JPS6310392B2 - - 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, there has been an increasing need to accurately measure groundwater flow (velocity and/or flow direction) in the field of civil engineering and construction, in order to determine whether or not to adopt freezing methods for soft ground, and to investigate groundwater contamination. ing. Conventionally, a so-called tracer method has been widely used as a method for measuring groundwater flow. This method involves drilling multiple boreholes, injecting salt or dye into one of the central boreholes, examining changes in electrical resistance or concentration over time between the other boreholes, and determining the arrival time and its location. It calculates and measures the flow from the flow. However, in the above-mentioned conventional technology, it is necessary to drill a large number of boreholes, which increases the survey cost, and also requires a long time to measure when the groundwater flow velocity at the measurement location is slow. This has the inherent disadvantage that groundwater flow often changes due to the groundwater flow, making it difficult to make accurate measurements.

Recently, as an attempt to improve the drawbacks of the above-mentioned conventional techniques, a method has been devised to inexpensively and quickly measure the flow of groundwater by only drilling one borehole. For example, this method involves lowering a propeller-type current meter as a measuring means into the borehole and measuring the flow direction and flow velocity from the rotational speed of the propeller and its changes. According to the invention, a disk is lowered into a borehole, and the groundwater flow condition is estimated from the pressure difference due to the upward and downward flows of water in the hole acting on the disk.

However, in all of the above conventional techniques, the flow is measured by treating the flow of water in the borehole as the flow of groundwater, but when the groundwater flowing in the ground such as a gravel layer reaches the borehole,
Turbulent flow occurs due to discontinuity of frictional resistance (soil properties against the flow of groundwater) within the borehole, and therefore, the flow velocity of groundwater is extremely small in a borehole with a relatively small diameter. However, it has the disadvantage that accurate flow measurement is difficult.

Furthermore, in the method of driving a mechanical measuring means using groundwater, if the flow velocity is minute, such as 2 cm per second or less, it is almost impossible to measure the flow velocity or flow direction due to the effects of frictional force, etc.

[Purpose of the invention]

The present invention improves the disadvantages of the conventional example, and creates an observation environment that approximates the actual flow of groundwater underground, especially in the observation section, thereby making it possible to measure the flow of groundwater more accurately. The object of the present invention is to provide a fluid flow measurement device that improves reliability of values.

[Means for solving problems]

Therefore, in the present invention, a groundwater observation section is provided by arranging a plurality of measurement electrodes at equal intervals on the same circle, and a replacement substance output means is provided around this observation section, and the observation section is cylindrical and conductive. surrounded by a net-like member made of a sexual material, and filled with a granular member therein;
The above objective is achieved by adopting a configuration in which the side surface of the probe body supporting the groundwater observation section is equipped with a pressure water injection means for injecting pressurized water toward the side wall of the bottom of the borehole. It is something.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 8.

FIG. 1 is a schematic explanatory diagram showing an example of actual measurement using the flow measuring device according to the present invention. In the figure, reference numeral 1 indicates a measurement borehole drilled in the ground E from the ground surface to a predetermined depth into the groundwater layer (fine sand layer, medium sand layer, etc.). A casing (not shown) is driven into the side wall of the borehole 1 to a point above the measurement depth, and this casing prevents collapse of the hole side wall 1A and connects the stratum to be measured with other strata. are increasingly being blocked.

A boring rod 3 is inserted into this borehole 1.
A measurement probe (hereinafter simply referred to as "probe") 4, which is an example of a flow measuring device, is lowered to the test depth, and the observation part provided below the probe 4 is Hole bottom wall 1B
It is buried inside. Here, the direction of the probe 4 is confirmed by a compass 5 (see FIG. 2) built into the upper part of the probe 4, and the probe 4 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 arrow F in the figure, and in the borehole 1
Groundwater W gushes out from the groundwater layer, and therefore the probe 4 is immersed in the groundwater W.

