JP2019078549A - Face front probing method - Google Patents

Abstract

To easily install a receiver in a tunnel hole without major preparation work and to accurately estimate a direction in which a three-dimensional distribution state or a reflection surface position of a face front reflection surface.SOLUTION: A vibration reception unit having vibration sensors in the x direction, the y direction and the z direction is in pressure contact with a pit wall surface via a lock bolt. The reception unit captures seismic waves propagating through the pit wall. The waveform data of each of the acquired seismic waves are processed to extract a measurement waveform of a specific low frequency range. A waveform of a reflected wave having characteristics similar to those of the initial waveform is extracted from respective measurement waveforms. The reflection surface position is measured based on the waveform data of the reflection waves.SELECTED DRAWING: Figure 2

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method for searching a face in advance, which is used to predict a geological structure in front of a face when drilling and constructing a tunnel or the like.

  When drilling a mountain tunnel, it is important to grasp the nature of the ground that extends to the front of the face with high accuracy and with high precision, in order to proceed efficiently and safely the entire excavation work including support work.

  In recent tunnel excavation construction, an HSP (Horizontal Seismic Profiling) method that generates elastic waves from one oscillation point to the ground and receives reflected waves on the reflection surface at multiple receiving points located near the wellhead. Or, blast for exploration, measure the elastic wave by this blasting with a seismometer, and estimate the geological change in front of the face by this measured elastic wave, such as TSP (Tunnel Seismic Prediction) method, elastic wave (elastic wave reflection) The technique of face forward exploration using the method is widely used.

Patent Document 1 proposes a method for searching in front of a face using this type of elastic wave reflection method.
This face forward search method is shown in FIG. In this face forward exploration method, a plurality of geophones are provided in the vicinity of the tunnel wall surface, and generated by blasting for excavating the face, drilling drill or the like, and the waveform reflected back to the discontinuous face in front of the face is measured.

  In this method, first, holes H are opened with a drill or the like on the left and right of the wall surface of the tunnel T separated from the face T1, and a plurality of geophones S (receiver points) are installed on each. In this case, for example, four geophones S are installed on the left and right. Further, a plurality of geophones S are installed on the wall surface of the tunnel T at the rear thereof. In this case, a plurality of geophones S are installed on the circumference of the wall of the tunnel T. For example, five geophones S on the circumference are disposed at two ends of the horizontal line, one at the upper end of the vertical line, and two in between. Also in this case, the geophone S is attached to the tunnel wall using a hook-shaped plate. The hook-shaped plate comprises a receiver mounting portion and a base portion, and the base portion is provided with a hole at the center for the anchor, and the receiver mounting portion is provided with a hole for the geophone at the center. Drill holes for anchors on the wall of the tunnel T, set the base of the hook plate to the holes, install the anchors in the holes, and connect to the rock. The anchor grouts the wall around the anchor, tightens it with a screw, and fixes it to the wall of the tunnel T. Then, the receiver S is attached to the hole of the receiver mounting portion.

Next, for face drilling, vibration is generated by blasting, a breaker, a drilling drill or the like to generate a vibrating wave. The point at which vibration such as blasting, breaker, drilling drill, etc. occurs at this time is the oscillation point.
Thus, vibration is generated from an oscillation point generated by face drilling, and vibration waves reflected back to the fault in front of the face and returned into the tunnel T are measured by a plurality of geophones S on the wall surface of the tunnel T. A large number of measurement waves are obtained from a combination of a plurality of oscillation points and a plurality of geophones S.

Then, the geological structure in front of the face is estimated by the following processing procedure.
First, tomographic analysis is performed using the direct wave propagated from the oscillation point to the receiving point. The data acquisition device storing direct wave data measured at the receiving point is removed and connected to a personal computer. Tomographic analysis is performed based on the direct wave data read from the data acquisition device on a personal computer. By performing tomography analysis, the velocity distribution of the ground between the oscillation point and the receiving point is calculated. The velocity distribution of the ground in front of the face is assumed from the geological condition of the tunnel T and the velocity distribution of the ground between the oscillation point and the receiving point.
Next, a grid point is set in front of the face including the oscillation point and the receiving point.
Subsequently, using the assumed velocity distribution, the theoretical propagation time from the oscillation point to the lattice point and reflected to the receiving point is calculated.
Then, for each grid point, the waveforms measured at a plurality of the receiving points via the grid point are shifted by the theoretical transmission time, and all the amplitudes of the waveforms are added.
Then, based on the amplitude of the added waveform, a grid point having a positive value and a large absolute value is regarded as a hard rock portion, and a soil point having a negative value and a large absolute value as a weak layer portion. Estimate the geology and the means to estimate the

  As described above, in this face forward exploration method, a reflection wave specularly reflected by the reflecting face in front of the face of the seismic wave artificially generated in the tunnel pit is detected, and the geological change in front of the face is estimated using this reflected wave data Do. By using a multi-wall geodetic device embedded in a pit wall, the incident direction of the seismic wave becomes accurate, and the estimation accuracy of the reflecting surface in front of the face can be improved.

