JP6902342B2 - Geological exploration method - Google Patents

Description

The present invention relates to a suitable geological exploration method is applied to probe the geological construction area when performing such tunneling.

As is well known, when excavating a tunnel, it is important to explore the geology of the construction area in advance or while excavating in order to perform efficient excavation or to check for obstacles. ..

As means for that purpose, for example, the soil detection device shown in Patent Document 1 and the measuring device shown in Patent Document 2 have been proposed and put into practical use. All of these devices are constructed by mounting a resistivity sensor equipped with a pair of current electrodes and a pair of voltage electrodes on a tunnel excavator such as a shield excavator or a tunnel boring machine and measuring the resistivity of the ground. It is configured to explore and understand the geological conditions of the area.

Here, as a construction method for constructing a large-scale underground cavity such as a large-section tunnel, for example, a construction method for an underground cavity (SR-JP construction method (registered trademark)) shown in Patent Document 3 has been proposed and put into practical use. Has been done.

In this underground cavity construction method, prior to excavation of a large-section tunnel, a large number of roof shield tunnels as pre-construction work are constructed side by side at intervals, and adjacent roof shields are constructed by working from inside the roof shield tunnel. The ground between the tunnels will be excavated and the main lining wall will be constructed. Then, the inside of the main lining wall is excavated to construct a large-section tunnel.

When excavating between adjacent roof shield tunnels, it is necessary to improve the ground by auxiliary construction methods such as freezing method and chemical injection method, but the optimum auxiliary construction method and construction range are optimized according to the geology. In order to set it, it is important to accurately grasp the ground condition between the roof shield tunnels in advance.

In particular, in the ground where intervening sand layers are scattered in the soil layer, it is necessary to perform water stoppage injection (chemical solution injection) into the intervening sand layers reliably and carefully, so excavate between the roof shield tunnels. Prior to this, it is necessary to sufficiently explore the geology around the entire circumference of the roof shield tunnel and over the entire length to accurately grasp the position of the intervening sand layer and its condition.

Conventionally, this type of sand layer exploration is carried out by boring survey from the ground surface, but conducting boring survey from the ground surface when constructing a deep and large cross-section tunnel not only requires a great deal of labor and cost. High-precision exploration is difficult, and this conventional method cannot be applied realistically.

Therefore, instead of the boring search, the adoption of a search method using a resistivity sensor as shown in the above-mentioned Patent Documents 1 and 2 is being considered. That is, the adoption of a method of exploring the condition of the surrounding ground with a resistivity sensor while excavating a roof shield tunnel is being studied.

Jikkenhei 2-140350 Gazette Japanese Unexamined Patent Publication No. 10-22182 Japanese Unexamined Patent Publication No. 2008-156907

However, with the method shown in Patent Document 1, although the soil quality of the ground in front of the face can be searched while excavating the tunnel, the soil quality of the ground on the side of the tunnel cannot be searched, and Patent Document 2 Although it is possible to explore the lateral ground by the method shown in, the exploration area is very narrow because the explorable range is only a limited area around the installation position of the specific resistance sensor. Therefore, it is not possible to grasp the ground condition over the entire length and circumference of the roof shield tunnel by these conventional methods.

As described above, it is difficult to conduct a wide range of geological exploration with the conventional exploration methods shown in Patent Document 1 and Patent Document 2, and a large-scale tunnel is constructed by a special construction method such as the above-mentioned underground cavity construction method. In this case, it cannot always be applied effectively, so there is a strong demand for the development of effective and appropriate means to enable this.

In addition, by using the resistivity sensor and grasping the soil condition of the entire circumference of the excavation section in real time during excavation, it is possible to perform excavation construction safety and efficient excavation construction management.

However, as a result of conducting on-site demonstration experiments by the inventors of the present application, the ratio (hit rate) of accurately distinguishing the sand layer from the sand layer was as high as about 80%, which was high accuracy, but overall. The medium rate was about 50% to 80%, and it could not be said that it was established as a sufficiently satisfactory soil exploration method. The causes of this error were the influence of the overcut excavated mud in the exploration range and the influence of the sand in the mud settling down.

Therefore, it is required to grasp the influence of such overcut excavated mud and to enable accurate ground exploration.

To achieve the above object, the present invention provides the following means.

