JP2000008784A - Tunnel timbering pattern selecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clarify a timbering pattern change standard. SOLUTION: A seismic exploration is made prior to excavating an unexcavated part of a tunnel 10. In the case of making the seismic exploration, an oscillating hole and a receiving hole are excavated. Elastic wave emitted from the oscillating hole is propagated to the unexcavated natural ground on the working face side and reflected by the natural ground at a boundary of different texture, and the reflected elastic wave is received by an accelerometer installed in the receiving hole. In this seismic exploration, a large number of reflection surfaces 16a-16e appear, and parts indicated by dotted lines are reflection surfaces where rock texture changes from soft to hard, while a part indicated by a two-dot chain line is a reflection surface where rock texture changes from hard to soft. In the appearing status of the reflection surfaces 16a-16e, the reflection surfaces where rock texture changes from soft to hard are dominant, and the reflection surface 16b with largest reflection energy also changes from soft to hard, so that the natural ground in front of the working face is predicted to be better. In an execution timbering pattern, a timbering pattern CI is therefore changed to simpler CII in correspondence with natural ground classification C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for selecting a tunnel support pattern.

[0002]

2. Description of the Related Art Before excavating a mountain tunnel, drilling and elastic wave exploration are performed from the ground surface in advance before excavation, and rock types (mountain grade) are estimated for each section to respond to rock types. Initially, the supported shoring pattern is set.

However, when actually excavating a tunnel,
In the exploration from the ground side, there are unpredictable cracks and crush zones, etc., and it may be necessary to change the initially set support pattern, and in the construction work, excavation while predicting the ground grade in front of the tunnel face That is being done.

[0004] Such prediction of the ground mass grade is usually performed by a boring survey from a face or a non-core drilling survey by a jumbo, but has the following problems.

[0005]

That is, in the boring survey, since the core can be directly observed, the ground grade can be accurately determined, but the excavation work of the tunnel must be stopped for several days, and the construction efficiency is reduced. However, there is a problem that the temperature is greatly reduced.

[0006] In addition, the non-core drilling investigation using a jumbo has a problem that the drilling length is limited, and if jamming occurs, the rod cannot be collected.

To solve such a problem, an elastic wave generated in a tunnel is projected onto an unexcavated portion, and an elastic wave survey in which an elastic wave reflected on a portion having a different rock quality is applied is used. A method is conceivable in which the construction is performed while predicting the ground grade in front of the tunnel face.

[0008] Such elastic wave exploration can be performed 100 to 100 times at one time.
Since the exploration of about 150 m is possible and the exploration is completed in about 60 minutes, the above-mentioned problem can be solved without affecting the tunnel excavation work and without necessity of drilling.

However, in such an elastic wave exploration, a plurality of anti-slope surfaces are usually detected, and based on which reflection surface,
There is a problem that it is difficult to determine whether to use the support pattern.

The present invention has been made in view of such a conventional problem, and an object of the present invention is to clarify a change standard of a shoring pattern so as to reduce the actual ground grade. It is an object of the present invention to provide a method of selecting a tunnel support pattern capable of selecting an appropriate support pattern.

[0011]

In order to achieve the above object, the present invention provides a method for selecting a shoring pattern to be installed along an excavation wall surface of a tunnel. Seismic wave exploration of the unexcavated ground side is performed sequentially from the inside, and the initial support pattern selected by the exploration from the surface side is changed based on the reflection surface with the highest reflected energy obtained by this elastic wave exploration I did it. According to the method of selecting the tunnel support pattern configured in this manner, the reflection surface having the largest reflected energy in the elastic wave exploration most clearly indicates the place where the rock quality changes from hard to soft or from soft to hard. Therefore, it is most suitable as a reference when changing the shoring pattern. Further, the reflection surface having the largest reflection energy can be easily and clearly recognized by anyone.
Therefore, by changing the initial support pattern according to this criterion, it is possible to select a support pattern suitable for the actual ground grade while avoiding mistakes in the change, and to overdesign the initial support pattern. Without this, it is possible to secure economical efficiency and to make the defect of the initial support pattern appropriate. The change of the shoring pattern by the elastic wave exploration can be applied to the shoring pattern immediately before the face in which the initial setting pattern is changed in the execution work. According to this configuration, the above-described criterion can be applied even when the initial setting support pattern is appropriately changed at the execution site according to the properties of the ground. The change of the initial setting support pattern can be performed based on the measurement result obtained in the elastic wave exploration in the vibration receiving hole provided on the same side as the oscillation hole. According to this configuration, the reliability of the elastic wave exploration is increased as compared with the case where the measurement result obtained from the vibration receiving hole provided on the side different from the oscillation hole is used.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG.
1 shows an embodiment of a method for selecting a tunnel support pattern according to the present invention.