JP, 2001-99945, A

  However, in the conventional face forward exploration method (hereinafter referred to as method 3), holes are drilled on the left and right sides of the tunnel wall away from the face and a plurality of geophones are installed inside the left and right rock. Also, in actual construction, it is necessary to drill a hole at a depth of about 4 m from the tunnel wall, install the geophone in the hole, and then unify the rock with the geophone by grout etc. There is a problem that the installation work of the tunnel requires a large amount of preparatory work and that the construction work of a normal tunnel must be interrupted because the face area is occupied.

  The present invention solves such conventional problems, and in this type of face forward exploration method, it is possible to easily install a seismograph in a tunnel pit without requiring a large preparatory work, and The purpose is to be able to accurately estimate the three-dimensional distribution of the reflecting surface in front of the face and the direction in which the reflecting surface position appears, although it is a simple installation of the seismograph.

In order to solve the above-mentioned subject, the face forward search method of the present invention (1) is
A seismograph is installed in the tunnel, a seismic wave is generated in the tunnel, a reflected wave reflected on the geological boundary surface in front of the tunnel face is received by the seismograph, and waveform data of the reflected wave is analyzed by known analysis processing In the face-to-face exploration method for estimating the geological boundary surface in front of the face by measuring the reflection surface position of the reflected wave by performing
As a seismometer, using a vibration receiving unit in which a multi-component vibration receiving sensor having a three-dimensional vibration receiving sensor in at least the x direction, y direction and z direction is disposed in a case having a lock bolt insertion portion in the center,
A lock bolt is driven from one end to a predetermined position on the tunnel wall surface where the vibration receiving unit is to be installed, and the other end of the lock bolt is left on the shaft surface as a vibration receiving unit attachment portion.
The vibration receiving unit mounting portion of the lock bolt is inserted through the lock bolt insertion portion through the lock bolt insertion portion, the vibration receiving sensor of the x direction in the axial direction of the tunnel, the vibration receiving sensor of the y direction in the tunnel The vibration receiving sensor for the z direction is installed on the wall surface so as to be in the axial direction of the lock bolt in the vertical direction, and then the nut is tightened on the vibration receiving unit attachment portion of the lock bolt to receive the vibration receiving The unit is pressed onto the well surface and integrally installed on the well surface,
Each seismic sensor of the seismic receiving unit captures seismic waves propagating through the wellhead, processes the acquired waveform data of each seismic wave, and extracts a measured waveform of a specific low frequency region from the respective waveform data, and the individual measurement The waveform of the reflected wave having the same feature as the initial movement waveform is extracted from the waveform, and the reflection surface position of each reflected wave is measured based on the waveform data of each reflected wave.
Make it a gist.
In this case, a plurality of lock bolts are driven at least at the top end and the right and left side walls of the tunnel wall at right angles to the wall surface, and the plurality of vibration receiving units are at least via the lock bolts. It is preferable that the end and the left and right side walls be in pressure contact.
Further, in this case, it is preferable to extract a measurement waveform of a specific low frequency region from the acquired waveform data of seismic waves by capturing with the multi-component vibration receiving sensor of the vibration receiving unit by filter processing.

Moreover, the face forward search method of the present invention (2) is
A seismograph is installed in the tunnel, a seismic wave is generated in the tunnel, a reflected wave reflected on the geological boundary surface in front of the tunnel face is received by the seismograph, and waveform data of the reflected wave is analyzed by known analysis processing In the face-to-face exploration method for estimating the geological boundary surface in front of the face by measuring the reflection surface position of the reflected wave by performing
As a seismometer, using multiple receiving sensors,
A plurality of lock bolts are driven in different directions from one end in a predetermined position of the tunnel wall surface where the vibration receiving sensor is installed, and the other end of the lock bolt is left on the tunnel wall and the other is the lock bolt Let the other end face of the end be the vibration sensor mounting part,
The vibration receiving sensor is attached as a single component sensor having directivity in the major axis direction of the lock bolt to the vibration receiving sensor mounting portion of the lock bolt which is driven into the wall surface of the borehole,
Each seismic sensor captures seismic waves propagating through each rock bolt, processes the acquired waveform data of each seismic wave, and extracts a measured waveform of a specific low frequency area from each waveform data, and from the respective measured waveforms The waveform of the reflected wave having the same feature as the initial movement waveform is extracted, and the reflection surface position of each reflected wave is measured based on the travel time difference of each reflected wave.
Make it a gist.
In this case, a plurality of lock bolts are driven at least at the top end and the right and left side walls of the tunnel wall at right angles or diagonally to the tunnel wall respectively, and a plurality of vibration receiving units are drilled via the respective lock bolts. It is preferable to install at the ceiling end of the wall, left and right side walls.
Further, in this case, the lock bolts are driven at the same position on the tunnel wall surface at the same position with the lock bolts orthogonal to each other, and the plurality of vibration receiving units are arranged at the same location on the tunnel wall surface via the lock bolts. You may install it.
Further, in this case, it is preferable to extract a measurement waveform of a specific low frequency region of 20 Hz or more and 250 Hz or less by filter processing from the acquired waveform data of seismic waves captured by a plurality of vibration receiving sensors.

