JPS624662B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for measuring microflow velocity and flow direction of groundwater.

Conventionally, various attempts have been made to measure the flow velocity and flow direction of microflow groundwater. A typical method is to lower a current meter with a rotating propeller in flowing water into a borehole and measure the flow speed and direction as changes in the propeller rotation speed. As if to be done,
An attempt was made to lower the disk into a borehole and estimate the flow status of groundwater from the pressure caused by the upward and downward flow of water in the hole acting on the disk, or to inject radioisotopes into flowing water to estimate the radiation dose from the flowing water. There are attempts to measure flow velocity and direction by tracing distribution changes. However, in the case of a method in which the mechanical measuring means is driven by running water, for example,
Accurately measuring flow velocities of less than cm is extremely difficult, and methods that use radioactive materials require a license and are not only difficult to handle, but also require extremely expensive equipment.

The present invention eliminates these drawbacks in the prior art, and its purpose is to provide an economical measuring method and apparatus that are easy to use, capable of accurately measuring the velocity and direction of extremely small flows. .

The present invention will be explained in detail below with reference to drawings of one embodiment.

FIG. 1 shows a pick-up section located below the main body of the measuring device according to the present invention, and the pick-up section is provided with a plurality of electrodes 1 to 5 located at equal intervals from a specific electrode in an internal electrode chamber 9. A sleeve 6 that surrounds the pick-up part and is movable upwardly along the main body of the measuring device is provided on the circumferential surface that opens laterally. The sides can be opened all around at the same time.

In the figure, 7 denotes a mesh part that constantly covers the entire circumference of the side opening of the electrode chamber 9 in the pick-up part, and 8 denotes the electrodes 1 to 1 described above.
5 represents the electric wire connected to 5.

Further, the electrode chamber 9 of the pick-up section is filled with an electrolytic solution such as NaCl solution. FIG. 2 is a cross-sectional view including the electrode section of the pick-up section shown in FIG. A plurality of electrodes are arranged radially from the center.

Figures 3a to 3c are diagrams showing the pick-up section shown in Figure 1 in a simplified manner and the situation during measurement, in which reference number 10 indicates the flow of groundwater, and reference number 11 indicates the flow of groundwater. NaCl solution is shown.

The measuring method and operation using the measuring device according to the present invention will be explained below. For measurement, the pick-up section shown in FIG. 1 is lowered into the borehole to the measurement depth, and after the turbulent flow in the borehole due to the descent has subsided, the sleeve 6 is gradually pulled up. When the sleeve 6 is pulled up, groundwater 10 flows into the pickup section through the mesh 7, as shown in FIG. 3b. At the same time, the NaCl solution 11 and groundwater 10 that were inside the pick-up part flow in, the NaCl solution is replaced and diluted, and the NaCl solution 1
1 is pushed out of the pickup section. Now, if we pay attention to the changes in the resistance values between electrodes 1 and 3 and between electrodes 3 and 5, we can see that when all electrodes 1, 3, and 5 are in the NaCl solution 11, the concentration of NaCl changes as shown in Figure 3a. However, in the state shown in FIG. 3b, a portion of the NaCl solution is replaced and diluted with groundwater 10, so that the resistance value between electrodes 1-3 increases. As the substitution dilution progresses further, Figure 3c
As shown in FIG. 2, since all of the electrodes are placed in the groundwater 10, the resistance values between electrodes 1 and 3 and between electrodes 3 and 5 both increase. Note that during actual measurement, a weak current is passed between each electrode, and a change in resistance value is detected as a voltage change between each electrode. Also, the third
In the illustrated embodiment, three electrodes 1, 3, and 5 are shown, but in reality, as shown in FIG. 2, a plurality of electrodes are provided radially from the center in, for example, eight directions.
By measuring the resistance value of each electrode arranged radially in this manner, the flow direction of groundwater can be easily determined. Next, how to determine the flow direction will be explained with reference to FIGS. 2 and 4. FIG. 4 is a diagram in which, for example, changes in resistance values between electrodes 12-13, 14-15, and 16-17 shown in FIG. The axis shows the potential V between each electrode. When the sleeve 6 is pulled up for measurement, groundwater flows into the pick-up section. When the potential between each electrode is measured in this state, the potential V shows an unstable value for a while due to the initial disturbance, but becomes a stable value as time passes. In this case, if the pickup section is filled with granules, the above-mentioned initial instability can be eliminated. Subsequently, when the NaCl solution is diluted with underground water, for example, the time difference between electrodes 12 and 13
At t ₂ , the interelectrode potential begins to rise between electrodes 14 and 15 at time t ₁ and between electrodes 16 and 17 at time t ₃ . In the example shown in FIG. 4, the potential between electrodes 14 and 15 starts to rise earliest at time _t1 . This indicates that the velocity of the flow toward electrodes 14-15 is greater than the velocity of the flow toward other electrodes, and the flow direction of groundwater is
It is easily inferred that the direction is

