure, the difference in speed shown by the dashed line B has a small change, so it is difficult to clearly distinguish it from measurement errors, and it can be seen that issuing warnings and alarms will be delayed. Regarding the grasping of ground deformation, it is described in, for example, Figs. 15 and 16 of Non-Patent Document 2, and Figs. 2, 9, and 10 of Non-Patent Document 3 that the change in amplitude or attenuation rate is more sensitive than the speed.

[0027] Between the cylindrical sensor 30 and the signal generation / reception unit 32, as shown in detail in Fig. 6, a Siebel joint portion 36 is provided to prevent the twisting of the signal line 34 when the boring drill 26 rotates.

[0028] As shown in FIG. 7, the signal generation / reception unit 32 is provided with a signal generation unit 32A, a signal amplification unit 32B, a signal filter unit 32C, and a signal reception unit 32D. A changeover switch 38 is provided between these units and the signal line 34. By switching the connection to the cylindrical sensor 30, the cylindrical sensor 30 can be used for both oscillation and reception. Therefore, in the present embodiment where three cylindrical sensors 30 are respectively provided in three boring drills 26 as shown in FIG. 4, it is possible to conduct investigations in a maximum of six directions, including three directions or with the oscillation and reception directions switched. Note that the changeover switch 38 may be omitted and the signal propagation direction between the cylindrical sensors 30 may be fixedly set unidirectionally.

[0029] As shown in FIG. 8, a sound-absorbing material 40 is provided inside the cylindrical sensor 30. This is because, without the sound-absorbing material 40, as illustrated in FIG. 9, sound propagates inside the cylindrical sensor 30, interfering with the vibration of the vibration part of the facing cylindrical sensor and reducing the output. Therefore, this is to prevent such a situation.

[0030] The sound-absorbing material 40 is, for example, formed into a cylindrical shape with an outer diameter substantially the same as the inner diameter of the cylindrical sensor 30 using cork or rubber, or a plate material is rolled up and inserted between the cylindrical sensor 30 and the sound-absorbing material 40 so that there is no gap, and it is desirable to prevent sound waves from propagating through the gap.

[0031] The signal propagating between the cylindrical sensors 30 can be a pseudo-random signal to improve the detection accuracy, but the signal propagating between the cylindrical sensors 30 is not limited to a pseudo-random signal.

[0032] The excavation state in the present embodiment is shown in FIG. 10. In order to perform excavation, it is necessary to supply water for mud discharge (referred to as mud discharge water) into the boring drill 26 as indicated by arrow C, so the cylindrical sensor 30 is essential. Using this mud discharge water, the excavation mud 16 generated at the tip of the boring drill 26 (the right end in the figure) is discharged as indicated by arrow D through the gap between the boring drill 26 and the boring hole 18.

[0033] In the above embodiment, three boring drills 26 were provided, and one hollow cylindrical sensor 30 was disposed in each of all the boring drills 26. However, the number of boring drills 26 and the number of cylindrical sensors 30 disposed in the boring drills 26 are not limited thereto. As in the above embodiment, when there are three or more boring drills 26, the cylindrical sensor 30 may be disposed in two of the boring drills 26 to reduce costs, or two or more cylindrical sensors 30 may be disposed in each boring drill 26 to improve the detection accuracy.

[0034] The applicable object is not limited to the exploration of the ground condition in front of the shield machine, but also includes the exploration of the sides above, below, left, and right of the shield machine, the exploration related to the mountain tunnel construction method (NATM) which is an open excavation method using a drill machine, the exploration of the general ground cut by the boring drill, and further, it can be applied to all the survey methods of excavating the measurement hole using the boring rod.

Explanation of Signs

[0035] 10…Ground 12…Tunnel 18…Boring hole 20…Shield machine 26…Boring drill 30…Cylindrical sensor 32…Signal creation / reception unit 32A…Signal creation part 32B…Signal amplification part 32C…Signal filter part 32D…Signal reception part 34…Signal line 36…Sieve joint part 38…Changeover switch 40…Sound absorption material

Claims

1. When exploring the state of the ground excavated by a boring drill, a hollow cylindrical sensor through which the muddy water during excavation can pass is disposed inside at least two of the plurality of hollow boring drills, A ground exploration method using a boring drill, characterized in that the state of the ground is explored by using an acoustic signal that directly propagates between the cylindrical sensors installed in a plurality of boring holes.

2. The ground exploration method using a boring drill according to claim 1, characterized in that the transmission and reception directions of the cylindrical sensor are switched.

3. The ground exploration method using a boring drill according to claim 1 or 2, characterized in that the cylindrical sensor is an acoustic sensor, and a soundproof material for preventing interference of the acoustic signal is inserted inside it.

4. An apparatus for exploring the state of the ground excavated by a boring drill, comprising: a hollow cylindrical sensor disposed inside at least two of the plurality of hollow boring drills, through which the muddy water during excavation can pass; and a circuit for exploring the state of the ground by using an acoustic signal that directly propagates between the cylindrical sensors installed in a plurality of boring holes. A ground exploration apparatus using a boring drill, characterized by comprising the above.

5. The ground exploration apparatus using a boring drill according to claim 4, characterized in that the transmission and reception directions of the cylindrical sensor are switched.

6. The ground exploration apparatus using a boring drill according to claim 4 or 5, characterized in that the cylindrical sensor is an acoustic sensor, and a soundproof material for preventing interference of the acoustic signal is inserted inside it.

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