  According to the method of the present invention (1), as the seismometer, a multi-component vibration receiving sensor having at least the x direction, y direction and z direction vibration receiving sensor is disposed in the case having the lock bolt insertion portion at the center. The lock bolt is driven at a predetermined position on the tunnel wall surface using the vibration receiving unit, and the vibration receiving unit is attached to the other end of the lock bolt through the lock bolt insertion part. In the axial direction of the tunnel, install the vibration sensor in the y direction in the vertical direction of the tunnel, and install the vibration sensor in the z direction in the axial direction of the lock bolt on the pit wall surface, By tightening the nut, the vibration receiving unit is pressed against the wall surface and integrally installed on the wall, and each vibration receiving sensor of the vibration receiving unit Capture seismic waves to be planted, process the waveform data of each acquired seismic wave data, extract the measurement waveform of a specific low frequency area from each waveform data, and obtain the same characteristics as the initial movement waveform from the individual measurement waveforms Since the waveform is extracted and the reflection surface position of each reflected wave is measured based on the waveform data of each reflected wave, the seismograph is easily installed in the tunnel pit without requiring a large preparatory work. In addition, according to this method as well, a plurality of geophones are embedded inside the well wall and the reflected wave is measured In the same way as with the conventional method, it is possible to accurately estimate the three-dimensional distribution of the reflecting surface in front of the face, while simply installing such a seismometer on the tunnel pit wall surface. Can exhibits the individually effect of its own invention that.

  According to the face forward search method of the present invention (2), a plurality of vibration receiving sensors are used as seismometers, and a plurality of lock bolts are mutually set at predetermined positions in the tunnel wall where the respective vibration receiving sensors are installed. Each vibration sensor is attached as a single component sensor with directivity of the long axis direction of the lock bolt to the vibration sensor mounting part of the other end of the lock bolt at the other end by driving in different directions and leaving each vibration sensor on the wall surface Seize seismic waves propagating through each rock bolt, process the acquired waveform data of each seismic wave, extract measurement waveform of specific low frequency area from each waveform data, and obtain the same characteristics as the initial movement waveform from the individual measurement waveforms. Since the waveform of the reflected wave is extracted and the reflection surface position of each reflected wave is measured based on the travel time difference of each reflected wave, the tunnel The seismograph can be easily installed without the need for extensive preparatory work. Furthermore, even with this method, a plurality of geophones are embedded in the bedrock and the reflected wave is measured, for example, according to the conventional method 3 or the like The similar behavior can be obtained in the method of and the reflected wave of the component in the direction of the major axis of the lock bolt, and such a simple installation of the seismograph on the tunnel pit wall surface, similar to the conventional method The effects unique to the present invention are that the three-dimensional distribution of the reflecting surface in front of the face can be accurately estimated.

The figure which shows the face front exploration method (method 1) by the 1st Embodiment of this invention. Diagram showing installation type of vibration sensor in method 1 Diagram showing the concept of method 1 The figure which shows the face forward exploration method (method 2) by a 2nd embodiment of the present invention Diagram showing installation type of vibration sensor in method 2 Diagram showing the concept of method 2 Diagram showing the frequency characteristics of measurement data by method 1, method 2 and conventional method (method 3) The figure which extracted and displayed the measurement waveform of the frequency band of 20-250Hz by filter processing from the measurement data of the seismic wave of three components of x direction, y direction, and z direction by method 1 and method 3. The figure which drew the locus of the initial movement waveform (waveform of the first wavelength (1st wavelength)) extracted from the measurement waveform of the x direction of the method 1, the method 2 and the method 3 and the z direction (Lissajous figure) Diagram showing the conventional method (3)

Next, an embodiment of the present invention will be described with reference to the drawings.
The first embodiment is shown in FIG. 1, FIG. 2 and FIG.
As shown in FIG. 1, this face forward exploration method (hereinafter referred to as “method 1”) utilizes elastic wave reflection method, installs seismometer 1 in tunnel T, generates seismic waves in tunnel T The reflection wave reflected at the geological boundary in front of the tunnel face is received by the seismograph 1, and the waveform data of the reflection wave is analyzed by known analysis processing to measure the position of the reflection face of the reflection wave. Estimate the geological boundary ahead.

In this method 1, as shown in FIG. 2, the seismometer 1 has the vibration receiving sensor 12 in at least the x direction, y direction and z direction in the three-dimensional direction in the case 11 having the lock bolt insertion portion 10 at the center. A receiving unit 12U in which the multi-component receiving sensor 12 is disposed, and a recording device (not shown) such as a data logger for recording waveform data acquired by the receiving unit 12U are used. Also, in order to install the vibration receiving unit 12U in the tunnel T, attention is paid to the lock bolt driven into the rock in the support work of the NATM method, and the lock bolt 2 is used as an installation anchor of the vibration receiving unit 12U.
The lock bolt 2 is driven from one end of the lock bolt 2 at a predetermined position on the tunnel wall surface where the vibration receiving unit 12U is installed, and a part of the other end of the lock bolt 2 (about 3 cm in this case) It is left as a receiving unit attachment part 21 in FIG. The vibration receiving unit 12U passes the vibration receiving unit attachment portion 21 of the lock bolt 2 drilled into the pit W in the center lock bolt insertion portion 10, and the vibration receiving sensor 12 in the x direction receives the vibration receiving sensor 12 in the y direction in the axial direction of the tunnel T. After installing the vibration sensor 12 in the z direction in the vertical direction of the tunnel T and the axial direction of the lock bolt 2 on the pit wall surface of the pit wall W of the tunnel T, The reaction force is applied to the pit wall W by tightening the nut 3 and the vibration receiving unit 12U is pressed against the pit wall surface and integrally installed on the pit wall W. Then, a recording device is connected to each of the vibration receiving sensors 12 of the vibration receiving unit 12U via a communication cable or wirelessly, and the recording device is installed near the vibration receiving unit 12U (not shown).

