JPH11174046A - Tunnel facing front surveying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly predict geological condition on the front side in a tunnel and the like to be dug for preparing a countermeasure against a defective geologic part part previously so as to safely perform construction economically by means of a combination of four processes such as TSP, drilling logging, speed logging, and facing image processing. SOLUTION: In advance examination of a tunnel to be dug by means of a facing front survey general system, elastic wave velocity of the natural ground is measured along a track and approximate position and dimension of a fracture zone are estimated. From this information, a survey requiring section in front of the facing is determined, and firstly, existence of a surface of discontinuity to a predetermined distance in front of the facing is predicted according to an elastic wave research reflection method. When the facing approaches the surface of discontinuity, drilling logging is carried out while using a hole bored by a drill jumbo, and a fracture energy coefficient is found. Then, speed logging is carried out in the hole, in which drilling logging is carried out, and a geological condition is predicted on the basis of the elastic wave velocity. If a correlative relationship between the elastic wave velocity and the fracture energy coefficient is confirmed, from then on, a geological condition is predicted only by drilling logging.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prediction method for predicting a geological situation in front of a face as accurately as possible when excavating a tunnel or the like.

[0002]

2. Description of the Related Art Conventionally, surveys at the planning and design stages include only surface geological surveys, surface acoustic wave exploration, and boring surveys near an entrance, mainly based on elastic wave velocity and along a tunnel route. Ground classification was performed, and support patterns were set based on the ground classification. However, especially when the earth cover is large, the accuracy of the position and scale of the fault crush zone is poor at present, and a method of compensating for the survey during construction is adopted.

[0003] An advanced boring method is a reliable method for investigating the front face of a face during construction. Although this method can grasp the geological condition without fail, it cannot be carried out in parallel with the tunnel excavation, which hinders the construction.

[0004] On the other hand, there is a drill boring in which non-core boring is performed from a face with a drill jumbo used for construction. However, it is difficult to accurately predict the geological condition only by drilling speed and slime. is there.

Therefore, the present applicant discloses a method of performing rock evaluation and prediction of geology ahead of a face by using non-core boring with a drill jumbo, depending on the fracture energy of a rock (referred to as a borehole logging). (See Japanese Patent Publication No. 7-49756).

[0006] Furthermore, a method has been proposed in which a geophone is inserted into a hole formed by a drill jumbo, and an elastic wave velocity is obtained by measuring vibration from a face position. It predicts geological conditions (referred to as velocity logging).

[0007] In addition, T using the principle of the elastic wave exploration reflection method.
SP (Tunnel Seismic Predict)
There is a method called “ion”, in which a plurality of blast holes and vibration receiving holes are provided on the tunnel wall surface, and the position and inclination of the discontinuous surface in front of the face are calculated and displayed.

[0008] On the other hand, face observation is usually performed in tunnel excavation. Therefore, a face image processing system has been developed in which the face is photographed by a digital camera and the geological determination is performed. However, if the work of photographing the face and performing the geological determination is continued, the geological situation can be predicted about 5 meters in front of the face. .

[0009]

However, in the above-mentioned technology, for example, advanced boring must interrupt tunnel excavation, and exploratory boring does not affect the process, but the geological condition is determined only by slime and drilling speed. Cannot be determined accurately.

[0010] In addition, in the above-mentioned borehole logging with improved drilling, although the process is not affected, the rock mass is evaluated by using the fracture energy. Sex remains a question.

Further, the velocity logging can provide an elastic wave velocity which is a good index. However, the implementation of all sections is time-consuming and impractical, and the TSP is difficult to judge the degree of failure. It is difficult to predict any of them independently because there is an error.

Accordingly, the present invention provides a method for exploring the front face of a tunnel face, which can accurately predict the geological condition ahead of a tunnel to be excavated, take measures against a defective geological portion in advance, and can safely and economically construct the tunnel face. It is intended to be.

[0013]

According to the present invention, a preliminary survey of a tunnel to be excavated is performed to measure the elastic wave velocity of the ground along the route to estimate the approximate position and scale of the crush zone, and from this information the face is estimated. First, the required section for forward exploration is determined, and the existence of a discontinuous surface up to a predetermined distance in front of the face is first predicted by the elastic wave exploration reflection method. Then, when the face approaches the discontinuous surface, the hole using the drill jumbo A drilling log is used to determine the fracture energy coefficient, a velocity logging is performed in the drilled hole, and the geological condition is predicted by the elastic wave velocity. If the correlation with the coefficient can be confirmed, the feature is that the geological situation is predicted only from the borehole logging.

Further, according to the present invention, at the time of excavation, the excavation is performed by grasping the geological condition near the face by the face image processing system.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the entire configuration of a method for exploring the front of a tunnel face according to the present invention, and includes four sub-systems: a TSP system 1, a borehole logging system 2, a speed logging system 3, and a face image processing system 4. System, and each system has general-purpose personal computer software (for example,
Windows), and the system is integrated in the same output format. Each system is configured to input a search result to a search result evaluation system, and comprehensively evaluates a result from each system and analyzes a correspondence with a geological situation.

Further, these search results are stored in a database and can be fed back to the next search, so that the accuracy can be further improved. FIG. 2 shows an output image of the system shown in FIG. 1, which is constructed so that the search results of the respective subsystems are displayed together and the predicted geological situation can be entered. Here, reference numeral 5 denotes a tunnel, 6 and 7 denote crush zones, and 8 denotes a face.

