JPH05113097A - Probing method of tunnel facing front ground - Google Patents

Abstract

PURPOSE:To get the accurate information of facing front ground by enabling a ground survey to be done in a short time from a facing plane without hindering a tunnel boring operation, while facilitating the work and expanding the probing frequency and its area. CONSTITUTION:In a probing method of tunnel facing front ground, a facing plane is excited by an exciter 11 attached almost to the center of the tunnel facing plane, thereby generating a Rayleigh wave 50 there. Then, the Rayleigh wave 50 propagating the facing plane is detected by both detectors 12A, 12B at two spots set up as long as the specified length apart from the exciter 11 in the radial direction, and a propagation time difference of the Rayleigh wave 50 is analyzed, thus the state of ground such as a fault breaking zone 18 or the like is probed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for exploring the ground in front of a tunnel face, and more particularly to a method for exploring the ground in front of a tunnel face used for exploring a fault crush zone, a geological boundary, etc. in front of the face.

[0002]

2. Description of the Related Art In conventional construction method, NATM construction method, or construction of a tunnel such as a mountain tunnel using a tunnel excavator, if the excavation line hits a weak geology such as a fault crush zone or a geological boundary, the rock mass may collapse. Since spring water causes an accident, increases in construction period, construction cost, etc., it is preferable to investigate the condition of the ground in front of the tunnel face in advance and take measures to minimize the influence by an auxiliary construction method.
And, as a method of investigating such fault fracture zones in advance, conventionally, surface exploration on the planned tunnel line, boring from the surface, elastic wave exploration, etc. were performed, but accurate data could not be obtained, and It is difficult to adopt these methods when there are steep mountain areas and large overburdens.
Therefore, in such a case, a method of exploring the condition of the ground in front of the face by adopting horizontal boring from the face of the tunnel was adopted.

[0003]

However, in the method based on the horizontal boring, there is a problem that the preparation and exploration work take time and the tunnel excavation work cannot be performed during that time, which causes a delay in the work. ..

Further, since the number of borings per cutting face is limited due to time constraints and the like, the obtained data will be local, so data representative of the geology of the ground in front of the cutting face should be obtained. There was a problem that it was difficult.

Therefore, the present invention has been made to solve the above problems, and it is possible to easily search the ground from a tunnel face in a short time and to accurately grasp the geology of the ground in front of the face. We will provide a method for exploring the ground in front of the cutting face of a tunnel.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above object, and is mounted on a tunnel face.
For example, an electromagnetic exciter excites the face to generate a Rayleigh wave on the face, and a detector installed at least two places apart from the exciter by a predetermined distance in the radial direction, The gist is a method for exploring the ground in front of a tunnel face by detecting only the vertical component of the propagating Rayleigh wave and analyzing the propagating waveform to investigate the condition of the ground.

Here, the Rayleigh wave is a surface wave that oscillates elliptically on a free surface and propagates in a radial direction from an exciter.
This Rayleigh wave propagates from the surface to a predetermined depth with uniform intensity, and this depth depends on the height of the frequency. That is, when the frequency is high, the depth is shallow, and when the frequency is low, the depth is deep. Therefore, by changing the frequency, it is possible to search the ground for each depth from the face face. Then, in order to analyze the ground condition, the propagation velocity of Rayleigh waves is calculated. That is,
For example, by dividing the distance between the detectors installed at two points by the time difference until the Rayleigh wave reaches each detector, the propagation velocity of the Rayleigh wave for each frequency, that is, the ground for each depth is calculated. The condition of the ground is analyzed from the obtained characteristics.

[0008]

Since the present invention is a non-destructive test using Rayleigh waves, unlike the destructive test for directly confirming the formation such as horizontal boring, its work, preparation, etc. are facilitated. Since Rayleigh waves are surface waves that propagate along the surface of the ground, unlike S waves that are difficult to generate large waves sufficient for exploration, they can easily generate waves of a certain depth. You can Moreover, since the propagation velocity of the Rayleigh wave is substantially equal to that of the S wave, it is possible to calculate the N value obtained from the propagation velocity of the S wave and other characteristic values indicating the properties of the ground.