  Also, in this case, as shown in FIG. 1A, the vibration receiving unit 12U is installed at one point of the pit wall surface in the tunnel T, and the behavior of the pit wall W (rock mass) (multicomponent (3 Component) reflected wave) to estimate the distribution of the reflecting surface in front of the face, but at least the rock bolts 2 should be drilled at the top end of the tunnel wall W and the left and right side walls respectively. Preferably, a plurality of vibration receiving units 12U are installed in pressure contact with at least the top end and the left and right side walls of the tunnel wall W via the respective lock bolts 2 by driving them perpendicularly to the wall surface. As shown in (b), three lock bolts 2 are used, one of which is vertically driven in the top end wall surface of the pit wall W of the tunnel T, and the remaining two are respectively left and right of the tunnel T Drive horizontally on both sides of the wall Three geophone units 12U (hereinafter sometimes referred to as multicomponent geophone sensor 12.) The through each lock bolt 2 crest of the tunnel T, placed in pressure contact with the walls of the left and right side walls. By doing this, seismic waves for a total of nine channels can be obtained, and the estimation accuracy of the reflecting surface in front of the face can be improved.

In this manner, as shown in FIG. 1, in the face of the tunnel T, as in the prior art, vibrations are generated by blasting for cutting the face, breaker, drilling drill, etc. to generate seismic waves, and each of the receiving units 12U Seismic waves propagating through the well wall W (rock mass) are captured by the vibration receiving sensor 12, and the acquired waveform data of each seismic wave is subjected to known data processing and analysis processing, and the reflection surface position of the reflected wave is measured from each waveform data.
In data processing and analysis of each waveform data, as shown in FIG. 3, the measurement waveform of a specific low frequency region is extracted from each waveform data of each seismic wave captured by each vibration receiving sensor 12 of the vibration receiving unit 12U and recorded in the recording device The waveforms of the reflected waves having the same characteristics as the waveform of the initial movement (the first wavelength (first wavelength)) are extracted from the respective measurement waveforms, and the respective reflected waves are extracted based on the waveform data of the respective reflected waves. Measure the reflective surface position of. And the geological boundary front of the face is estimated from this measurement result.

  Now, as in this method 1, the multi-component vibration sensor installed inside the bedrock in the conventional method such as method 3 is installed only on the tunnel wall surface of the tunnel T, and as in the conventional method, the reflected wave data is Although the general view is that, in the method of acquiring and recording in the recording device, waveform data similar to the waveform data acquired by the multi-component vibration receiving sensor inside the rock can not be obtained, the inventors of the present invention Even in the installation format of the multi-component vibration receiving sensor 12 as in method 1, in a certain frequency range obtained by applying the acquired waveform data to the band pass filter, the multi-component vibration receiving sensor inside the rock is used It has been found that waveform data can be obtained with a signal-to-noise ratio (S / N ratio) that is close to that of waveform data. The measurement characteristics by both methods 1 and 3 have been confirmed by basic experiments, and the results are shown in FIG. 7, FIG. 8 and FIG.

FIG. 7 shows frequency characteristics of measurement data according to method 1 shown in FIG. 1 (b), method 2 described later, and method 3. By this frequency analysis, the frequency component contained in the original waveform of the seismic wave is examined. The frequency characteristics of the measurement data according to method 2 will be referred to in the second embodiment.
As shown in FIG. 7, the waveform data of the three components (x direction, y direction, z direction) of the methods 1 and 3 have characteristics as shown in the figure, and it can be seen that there is a center frequency around 100 Hz. In the method 1, about 20-250 Hz (preferably about 50-200 Hz) is targeted with this 100 Hz as a center frequency.

FIG. 8 is a graph in which the measurement waveform of the frequency band of 20-250 Hz is extracted and displayed by a band pass filter from measurement data of reflected waves of three components in the x direction, y direction and z direction according to method 1 and method 3. In the graph, the measurement waveform in the x direction by method 1 is shown by the solid line, and the measurement waveform in the x direction by method 3 is shown by the broken line. The measurement waveform in the y direction by method 1 is shown by the solid line in the middle graph, the y direction by method 3 The measurement waveform of each is shown by a broken line, the measurement waveform in the z direction by the method 1 is shown by a solid line in the lower graph, and the measurement waveform in the z direction by a method 3 is shown by a broken line.
As shown in FIG. 8, the behavior of the pit wall surface in the tunnel T acquired by method 1 from each measurement waveform in the x direction, y direction and z direction and the pit wall W acquired by method 3 (inside the rock (deep portion)) The same behavior is seen in the low frequency (20-250 Hz) region of the behavior of the first wave of the measurement waveform of the method 1 (first wave (first wavelength)) and the measurement waveform of the method 3 It can be seen that a similar waveform is obtained in the initial movement waveform (the waveform of the first wavelength (the first wavelength)). The first one wavelength is a P wave, and the same method of swinging is applied to both the waveform of method 1 and the waveform of method 3, and S waves and surface waves are mixed in the waveform of the subsequent wave that follows this It is considered that the P wave also moves in the same manner, and the P wave component of the reflected wave, that is, the primary reflected wave also moves in the same manner. So, in this method 1, the P wave which comes especially to the 1st wavelength of a seismic wave is made into the source of a forward search.

