JPS649587B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a fluid flow measuring device, and particularly to a fluid flow measuring device suitable for measuring the dynamics of groundwater, etc., which exhibit minute movements.

[Prior art and its problems]

In recent years, basic construction departments in fields such as civil engineering and construction have been using groundwater flow (flow velocity, flow direction, or There is an increasing need to measure both as accurately as possible.

On the other hand, a so-called tracer method has been widely used as a method for measuring groundwater flow.
This method involves injecting salt or dye into a specific borehole out of multiple boreholes, examining changes in electrical resistance or concentration over time between it and other boreholes, and determining the time at which the maximum change occurs and The purpose is to perform four simple arithmetic operations based on the position and thereby measure the groundwater flow situation.

However, in this conventional technique, it is necessary to drill a large number of boreholes with a depth of 20 to 40 m, resulting in an extremely high overall survey cost. Furthermore,
In cases where the flow rate of groundwater is extremely slow, measurement takes a long time, and changes in flow due to rainfall occur during long measurements, making accurate measurements overall very difficult. It was presenting a situation.

On the other hand, in recent years, with the intention of improving the above-mentioned drawbacks, propeller-type flow measuring devices, the invention disclosed in Japanese Patent Publication No. 45-25029, or radioisotopes are introduced into flowing water, and the Various methods have been proposed, including methods for measuring flow by tracing changes in the radiation dose distribution due to flowing water.

However, when measuring flow using a propeller type, it is difficult to measure minute flow velocities of, for example, 2 [cm/sec] or less. Also, special public service in 1977-
The method described in Publication No. 25029 attempts to estimate the groundwater flow situation from the pressure difference due to the upward and downward flow of water in the borehole that acts on the disk by lowering the disk into the borehole. Although it is a thing,
Even in this method, as with the above propeller type, it is actually difficult to accurately measure minute flows in which there is a small pressure difference between the upward flow and the downward flow. Furthermore, the methods using radioactive materials always have drawbacks, such as not only being dangerous to handle, but also making the entire device extremely expensive.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned drawbacks of the prior art. To provide a fluid flow measuring device which can be repeatedly measured for a long period of time in a fixed state, has a simple structure, and has sufficient durability.

[Problem that the invention seeks to solve]

The present invention includes an observation section in which a plurality of measurement electrodes are arranged concentrically and radially at regular intervals. A displacement fluid pouring mechanism for pouring out a predetermined amount of displacement fluid having electrical or chemical properties different from groundwater into the observation section by an external operation is installed near the observation section. Of these, each of the measurement electrodes includes a first electrode formed of a relatively thin single electrode wire, and a second electrode disposed at a constant interval on the outside of the first electrode, and one end surface of which is generally aligned. and a second electrode that is slightly protruding to form an annular shape and functions as a common electrode. This aims to achieve the above-mentioned purpose.

〔Example〕

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

First, the basic technical configuration forming the background of the present invention will be explained based on FIGS. 1 to 7, and then specific embodiments will be explained based on FIGS. 8 to 10.

FIG. 1 is a schematic explanatory diagram showing an example of actual measurement using the fluid flow measuring device according to the present invention. In FIG. 1, reference numeral 1 designates a measuring borehole drilled in the ground E from the ground surface to a predetermined depth into the groundwater layer (sand layer, gravel layer, etc.). A measurement probe (hereinafter simply referred to as "probe") 3 suspended through a support conduit 2 is inserted into the borehole 1 down to the test depth. Here, the direction of the probe 3 is confirmed by a compass 4 (see FIG. 2) built into the upper part of the probe 3, and the probe 3 is installed and fixed in a predetermined direction. In the groundwater layer in the ground E, there is a flow of groundwater as shown by the arrow F in the figure, so that there is groundwater W in the borehole 1.
The probe 3 is immersed in this underground water W.

The probe 3 is electrically connected to an external measuring device (not shown) through a multicore cable 5 (see Figure 2) disposed within the support conduit 2, and is thereby capable of measuring underground water flow. and recording.