The geological exploration method of the present invention is a geological exploration method for measuring the specific resistance value of a ground by using a specific resistance sensor having a current electrode and a voltage electrode arranged side by side at predetermined intervals, and the specific resistance. As sensors, a first current electrode and a second current electrode provided on both outer sides, a first voltage electrode and a second voltage electrode provided between the first current electrode and the second current electrode, and the first voltage electrode. It is provided with only five electrodes consisting of a third voltage electrode provided between the voltage electrode and the second voltage electrode, and is energized by the first current electrode and the second current electrode, and the first voltage electrode and the second voltage electrode are energized. By measuring the potential between the second voltage electrodes, the first resistance value, which is the sum of the overcut range mud in the surface layer and the ground deeper than it, is measured, and the first voltage electrode and the third voltage are measured. By measuring the electrode and / or the potential between the second voltage electrode and the third voltage electrode, the second resistance value of only the surface layer portion is measured, and the second resistance value is calculated from the first resistance value. It is characterized in that the specific resistance value of the ground portion is obtained by deducting it.
Further, in the geological exploration method of the present invention, the resistivity sensor is attached to the outer peripheral end surface of the rotary cutter of the tunnel excavator, and as the rotary cutter moves, the entire region of the moving range of the resistivity sensor is described. The specific resistance value may be obtained.

In geological exploration process of the invention, set at a predetermined distance dimension the spacing between the spaced apart (distance) and / or the second voltage electrode and the third voltage electrode between the first voltage electrode and the third voltage electrode By setting the voltage, the resistance value of the two outer first voltage electrodes and the second voltage electrode, which is the sum of the overcut range mud on the surface layer and the ground deeper than it, can be measured, and the first voltage can be measured. With the electrodes and the third voltage electrode, and / or the second voltage electrode and the third voltage electrode, it is possible to measure the resistance value of only the surface layer portion such as the overcut portion mud.

Therefore, subtract the resistance values measured by the first voltage electrode and the third voltage electrode, or the second voltage electrode and the third voltage electrode from the resistance values measured by the two outer first voltage electrodes and the second voltage electrode. As a result, the influence of mud in the overcut range can be removed, and the resistance value of the ground portion can be measured purely with high accuracy.

Therefore, according to the geological exploration process of the present invention, by providing a third voltage electrode, it is possible to measure the resistance of only the surface layer portion of such overcut minute mud, the influence of mud overcut range By removing it, it becomes possible to measure the resistance value of deep ground with high accuracy, and it becomes possible to carry out accurate and reliable geological exploration / geological exploration.

It is a figure which shows the geological exploration apparatus which concerns on one Embodiment of this invention, and is the figure which shows the geological exploration apparatus which was configured by providing the specific resistance sensor in the tunnel excavator. It is a figure which shows the geological exploration apparatus which concerns on one Embodiment of this invention, and is the figure which shows the geological exploration apparatus which was configured by providing the specific resistance sensor in the tunnel excavator. It is a figure which shows the resistivity sensor of the geological exploration apparatus which concerns on one Embodiment of this invention, (a) is a plan view, (b) is a sectional view (X1-X1 line arrow view of (a)). It is a figure which shows the situation which the resistivity of a ground is measured by the resistivity sensor of the geological exploration apparatus which concerns on one Embodiment of this invention.

Hereinafter, the geological exploration apparatus and the geological exploration method according to the embodiment of the present invention will be described with reference to FIGS. 1 to 4. Here, in the present embodiment, when excavating a roof shield tunnel having a small cross section by the SR-JP method or the like, the geological exploration device and the geological exploration method according to the present invention are used to explore the geology of the surrounding ground. Give an explanation.

First, as shown in FIG. 1 (or FIG. 2), the geological exploration device of the present embodiment measures the resistivity of the ground on the tunnel excavator (base machine) 1 for excavating the roof shield tunnel. It is configured to be equipped with a resistivity sensor 5.

Specifically, the tunnel excavator 1 as a base machine is provided with a rotary cutter 3 at the front portion of the skin plate 2 like a normal shield excavator, and the rotary cutter 3 is rotated to excavate a face and the skin plate 2 The purpose is to take the reaction force from the segment (not shown) assembled at the rear by the propulsion jack (not shown) inside, excavate, and build the roof shield tunnel.

