JPH063210A - Multiple depth pore water pressure measuring device - Google Patents

Abstract

PURPOSE:To provide a multi depth pore water pressure measuring device in which multi depth pore water pressure can be measured with one boring, equipment can be recovered after completion of measurement, water permeability test and water examination can be conducted after that and water pressure can be measured with the simple constitution. CONSTITUTION:A multi depth pore water pressure measuring device is provided with a plurality of tubes 6 made of insulating materials whose one ends are opened in a plurality of water pressure measuring compartments 4 in a boring 1 and a conductive layer 8 having electric resistance formed on the inner circumferential face of each of the tubes 6. It is also provided with a pair of electrodes 9, 10, 11 and 12 provided on the conductive layer 8 at two points under water with the water surface of underground water intruding into each of the tubes 6 between them and a processing unit for calculating water pressure for water level and each depth of the underground water from resistance value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-depth pore water pressure measuring device for measuring water pressure in a multi-depth pore of a ground by using a boring hole.

[0002]

2. Description of the Related Art Measuring the pore water pressure in the ground is an indispensable item for knowing the flow direction of groundwater. Conventionally, a pore water pressure gauge is buried at the depth to be measured to measure the pore water pressure. The method of measuring was common. However, in this method, in order to measure the water pressure distribution in the depth direction, it is necessary to dig a separate boring hole for each measurement depth and bury the water pressure gauge, and it takes too much time for the boring work. As shown in FIG. 4, one boring hole 1 is excavated in the ground 2, and the inside of this boring hole 1 is partitioned by a sealing material 3 to install one water pressure gauge 5 for each water pressure measurement section 4. The method of doing was adopted.

[0003]

However, in such a multi-depth pore water pressure measuring device, as described above, after the water pressure gauges 5 are installed in the water pressure measuring space 4, they cannot be recovered. , In addition to the inconvenience that it is not possible to conduct permeability tests, water quality surveys and other surveys related to groundwater using the same boring hole, and because the diameter of the water pressure gauge 5 is as large as about 3 cm, there are restrictions on the number of installations. There was a point.

The invention of claim 1 is made by paying attention to the conventional problems as described above, and it is possible to measure the pore water pressure at multiple depths with a single boring hole and to measure the pore water pressure at multiple depths. A multi-depth pore water pressure measuring device that allows easy collection of measuring instruments after the end, allows subsequent water permeability tests and water quality surveys, and can measure water pressure with an extremely simple configuration without using a large water pressure gauge. The purpose is to provide.

It is another object of the present invention to provide a multi-deep pore water pressure measuring device which can measure the water pressure in a multi-deep pore with higher accuracy based on the specific resistance and electrical conductivity of groundwater.

[0006]

According to a first aspect of the present invention, there is provided a multi-depth pore water pressure measuring device comprising: an insulating material provided at one end thereof in a plurality of water pressure measuring sections in a boring hole. A plurality of tubes, a conductive layer having an electric resistance formed on the inner peripheral surface of each of the tubes, and two conductive layers provided above and below the surface of the groundwater invading the tubes. And a pair of electrodes, and the arithmetic processing unit calculates the water level and the water pressure for each depth from the resistance value between the electrodes.

The multi-depth pore water pressure measuring device according to the second aspect of the present invention comprises a plurality of tubes made of an insulating material, each of which is provided with one end open in a plurality of water pressure measuring sections in the boring hole. And a conductive layer having an electric resistance formed on the inner peripheral surface of each of these tubes, and provided on the conductive layer of each of the above tubes, outside the water surface in each tube, and isolated for a certain amount in the vertical direction. Arranged first electrode and second
An electrode, a third electrode and a fourth electrode which are provided on the conductive layer of each of the tubes and are vertically spaced below the water surface of the ground water in the same direction as the above, and the first electrode and The third when the current is applied between the second electrodes
A specific resistance measuring device that measures a potential difference between the electrode and the fourth electrode, and measures the specific resistance between the second electrode and the third electrode from the potential difference; At least the electric conductivity of groundwater measured using the third electrode and the fourth electrode is corrected to calculate the water level and the water pressure for each depth.

[0008]

Since the pair of electrodes in the invention of claim 1 are located at two points across the water surface in the tube and are connected to the conductive layer on the inner circumference of the tube, a current is applied between these two points. By flowing, the conductive layer below the water surface forms a circuit that is short-circuited with groundwater, and thus exhibits a resistance value corresponding to the water surface. That is, by measuring this resistance value, the height of the water surface, that is, the water pressure at this depth can be measured.