FIG. 2 shows a specific configuration of the probe 3 mentioned above. As will be described later, the structure of the electrode portion of this probe 3 is partially different from that of the embodiment shown in FIG. 8. In FIG. 2, reference numeral 6 indicates a cylindrical probe body.
One end of the probe body 6, which is the lower end in the figure, is surrounded by a disc-shaped head board 7 made of an insulating material, and a bottom board 8 mounted opposite the head board 7 at a predetermined distance. An observation section 20 is provided. In addition, in this observation unit 20, a substituting fluid having electrical or chemical properties different from that of groundwater, which is the object to be measured (for example, an electrolytic solution such as NaCl solution when groundwater has low conductivity), or Displacement fluid pouring mechanism 30 for pouring out pure water, etc., if it contains NaCl etc. and has relatively high conductivity)
is built into the probe body 6. The above-mentioned compass 4 is housed in the probe body 6 above the displacement fluid pouring mechanism 30. The azimuth signal output from the azimuth meter 4 is transmitted to the outside via wiring (not shown) within the support conduit 2 connected to the center of the upper end of the probe body 6.

Next, each component of the probe 3 will be explained in more detail.

The head panel 7, which forms the main part of the observation section 20, includes a second
As shown in the figure and FIG. 4, a plurality of electrode wire groups 9 (specifically described later) projecting downward in FIG. 2 are arranged concentrically and at regular intervals.
The head board 7 is screwed to the lower end surface of the probe body 6 via a waterproof rubber ring 21A by four threaded supports 21, 21, . It is attached to the probe body 6 in a hermetically sealed manner. Further, a terminal plate 19 for connecting the electrode wire group 9 to an external circuit is attached to the upper surface of the head panel 7 in FIG. The electrode wire group 9 is fixed to the
Each electrode wire is individually connected to an external signal detection and display means (not shown).

A bottom plate 8, which is provided opposite to the head plate 7, is fixed at the lower end portions of threaded columns 21, 21, . . . with nuts. A space 2 as an observation section is formed between the bottom plate 8 and the head plate 7.
0, groundwater W as a fluid to be measured can flow into the groundwater. On the other hand, the bottom plate 8 has a function of locking a wire mesh 25, which will be described later, and also has the function of locking a wire mesh 25, which will be described later.
When lowering the whole into the borehole 1, if the whole is pressed against the bottom of the borehole 1 by mistake, it has a function to prevent damage to the electrode wire group 9 part, and also has a function to prevent the electrode wire group 9 from being damaged. It also has the function of stabilizing the flow of fluid within 20.

Further, a wire mesh 25 is arranged in a cylindrical shape between the peripheral end of the head board 7 and the peripheral end of the bottom board 8 so as to surround the electrode wire group 9. This wire mesh 25
In addition to preventing the intrusion of foreign matter into the space 20 serving as the observation section due to collapse of the hole wall 1A of the borehole 1 shown in FIG. In addition to having the function of removing the influence of external noise, it is also capable of rectifying the water flow in the space 20 serving as the observation section together with the bottom panel 8.

The replacement fluid pouring mechanism 30 that pours out a certain amount of replacement fluid into the observation section 20 includes spacers 31A, 3
1A, . . . , a cylinder 31 as a fluid storage section fixed to the upper end surface of the head board 7 in FIG. The cylinder 31 includes a rod guide member 34 that guides the cylinder 31 at its upper end, and a piston drive unit 35 that is fixedly mounted on the rod guide member 34 and that transmits reciprocating force to the piston 32 via the piston rod 33. Also,
Water conduit pipes 36, 36 leading from the center of the lower end of the cylinder 31 in FIG. 2 to the observation section 20 are disposed via check valves 36B, 36B, respectively. These water conduit pipes 36, 36 are configured to be able to discharge a replacement fluid 80 (see FIG. 6) from a single discharge hole 36A in the center of the head panel 7 to the observation section 20.

On the other hand, small ventilation holes 37, 37 are provided in the upper end side wall of the cylinder 31, so that the piston 32 can be easily lowered. Further, a sealing mechanism 32A is attached to the center of the piston 32, thereby preventing the replacement fluid 80 from leaking into the probe body 6.

