JP6688605B2 - Front face exploration method - Google Patents

Description

The present invention relates to a front face exploration method , and more particularly to a front face exploration method using interhole resistivity tomography technology.

  When excavating a tunnel, it is necessary to grasp the condition of the ground in advance in order to carry out safe, appropriate and prompt construction. Therefore, various technologies have been proposed for grasping the condition of the ground before the tunnel excavation or as the tunnel excavation progresses. As such a conventional technique, there is a direct method using boring (hole drilling method, advanced boring). Indirect methods include elastic wave exploration by reflection method (HSP method, TSP method, reflection tomography), FDEM, and the like.

  In addition to the electrical characteristics of the soil particles and rocks that make up the ground, the resistivity value of the ground is determined by the electrical characteristics of groundwater, air, clay minerals, etc. present in the soil gaps and bedrock cracks. Strongly reflected. Therefore, based on the determination of the specific resistance value, it is possible to search for “geological boundary”, “fault”, “groundwater”, “underground cavity”, “underground buried object” and the like. The interhole resistivity tomography exploration method is known as a technique for exploring the condition of the ground using this resistivity value.

  In the interhole resistivity tomography exploration method, when a primary magnetic field is generated in the ground by a current generated from a current electrode, an overcurrent is generated in the ground, and the eddy current induces a secondary magnetic field. The specific resistance of the ground can be obtained by measuring the response of the secondary magnetic field to the primary magnetic field with the potential electrode (see Patent Document 1).

  In the technique described in Patent Document 1, an electrode rod having an electrode portion at its tip is extended inside a casing rod, and a predetermined depth with respect to the ground in front of the tunnel face by the rotational propulsive force applied to the casing rod. Now drill the horizontal boring hole. Then, the mouth of the horizontal boring hole is closed with a mouth cap, and the hole is filled with inflowing groundwater. Further, the electrode portion (current electrode) connected to the electrical logging measuring device installed in the tunnel pit is projected from the tip of the casing rod into the boring hole via the end of the electrode rod on the tunnel side. Thereby, the specific resistance of the ground is measured between the grounding electrode (potential electrode) connected to the electrical logging device and the electrical logging is performed at the position of the electrode portion (current electrode).

JP, 2002-267764, A

  In the technique described in Patent Document 1 described above, the current is propagated by filling the horizontal boring hole with water, but it is difficult to store the water in the horizontal boring hole. That is, since the water stored in the horizontal boring hole flows out from the mouth of the hole, the mouth of the horizontal boring hole is closed using a mouth cap, but since the water has low viscosity, water leaks from rock cracks and It is difficult to completely prevent water leakage from water. Also, groundwater is used as the water stored in the horizontal borehole, but if sufficient groundwater cannot be collected, the horizontal borehole cannot be filled with water, and accurate inter-hole resistivity measurement is required. It may not be possible.

  Further, in the technique described in Patent Document 1, boring is performed using a casing rod, and the casing rod is left after drilling. This is because the hole wall of the horizontal boring hole is likely to collapse, but if a casing rod exists between the ground and the current electrode and the potential electrode, it may interfere with accurate measurement of the inter-hole resistivity. .

The present invention has been proposed in view of the above-mentioned circumstances, and using the inter-hole resistivity tomography technology, the front face of a cutting face capable of easily and accurately exploring the ground condition (specific resistance distribution) in front of the face face. The purpose is to provide a method .

The face exploration method of the present invention has the following characteristic features in order to achieve the above-mentioned object. That is, the front face exploration method of the present invention is a method for exploring the ground condition in front of a tunnel face, and at least one boring hole for installing a potential electrode in a substantially horizontal direction toward the front of the face face. And at least one boring hole for installing the current electrode, and a gel-like filling material from the tip of the hollow rod for drilling inserted in the boring hole for installing the potential electrode or the current electrode. By pulling out the hollow rod while supplying, the gel filling material is filled in the boring hole, and the hollow support rod having either the potential electrode or the current electrode attached is filled with the gel filling material. Inserting the support rod into the boring hole while sucking the filling material from the boring hole through the hollow part of the supporting rod while inserting it into the boring hole. , The potential electrode or the current electrode is installed, the potential generated by the current generated from the current electrode is measured by the potential electrode, and the geology of the ground in front of the cutting face is analyzed based on the specific resistance distribution between the current electrode and the potential electrode. It is characterized by doing.

  Further, in addition to the above-described configuration, it is preferable that a plurality of potential electrodes and current electrodes are installed along the length direction of the boring hole.

In the front face exploration method according to the present invention, a filling material (for example, a gel-like substance) is filled in the horizontal boring hole in which the current electrode and the potential electrode are installed, so that the current electrode is generated in the same manner as the vertical boring hole. However, the current for measuring the potential with the potential electrode can be reliably propagated. That is, in the horizontal boring hole, unlike the vertical boring hole, even if an attempt was made to fill the water, the water leaked from the hole, and the current could not be reliably transmitted.