The probe 4 is mechanically and electrically connected to an external measuring device (not shown) by a hose 6 and a captire cable 8 extending along the boring rod 3. This makes it possible to measure and record groundwater flow.

FIG. 2 shows a specific configuration of the probe 4 mentioned above. In this figure, 9 is attached to the lower end of the boring rod 3.
This is a cylindrical probe body fixed via a connecting tube part 2 that is detachably screwed into the probe body.
0 and a bottom plate 11 that is mounted opposite to the head plate 10 at a predetermined interval.
2 is provided.

The head board 10 is made of an insulating material, and is provided with a tapered portion 13 formed in a tapered shape on its peripheral side. On the outer periphery of this tapered part 13, a first ion generation electrode 14 for forming an ion layer as a displacement fluid mass is attached in a ring shape, and inside the first ion generation electrode 14. A wire mesh 15, which will be described later, is provided below as a second ion generation electrode. In addition, the head board 10
A plurality of measurement electrode groups 30 (specifically described later) are arranged concentrically and at equal intervals on the lower surface of the electrode. The head board 10 has a predetermined length.
The probe body 9 is screwed to the lower end surface of the probe body 9 by real threaded supports 16, 16, . Further, on the upper surface of the head board 10 in FIG. 2, a terminal plate 17 is provided for connecting each electrode to a measuring circuit.

A bottom plate 11 is provided opposite to the head plate 10.
are fixed by nuts at the lower ends of the threaded columns 16, 16, . And a space 1 as an observation part formed between this bottom plate 11
2, underground water W as a fluid to be measured can flow into the pipe. On the other hand, the bottom plate 11 not only locks the wire mesh 15 but also functions as a container bottom for filling particulate matter into the observation section 12, and even when the entire probe 4 is pushed down to the bottom of the borehole 1.
It also has the function of preventing damage to the observation section 12. Further, an opening 19 is formed in the center of the bottom plate 11 for taking in and out the granular filler 18, and a rubber stopper 20 is removably fitted under the opening 19.

A cylindrical wire mesh 15 is disposed between the peripheral edge of the lower surface of the head board 10 and the bottom board 11 so as to surround the measurement electrode group 30. This wire mesh 1
5 is made of a conductive material such as platinum or stainless steel, and in addition to having a function as a second ion generation electrode, it also electrically shields the measurement electrode group 30 during flow measurement to eliminate external noise due to earth current, etc. It plays the role of removing the influence of Furthermore, the mesh size of the wire mesh 15 is set to such an extent that it prevents the filler 18 from dissipating and does not prevent the flow of underground water.

Here, the granules 18 that are filled in the observation section 12 in advance make the frictional resistance (soil properties) against the flow of groundwater in the observation section 12 the same as the frictional resistance of the groundwater layer that is the object to be measured. By this,
This is to cause the same flow in the observation section 12 as groundwater that flows in the actual ground E.

Four vertically extending fins 21, 21, . , the entire probe 4 can be fixed non-rotatably. Inside the fins 21, 21, . . . are provided with injection pipes 22, 22, . One end of the injection pipes 22, 22, . . . is connected to a donut-shaped water supply distributor 23 mounted on the upper shoulder of the probe main body 9, and the other end is connected to the fins 21, 21, . The fins 21, 21, . . . are bent in the horizontal direction slightly below the center thereof, and then opened at the tip surfaces of the fins 21, 21, . . . to form injection ports 22A, 22A, . Furthermore, injection piping 22, 22,
Check valves 24, . . . for preventing foreign matter from entering are interposed in the middle of the . . . On the other hand, the water supply distributor 23 is connected to a pressure hose 6 extending from the ground. This water supply distributor 23 has a function of sending out equal pressure water to each injection pipe 22, 22, . . . when pressure water is injected from the outside. Therefore, the bottom wall 1B of the borehole 1 (see FIG. 5A)
After the observation part 12 of the probe 4 is lowered and installed nearby, when pressurized water is sent out through the pressure hose 6, the hole side wall 1A is discharged from each injection port 22A, 22A, . . .
The pressurized water is sprayed towards. When this jet flow hits the hole side wall 1A, the hole side wall 1A collapses and becomes soft, and the collapsed soil descends around the observation section 12, so that the observation section 12 can be backfilled. It's getting old. At this time, if the injection ports 22A, 22A, . . . are arranged above the fins 21, 21, . . ., the fins 21, 21, .