As shown in FIG. 3 (FIGS. 1 and 2), the specific resistance sensor 5 mounted on the tunnel excavator 1 as a base machine has five electrodes (7a, 7b, 7c, 7d) with respect to the base 6. , 7e), and the two electrodes on both side ends of the base 6 are the first current electrode 7a, the second current electrode 7b, and the two electrodes on the center side between the first current electrode 7a and the second current electrode 7b. Is the first voltage electrode 7c and the second voltage electrode 7d. Further, an energizing device and an arithmetic unit (not shown) are connected to the resistivity sensor 5.

Then, as shown in FIG. 4, a predetermined current is passed through the first current electrode 7a and the second current electrode 7b by the energizing device, and the voltage is measured by the first voltage electrode 7c and the second voltage electrode 7d. The device can calculate the specific resistance of the ground G from those measured values, and based on this, the situation of the ground G can be grasped.

Further, in the geological exploration device of the present embodiment, the resistivity sensor 5 is installed on the outer peripheral end surface of the rotary cutter 3, whereby the resistivity sensor 5 draws a rotation locus in the ground as the rotation cutter 3 rotates. The position moves every moment, and the resistivity sensor 5 moves forward in the ground as the tunnel excavator 1 excavates. With this configuration, the resistivity sensor 5 moves sequentially with the rotation of the rotary cutter 3, and the resistivity in the entire region of the movement range can be measured and calculated to obtain three-dimensional data. Therefore, it is possible to accurately grasp the geological condition of the outer ground G of the roof shield tunnel over the entire circumference and the entire length.

On the other hand, the resistivity sensor 5 of the present embodiment is different from the conventional one, and as shown in FIGS. 3 (1 and 2), the resistivity sensor 5 is located between the two central voltage electrodes 7c and 7d. It is configured to include a three-voltage electrode 7e.

As a result, the voltage is measured between the first voltage electrode 7c and the second voltage electrode 7d on the center side, and the voltage is also measured between the first voltage electrode 7c (or the second voltage electrode 7d) and the third voltage electrode 7e. Can be measured.

That is, in the specific resistance sensor 5 of the present embodiment, a current is passed from the two outer first current electrodes 7a and the second current electrode 7b, and the central 2 between the first current electrode 7a and the second current electrode 7b. The potential (resistance value) is measured by the first voltage electrode 7c and the second voltage electrode 7d of the book, converted into the specific resistance value, and the state of the ground G such as the sand layer and the clay layer is discriminated.

Further, by providing the third voltage electrode 7e between the first voltage electrode 7c and the second voltage electrode 7d, the first voltage electrode 7c and the third voltage electrode 7e, and / or the second voltage electrode 7d and the third The potential (resistance value) between the voltage electrodes 7e can be measured.

At this time, as shown in FIG. 4, the separation (distance) between the first voltage electrode 7c and the third voltage electrode 7e and / or the separation between the second voltage electrode 7d and the third voltage electrode 7e is a predetermined distance. By setting the dimensions, the resistance value of the two outer first voltage electrodes 7c and the second voltage electrode 7d, which is the sum of the overcut range mud of the surface layer G1 and the ground G deeper than it, is measured. At the first voltage electrode 7c and the third voltage electrode 7e, and / or the second voltage electrode 7d and the third voltage electrode 7e, the resistance value of only the surface layer portion G1 such as overcut mud is measured. Becomes possible.

Therefore, from the resistance values measured by the two outer first voltage electrodes 7c and the second voltage electrode 7d, the resistance values were measured by the first voltage electrode 7c and the third voltage electrode 7e, or the second voltage electrode 7d and the third voltage electrode 7e. By "deducting" the resistance value, the influence of mud in the overcut range can be removed, and the resistance value of the ground G portion can be measured purely with high accuracy.
In the present embodiment, the above "deduct" means the first voltage electrode 7c and the third voltage electrode 7e, or the third voltage electrode 7e, from the resistance values measured by the two outer first voltage electrodes 7c and the second voltage electrode 7d. Instead of performing a simple calculation of subtracting the resistance values measured by the 2nd voltage electrode 7d and the 3rd voltage electrode 7e, the resistance values measured by the 2 outer 1st voltage electrodes 7c and the 2nd voltage electrode 7d are over. The theoretical predicted value including the influence of the mud in the cut range is the resistance value of the ground G part, which is tentatively determined, and the first voltage electrode 7c and the third voltage electrode 7e, or the second voltage electrode 7d and the third. Calculated using one or both of the resistance values measured by the voltage electrode 7e, the theoretical predicted values by the first voltage electrode 7c and the second voltage electrode 7d including the influence of this mud are sufficiently close to the actual measured values. It means that the resistance value of the ground G portion is obtained by sequential approximation calculation so as to be.

