JP2013142659A - Tunnel face front investigation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tunnel face front investigation method capable of minimizing an influence of tunnel construction on cycle time and effectively grasping a width and physical property of a fault crushing belt existing in front of a tunnel.SOLUTION: A tunnel face front investigation method includes: a first investigation step S1 for extracting a reflection face having probability of a fault crushing belt in front of a tunnel face by a first elastic wave investigation method; and a second investigation step S2 for investigating a detailed position and physical property of the reflection face extracted in the first investigation step S1 by a second elastic wave investigation method.

Description

  The present invention relates to a tunnel face forward exploration method for grasping the position and width of a weak layer in front of a tunnel face.

  In the construction of a mountain tunnel, if the state of the ground in front of the face can be grasped in advance, excavation can be carried out more safely and more economically.

  In the construction of tunnels, ground conditions such as ground reconnaissance and elastic wave exploration from the ground surface are predicted in advance in the planning and design stages. It was difficult to fully understand the state of the ground of the tunnel, which is a linear structure, through the survey.

For this reason, there is a case where an exploration from the face to the front of the face is performed at the construction stage, and a position of a possible fault crushing zone is specified.
For example, in Patent Document 1, seismic waves sequentially oscillated from an oscillation point installed in a tunnel mine are received by a receiving point installed in the tunnel mine, and the estimated propagation speed of the seismic wave in front of the face by the received seismic wave data. In addition, an analysis map is created from this seismic wave data and an estimated propagation velocity, and a tunnel face front exploration method for estimating the position of the reflecting surface based on the analysis map is disclosed.

  Patent Document 2 discloses a method for exploring the front face of a face using a shallow layer reflection method, and includes a plurality of geophones arranged linearly in pores dug in the surface of the face and the outer circumferential direction of the tunnel. Investigate the front of the face by receiving elastic waves oscillated from a plurality of oscillation points arranged in a straight line on the face of the face and analyzing them based on the seismic source, propagation speed, angle, etc. A face front exploration method is disclosed.

JP 2002-139574 A JP 05-248174 A

  Although the exploration method of Patent Document 1 can capture the position of the reflective surface that may be a fault fracture zone over a section of about 100 m in front of the face, until it obtains information on the width and physical properties of the fault fracture zone. could not.

  In the exploration method of Patent Document 2, it is necessary to form pores for installing a geophone in four directions intersecting the tunnel axis direction, and to install a large number of geophones on the face surface and in the pores. Executing a large number of times may affect the cycle time of tunnel construction.

  The present invention aims to solve the above-mentioned problems, minimizes the influence on the tunnel construction cycle time, and effectively reduces the width and physical properties of the fault crushing zone existing in front of the tunnel. It is an object to propose a method for exploring the front of the tunnel face that makes it possible to grasp.

  In order to solve the above-mentioned problem, the tunnel face front exploration method of the present invention includes a first exploration step of extracting a reflection surface that may be a fault fracture zone in front of the face by a first elastic wave exploration method, And a second exploration step for grasping the detailed position and physical properties of the reflecting surface extracted in the first exploration step by the second elastic wave exploration method.

According to this tunnel face front exploration method, the first exploration process grasps the presence or absence of a reflective surface that may be a fault fracture zone, and if such a reflective surface is extracted, the second exploration process investigates in detail. By doing so, it is possible to grasp the detailed position and physical property information of the reflecting surface.
If the second exploration process is carried out only where it is necessary, the impact on the tunnel construction cycle time can be minimized.
In other words, by implementing two types of exploration methods, it is possible to efficiently estimate the position and width of a fault fracture zone of a scale that affects tunnel excavation.

When the exploration depth of the first elastic exploration method is a (m) and the exploration depth of the second elastic exploration method is b (m) shorter than a (m), When a reflective surface that may be a fault fracture zone is extracted within the front b (m), the second exploration step may be performed following the first exploration step.
Further, in the first exploration step, when a reflection surface that may be a fault fracture zone is extracted in front of the face front b (m) and within the face front a (m), b (m ) The excavation process for excavating forward may be performed between the first exploration process and the second exploration process.