FIG. 9 (method 1) is a Lissajous drawing of the locus of the initial movement waveform (the waveform of the first wavelength (the first wavelength)) extracted from the measurement waveforms in the x direction, y direction and z direction of method 1 and method 3 of FIG. It is a figure, and these waveforms represent the measurement characteristics of method 1 and method 3. In FIG. 9 (Method 1), the waveform represented by the solid line is the waveform of Method 1, the waveform represented by the broken line is the waveform of Method 3, and both have similar waveforms. It can be seen that similar measurement characteristics are obtained for the components.
As described above, it is confirmed that the measurement waveform according to the method 1 is not inferior to the measurement waveform according to the method 3 and that the method 1 can also perform measurement with substantially the same three-dimensional directivity as the method 3 did.

  Thus, an initial movement waveform (first wavelength (first wavelength)) is extracted from the individual measurement waveforms in the low frequency region described above, and a subsequent wave having characteristics similar to the initial movement waveform from the individual measurement waveforms, that is, primary reflected waves If the waveform is extracted, imaging of the reflection surface of each reflected wave can be performed by performing known analysis processing (stacking processing, migration processing, etc.) on the waveform data of these reflected waves.

  Therefore, in this method 1, as shown in FIG. 3, three component seismic waves propagating through the tunnel wall W are captured by the multi-component seismic sensor 12 and waveform data (original waveform) of each acquired seismic wave is firstly Filter processing with a band pass filter to extract a measured waveform in the low frequency region of 20-250 Hz from each waveform data of three components, and the same as the initial movement waveform (first wavelength (first wavelength)) from the respective measured waveforms Extract the waveform of the reflected wave having features. Next, so-called stacking processing is performed to superimpose a plurality of measurement data, and waveform data of the same component is superimposed to improve resolution of the waveform data, and thus an initial movement waveform (first The waveform of the primary reflected wave having the same characteristics as the wavelength (first wavelength) is extracted. Then, the time cross section obtained by the above processing is converted to a distance cross section by migration processing (for example, the difraction stack method), the arrival direction and reflection position of each reflected wave of the three components are calculated, and each reflection The reflection point of the wave is extracted to predict the reflection surface three-dimensionally. Thus, the geological boundary that appears vertically and horizontally in the tunnel T at the time of tunneling is estimated.

As described above, according to this method 1, even if the multi-component vibration receiving sensor 12 is installed on the wall surface of the tunnel T as the seismometer 1, the multi-component vibration receiving sensor 12 is locked to the wall surface of the tunnel T The pressure wave is installed integrally by bolt 2 and nut 3 and the seismic wave which propagates the pit wall W by this multi-component vibration receiving sensor 12 is captured, the waveform data of each acquired seismic wave is data processed, and the low frequency wave from each waveform data The measurement waveform of the region is taken out, the waveform of the reflected wave having the same feature as the initial movement waveform is extracted from the individual measurement waveform, and the arrival direction of each reflected wave acquired based on the waveform data of the respective reflected waves Since the reflection surface position is measured, the seismograph 1 can be easily installed in the tunnel T without any large preparatory work, and moreover, according to the method 1, a plurality of seismometers can be provided. For example, it is possible to obtain substantially the same measurement characteristics in the three-component reflected wave as in the conventional method such as the method 3 in which a geophone is embedded in a tunnel wall and the reflected wave is measured. The three-dimensional distribution of the reflecting surface in front of the face, that is, the geological boundary surface in front of the face can be accurately estimated, as in the conventional method, though it is a simple installation on the tunnel pit wall surface.
And, in this method 1, particularly, since the lock bolt 2 used for supporting is used for the installation anchor of the vibration receiving sensor 12, the preparation work can be easily performed in a short time as compared with the conventional method such as the method 3. Also, because it measures using construction equipment, it is easy to measure and inexpensive.
In addition, since the geological boundary surface ahead of the tunnel face can be grasped three-dimensionally, it is possible to predict the location where the change of geology starts (descent side or step before, right side or left side) when the tunnel is excavated. It can be used for construction management and safety management at the time of excavation.

The second embodiment is shown in FIG. 4, FIG. 5 and FIG.
As shown in FIG. 4, this face forward exploration method (hereinafter referred to as method 2) uses the elastic wave reflection method as in method 1, and the seismometer 1 is installed in the tunnel T, and the tunnel The seismic wave is generated in T and the reflected wave reflected on the geological boundary surface in front of the face of the tunnel T is received by the seismograph 1, the waveform data of the reflected wave is analyzed by known analysis processing and the reflecting surface of the reflected wave Geological boundaries in front of the face are estimated by measuring the position.