In the method of selecting a tunnel support pattern shown in FIG. 1, first, before excavation of the tunnel 10, a boring survey, an elastic wave exploration, and the like are performed from the surface side of the ground to determine the ground grade. .

The criteria for determining the ground mass grade are determined, for example, as shown in Table 1 below for a boring survey in a road tunnel.

[0015]

[Table 1]

Using this Table 1, a boring survey is carried out at predetermined intervals, and the state of the collected core is applied to Table 1.
The ground grade along the length direction of the tunnel 10 to be constructed is uniquely determined.

In the example shown in FIG. 1, about 115 m from the wellhead
The section up to is ground grade D, and then there is a section of ground grade C of about 93 m, and the ground grade B section of 52 m, the ground grade C section of 72 m, and the ground grade C of 82 m Sections are continuous.

When the ground grade is determined in this way,
A shoring pattern corresponding to this ground grade is initially set. Table 2 below shows the relationship between the ground grade used for excavation of the road tunnel and the support pattern, and using this table, when the ground grade is determined, The shoring pattern is determined almost uniquely.

[0019]

[Table 2]

When the ground grade is determined as described above and the initial support pattern is selected, the tunnel 10 is actually excavated. In the example illustrated in FIG. 1, the section from the wellhead to about 300 m is provided with the shoring according to the initially set shoring pattern.

In the section immediately before the face, the initially set support pattern was CI, but this support pattern is changed based on the excavation condition when the work is actually performed, and the support pattern immediately before the face is changed. CII.

Then, before excavating the unexcavated portion, elastic wave exploration is performed. When performing elastic wave exploration, a plurality of oscillation holes 12 are provided on one excavation side of the already excavated tunnel 10, and one vibration receiving hole 14 is provided on the side of the tunnel 10 on the same side as the oscillation hole 12. Excavated.

A high-speed explosive and an electric detonator are inserted into each of the oscillating holes 12 to explode sequentially. The elastic wave generated by the explosion propagates to the unexcavated ground on the face side, and if there is a part with different geology in the ground, it is reflected at the boundary, and the reflected elastic wave is installed in the receiving hole 14. The data is received by a high-sensitivity accelerometer, converted into an electric signal, and recorded on a recording device.

In such an elastic wave exploration, an exploration of about 100 to 150 m ahead of the face is possible, and a large number of reflecting surfaces 16 are provided corresponding to boundaries of different geological features.
a to 16e appear.

The appearance of the reflection surfaces 16a to 16e is shown at the bottom of FIG. The reflection surfaces 16a to 16d shown in FIG.
16e is a reflection surface 16a, 16b, 16c, 16e in which the rock quality changes from soft to hard in the portion indicated by the dotted line, and a reflection surface 16 in which the rock quality changes from hard to soft in the portion indicated by the two-dot chain line.
d.

Of these reflecting surfaces 16a to 16e, the portion indicated by a double dotted line is the reflecting surface 16b having the largest reflected energy. Such reflection surfaces 16a-
When 16e is obtained, in the present embodiment, the initial support pattern is changed based on the reflective surface 16b having the largest reflected energy.