The first electrode and the second electrode according to the second aspect of the present invention are such that when a current is applied to them,
A potential difference is obtained between the third electrode and the fourth electrode below the surface of the water, and the specific resistance is measured by the specific resistance measuring device based on this potential difference and the length and cross-sectional area of the conductive layer, and this specific resistance is corrected and calculated. The processing device corrects the electrical conductivity of groundwater to enable accurate measurement of the accurate water level in the tube, that is, the water pressure at this depth.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 is one thin boring hole formed in the ground 2, and 3 is a plurality of air packers provided in the boring hole 1 at substantially equal intervals in the vertical direction. It is made of, for example, rubber so as to expand. Therefore, by supplying the air pressure, it can be fixed at a predetermined position in the boring hole 1, while by removing the air pressure, the air packer 3 can be recovered from the boring hole 1.
3A is a strainer provided in each water pressure measurement section so as to take out only pore water.

Reference numeral 4 denotes a plurality of water pressure measuring sections defined by the air packers 3, and one water pressure measuring tube is provided so that the lower end faces each of the water pressure measuring sections 4. 6 is supported so as to penetrate the air packer 3.

As shown in FIG. 2, each of the tubes 6 has at least a two-layer structure, of which 7 is an insulating layer, inside of which a conductive layer 8 having a uniform electric resistance as a whole is provided. It is provided.

The conductive layer 8 has a boring hole 1
The first electrode 9 and the second electrode 10 are embedded in the upper part (outer side) of this water surface at a distance a so that the water surface W penetrates into the tube 6 by being inserted into the tube 6, and The third electrode 11, the fourth electrode 12, the fifth electrode 13, and the sixth electrode 14 are buried under the water surface (in water) at intervals of a, respectively, and are buried in the conductive layer 8.

The second electrode 10 and the third electrode 11 are separated by a length of na, and each tube 6 shown in FIG.
The water level inside is W relative to the average water level W1 in the borehole 1.
2 to W4.

The first electrode 9 to the sixth electrode 14 are
As shown in FIG. 3, they are arranged in a straight line in the vertical direction, and lead wires 1 are connected to each of them, and are connected to an arithmetic processing unit 15 installed on the ground. Reference numeral 16 is a resistivity measuring device which constitutes a part of the arithmetic processing device 15, and 17 is a correction arithmetic processing device.

In the multi-depth pore water pressure measuring device having such a structure, the second electrode 10 and the third electrode 11 in the tube 6 are electrically connected to, for example, the conductive layer 8 which is located at the position where the water surface of the water level W1 is sandwiched. Therefore, when an electric current is passed between the second electrode 10 and the third electrode 11, the conductive layer 8 at the portion in contact with groundwater is electrically short-circuited by the groundwater.

That is, the resistance value between the electrodes 10 and 11 changes, and this change in resistance value can be grasped as a change in water level. In the present invention, the resistance value is calculated from the current value taken in through each lead wire 1 and the arithmetic processing unit 15
The water level and the water pressure corresponding to the water level are calculated from this resistance value. Since the resistance value of groundwater differs for each point and each depth, if the resistance of the groundwater itself is measured in the same manner, the water level can be more accurately determined.

Next, another embodiment for obtaining such a water level with high accuracy will be described with reference to the drawings. That is, a current is caused to flow between the first electrode 9 and the second electrode 10 in each tube 6 having, for example, an Eltran electrode arrangement, and the potential difference between the third electrode 11 and the fourth electrode 12 at this time is measured to obtain the second The specific resistance ρ between the electrode 10 and the third electrode 11 (the characteristic of the substance that resists the flow of current) can be measured.

This specific resistance ρ is given by I being a current flowing between the first electrode 9 and the second electrode 10, v being a potential difference between the third electrode 11 and the fourth electrode 12, and n being a multiple of the interval a. , Ρ = n (n + 1) (n + 2) π · V / I. Then, the calculation of the specific resistance ρ is performed by the specific resistance measuring device 16 and further converted into data of water level and water pressure.

Since the value of the specific resistance ρ thus obtained changes depending on the electric conductivity of groundwater in the tube 6 (the reciprocal of the specific resistance), the third to fourth electrodes 11 to 14 are further added. To measure the electrical conductivity of groundwater. As a result, this measured value can be used for correction of data when the water level and water pressure are obtained from the specific resistance ρ.

As described above, according to the present invention, the water level in the thin tube 6 connected to each water pressure measuring section 4 is measured by using the conductive layer 8 in the tube 6, whereby the water level and the water pressure in the water pressure measuring section 4 are measured. Can be easily and accurately measured with a simple configuration.