Furthermore, an introduction pipe 38 for feeding replacement fluid into the cylinder 31 from the outside is provided on the side wall of the lower end of the cylinder 31 . This introduction pipe 3
8 is equipped with a check valve 38A, which prevents the liquid in the cylinder 31 from upwardly flowing back to the outside through the introduction pipe 38 even if the piston 32 moves downward.

The piston drive unit 35 of the replacement fluid dispensing mechanism 30 includes a small motor 35A whose startup, stop, and forward/reverse operation are freely controlled by an externally provided motor control unit (not shown), and a small motor 35A. 35A, and a gear mechanism 39 consisting of a rack 33A and a pinion 33B for transmitting the output of the reducer 35B to the piston rod 33 (see FIGS. 2 and 3). reference). Of these, the rack 33A is formed on the side surface of the piston rod 33. The piston rod 33 is also equipped with a rotation prevention mechanism 70 to prevent it from rotating when it moves up and down (see FIG. 3).

In the displacement fluid dispensing mechanism 30 configured in this manner, when the piston 32 is biased by the piston drive unit 35 and slightly descends after a predetermined time as described later, the displacement fluid 80 in the cylinder 31 is kept constant. The amount is periodically discharged from the single discharge hole 36A of the head disk 7.

Next, the configuration of the electrode wire group 9 protruding from the head panel 7 and the specific method of measuring the flow of groundwater described above will be explained.

First, as shown in FIG.
A,...18A are arranged concentrically at equal intervals,
Corresponding to the outer electrodes 11A to 18A, inner electrodes 11B, 12B, . . . , 18B are similarly arranged concentrically at equal intervals. Therefore, in the embodiment shown in FIG. 4, the electrode wires are arranged radially in eight directions with the single discharge hole 36A as the center. Each of these electrode wires 11A, 11
B, 12A, 12B, ..., 18A, 18B are
Of the parts protruding from the head board 7, about 1/2 of the parts on the head board 7 side are insulated.

Of each electrode wire group 9, electrode wires forming one direction, for example, the outer electrode 11A, the inner electrodes 11B, 15B, and the outer electrode 15A constitute a set of measurement electrode groups, and at the same time, the inner electrodes 11B, 15B are mutually conductive. has been done. For example, when using the difference in resistivity between the displacement fluid and _groundwater , as shown in _FIG . A resistance (liquid resistance) RX ₁₁ between one inner electrode 11B and a resistance RX ₁₅ between the other inner electrode 15B and the other outer electrode 15A are bridge-connected as shown in FIG. After applying a predetermined AC voltage between 11A and 15A, the fixed resistor
Terminal S between R ₁ and R ₂ and inner electrode 11B or 15
This is to measure the change in voltage V ₁₅ between V and B. When the measurement circuit 81 as a signal detection and display means is configured in this way, by discharging a predetermined amount of replacement fluid, for example, a small amount of the electrolyte 80, from the single discharge port 36A in the center of the head panel 7, the electrolyte 80 is is moved inside the observation unit 20 together with groundwater and sent out to the outside, but during this time, one of the outer electrodes 11
Since the resistance value of the resistance RX ₁₁ between A and the inner electrode 11B or the resistance RX ₁₅ between the other inner electrode 15B and the outer electrode 15A changes sequentially, the state of this resistance change can be observed using the measurement voltage V described above. This can be seen as ₁₅ changes. Other collinear electrodes such as outer electrode 12A, inner electrode 12B, 16
B For example, the outer electrode 16A is configured in the same manner, and voltage changes are individually measured in each bridge circuit.

Next, the overall operation of the basic technical configuration shown in FIG. 2 will be explained.

First, the probe 3 is lowered to a predetermined depth within the borehole 1. At this time, the probe 3 is placed in a predetermined direction by the built-in compass 4. Next, after the agitation of the groundwater W due to the descent of the probe 3 has subsided, the displacement fluid dispensing mechanism 30 in the probe body 6 is operated by an external operation, and the cylinder 3
1 is slightly lowered to discharge a predetermined amount of electrolyte into the observation section 20 as shown in FIG. 6A.