In this method 2, as shown in FIG. 5, a plurality of vibration receiving sensors 13 and a recording device (not shown) for recording waveform data acquired by these vibration receiving sensors 13 are used as the seismograph 1. Also, in order to install these vibration receiving sensors 13 in the tunnel T, attention is paid to the lock bolt 2 driven into the rock in the support of the NATM method, and the lock bolt 2 is used as an installation anchor of the vibration receiving sensor 13.
The plurality of lock bolts 2 are respectively driven in different directions from one end of the lock bolt 2 at predetermined positions on the pit wall surface of the pit wall W of the tunnel T at which the vibration receiving sensor 13 is installed. The other end face of the lock bolt 2 is used as a vibration sensor attachment portion 22 while leaving a part of the above on the pit wall surface.
Each vibration receiving sensor 13 is attached as a single component sensor having directivity in the long axis direction of the lock bolt 2 to the vibration receiving sensor attachment portion 22 of each lock bolt 2 punched into the borehole wall surface. Since the lock bolt 2 has the property of being easily vibrated in the long axis direction as described later, the vibration receiving sensor 13 is treated as a single component sensor in the insertion direction of the lock bolt 2 and a multicomponent vibration receiving sensor 13 is combined. It is possible to function as a sensor. Then, a recording device is connected to each vibration receiving sensor 13 via a communication cable or wirelessly, and this recording device is installed in the tunnel T (not shown).
In this method 2, when the cross section of the tunnel is sufficiently small relative to the search range and can be ignored, in order to measure the reflected wave in a three-dimensional manner, as shown in FIG. To the top end and left and right side walls of the pit wall W, respectively, orthogonally or diagonally with respect to the pit wall (preferably in a ± 45 ° direction with respect to the side wall) and driving the plurality of vibration sensors 13 into each lock bolt 2 It is preferable to install at least at the top end and the left and right side walls of the well wall W of the tunnel T via In the case where the lock bolt 2 is driven obliquely to the wall surface of the pit, it is desirable to drive the end of the lock bolt 2 (tip end) in the direction of the cutting face. Further, as shown in FIG. 4 (b), a plurality of three or more lock bolts 2 are driven at the same position on the wall surface of the tunnel T with the respective lock bolts 2 orthogonal to each other, and a plurality of vibration sensors 13 are provided. The lock bolt 2 may be installed at the same position on the tunnel wall surface of the tunnel T. By doing this, it is possible to handle it as a multi-component vibration sensor as a whole. Also in this case, it is desirable to drive the lock bolt 2 into the wall of the well with one end (tip) of the lock bolt 2 in the face direction.

In this way, as shown in FIG. 4, in the same way as in method 3, vibrations are generated by blasting for cutting the face, breakers, drilling drills and the like at the face in the tunnel T to generate seismic waves.
Then, each seismic sensor 13 captures the seismic wave propagating through each rock bolt 2 driven into the tunnel wall W of the tunnel T, processes the acquired waveform data of each seismic wave, and generates waveform data from each waveform data in a specific low frequency region. The measurement waveform is taken out, and the waveform of the reflected wave having the same characteristics as the initial movement waveform is extracted from the individual measurement waveforms, and the travel time difference (arrival time) of the respective reflected waves from the travel time (arrival time) of each reflected wave The time difference between the two) is calculated, and the reflection surface position of each of the reflected waves is measured based on the travel time difference of each of the reflected waves.

  Now, the inventors of the present invention drive the lock bolt 2 into the wall surface of the tunnel T as in the method 2 and apply a single component vibration in the z direction to the head of the lock bolt 2 (end face of the other end of the lock bolt 2). Also in the installation type of the vibration receiving sensor to which the sensor 13 is attached, the vibration of the lock bolt 2 is taken by the vibration receiving sensor 13 and the waveform data of one component in the long axis direction of the obtained lock bolt 2 is subjected to a band pass filter. It has been found that waveform data that approximates one-component waveform data in the z-direction acquired by a multi-component vibration sensor inside a rock can be obtained only in a certain frequency region obtained. The measurement characteristics by both methods 2 and 3 have been confirmed by basic experiments, and the results are shown in FIG. 7 and FIG. In this case, similarly to the first embodiment, the vibration receiving sensors 13 in the x direction and the y direction are attached together around the head of the lock bolt 2.

FIG. 7 (Method 2) shows frequency characteristics of measurement data according to Method 2 shown in FIG. 4 (a). By this frequency analysis, the frequency component contained in the original waveform of the seismic wave is examined. As shown in FIG. 7 (Method 2), in the frequency characteristics of the measurement data according to Method 2, any waveform data in the x direction, y direction, and z direction appears larger than those of the other methods 1 and 3, and the peak shape is also Characteristically, there is a center frequency around 100 Hz, and the largest response is seen especially in the waveform data in the z direction. Therefore, this method 2 also targets about 20-250 Hz (preferably, about 50-200 Hz) with the 100 Hz as the center frequency. In the frequency characteristic of method 2, there is a peak not found in the frequency characteristic of method 3 per 500 Hz. This is considered to be due to the resonance (300 Hz-500 Hz) of the lock bolt 2. In this method 2, since it differs from the target frequency band, the resonance of the lock bolt 2 does not greatly affect.
Then, as in the first embodiment, measurement of the frequency band of 20-250 Hz by the band pass filter from the actual measurement data of the reflected wave of three components in the x direction, y direction and z direction by method 2 and method 3 When the waveform was taken out, in the method 2, the component in the x direction and the component in the y direction were not properly obtained. However, the waveform data in the z direction has almost the same movement as the waveform data in the z direction in method 3. It can be seen that, among other things, a similar waveform is obtained in the range within the first half wavelength of the initial movement waveform of the measurement waveforms of both methods 2 and 3, and the response in the z direction can be properly obtained. This initial movement waveform is a P wave, and the same method of swinging is applied to both the waveform of method 2 and the waveform of method 3. The S wave and the surface wave are mixed in the waveform of the subsequent wave that follows this, but the subsequent P wave It is considered that the P wave component of the reflected wave, that is, the primary reflected wave also performs the same movement. So, in this method 2, especially the P wave which comes in the half wavelength of a seismic wave is made into the source of a forward search.