Further, in the present invention, by using the tube 6, the spring pressure can be easily measured by connecting a water pressure gauge at the borehole at the location where water is springing, such as in a tunnel or underground cavity. You can also
After the measurement work is completed, the air of the air packer 3 is evacuated and the tube 6 is lifted to the ground so that the equipment and parts can be collected and reused. It can be used for measurements such as water quality surveys.

[0023]

As described above, according to the first aspect of the present invention, a plurality of tubes made of an insulating material are provided so that one ends of the tubes are provided in a plurality of water pressure measurement sections in the boring hole. And a conductive layer having an electric resistance formed on the inner peripheral surface of each of these tubes, and a pair of electrodes provided on the above-mentioned two conductive layers at the upper and lower sides of the surface of the groundwater invading the respective tubes. Since the arithmetic processing unit is configured to calculate the water level of the groundwater and the water pressure for each depth from the resistance value between the electrodes, a single borehole having a small diameter can provide a gap of multiple depths. Since the water pressure can be measured and it is not necessary to use several water pressure gauges, the structure can be simplified and the cost can be reduced.Furthermore, after the measurement is completed, the above tube is taken out from the boring hole and used for various types of water permeability tests. Use Practical effect that use can be obtained.

According to the second aspect of the present invention, a plurality of tubes made of an insulating material are provided so as to open at one end in a plurality of water pressure measurement sections in the boring hole, and each of these tubes. A conductive layer having an electric resistance formed on the inner peripheral surface of the tube, and a first electrode provided on the conductive layer of each of the tubes and vertically spaced apart from the water surface in each tube in the vertical direction. And a second electrode, a third electrode and a fourth electrode which are provided on the conductive layer of each of the tubes and are vertically spaced below the water surface of the ground water by a predetermined distance equal to the above. A specific resistance for measuring a potential difference between the third electrode and the fourth electrode when a current is applied between the first electrode and the second electrode, and measuring a specific resistance between the second electrode and the third electrode from the potential difference. Compensation calculation processing equipment Therefore, the specific resistance is corrected by the electrical conductivity of groundwater measured using at least the third electrode and the fourth electrode, and the groundwater level and the water pressure for each depth are configured to be calculated. In addition to the above effects, the water level can be measured by measuring the resistivity of groundwater and the measurement results can be calibrated, and as a result, the water pressure measurement system can be further improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a multi-depth pore water pressure measuring device according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a part of the tube in FIG.

FIG. 3 is a horizontal sectional view of the tube in FIG.

FIG. 4 is a configuration diagram showing a conventional multi-depth pore water pressure measuring device.

[Explanation of symbols]

 1 Boring Hole 4 Water Pressure Measurement Section 6 Tube 8 Conductive Layer 9 First Electrode 10 Second Electrode 11 Third Electrode 12 Fourth Electrode 15 Arithmetic Processing Device 16 Resistivity Measuring Instrument 17 Correction Arithmetic Processing Device

Claims (2)

[Claims] 1. A plurality of tubes made of an insulating material, each end of which is opened in a plurality of water pressure measuring sections in a boring hole, and an electric wire formed on the inner peripheral surface of each of the tubes. The resistance value between the conductive layer having resistance, the pair of electrodes provided on the conductive layer at two points above and below the surface of the groundwater entering the tubes, and the resistance value between the electrodes are measured. From the above, a multi-depth pore water pressure measuring device comprising the above-mentioned ground water level and an arithmetic processing unit for calculating the water pressure for each depth. 2. A plurality of tubes made of an insulating material, each of which is provided with one end open in a plurality of water pressure measuring sections in the boring hole, and an electric wire formed on an inner peripheral surface of each of the tubes. A conductive layer having resistance and a first electrode and a second electrode provided on the conductive layer of each of the tubes and vertically spaced apart from each other outside the water surface in each tube in the vertical direction.
An electrode, a third electrode and a fourth electrode which are provided on the conductive layer of each of the tubes and are vertically spaced below the water surface of the ground water in the same direction as the above, and the first electrode and The third when the current is applied between the second electrodes
A resistivity measuring device for measuring a potential difference between the electrode and the fourth electrode, and measuring a resistivity between the second electrode and the third electrode from the potential difference; and a resistivity for measuring at least the third electrode and the fourth electrode. A multi-depth pore water pressure measuring device comprising: a correction calculation processing device that corrects the electric conductivity of ground water measured using the above to calculate the water level and the water pressure at each depth.