That is, first, the reflecting surface 1 shown in FIG.
In the appearance situation of 6a to 16e, the reflection surface where the rock quality changes from soft to hard is dominant, and the reflection surface 16b having the largest reflection energy also changes from soft to hard, so the ground in front of the face is Is expected to be better than now.

Therefore, the portion excavated immediately before the elastic wave exploration, that is, the support pattern immediately before the face is CII
Is changed to a simpler CI.

When the change of the shoring pattern is determined in this way, excavation of the ground in front of the face is performed, and the changed shoring pattern CI is installed on the excavation wall surface to spray lining concrete or the like. Thereby, the tunnel 10 corresponding to the ground grade C is constructed.

When the tunnel 10 of a predetermined section is constructed,
The oscillating hole 12 and the vibration receiving hole 14 are excavated again in the tunnel 10 to perform an elastic exploration, and based on the result, the initial setting support pattern is changed, and the excavation is continued.

Such an elastic wave exploration is performed at a distance of about 100 to 150 m, and the support pattern is changed with reference to the reflection surface having the largest reflection energy.

In the above embodiment, the case where the supporting pattern immediately before the face is changed based on the reflecting surface 16b having the largest reflected energy in the elastic wave exploration has been exemplified. This was also done because the actual support pattern was more in line with the actual condition.However, if the initial support pattern and the support pattern match, the reflected energy of the elastic wave Will substantially change the initial support pattern based on the largest reflective surface 16b.

Now, when the support pattern is selected as described above, the reflection surface 16b having the largest reflected energy in the elastic wave exploration most clearly shows the place where the rock quality changes from soft to hard. It is most suitable as a standard when changing the shoring pattern.

The reflection surface 16b having the largest reflection energy can be easily and clearly recognized by anyone.

Therefore, by changing the initial support pattern or the support pattern immediately before the elasticity exploration according to this criterion, it is possible to select a support pattern suitable for the actual ground grade while avoiding an error in the change. This makes it possible to eliminate the over-design of the initial support pattern and thereby secure the economy, and to make the defect of the initial support pattern appropriate.

Further, in the present embodiment, the change of the initial support pattern and the support pattern immediately before the elastic exploration are performed by the measurement obtained by the vibration receiving hole 14 provided on the same side as the oscillation hole 12 in the elastic wave exploration. The method can be performed based on the result. According to this method, the reliability of the acoustic wave exploration is increased as compared with the case where the measurement result obtained from the vibration receiving hole 14 provided on the side different from the oscillation hole 12 is used.

[0037]

As described above in detail in the embodiments,
According to the method for selecting a tunnel support pattern according to the present invention, it is possible to select a support pattern suitable for an actual ground grade by clarifying a change criterion of the support pattern.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of a method for selecting a tunnel support pattern according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Tunnel 12 Oscillation hole 14 Vibration receiving hole 16 Reflection surface

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yasuyuki Onishi 1-10-19 Higashisakura, Higashi-ku, Nagoya-shi, Aichi F-term in Obayashi-gumi Nagoya Branch Co., Ltd. 2D055 FB00 2G047 AA10 BA03 CB01 EA11 EA16 GG24

Claims (3)

[Claims] 1. A method for selecting a support pattern to be installed along an excavation wall surface of a tunnel, wherein, as the excavation of the tunnel progresses, an elastic wave exploration of an unexcavated ground side from inside the tunnel is sequentially performed. A method for selecting a tunnel support pattern, comprising changing an initial support pattern selected by an exploration from the ground surface based on a reflection surface having the largest reflected energy obtained by an elastic wave search. 2. The tunnel support pattern according to claim 1, wherein the change of the support pattern by the elastic wave exploration is performed on a support pattern immediately before a face whose initial setting pattern has been changed in the execution work. Selection method. 3. The change of the initial setting support pattern,
2. The method for selecting a tunnel support pattern according to claim 1, wherein the elastic wave exploration is performed based on a measurement result obtained by a vibration receiving hole provided on the same side as the oscillation hole.