Here, the groundwater W is, for example, external electrode 11A→1
To explain the case of flowing in the direction 5A, it takes a certain time T ₁ for the electrolyte mass 80 to first reach the inner electrode 15B. This electrolyte mass 80 diffuses, albeit slightly, and reaches the inner electrode 15B as shown in FIG. 6B, but also reaches the adjacent inner electrode, for example 16B. Therefore, at the same time as the resistance RX ₁₅ between the inner and outer electrodes 15A and 15B starts to change along the flow direction, the resistance between the adjacent inner and outer electrodes, for example, the resistance RX ₁₆ between the electrodes 16A and 16B also changes. The voltages V ₁₅ and V ₁₆ change almost simultaneously. Subsequently, after time T ₂ has elapsed, the electrolyte mass 80 is transferred between the inner electrode 15B and the outer electrode 15A (see FIG. 6C). Voltage V ₁₅ shows the peak. In this case, if the width of the electrolyte mass 80 is relatively large, the voltage V ₁₅ peaks until the left end of the electrolyte mass 80 in FIG. 6 reaches the inner electrode 15B, that is, from time T ₂ to T ₃ . The value continues. On the other hand, in this case, the other voltage V ₁₆ also shows a peak value. Although it varies depending on the size of the electrolyte mass 80, on average it passes through adjacent electrodes, for example, 16B and 16A, while diffusing.
The peak value of V ₁₆ is quite low as shown in FIG.

As a result, it is first confirmed that the flow direction of the groundwater is that the other sewage W is flowing in the direction of the measurement electrode group 11A, 11B, 15B, 15A showing the maximum peak value _V15 . This direction is designed to accurately identify the flow direction using the above-mentioned compass as a reference.

Furthermore, when measuring the time from when the electrolytic solution mass 80 reaches the other inner electrode 15B until it further advances and reaches the outer electrode 15A, that is, (T ₂ - T ₁ ),
The groundwater flow velocity can be easily determined by calculating L/(T ₂ -T ₁ ), where L is the distance between the electrodes 15A and 15B.

Next, when the electrolyte mass 80 flows away together with the groundwater and the V ₁₅ and V ₁₆ show zero values, the replacement fluid pouring mechanism 3 is removed in exactly the same manner as described above.
0 is activated to form an electrolyte mass 80 in the observation section 20, thereby making it possible to start the second flow measurement.
Such operations can be performed any number of times under exactly the same conditions.

Therefore, in this embodiment, it is possible to accurately and easily measure the flow direction and velocity of groundwater by simply pouring a predetermined amount of a small amount of electrolyte into the center of the observation unit 20 disposed in the groundwater. Since the displacement fluid dispensing mechanism 30 is constructed so that it can be operated externally, it is possible to repeat measurements as many times as necessary under exactly the same conditions, thereby improving measurement accuracy and speeding up measurement work. It has the advantage of being able to

Here, in the basic technical configuration described above, a single discharge port 36A is formed in the center of the head board 7 for discharging the electrolytic solution.
Although the case where the probe is poured from the probe body 6 is illustrated, the probe body 6
It may also be configured to pour out an appropriate amount of electrolyte outside of the container. In addition, as a replacement fluid, in addition to electrolytes, insulating oil with a high dielectric constant may be used to take advantage of the difference in capacitance with groundwater, or liquids with different PH values (acid or alkaline solutions) may be used. PH measurement electrodes may be used to detect replacement with groundwater.Furthermore, composite materials mixed with metal particles etc. may be used to improve measurement sensitivity. Any liquid substances (including sol substances) with different electrical (conductivity, dielectric constant, etc.) or chemical (PH, etc.) properties, corresponding electrodes, and measurement circuits may be used. Furthermore, the measurement electrodes may be arranged not only radially but also in a mesh pattern.

Next, a specific example of the present invention will be explained based on FIGS. 8 to 10. Here, the same reference numerals are used for the same components as those in FIGS. 2 to 7 described above (hereinafter the same).