[0009]

An embodiment of the present invention will now be described in more detail with reference to the accompanying drawings.

FIG. 1 shows that a worker enters a face of a mountain tunnel having a diameter of about 2 to 5 m by a tunnel boring machine such as a tunnel boring machine and directly mounts an exciter or a detector on the face to conduct an exploration work. It shows a configuration when performing. That is, the exploration system 10 includes an exciter 11 closely attached to the center of the face of a face, and two detectors 12A and 12B arranged in a line at a predetermined distance in the radial direction from the exciter 11. , A measurement control device 13 for controlling the frequency of vibration by the exciter 11 and processing the signals from the detectors 12A and 12B to determine the geological condition;
An output device 14 such as a display or a printer that displays the determination result, and a power amplification device 15 that supplies power to the exciter 11.

The vibrator 11 is of an electromagnetic type which vibrates the center weight 16 left and right by the action of a coil spring, and is attached to the face of the face by anchor bolts or the like via a bottom plate 17. Further, between the face surface and the bottom plate 17, a quick-setting cement or the like is interposed so as to accurately and closely fix these to efficiently generate a desired Rayleigh wave 50. Then, the exciter 11 vibrates at a predetermined frequency according to a command from the measurement control device 13 that is programmed in advance according to the type of ground, and cuts the face with a predetermined depth,
For example, a Rayleigh wave 50 that moves at a depth of 0 to 20 m is generated. The vibration of the vibration exciter 11 can be controlled stepwise for each predetermined frequency, that is, for each depth of the Rayleigh wave 50, but if a so-called random method for randomly giving vibration of a frequency within a predetermined range is adopted, It is possible to search the ground in a shorter time.

The Rayleigh wave 50 generated on the face face by the vibration of the exciter 11 propagates radially around the exciter 11 and is a set of detectors closely fixed to the face face by a quick-setting cement or the like. The vertical component is detected by 12A and 12B. Here, the exciter 11, the detectors 12A and 12B are arranged in a line, and since the distance from the detector 12A to the detector 12B is predetermined, the detector 12A closer to the exciter 11A. And the detector 12 far away
If the time difference of electroplating wave due to B is measured, the detector 12
The propagation velocity Vr of the Rayleigh wave 50 between A and 12B is calculated. And the depth of Rayleigh wave 50 increases,
When the tip reaches the fault crush zone 18 as shown in FIG. 1, its propagation velocity is affected and becomes, for example, a low velocity, so that the distance from the face to the fault crush zone 18 is estimated. In addition, the detectors 12A and 12B are connected to the exciter 1
By moving in any radial direction centered on 1 and conducting exploration in a wide range of the face, quantitatively measuring the running and dipping of the fault crush zone 18 and fault, and the accuracy suitable for tunnel construction You can get good information. If a plurality of sets of detectors 12A and 12B are used and provided in a plurality of radial directions, preferably in the vertical direction and the horizontal direction as shown in FIG. Information can be obtained more quickly. Further, the distance between the detectors 12A and 12B is preferably 1/2 of the distance from the vibration generator 11 to the detector 12A closer thereto, and the distance between the vibration generator 11 and the detector 12A is preferable. The distance is preferably about 1 m to 2 m.

Further, in the method for exploring the ground in front of the tunnel face according to the present embodiment, the exciter 11 and the detectors 12A, 12B are easily and quickly attached to the face of the face using anchor bolts or quick-setting cement. Further, since the work from the start of vibration of the vibration exciter 11 to the measurement process can be performed in a short time of about 5 minutes, for example, if a rest time or a change time of workers is used, It is possible to perform ground exploration without hindering the progress of tunnel excavation work. Further, if the pitch of the excavation direction to be searched is adjusted to be smaller than the set maximum depth of the Rayleigh wave 50 so that a part of the search data overlaps, the data of the overlapping parts are compared and the mutual measurement results are compared and corrected. By doing so, more accurate search results can be obtained.