The procedure for exploring the face in front of the tunnel will now be described with reference to FIG.

First, the preliminary survey has estimated the elastic wave velocity along the tunnel route and the approximate position and scale of the shatter zone, and based on this information, the forward geology is predicted (step S1). It is determined whether or not a forward search from inside is necessary (step S2). If there is no need, the excavation is continued (step S8), and if forward exploration is necessary, a predetermined distance in front of the face by TSP, for example, 100 to
The existence and approximate position of the crush zone up to 150 m ahead are predicted (step S3). Next, based on the above results, it is determined whether further detailed investigation is necessary (step S4). If unnecessary, the drilling operation is continued (step S8), and if investigation is necessary, drilling is performed using non-core boring holes using a drill jumbo (step S5), and calibration of the drilling log is performed. For this purpose, velocity logging is performed several times (step S9). If the correlation between the fracture energy coefficient of the borehole logging and the elastic wave velocity of the velocity logging can be grasped at the early stage of excavation, only the borehole logging may be performed thereafter. Based on the results of these investigations, the size of the crush zone, the size of the spring water, the necessity of water stoppage measures, and the like are determined (step S6).
If there is no obstacle to the excavation, the excavation is continued (step S
8) If there is a problem, measures such as ground improvement and drainage boring are performed (step S7), and excavation is performed (step S8). Then, in order to perform the excavation work while grasping the geological condition in the vicinity of the face, observation can be performed by a geological observation system using a digital camera (step S10), and the observation can be reflected on the support pattern.

FIGS. 4 to 10 show examples in which the method for exploring the front face of a face of the present invention is applied to a tunnel excavated in soft rock, and FIG. 4 shows the fracture energy coefficient on the vertical axis and the depth on the horizontal axis. This is an example in which drilling is performed using a hole formed by a drill jumbo. The fracture energy coefficient at each depth obtained by the drilling log is shown in FIG. 5, and the vertical axis represents the average fracture energy coefficient. FIG. 6 shows the slime observation results by expressing the depth on the horizontal axis, FIG. 7 shows the section speed for each 1 m obtained by velocity logging on the vertical axis, and FIG. The vertical axis represents the propagation time, and the horizontal axis represents the velocity in a section where the slope is constant in a travel time curve representing depth.

FIG. 9 shows the average fracture energy coefficient on the vertical axis and mudstone, alternation and tuff on the horizontal axis, and shows the results of drilling logs at a plurality of holes in the same tunnel including the holes shown in FIGS. It shows the relationship between the geology and the average energy coefficient, and indicates that the approximate geology can be determined by the average energy coefficient.

FIG. 10 shows the section speed on the vertical axis and the average fracture energy coefficient on the horizontal axis, and shows the average fracture energy coefficient obtained by drilling a hole in the same hole as in FIG. This shows the correlation with the travel time curve (the speed in the section where the slope is constant), but has a fairly good correlation (correlation coefficient 0.71). This is because, in the early stage of drilling, drilling and velocity logging are performed in the same hole, and if the correlation between the average fracture energy coefficient and the section speed is grasped, a simple drilling It indicates that only the implementation is required.

[0023]

The present invention is configured as described above,
The combination of TSP, drilling logging, velocity logging, and face image processing makes it possible to predict the geological condition ahead of the face, change the support pattern, inject, fore piling, etc., in advance for poor geological features Therefore, it is possible to improve the safety and economy of construction.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a method for exploring a front face of a face showing an embodiment of the present invention.

FIG. 2 is a view showing an image of an output by the method for exploring a face in front of FIG. 1;

FIG. 3 is a flowchart illustrating a search procedure of the method of FIG. 1;

FIG. 4 is a diagram showing a fracture energy coefficient as an example of a drilling log result.

FIG. 5 is a diagram showing an average fracture energy coefficient as an example of a borehole logging result.

FIG. 6 is a view showing an example of a slime observation result.

FIG. 7 is a diagram showing a section speed every 1 m, which is an example of a speed logging result.

FIG. 8 is a diagram illustrating a section speed as an example of a speed logging result.

FIG. 9 is a diagram showing an example of a relationship between geology and an average fracture energy coefficient.

FIG. 10 is a diagram illustrating a correlation between an average breaking energy coefficient and a section speed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... TSP system 2 ... Drilling logging system 3 ... Velocity logging system 4 ... Face image processing system

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takuharu Yamamoto 2-9-1, Tobita-Ki, Chofu-shi, Tokyo Kashima Construction Co., Ltd. (72) Inventor Yasuyuki Miyajima, 2-chome Tobita, Chofu-shi, Tokyo No. 19-1 Kashima Construction Co., Ltd.

Claims (2)

[Claims] 1. Preliminary survey of a tunnel to be excavated, measurement of the elastic wave velocity of the ground along the route,
The scale is estimated, the necessary section for exploration of the face in front is determined from this information, and the existence of a discontinuous surface up to a predetermined distance in front of the face is first predicted by the elastic wave exploration reflection method. At the time of the drilling, the drilling logging was performed using the hole by the drill jumbo to determine the fracture energy coefficient, and the velocity logging was performed on the drilled hole, and the geological condition was predicted by the elastic wave velocity. A method for exploring a tunnel face in front of a tunnel face, in which a geological situation is predicted only by drilling logs if a correlation between elastic wave velocity and fracture energy coefficient can be confirmed. 2. The method for exploring the front of a tunnel face according to claim 1, wherein the excavation is performed by grasping the geological condition near the face by the face image processing system during the excavation.