The aforementioned azimuth gauge 5 is housed near the upper end of the probe body 9, and its azimuth signal is transmitted to the outside via the captire cable 8. The captire cable 8 is inserted into the probe body 9 from the outside through a hole 25 provided in the connecting pipe portion 2 and a seal plug 26 sealed by a rubber member 26A provided at the upper end of the probe body 9. It has been introduced.

Next, the configuration of the measurement electrode group 30 provided on the head panel 10 and the specific method of measuring the flow of groundwater described above will be explained.

First, the measurement electrode group 30 includes a first electrode 31 and a fourth electrode 32 that are flush with the lower surface of the head board 10, concentrically, and exposed in an annular band, as shown in FIGS. 2 and 3.
A plurality of sets of second electrodes 33A to 40A and a third electrode 33 are provided between the first electrode 31 and the fourth electrode 32, projecting linearly downward from the head board 10.
B to 40B. To explain these in detail, first, as shown in FIG. 3, the first electrode 31 is provided in a ring shape along the vicinity of the outer peripheral edge of the lower surface of the head board 10. As shown in FIG. Next, this first
Inside the electrode 31, a plurality of second electrodes 33A~
40A are arranged concentrically at equal intervals, and third electrodes 33B-40B are similarly arranged concentrically at equal intervals inside the second electrodes 33A-40A. Therefore, in the embodiment shown in FIG. 3, the second and third electrodes 33A to 40A and 33B to 40B are arranged radially in eight directions. These second and third electrodes 33A
40A, 33B and 40B, among the parts protruding from the head board 10, the parts near the head board are insulated. Further, the third electrodes 33B to 40
A ring-shaped fourth electrode 32 is arranged concentrically inside B.

Among the measurement electrode group 30, the second and third electrodes arranged in one direction, for example, the second electrode 33A and the third electrode
The electrodes 33B constitute one set of detection electrode group 33.

Next, each measurement electrode group 30 and the first,
An example of the configuration of the measurement circuit 41 that electrically drives and measures the second ion generation electrodes 14 and 15 will be described based on FIG. 4.