Therefore, according to the geological exploration device and the geological exploration method of the present embodiment, by providing the third voltage electrode 7e, it is possible to measure the resistance value of only the surface layer portion G1 such as the overcut cob, and the overcut range. It is possible to accurately measure the resistance value of the ground G by removing the influence of mud and the like. Therefore, accurate and highly reliable geological exploration / geological exploration can be performed.

Although one embodiment of the geological exploration apparatus and the geological exploration method according to the present invention has been described above, the present invention is not limited to the above one embodiment and can be appropriately changed without departing from the spirit of the present invention. ..

For example, in the present embodiment, a case of exploring the surrounding ground when constructing a roof shield tunnel in the SR-JP method is taken as an example, and a tunnel excavator (shield excavator) 1 for excavating the roof shield tunnel. Was used as the base machine for installing the specific resistance sensor 5, but the base machine may be any one that has a rotating cutter on the front surface and can be equipped with the specific resistance sensor on the outer peripheral end face thereof, and is not limited to the shield excavator. Various tunnel excavators can be adopted.

Further, the geological exploration device (and the geological exploration method) of the present invention does not need to be limited to using various tunnel excavators as a base machine for the purpose of geological exploration at the time of tunnel excavation as in the present embodiment. It is widely applicable to the case of performing geological exploration for various purposes in various fields, and the specific configuration of the geological exploration device (and geological exploration method) of the present invention can be changed according to the purpose and usage conditions. ..

That is, since the purpose of this embodiment is to explore the surrounding ground during tunnel excavation, the base machine for installing the specific resistance sensor 5 is used as the tunnel excavator 1 and the outer circumference of the rotary cutter 3 is used as the tunnel excavator 1. Although the specific resistance sensor 5 is installed on the end face (that is, it can be said that the rotary cutter 3 of the tunnel excavator is used as a rotating body for rotating the specific resistance sensor 5), the present invention is based on the tunnel excavator. It is not limited to the machine, and it is not necessary to limit the use of the rotary cutter 3 of the tunnel excavator as a rotating body for rotating the specific resistance sensor 5.

1 Tunnel excavator (base machine)
2 Skin plate 3 Rotating cutter (rotating body)
5 Specific resistance sensor 6 Base 7 Electrode 7a 1st current electrode 7b 2nd current electrode 7c 1st voltage electrode 7d 2nd voltage electrode 7e 3rd voltage electrode G Ground G1 Surface layer

Claims (2)

It is a geological exploration method that measures the specific resistance value of the ground using a specific resistance sensor that has a current electrode and a voltage electrode that are arranged side by side at a predetermined interval.
As the specific resistance sensor, a first current electrode and a second current electrode provided on both outer sides, and a first voltage electrode and a second voltage electrode provided between the first current electrode and the second current electrode, respectively, It is provided with only five electrodes including a third voltage electrode provided between the first voltage electrode and the second voltage electrode.
By energizing the first current electrode and the second current electrode and measuring the potential between the first voltage electrode and the second voltage electrode, the overcut range of the surface layer is mud and the ground deeper than it. The surface layer portion is measured by measuring the combined first resistance value and measuring the potential between the first voltage electrode and the third voltage electrode, and / or between the second voltage electrode and the third voltage electrode. A geological exploration method characterized in that the specific resistance value of the ground portion is obtained by measuring the second resistance value of the electric current and subtracting the second resistance value from the first resistance value. The resistivity sensor is attached to the outer peripheral end face of the rotary cutter of the tunnel excavator.
The geological exploration method according to claim 1, wherein the specific resistance value of the entire region of the moving range of the specific resistance sensor is obtained as the rotary cutter moves.

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