This specific example is based on the outer electrodes 11A and 12 of the electrode line group 9 in FIGS. 2 to 7 described above.
A, . . . , 18A are integrated to form an annular electrode 10S as a second electrode, and inner electrodes 11B, 12B, . . . 1 in FIGS. 2 to 7 are integrated.
8B are independent inner measuring electrodes 11, 12, 13, ..., 18 as first electrodes, and each electrode located on the same diameter line including these inner measuring electrodes 11 to 18 and the annular electrode 10S is It is configured to be handled as a group of measurement electrodes.
The measuring circuit 82 serving as the signal detection and display means is configured as shown in FIG. 10, for example. In this FIG. 10, RX _1S indicates the electrical resistance between the inner measuring electrode 11 and the annular electrode 10S, and RX _5S indicates the electrical resistance between the inner measuring electrode 15 and the annular electrode 10S. The other configurations are the same as those shown in FIGS. 2 to 7 described above.

Even with this configuration, there are advantages in that it not only has the same working effect as the first embodiment described above, but also simplifies assembly and can further increase durability.

In the specific embodiment shown in FIGS. 8 to 10, the inner measuring electrodes 11 to 18 may be arranged outside the annular electrode 10S.

Next, we will discuss other technologies similar to the present invention in the 11th section.
This will be explained based on FIGS. 13 to 13.

The devices shown in FIGS. 11 to 13 have a single discharge hole 36A for the electrolytic solution in the basic technique shown in FIGS. 1 to 7 described above, which is provided on the bottom plate 8 side. To explain this more specifically, the water pipe 36 in the first embodiment is connected from the bottom of the cylinder 31 to the bottom plate 8 of the observation unit 20 as shown in FIG.
The opening end is directed upward from the center of the bottom plate 8. In this case, a porous member 90 of a predetermined size and a tubular covering member 91 surrounding the porous member 90 are fixedly attached to the central portion of the bottom plate 8 on the observation unit 20 side. The replacement fluid pouring mechanism 30 described above is configured to be externally operated so that the electrolyte is poured out relatively slowly.
The other configurations are the same as those shown in FIGS. 1 to 7 described above.

For this reason, here, especially when an electrolyte slightly lighter than groundwater is used, the electrolyte mass 80 is
Since the electrolyte mass 80 is formed as shown in Figure C after passing through each figure of Figures A and B, the electrolyte mass 80 is prevented from descending, and therefore
For example, the electrolyte mass 8 is placed along the electrodes 15B, 15A, etc.
0 flows reliably, which has the advantage that its flow velocity and flow direction can be detected accurately.

In the case of FIGS. 11 to 13, the tubular covering member 91 (see FIG. 11) protruding from below into the observation section 20 is shown in FIGS. 14A, B, and C.
As shown in , it may be configured to be formed of a thin tube 96 and equipped with a disk-shaped liquid discharge mechanism 95 having an open upper end at its tip.

In this way, due to the action of the streamlines on the upper and lower outer peripheries of the disk-shaped liquid discharge mechanism 95, the electrolytic solution discharged into the observation section 20 flows in a substantially horizontal direction together with the groundwater as shown in A, B, and C of the same figure. Therefore, the electrolyte mass 80 described above flows approximately perpendicular to the electrode wires 15B and 15A. In this respect, there is an advantage that the flow direction of groundwater can be detected accurately.

Next, other approximation techniques are shown in Figures 15 to 1.
This will be explained based on FIG.

What is shown in FIGS. 15 through 17 differs from the examples shown in FIGS. 16th via member 93
As shown in FIG. A, the liquid is intended to be ejected to the entire area inside the observation section 20. The other configurations are the same as those shown in FIGS. 2 to 7.

In this way, as shown in FIG. 16, the observation section 20 is uniformly filled with the displacement fluid mass 92, and is then washed away by the groundwater W. Therefore, in the case shown in FIG. 16, first a resistance change occurs between the electrodes 11A and 11B, and the voltage V ₁₁ is detected, and then a sudden rise of V ₁₂ occurs due to the resistance change between the adjacent electrodes 12A and 12B. Detected in Therefore, the flow direction is first revealed by the first voltage change,
At the same time, the flow velocity can be determined by measuring the time it takes to reach the peak.