First, regarding the detection section 41A built into the probe body 9, the first and fourth electrodes 3
A predetermined AC voltage is applied by an oscillator 42 between the first and third electrodes.
Electricity is supplied between the fourth electrodes 31 and 32 through underground water within the observation section 12 . This energization within the observation unit 12 generates a voltage between each set of the second and third electrodes 33A, 33B, 34A, 34B, . . . . This voltage is detected separately for each detection electrode group 33-40, and is detected by amplifiers 43-40.
It is now being sent to the 50th. On the other hand, between the first and second ion generation electrodes 14 and 15,
A one-shot pulse generator 51 applies a pulse for ion generation having a predetermined wave height and pulse width. This one-shot pulse generator 51 has a function of outputting a pulse for the ion generator when a start signal is input from the outside, and also has a function of outputting a pulse for the ion generator when a start signal is input from the outside. is the first ion generation electrode 1 which is on the negative side when a pulse voltage is applied.
It has a function of accumulating and generating positive ions (H ⁺ etc.) P in the vicinity of 4, and negative ions (OH ^- etc.) Q in the ion generation electrode 15 on the positive side (see Fig. 6A). . The cylindrical ion layer (displacement fluid mass) 60 generated near the second ion generating electrode 15 moves within the observation section 12 as the groundwater flows and is sent out to the outside.
During this time, since the conductivity of the ion layer is higher than that of groundwater, the resistance value near the detection electrode groups 33 to 40 changes sequentially. This can be interpreted as a change in the detection signal voltage (measured voltage) V ₃₃ to V ₄₀ . The measured voltages V ₃₃ to V ₄₀ are sent to the amplifiers 43 to 50, amplified, and then output to the analog switch 52. On the other hand, a clock pulse generator 53 is connected to the output side of the oscillator 42, and a counter 54 is further connected to the output side of the clock pulse generator 53. This counter 54 has the function of cyclically counting the clock pulses sent from the clock pulse generator 53 and sending this counted value to the analog switch 52 as a synchronization signal. This analog switch 52 is connected to the counter 54.
Based on the synchronization signal sent from each amplifier 43 to
The measured voltages V ₃₃ to V ₄₀ outputted from the analog switch 50 are time-divided and sent to a full-wave rectifier circuit 56 connected to the output side of the analog switch 52 . This full-wave rectifier circuit 56 has each measured voltage V ₃₃ ~
After full-wave rectification of V ₄₀ and converting it into a DC component, each measured voltage is sent via the aforementioned captire cable 8.
V ₃₃ to V ₄₀ are sent to a recording section 41B provided on the ground. On the recording section 41B side, an analog switch 57 to which a synchronization signal is input from the counter 54 synchronizes the output of the full-wave rectifier circuit 56 with the analog switch 52 for each measured voltage V ₃₃ to V ₄₀ . The signals are time-divided while being processed and output to a recorder (not shown) such as a multi-channel recorder via corresponding offset circuits 58-65. Here, the offset circuits 58 to 65 are connected to the detection electrode group 33.
This is for individually adjusting the level error that occurs every .about.40. The measuring circuit 41 configured in this manner makes it possible to measure and record the movement of the ion layer formed by the first and second pulse generating electrodes 14 and 15 over time.

Next, the overall operation of the above embodiment will be explained.

First, the observation part 12 of the probe 4 is filled with granular material (basically sand material collected from the layer to be measured), and then the probe 4 is placed in a predetermined direction using the compass 5. When the bottom plate 11 reaches the hole bottom plate 1B (see FIG. 5A), pressurized water is sent from the outside via the pressure hose 6. Then, the spout 2
Pressurized water is injected from 2A, 22A, . At this time, since the tapered part 13 of the head disk 10 is formed diagonally inward, the area around the observation part 12 is backfilled without any gaps. Finally, the lower end of the probe 4, including the inside and outside of the observation section 12, is buried in the groundwater aquifer. (See Figures 5B and C). For this reason, observation section 1
2 is integrated with the groundwater aquifer and has the same soil properties, so that almost the same flow as the groundwater in the groundwater aquifer is obtained.