Fig. 9 (Method 2) is a Lissajous figure depicting the locus of the initial movement waveform (waveform of the first wavelength) extracted from the measurement waveforms in the x direction, y direction and z direction of Method 2 and Method 3, and these waveforms are methods The measurement characteristics of 2 and method 3 are shown. In FIG. 9, the waveform represented by the solid line is the waveform of the method 2 and the waveform represented by the broken line is the waveform of the method 3. In the method 2 and the method 3, both the x component and the y component are different waveforms. The same waveform is seen for the z component as well, and it can be seen that the behavior similar to that of the method 3 is obtained with the z component (the component in the major axis direction of the lock bolt) of the method 2.
As described above, the measurement waveform according to method 2 is not inferior to the measurement waveform according to method 3 for the z component, and the vibration sensor 13 of the head of the lock bolt 2 uses the propagation characteristic of the vibration of the lock bolt 2 to use the z direction It was confirmed that waveform data (in the direction of the major axis of the lock bolt) could be measured.

Therefore, the reflected wave can be estimated by extracting the initial movement waveform from the individual measurement waveforms in the low frequency region described above and extracting the subsequent wave having the same feature as the initial movement waveform from the individual measurement waveforms. That is, the subsequent wave having the same characteristics as the initial movement waveform becomes the primary reflected wave. Since these primary reflected waves are measured by the vibration receiving sensor 13 at different measurement positions as shown in FIG. 4A, the time for returning from the reflecting surface is different, and a difference in arrival time occurs between the reflected waves. . The arrival direction and position of each primary reflected wave can be determined using this time difference, that is, the travel time difference.
In addition, as shown in FIG. 4B, the same applies even in the case where a plurality of lock bolts 2 are driven in different directions at the same point, and the time for each reflected wave to reach each receiving sensor 13 is different. The arrival direction and position of each reflected wave can be determined. In this case, for example, when it is expected that there is a geological boundary on the right side in front of the face, a plurality of lock bolts 2 are concentrated on the right pit W and driven in different directions. If the vibration sensor 13 is attached to the part, the arrival direction and position of each reflected wave can be determined more appropriately. Further, in this case, a stronger reaction can be taken by inserting each lock bolt 2 into the borehole wall W of the tunnel T in the face direction.

  Thus, the initial movement waveform is extracted from the individual measurement waveforms in the low frequency region described above, and the waveforms of subsequent waves having characteristics similar to the initial movement waveform, that is, the primary reflection waves are extracted from the individual measurement waveforms, and these primary reflection waves are extracted. If the travel time differences of these primary reflected waves are calculated from the travel times different from each other, the reflection surface position of each primary reflected wave can be measured based on the travel time difference of each primary reflected wave.

  Therefore, in this method 2, as shown in FIG. 6, seismic waves propagating through each rock bolt 2 driven into the pit W by a plurality of vibration receiving sensors 13 are captured, and the acquired waveform data of each seismic wave is filtered The measurement waveform of a specific low frequency region of 20-250 Hz is taken out from each waveform data, the waveform of the primary reflection wave having the same feature as the initial movement waveform is extracted from the individual measurement waveform, and the travel time of these primary reflection waves The travel time difference of each primary reflection wave is calculated from the above, the reflection position of each primary reflection wave is measured based on the travel time difference of each temporary reflection wave, the reflection point of each reflection wave is extracted, and the reflection surface is predicted. Thus, when excavating the tunnel T, the geological boundary that appears vertically and horizontally in the tunnel T is estimated.

As described above, according to method 2, even if a plurality of vibration receiving sensors 13 are installed on the wall surface of the tunnel T via the lock bolt 2 as the seismometer 1, the predetermined position of the wall surface of the tunnel T A plurality of lock bolts 2 are driven in mutually different directions, and a plurality of vibration receiving sensors 13 are left on the wall surface of the lock bolt 2 Attached as a single-component sensor with flexibility, each seismic sensor 13 captures seismic waves propagating through each lock bolt 2, processes the acquired waveform data of each seismic wave, and measures waveform of a specific low frequency area from each waveform data And extract the waveform of the reflected wave having the same characteristics as the initial movement waveform from the individual measurement waveforms, and, based on the travel time difference of the respective reflected waves, Since the position of the incident surface is measured, the seismograph 1 can be easily installed in the tunnel T with no need for a large preparatory work, and also according to this method 2, the plurality of geophones 13 are inside the rock. For example, a similar method can be obtained in the reflection wave of the component in the direction of the major axis of the lock bolt as in the conventional method such as the method 3 in which the reflection wave is embedded and measured. It is possible to accurately estimate the three-dimensional distribution of the reflecting surface in front of the face, that is, the geological boundary surface in front of the face, as in the conventional method, though it is a simple installation on the well wall of T .
And also in this method 2, since the lock bolt 2 used for support is used especially for the installation anchor of the vibration receiving sensor 13, compared with the conventional method such as the method 3, it is possible to carry out the preparation operation easily in a short time. In addition, because it measures using construction equipment, it is easy to measure and it is cheap.
In addition, since the geological boundary surface ahead of the tunnel face can be grasped three-dimensionally, it is possible to predict the location where the change of geology starts (descent side or step before, right side or left side) when the tunnel is excavated. It can be used for construction management and safety management at the time of excavation.