In the second elastic exploration method, an operation of forming a pore extending in a direction intersecting the tunnel axis on each of the left and right sides of the tunnel, an operation of arranging an oscillation means in one of the pores, What is necessary is just to perform the work of placing the geophone in the hole and the work of receiving the elastic wave oscillated from the oscillation means by the geophone.
Furthermore, the work includes receiving the elastic wave oscillated from the oscillating means for the second time by the vibration receiving device by replacing the oscillation means in the one fine pore and the vibration receiving device in the other fine pore. Also good.

  According to this tunnel face front exploration method, more accurate data can be secured in the second exploration process.

  According to the tunnel face front exploration method of the present invention, it is possible to minimize the influence on the tunnel construction cycle time and efficiently grasp the width and physical properties of the fault fracture zone existing in front of the tunnel.

It is a flowchart which shows the outline | summary of the tunnel face front search method which concerns on this embodiment. (A) is sectional drawing which shows the outline | summary of a 1st elastic exploration method, and a reflective surface distribution map, (b) is a tunnel sectional view in a 1st elastic exploration method. (A) is a sectional view schematically showing the outline of the second elastic exploration method and Vp velocity, Poisson's ratio change rate and S wave reflection coefficient distribution diagram, (b) is a tunnel sectional view in the second elastic exploration method. is there.

Embodiments of the present invention will be described with reference to the drawings.
In the present embodiment, a case will be described in which a tunnel is dug after grasping the position and width of a weak layer in front of the face by a tunnel face forward exploration method.

  As shown in FIG. 1, the tunnel face exploration method includes a first exploration step S1, an excavation step S2, and a second exploration step S3.

  The first exploration step S1 is a step of extracting a reflection surface that may be a fault crush zone in front of the face by the first elastic wave exploration method.

For the first elastic wave exploration method, a so-called TSP method, HSP method, or the like may be employed.
In the first elastic wave exploration method, as shown in FIG. 2A, the reflection surface 5 existing within about 100 m in front of the face 3 of the tunnel 1 is extracted.

  In the present embodiment, the first exploration process is performed every time 100 m of excavation of the tunnel 1 proceeds. The frequency of performing the first exploration process is not limited.

In the first elastic wave exploration method, the oscillating means 3 is installed on the face 2 of the tunnel 1, and a plurality of geophones 4, 4,.
Then, the elastic waves that are sequentially oscillated from the oscillating means 3, 3,... And reflected by the reflecting surface 5 that may be a fault fracture zone are reflected by the geophones 4, 4,. The distance to surface 5 is measured.

In the present embodiment, the case where the oscillating means 3 is set to the face 2 has been described. However, the setting method of the oscillating means 3 is not limited. The holes may be drilled and set in the pores.
The elastic wave is oscillated by blasting dynamite, but a vibrator or a hammer may be used.

The geophones 4, 4,... Are juxtaposed along the tunnel axis direction on the left and right sides of the inner wall surface in the tunnel 1 well. The installation interval and number of the geophones 4 are not limited, but may be arranged at a pitch of 1 to 3 m, for example.
The method of setting the geophone 4 is not limited. For example, a plurality of pores extending laterally of the tunnel 1 are formed along the tunnel axis direction, and the geophone 4 is placed in each of these pores. May be installed.

The excavation step S2 is a step of excavating the tunnel 1.
The tunnel 1 is excavated by various excavation methods such as a full-section excavation method, a bench-cut method, and a guide shaft advanced method according to the natural ground conditions.

If the reflecting surface 5 is not extracted in the first exploration step S1, as shown in FIG. 1, the excavation step S2 is performed immediately after the first exploration step S1, and the tunnel 1 is dug 100 m.
This is because, within the range of 100 m ahead of the face, it is expected that safe construction is possible because of the low risk of face collapse or sudden spring water due to the fracture zone during tunnel construction.

In the first exploration step S1, when a reflective surface 5 that may be a fault fracture zone is extracted in front of the face 50m and within 100m in front of the face, the excavation step S2 is performed immediately after the first exploration step S1. Then, tunnel 1 is dug 50m. And if it excavates 50m, 2nd exploration process S3 will be implemented.
This is because, within the range of 50 m ahead of the face, it is expected that safe construction is possible because of the low risk of face collapse and sudden spring water due to the fault fracture zone when the tunnel 1 is constructed.

In the first exploration step S1, when the reflecting surface 5 that may be a fault fracture zone is extracted within 50 m ahead of the face, the excavation step S2 is performed after the second exploration step S3.
When the position and width of the fault crushing zone are confirmed in the second exploration step S3, the tunnel 1 is dug while carrying out an auxiliary method corresponding to the fault crushing zone.