According to the face exploration method according to the present invention, since the filler (eg, gel-like substance) with which the horizontal boring hole is filled has a higher viscosity than water, horizontal boring can be performed by appropriately preventing leakage. Does not leak from the mouth of the hole. Therefore, it is possible to easily and appropriately search the ground condition (resistivity distribution) in front of the face using the technique of interhole resistivity tomography.

The block diagram which shows the structure of the face forward exploration device which concerns on embodiment of this invention. The schematic diagram which shows the installation state of the face forward exploration device which concerns on embodiment of this invention. Explanatory drawing which shows the procedure of the front face exploration method which concerns on embodiment of this invention.

Hereinafter, an embodiment of a front face exploration method according to the present invention will be described with reference to the drawings. 1 to 3 are diagrams for explaining a face forward exploration method according to an embodiment of the present invention, FIG. 1 is a block diagram showing a configuration of a face forward exploration device for implementing the face forward exploration method , and FIG. 2 is a face face. The schematic diagram which shows the installation state of a forward exploration apparatus, FIG. 3 is explanatory drawing which shows the procedure of a face front exploration method.

<Outline of front face exploration device and front face exploration method>
The cutting face forward exploration device and the cutting face forward exploration method according to the embodiment of the present invention are techniques for exploring the rock mass condition in front of the cutting face by using the interhole resistivity tomography technology, and particularly, in the rock mass in front of the cutting face. A horizontal boring hole is drilled in the hole and the resistivity distribution of the natural ground is investigated by using the boring hole by tomography. As shown in FIGS. 1 and 2, the front face exploration device of the present invention uses a boring hole 10 and a filling material 20 to fill the boring hole 10, a current electrode 30 for generating a current, and a current generated from the current electrode 30. It is provided with a potential electrode 40 for measuring the generated potential and a geological analyzer 50 for analyzing the geology of the ground in front of the cutting face based on the specific resistance distribution between the current electrode 30 and the potential electrode 40.

<Boring hole>
The boring hole 10 is drilled substantially horizontally toward the front of the face. The term “substantially horizontal” means not only a completely horizontal state but also a state in which a slight inclination is allowed. Although the number of boring holes 10 to be drilled is not particularly limited, a suitable number of boring holes 10 are drilled depending on the size of the tunnel cross section, the bending state of the tunnel, the condition of the ground known in advance, and the like. In order to form the boring hole 10, for example, as shown in FIGS. 3A to 3C, the hollow rod 60 may be inserted into the ground while supplying water from the tip portion of the hollow rod 60. . In addition, you may employ | adopt the drilling method of using a hole-holding pipe etc. according to the condition of the natural ground which drills the boring hole 10.

<Filler>
By filling the filling material 20 in the boring hole 10, it is possible to reliably propagate the current generated from the current electrode 30 and measuring the potential at the potential electrode 40 to the ground. Further, the filler 20 also contributes to protection of the hole wall and reduction of propulsive force and friction when the current electrode 30 and the potential electrode 40 are inserted. In addition, it is difficult for the hole wall to be self-supporting, and when the hole-holding pipe is built, it is possible to propagate the electric current by injecting the filler 20 along the outer periphery of the hole-holding pipe. As the filler 20, it is preferable to use a gel-like substance.

<Current electrode>
The current electrode 30 is an electrode for generating a current, and the generated current is sent to the ground. A power source (not shown) is required to generate a current from the current electrode 30. The number of the boring holes 10 in which the current electrodes 30 are installed may be one, or may be two or more.

<Potential electrode>
The potential electrode 40 is a device for measuring the potential generated by the current generated from the current electrode 30. As shown in FIGS. 2 and 3 (f) to (i), for example, a plurality of the potential electrodes 40 are arranged on a support rod 70 made of a vinyl chloride pipe or the like at a predetermined interval and are supported in the boring hole 10. By installing the rod 70, a plurality of potential electrodes 40 can be installed along the length direction of the boring hole 10. The position and number of the boring holes 10 in which the potential electrodes 40 are installed are not particularly limited. The electrode 40 is installed. By installing a plurality of potential electrodes 40, a plurality of current propagation paths from the current electrode 30 can be set, and the resistivity distribution of the ground in front of the face can be more accurately searched.

<Geological analyzer>
The geological analysis device 50 is a device for analyzing the geology of the ground in front of the cutting face based on the specific resistance distribution between the current electrode 30 and the potential electrode 40, and is, for example, a personal computer and an application program installed in the personal computer. And an accessory device of a personal computer. The accessory device of the personal computer is a peripheral device that operates together with the personal computer, such as an input device such as a keyboard or a mouse, an output device such as a display device or a printer, a storage device such as an HDD. In addition, the inter-hole resistivity tomography technique using the vertical boring holes is an already established technique, and the geological analyzer 50 of the present embodiment uses the inter-hole resistivity tomography using the vertical boring holes. The geology of the ground in front of the working face is analyzed using the analysis method in the technology.