T tunnel W mine wall 1 seismograph 10 lock bolt insertion part 11 case 12 seismic sensor (multi component seismic sensor)
12U Receiver Unit 13 Receiver Sensor (Single-component Receiver Sensor in Z direction)
2 Lock bolt 21 Vibration receiving unit mounting part 22 Vibration receiving sensor mounting part 3 Nut

Claims (7)

A seismograph is installed in the tunnel, a seismic wave is generated in the tunnel, a reflected wave reflected on the geological boundary surface in front of the tunnel face is received by the seismograph, and waveform data of the reflected wave is analyzed by known analysis processing In the face-to-face exploration method for estimating the geological boundary surface in front of the face by measuring the reflection surface position of the reflected wave by performing
As a seismometer, using a vibration receiving unit in which a multi-component vibration receiving sensor having a three-dimensional vibration receiving sensor in at least the x direction, y direction and z direction is disposed in a case having a lock bolt insertion portion in the center,
A lock bolt is driven from one end to a predetermined position on the tunnel wall surface where the vibration receiving unit is to be installed, and the other end of the lock bolt is left on the shaft surface as a vibration receiving unit attachment portion.
The vibration receiving unit mounting portion of the lock bolt is inserted through the lock bolt insertion portion through the lock bolt insertion portion, the vibration receiving sensor of the x direction in the axial direction of the tunnel, the vibration receiving sensor of the y direction in the tunnel The vibration receiving sensor for the z direction is installed on the wall surface so as to be in the axial direction of the lock bolt in the vertical direction, and then the nut is tightened on the vibration receiving unit attachment portion of the lock bolt to receive the vibration receiving The unit is pressed onto the well surface and integrally installed on the well surface,
Each seismic sensor of the seismic receiving unit captures seismic waves propagating through the wellhead, processes the acquired waveform data of each seismic wave, and extracts a measured waveform of a specific low frequency region from the respective waveform data, and the individual measurement The waveform of the reflected wave having the same feature as the initial movement waveform is extracted from the waveform, and the reflection surface position of each reflected wave is measured based on the waveform data of each reflected wave.
Face face forward exploration method characterized by   A plurality of lock bolts are driven at least at the top end and the right and left side walls of the tunnel wall at right angles to the wall respectively, and a plurality of vibration receiving units at least through the respective lock bolts. The method according to claim 1, wherein the method is installed in pressure contact with the side wall.   The method according to claim 1 or 2, wherein a measurement waveform of a specific low frequency region is extracted by filtering from the acquired waveform data of seismic waves captured by a multi-component vibration receiving sensor of the vibration receiving unit. A seismograph is installed in the tunnel, a seismic wave is generated in the tunnel, a reflected wave reflected on the geological boundary surface in front of the tunnel face is received by the seismograph, and waveform data of the reflected wave is analyzed by known analysis processing In the face-to-face exploration method for estimating the geological boundary surface in front of the face by measuring the reflection surface position of the reflected wave by performing
As a seismometer, using multiple receiving sensors,
A plurality of lock bolts are driven in different directions from one end in a predetermined position of the tunnel wall surface where the vibration receiving sensor is installed, and the other end of the lock bolt is left on the tunnel wall and the other is the lock bolt Let the other end face of the end be the vibration sensor mounting part,
The vibration receiving sensor is attached as a single component sensor having directivity in the major axis direction of the lock bolt to the vibration receiving sensor mounting portion of the lock bolt which is driven into the wall surface of the borehole,
Each seismic sensor captures seismic waves propagating through each rock bolt, processes the acquired waveform data of each seismic wave, and extracts a measured waveform of a specific low frequency area from each waveform data, and from the respective measured waveforms The waveform of the reflected wave having the same feature as the initial movement waveform is extracted, and the reflection surface position of each reflected wave is measured based on the travel time difference of each reflected wave.
Face face forward exploration method characterized by   A plurality of lock bolts are inserted at least at the top end and the right and left side walls of the tunnel wall at right angles or diagonally to the tunnel wall respectively, and a plurality of vibration receiving units are mounted via the respective lock bolts to at least the ceiling of the tunnel wall The face front searching method according to claim 4 installed in an end, right and left side wall.   A plurality of lock bolts are driven at the same position of the tunnel wall surface in such a manner that the lock bolts cross each other at right angles, and a plurality of vibration receiving units are installed at the same position on the tunnel wall surface via the lock bolts. Or the face front exploration method according to 5.   The method according to any one of claims 4 to 6, wherein a measured waveform in a specific low frequency region is extracted by filtering processing from acquired waveform data of seismic waves captured by a plurality of vibration receiving sensors.

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