  The auxiliary construction method may be appropriately selected and adopted from auxiliary construction methods such as foreground fore-polling, AGF construction method, chemical solution injection method, ground freezing method, etc., depending on the scale and situation of the fault crushing zone. .

The second exploration step S3 is a step of exploring the detailed position and physical properties of the reflecting surface 5 by a second elastic wave exploration method different from the first elastic exploration method.
The second elastic exploration method conducts exploration within a range of 50 m ahead of the face.

As shown in FIG. 1, in the first exploration process, when the reflecting surface 5 is extracted within 50 m ahead of the face, the second exploration process is performed immediately after the first exploration process.
On the other hand, in the first exploration step S1, when the reflecting surface 5 that may be a fault fracture zone is extracted in front of the face 50m and within 100m in front of the face, the excavation step S2 is performed after the first exploration step S1. After the implementation, the second exploration step S3 is performed.

In the second elastic exploration method, as shown in FIG. 3A, first, oscillation holes (pores) 6 extending in a direction intersecting the tunnel axis are formed on either the left or right side of the tunnel 1.
As shown in FIG. 3B, the oscillating hole 6 is formed by drilling in the lateral direction slightly downward from the vicinity of the spring line (SL) of the tunnel 1. In the present embodiment, the depth of the oscillation hole 6 is 23 m. The cross-sectional shape and depth of the oscillation hole 6 are not limited as long as the oscillation means 3, 3,.

When the oscillation hole 6 is formed, a plurality of oscillation means 3, 3,. In this embodiment, the oscillating means 3, 3,... Are arranged at a pitch of 1 m.
The arrangement of the oscillating means 3 is set so that the incident angle of the elastic wave oscillated from the oscillating means 3 to the reflecting surface 5 is within 25 °.
The arrangement pitch and the number of places of the oscillating means 3 are not limited.

As shown in FIG. 3A, on the opposite side of the oscillation hole 6, a vibration receiving hole (pore) 7 extending in the direction intersecting the tunnel axis is formed.
As shown in FIG. 3B, the vibration receiving hole 7 is formed by drilling in the lateral direction slightly downward from the vicinity of the spring line (SL) of the tunnel 1. In the present embodiment, the depth of the vibration receiving hole 7 is 23 m. The cross-sectional shape and depth of the vibration receiving hole 7 are not limited as long as the vibration receiving device 4 can be installed, and may be set as appropriate.

  When the vibration receiving hole 7 is formed, a plurality of vibration receivers 4, 4,... Are arranged inside the vibration receiving hole 7. In the present embodiment, the geophones 4 are arranged at a pitch of 1 m. In addition, the arrangement | positioning pitch and installation number of the geophone 4 are not limited.

  Next, elastic waves are sequentially oscillated from the oscillating means 3, 3..., And the reflected waves (elastic waves) reflected by the reflecting surface 5 are received by the receivers 4, 4.

The elastic wave is oscillated by blasting dynamite.
The elastic wave is oscillated a plurality of times (for example, 20 times) by selectively operating the plurality of oscillating means 3, 3,..., And is received by the geophones 4, 4,. Is done.

  From the data collected by the second elastic exploration method, the Vp velocity of the reflected wave is calculated from the distance between the epicenter (position of the oscillation means 3) and the receiving point (position of the geophone 4) and the arrival time of the reflected wave. The analysis method is the same as the normal shallow layer reflection method, and includes, for example, CDP ensemble creation, velocity analysis, NMO correction, CDP polymerization, migration processing, and the like.

  Based on the data collected by the second elastic exploration method, the change in the amplitude of the reflected wave is analyzed according to the distance between the hypocenter (position of the oscillation means) and the receiving point (position of the geophone 4), and the rate of change of the Poisson's ratio The S wave reflection coefficient is calculated.

Based on the calculated Vp velocity, Poisson's ratio change rate, and S-wave reflection coefficient, the detailed position and width of the reflecting surface 5 (fracture fracture zone) are estimated.
In this embodiment, so-called AVO (Amplitude Versus Offset or Amplitude Variation with Offset) analysis is applied to calculate the rate of change of Poisson's ratio and the S wave reflection coefficient, but the analysis method is not limited.