By analyzing the measurement results, as shown in FIG. 3, for example, the propagation velocity 20 of the average Rayleigh wave 50 for the ground having a thickness of 0 to 20 m is 20.
Then, the section velocity 21, which is the propagation velocity of the Rayleigh wave 50 for each layer, is calculated and displayed, and the position of the fault fracture zone 18 can be easily read from the abnormal portion 22 of this, that is, the low velocity zone. Further, these results can be output by various programs by an easily readable display method such as a color graphic display. Also, Rayleigh wave 50
The propagation velocity of is almost equal to the propagation velocity of the S wave used in the conventional elastic wave exploration method as a body wave, so the N value, the rigidity, the Young's modulus, etc. are calculated by the formula used for the propagation velocity of the S wave. It is possible to obtain characteristic values indicating the properties of various types of ground, and it is also possible to create a columnar diagram or the like.

FIG. 4 shows a tunnel boring machine 19
Fig. 2 shows the configuration when the exploration system according to the present invention is installed. That is, the exciter 23 and the detector 24 are housed in the exciter storage box 25 and the detector storage box 26 provided on the cutter surface at the tip of the tunnel boring machine 19, and the work is not supported when the ground is cut by the cutter. In addition, the cutting of the ground by the cutter is interrupted when exploring the ground, and the exciter 2 is operated by a hydraulic jack or the like.
3 and the detector 24 are pushed out and brought into close contact with the face of the face, whereby the ground is searched. The vibration of the exciter 23 is controlled by a command from the vibration control device 29 provided in the TBM operator's cab 28 or the control analysis device 31 provided in the ground control room 30, which is sent via the vibration control cable 27, and the detector is detected. The detection result of 24 is sent to the signal processing device 33 of the TBM driver's cab 28 and the control analysis device 29 via the data transmission cable 32, and these data are analyzed. According to such a system, even if the face is not open, it is possible to automatically and safely perform ground exploration without intruding a worker, and in addition to the operation control of the tunnel boring machine 19, a total is possible. By controlling and managing, it is possible to achieve safety, automation, and rationalization of mountain tunnel construction.

In this embodiment, the case where the exploration method for the ground in front of the tunnel face according to the present invention is adopted in a mountain tunnel by a tunnel boring machine is described.
The present invention is not limited to this, and can be applied to other tunnels such as mountain tunnels and shield tunnels manufactured by the conventional method or the NATM method.

[0017]

As described above, the method for exploring the ground in front of a tunnel face according to the present invention excites a face face to generate a Rayleigh wave, and analyzes the propagation waveform of the wave to perform a ground survey. Therefore, it is possible to easily perform the work and preparation in a short time without hindering the excavation work of the tunnel. Therefore, the excavation route can be determined by frequently performing the ground exploration and obtaining the accurate ground exploration data. Even when a geological point such as a fault crush zone or geological boundary is encountered, tunnel excavation work can be performed quickly and safely while adopting an appropriate auxiliary construction method.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of an exploration system that uses an exploration method for a ground in front of a tunnel face according to the present invention.

FIG. 2 is an explanatory diagram showing an example of a case where a plurality of sets of detectors are used to perform a search in the search system shown in FIG.

FIG. 3 is a chart showing the calculation results of the propagation velocity of Rayleigh waves by the method for exploring the ground in front of a tunnel face according to the present invention.

FIG. 4 is an explanatory diagram showing a configuration when the exploration system using the present invention is mounted on a tunnel boring machine.

[Explanation of symbols]

 10 Exploration System 11 Exciter 12A, 12B Detector 13 Measurement and Control Device 14 Output Device 15 Power Amplification Device 18 Fault Fracture Zone 50 Rayleigh Wave

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuji Tatsumi, Kita-Aoyama, Minato-ku, Tokyo 2-5-8 Co., Ltd. In-house (72) Inventor Masahiro Kurodai 2-5-8 Kita-Aoyama, Minato-ku, Tokyo Within the group

Claims (1)

[Claims] 1. A face exciter mounted on a tunnel face is used to generate a Rayleigh wave by vibrating the face, and the face is separated by a detector installed at least two places apart from the exciter by a predetermined length. A method for exploring the ground in front of a tunnel face, characterized by detecting propagating Rayleigh waves and analyzing the propagating waveform to investigate the condition of the ground.