<Combination with other exploration methods>
In the face forward exploration device and face forward exploration method of the present embodiment, inter-hole resistivity tomography technology is the main element of geological analysis, in addition to this, drilling logging data obtained during horizontal boring, etc. And the specific resistance distribution obtained by the exploration of this embodiment, it is possible to comprehensively evaluate two or more types of information at the same point, and a more accurate geological prediction in front of the face is possible. It will be possible.

<Procedure of exploration method>
Next, with reference to FIG. 3, an example of the method for exploring the face ahead of the present invention will be described. According to the front face research method of the present invention, when excavating a tunnel, the front face research device configured as described above is used to search the ground condition (geology) in front of the front face.

  In the front face exploration method of the present invention, first, the horizontal boring hole 10 is drilled in the ground in front of the front face. The boring hole 10 is formed by, for example, installing the hollow rod 60 in the ground and supplying water from the tip of the hollow rod 60 (a). After drilling the boring hole 10 to a predetermined length, the water supply is stopped. In this state, water existing in the boring hole 10 leaks from a rock crack or the mouth of the hollow rod 60 (b).

  Then, the filler 20 is supplied into the boring hole 10 from the tip of the hollow rod 60 (c), and the hollow rod 60 is pulled out while continuing the supply of the filler 20 (d). When the pulling out of the hollow rod 60 is completed, the inside of the boring hole 10 is filled with the filler 20 (e). The filling material 20 may be filled after the potential electrode 40 is installed in the boring hole 10.

  Further, a plurality of potential electrodes 40 are set at predetermined intervals in the length direction of the support rod 70 made of a hollow PVC pipe or the like. Then, the tip of the support rod 70 having the plurality of potential electrodes 40 attached is inserted into the boring hole 10 (f), and the filler 20 is sucked from the boring hole 10 through the hollow portion of the support rod 70. The support rod 70 is inserted into the boring hole 10 and installed (g). At this time, a negative pressure is generated in the boring hole 10 by sucking the filling material 20, and the support rod 70 having the plurality of potential electrodes 40 attached thereto is propelled into the boring hole 10 due to the friction reducing effect of the filling material 20. It is possible (h). When the support rod 70 is inserted to a predetermined position on the inner side of the boring hole 10, the installation of the plurality of potential electrodes 40 is completed (i).

  A plurality of current electrodes 30 are installed in the borehole 10 by the same procedure. Then, the current generated from the current electrode 30 is passed through the ground, and the potential generated by the current propagating in the ground is measured by the potential electrode 40. Then, the geological analyzer 50 analyzes the geology of the ground in front of the cutting face based on the specific resistance distribution between the current electrode 30 and the potential electrode 40 (j).

<Comparison with conventional technology>
According to the face forward exploration device and the face forward exploration method of the present invention, it is possible to concentrate the exploration of the tunnel excavation ground and the resistivity distribution around the tunnel, which is important information in tunnel construction. It is possible to study the excavation method, the tunnel support and the design of the auxiliary method.

  In the conventional face-front exploration, the construction range and specifications were determined based on the standard layout because the geology in front of the face was uncertain at the time of the front-end work, mirror bolt work, and water injection injection planning. On the other hand, in the face forward exploration device and the face forward exploration method of the present embodiment, it is possible to intensively construct the optimum specifications in the bad ground portion, and therefore it is possible to economically plan effective countermeasure work. Becomes In addition, by using a drill jumbo that can accurately record the hole position and the hole angle and has a computer control and a navigation function, it is possible to improve the search accuracy. Furthermore, by using the hole bending measurement together, the exploration accuracy can be further improved.

10 Boring Hole 20 Filling Material 30 Current Electrode 40 Potential Electrode 50 Geological Analyzer 60 Hollow Rod 70 Support Rod

Claims (2)

A method for exploring the ground conditions in front of the tunnel face,
Drilling at least one boring hole for installing a potential electrode and at least one boring hole for installing a current electrode in a substantially horizontal direction toward the front of the face ,
By pulling out the hollow rod while supplying the gel filler from the tip of the hollow rod for drilling inserted in the bore hole in which the potential electrode or the current electrode is installed, the gel rod is pulled into the bore hole. Fill the filling material of
While inserting a hollow support rod to which one of the potential electrode or the current electrode is attached into the boring hole filled with the gel-like filler, through the hollow portion of the support rod, into the boring hole. While sucking the filler from, insert the support rod into the boring hole, install the potential electrode or the current electrode,
The potential generated by the current generated from the current electrode is measured by the potential electrode, and the geology of the cut face forward ground is analyzed based on the specific resistance distribution between the current electrode and the potential electrode,
A front face exploration method characterized by the above. The face prospecting method according to claim 1, wherein a plurality of the potential electrodes and the current electrodes are installed along a length direction of the boring hole.

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