Incidentally, although V ₁₁ begins to decrease from the state shown in FIG. 16D, it is observed that V ₁₂ is already rapidly decreasing at this point. These series of changes are caused by the rectification effect of the wire mesh 25, so that when the displacement fluid 92 moves within the observation section 20 surrounded by the wire mesh 25, the upstream boundary surface 94 with the groundwater is formed in substantially the same plane in the vertical direction. It is something that arises because it is done.

Even in this case, substantially the same effect as in the case of FIGS. 2 to 7 can be obtained.

In the cases shown in FIGS. 15 to 17, the disc-shaped porous member 93 is attached to the bottom plate 8 side as shown in FIG. It may also be configured to pour out.

〔Effect of the invention〕

As described above, according to the present invention, an observation section equipped with a plurality of electrodes is disposed in a fluid to be measured, and a certain amount of substitution with different electrical or chemical properties is placed inside or outside the observation section. The structure is configured to detect the change in impedance between the measurement electrodes caused by the movement of this displacement fluid mass after pouring out the fluid, so the flow direction of the fluid to be measured can be detected from the electrode position where the maximum peak value is detected first. At the same time, the flow velocity can be detected with high precision from the distance between the electrodes and the timing of arrival at each electrode.

Furthermore, since a replacement fluid extraction mechanism is provided and the replacement fluid extraction mechanism is configured to be operated externally, measurements can be performed any number of times under exactly the same conditions. Therefore, it is possible to accurately measure the flow of fluid moving at extremely low flow speeds in a single borehole over and over again over a long period of time while keeping the measurement probe in place. . Furthermore, each of the measurement electrode parts includes a first electrode formed of a relatively thin single electrode wire, and a first electrode arranged at a constant interval on the outside of this first electrode, and one end surface of which has an annular shape as a whole. Since the second electrode is provided in a somewhat protruding manner and functions as a common electrode, the structure of the electrode part becomes simpler and more durable, and the outer surface of the second electrode becomes larger. Therefore, it is possible to provide an unprecedented and excellent fluid flow measuring device that can improve the overall measurement sensitivity.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the usage state of the embodiment according to the present invention, FIG. 2 is a longitudinal cross-sectional view showing an example of the basic technical configuration according to the present invention, and FIG. 3 is a view taken along the - line in FIG. 4 is a sectional view showing the arrangement of electrode portions taken along the - line in FIG. 2; FIG. 5 is a circuit diagram showing an example of a signal detection and display means; FIGS. 6A, B, and C. 7 to 7 are explanatory diagrams of the operation of FIG. 2, FIG. 8 is a partial sectional view showing a specific embodiment of the present invention, FIG. 9 is a sectional view taken along the - line in FIG. 8, and FIG. 11 is a partial sectional view showing another similar technical example; FIGS. 12A, B, C to 13 are explanatory diagrams of the operation of FIG. 11, and FIG. FIG. 14 is an explanatory diagram of the operation in a modified example of FIG. 12, FIG. 15 is a partial sectional view showing another similar technical example, and FIG. 16A,
B, C, D, E to 17 are explanatory diagrams of the operation of FIG. 15, and FIG. 18 is a partial sectional view showing a modification of FIG. 15. 3... Probe, 11, 12, 13, 14, 1
5, 16, 17, 18...first electrode as an inner measurement electrode, 20...observation section, 30...replacement fluid pouring mechanism, 31...cylinder as a fluid storage section,
38...Introduction pipe, 80,92...Displacement fluid mass, 8
1, 82...Measurement circuit as signal detection and display means.

Claims (1)

[Scope of Claims] 1. An observation section is provided in which a plurality of measurement electrode sections are arranged concentrically and radially at regular intervals, and within this observation section, there is a section that has electrical or chemical properties different from that of groundwater. A displacement fluid pouring mechanism for pouring out a fixed amount of displacement fluid by an external operation is provided near the observation section, and each of the measurement electrode sections is connected to a second electrode formed of a relatively thin single electrode wire. 1 electrode, and a second electrode which is disposed at regular intervals outside the first electrode and whose one end surface is slightly protruded in an annular shape as a whole and which functions as a common electrode. Characteristic fluid flow measuring device.