In this embodiment, more accurate data can be obtained by performing the operation (measurement operation) of receiving the elastic waves oscillated from the oscillation means 3, 3,... Secure it.
That is, first, the first measurement operation is performed with the excavation hole (pore) formed in either one of the left and right sides of the tunnel 1 as the oscillation hole 6 and the excavation hole (pore) formed in the other as the vibration receiving hole 7. To do. Next, the left and right sides are reversed, the excavation hole formed on one side is the vibration receiving hole 7, the excavation hole formed on the other is the oscillation hole 6, and the oscillation means 3, 3. The geophones 4, 4,... In the excavation holes are replaced, and the second measurement operation is performed.

  If the oscillation hole 6 is damaged by the blasting of dynamite in the first measurement operation, the vibration receiving hole 7 is newly recreated when the second measurement operation is performed.

As shown in FIG. 1, when the second exploration step S3 is completed, the excavation step S2 is performed.
If the excavation process S2 excavates 100 m from the face 2a when the first exploration process S1 is performed, the first exploration process S1 is performed again.

  In the first exploration step S1, when the reflecting surface 5 is extracted within the range of 50 m ahead of the face and within the range of 50 to 100 m ahead of the face, the second exploration step S3 is carried out (excavation step). S2) The second exploration step S3 is performed again.

  As described above, according to the tunnel face front exploration method of this embodiment, the detailed position and width of the fault fracture zone can be grasped by the second elastic exploration method. Tunnels can be excavated by design and the use of auxiliary construction methods, etc., and construction can be performed more efficiently and safely.

In addition, since the second elastic exploration method is implemented only within the range recognized as necessary by the first elastic exploration method, the influence on the tunnel construction cycle time can be minimized.
That is, by combining two types of elastic exploration methods, it is possible to effectively estimate the position and properties of the fault crush zone in front of the face.

  The second elastic exploration method obtains data with oscillation and receiving layout different from those of the first elastic exploration method, and further applies AVO analysis, which is used in the seismic exploration field. Information on width and physical properties can be obtained effectively.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiment, and the above-described components can be appropriately changed without departing from the spirit of the present invention.

  In the above-described embodiment, the case where the second elastic exploration method is performed twice in the second exploration step has been described. However, the second elastic exploration method is not necessarily performed twice, and may be performed once.

  In the above embodiment, the case where the reflecting surface is not extracted within 50 m in front of the face in the first exploration process has been described in the case of excavating up to 50 m in front of the face in the excavation process. There is no need. For example, when the reflecting surface is extracted within the range of 50 m to 60 m in front of the face, the second exploration process may be performed by excavating 30 to 40 m in the excavation process.

  In the embodiment, the exploration depth a of the first elastic exploration method is 100 m, but the exploration depth a of the first elastic exploration method is not limited to 100 m. Similarly, although the exploration depth b of the second elastic exploration method is 50 m, the exploration depth b of the second elastic exploration method is not limited to 50 m.

DESCRIPTION OF SYMBOLS 1 Tunnel 2 Face 3 Oscillating means 4 Receiver 5 Reflecting surface 6 Oscillation hole 7 Receiver hole

Claims (4)

A first exploration step of extracting a reflective surface that may be a fault fracture zone ahead of the face by the first elastic wave exploration method;
And a second exploration step for grasping a detailed position and physical properties of the reflection surface extracted in the first exploration step by a second elastic wave exploration method. When the exploration depth of the first elastic exploration method is a (m) and the exploration depth of the second elastic exploration method is b (m) shorter than a (m),
In the first exploration step, when a reflective surface that may be a fault fracture zone is extracted within b (m) in front of the face, the second exploration step is performed following the first exploration step,
In the first exploration step, when a reflecting surface that may be a fault fracture zone is extracted in front of the face b (m) and within the face a (m), the front of b (m) from the face The tunnel face front exploration method according to claim 1, further comprising a excavation step for excavating the first to the second exploration steps.   In the second elastic exploration method, an operation of forming a pore extending in a direction intersecting the tunnel axis on each of the left and right sides of the tunnel, an operation of arranging an oscillation means in one of the pores, The work of placing a geophone in a hole and the work of receiving an elastic wave oscillated from the oscillating means by the geophone are performed in front of a tunnel face according to claim 1 or 2. Exploration method.   Including replacing the oscillation means in the one pore with the geophone in the other pore and receiving the second elastic wave oscillated from the oscillation means by the geophone. The tunnel face front exploration method according to claim 3.

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