Next, after the descent of the probe 4 and the disturbance of groundwater etc. due to the burying work have subsided, power is applied to each part of the measurement circuit 41, and the first electrode, fourth electrode 31, 3
An alternating current voltage is applied between the two. Next, first, a start signal is sent to the one-shot pulse generator 51, and a pulse is applied to the first and second ion generation electrodes 14, 15. As described above, when the pulse is applied to the second ion generation electrode on the positive side, A cylindrical ion layer 60 as a displacement fluid mass is formed near the electrode 15 (see FIG. 6A). At this time, a positive ion layer is also formed near the first ion generation electrode 14, but it moves above the observation unit 12 as the groundwater W flows, so it does not affect the measurement of the groundwater flow.
At the same time, electrolysis is also performed and bubbles R are generated, but since the bubbles R are adsorbed to the soil or dissolved in groundwater, they have little effect on the measurement. Here, if the groundwater W is, for example, the detection electrode group 33→3
To explain the case of flowing in seven directions, the ion layer 60 also moves as the groundwater W flows,
When the leading edge of the ion layer 60 reaches the second electrode 33A after time _T1 (see FIG. 6B), the second,
First, the resistance value between the third electrodes 33A and 33B begins to decrease, and therefore the value of the measurement voltage _V33 begins to decrease (see _T1 in FIG. 7). Thereby, it is detected that the flow direction of the groundwater W is from the detection electrode group 33 to 37. This direction is accurately specified using the above-mentioned compass 5 as a reference. Subsequently, when time T ₂ elapses and the ion layer 60 is transferred to the middle between the second electrode 33A and the third electrode 33B (see FIG. 6C), the voltage V ₃₃ shows a peak (see FIG. 7). (see T ₂ ). Therefore, the time T ₂ from when the ion layer 60 is formed on the second ion generation electrode 15 to when the ion layer 60 reaches between the second and third electrodes 33A and 33B, and the second ion generation electrode 15 and Assuming that the distance between the detection electrode group 15 and the detection electrode group 33 is L, the groundwater flow velocity can be easily determined by calculating L/T ₂ . In this case, the flow velocity may be determined by l/( _T2 - _T1 ), where l is the distance between the second and third electrodes 33A and 33B.

On the other hand, in other detection electrode groups, for example, the voltage V ₃₄ related to the detection electrode group 34 is
The timing at which the ion layer 60 reaches A is delayed from the timing at which the ion layer 60 reaches the second electrode 33A,
In addition, since the voltage passes obliquely between the electrodes 34A and 34B, the rise of the voltage _V34 is delayed and the peak change is small. Therefore, it is also possible to perform the flow direction measurement by detecting the one with the earliest peak timing or the largest peak change among the measurement electrodes V ₃₃ to V ₄₀ .
When the rising or peak values of the measured voltages of adjacent detection electrode groups are the same, the direction between them indicates the flow direction of the groundwater. As time passes further and the ion layer 60 passes the detection electrode group 33, the voltage _V33 rises to its original value (Fig. 7).
(see T ₃ ).

Next, when the ion layer 60 flows away together with the groundwater and the voltage V ₃₃ etc. return to their original values, the first and second ion layer generation electrodes 14 and 15 are connected in exactly the same manner as described above. Applying a pulse, the ion layer 6
By forming 0, the second flow measurement can be started. Such operations can be performed any number of times.

Separately, if you wish to periodically measure groundwater flow over a long period of time, first bury the vicinity of the observation section 12 in the same manner as described above, and then further bury the outer circumference of the probe 4 as shown in Figure 8A. Backfill as shown. At this time, the probe 4 is fixed by the fins 21, 21, . . . , so that the boring rod 3 can be removed.
Furthermore, the inside of the borehole 1 is backfilled to near the ground surface (the casing is taken out as necessary). At this time, the lid 7 (see FIG. 2) inside the connecting pipe section 2 is adapted to receive pressure after backfilling.

Next, by sending a start signal to the one-shot pulse generator 51 at the desired time in the same manner as described above, the flow of groundwater can be measured at any time, and since the entire probe 4 is backfilled, it is extremely accurate. measurements can be made.

Therefore, in the first embodiment, since the detection voltage is transmitted in a time-division manner, the circuit configuration of the detection section is simplified, the length of the probe can be reduced, and the first and fourth Since each electrode is formed integrally with a plurality of detection electrode groups, the electrode structure is simplified and the arrangement is also easy.Furthermore, internal wiring can be simplified, making it possible to reduce the outer diameter of the probe. Therefore, along with the miniaturization of the probe length, the probe can be easily and reliably buried and measured even in a relatively small borehole. Furthermore, the time-division detection allows the cap tire cable to be made smaller. Furthermore, since the output of the generator used to generate the tick pulse is used as a power source to be applied to the first and fourth electrodes, there is no need to prepare a separate AC power source.