Next, a method for measuring the flow velocity will be explained. Since the flow velocity is expressed as the amount of movement per unit time, for example, in Fig. 3, the difference between the time when the resistance value change between electrodes 1 and 3 starts and the time when the resistance value change between electrodes 3 and 5 starts. It can be easily found by asking. For example, if the distance between electrodes 1 and 3 is 2.5 cm, and the difference in the time when the resistance value starts to change, or in other words, the time required for groundwater to reach electrode 3 from electrode 1 to 1 hour, then the flow rate is 2.5 cm/hour. become.

In addition, in the above measurement, a method was described in which the resistance value change between two electrodes was measured as a change in the potential between the electrodes. By connecting, the starting point of resistance value change can be found more efficiently. When a bridge connection is used, a potential change when groundwater reaches electrodes 1 and 3 appears in the form of a rising start point _t4 and a peak point _t5 , as shown in FIG. 5, for example.

As described above, the present invention includes a pick-up section located below the main body of the measuring device and provided with a plurality of electrodes arranged at regular intervals from a specific electrode, and a pick-up section that surrounds the pick-up section and extends along the main body of the measuring device. After immersing the pick-up part of the measuring device main body having an upwardly movable sleeve in underground water in a borehole, passing a predetermined current between the electrodes,
When measuring the minute flow velocity and flow direction of groundwater based on the difference or change in resistance value between each electrode, the pick-up part is covered with a sleeve until the turbulent flow of groundwater in the borehole that occurs when the measuring device is lowered subsides. At the same time, since the sleeve is moved upward after sedation and the electrode chamber in the pick-up section is exposed to groundwater, it is possible to measure extremely small flow velocities with high precision compared to conventional measurement methods.
Moreover, it enables measurement with a simple device.
It is also possible to measure the flow rate and flow direction without using electrolyte by inserting a pick-up section with multiple electrodes into flowing water, but since the difference in resistance between each electrode is extremely small, it is difficult to actually measure the flow rate and flow direction. When measuring, if special considerations such as the use of an amplifier are taken, it is not necessary to use a liquid having a resistance value different from that of the groundwater described above.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a pickup section of a measuring device according to the present invention, FIG. 2 is a partial sectional view of the pickup section shown in FIG. 1, and FIG. 3 is a diagram for explaining changes in state during measurement. FIG. 4 is a graph showing changes in the interelectrode potential during measurement, and FIG. 5 is a diagram showing an example of potential changes that occur when a bridge connection is used. 1-5...Electrode, 6...Sleeve, 7...Mesh portion, 8...Electric wire, 9...Inside electrode, 12-17
……electrode.

Claims (1)

[Scope of Claims] 1. A pick-up part located below the measuring device main body and provided with a plurality of electrodes arranged at regular intervals from a specific electrode, and a pick-up part surrounding the pick-up part and extending upward along the measuring device main body. After immersing the pick-up part of the measuring device body, which has a sleeve that can be moved freely, into groundwater in a borehole, a predetermined current is passed between the electrodes, and the minute flow velocity of groundwater is determined by the difference or change in resistance between each electrode. When measuring the flow direction, the pick-up section is covered with a sleeve until the groundwater turbulence in the borehole subsides, and after the turbulent flow subsides, the sleeve is moved upward to expose the electrode chamber of the pick-up section to the groundwater. A method for measuring microflow velocity and flow direction of groundwater, characterized by exposing the groundwater to water. 2. A pick-up part located below the main body of the measuring device and provided with a plurality of electrodes arranged at regular intervals from a specific electrode, and a pick-up part surrounding the pick-up part and attached to the main body of the measuring device to expose the electrode chamber of the pick-up part. A device for measuring minute current velocity and flow direction of groundwater, comprising a sleeve that is movable upward along the groundwater.