In addition, since the observation section is filled with granules in advance and the area around the observation section is backfilled by injecting pressurized water into the hole wall, the soil properties of the layer to be measured can be easily and reliably inspected inside and outside the observation section. They can be made substantially the same, and by simply applying a pulse to the ion generation electrode, it is possible to repeatedly perform highly accurate measurements without disturbing the measurement target. Furthermore, the wire mesh that surrounds the observation area prevents the dissipation of the filling material and has a shielding effect to block external noise, making it possible to further improve the measurement accuracy. Since it is used for both purposes, the structure can be simplified, and since the electrode surface area is large, the amount of ions generated can be increased, and the generation of bubbles can be suppressed. Moreover, since the ion layer is formed in a cylindrical shape, it always crosses one of the detection electrode groups regardless of the flow direction, so that reliable measurements can be performed.

Moreover, the fins and the pressure water injection means can be easily attached to and detached from the probe body.

In addition to the above-mentioned ionic layer, the displacement fluid mass has electrical (conductivity, dielectric constant, etc.) or chemical (PH
etc.) As shown in FIG. 9, liquid substances with different properties and similar specific gravity and viscosity are introduced into or outside the observation section from the tip of the spouting pipe 81 via the liquid supply hose 80 (not shown). pouring out to form a displacement fluid mass 82;
The groundwater flow may be measured by means of corresponding electrodes and measuring circuits. Also, the 10th
As shown in the figure, a vertically movable cylindrical sleeve 85 with fins 84 and an injection part 83 is provided on the outside of the wire mesh 15 of the observation section, and a displacement fluid 86 is uniformly mixed with the filling in the observation section in advance. Then, after lowering the probe, the probe 85 may be raised, and then pressurized water may be delivered to the injection portion 83 to collapse the wall of the hole.

In addition, regardless of the ground to be measured, any granular material filled into the observation part, such as sand material or glass beads, will produce sufficient effects.

〔Effect of the invention〕

As described above, according to the present invention, the gap between the observation section and the borehole can be reduced to zero by the action of the pressure water injection means, and thereby the observation section can be buried even in the ground. It is possible to measure the flow of groundwater in a state that approximates the actual flow of groundwater, and since the observation area is surrounded by a net-like member made of conductive material, it is possible to rectify groundwater. This is an unprecedented, superior fluid technology that can effectively eliminate the negative effects of external noise such as earth currents, thereby significantly improving the reliability of observed values. A flow measuring device can be provided.

[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 sectional view showing the first embodiment, Fig. 3 is a horizontal sectional view taken along the - line in Fig. 2, FIG. 4 is a block diagram showing an example of the measurement circuit, FIGS. 5A, B, and C are operation explanatory diagrams of a part of FIG. 2, and FIGS. An explanatory diagram showing the principle of flow measurement, Fig. 7 is a diagram showing an example of the measurement results, Fig. 8 is an explanatory diagram showing other effects of Fig. 2, and Figs. 9 to 10 are diagrams showing other implementations. It is an explanatory diagram showing an example. 1...borehole, 12...observation section, 14...
...First ion generation electrode, 15... Wire mesh, 18
... Granular filling, 22 ... Injection piping, 30 ...
Measuring electrode group, 31... First electrode as current-carrying electrode, 32... Fourth electrode, 33-40... Detecting electrode group, 41... Measuring circuit, 60... Ion layer, 82
...Displacement fluid mass, 86...Displacement fluid.

Claims (1)

[Scope of Claims] 1. A groundwater observation section is provided by arranging a plurality of measurement electrodes at equal intervals on the same circle, and a replacement substance output means is provided around the observation section, and the observation section is cylindrical. The probe body is surrounded by a net-like member made of an electrically conductive material and filled with granular members, and a pressure water injection means for injecting pressurized water toward the side wall of the bottom of the borehole is provided on the side surface of the probe body supporting the groundwater observation section. A fluid flow measuring device characterized by being equipped with.