JP2007256026A - Flow direction/flow rate measuring method and system for low flow rate groundwater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a system allowing to measure the flow direction and flow rate of low flow rate groundwater with high precision and easily. <P>SOLUTION: A measuring section 3 partitioned by a pair of packers 11, 12 is formed at the depth of low flow rate groundwater within an underground boring 2. The groundwater G within the section 3 is replaced with a liquid W having a predetermined density, and tracer particles S having the same density as the liquid W are allowed to flow into the section 3. The floating three-dimensional position of the tracer particles S is continuously detected by position detecting sensors 30a, 30b supported by the packer 11 or 12. The flow direction and flow rate of the groundwater G are measured from a temporal change in the detected value of the floating three-dimensional position. Preferably, an inflow path 21 to the section 3 for the tracer particles S includes a storage tank 20 for storing the tracer particles S together with the liquid W, allowing the tracer particles S floating within the storage tank 20 to selectively flow into the section 3. More preferably, the temperature and pressure in the section 3 are measured to correct the density of the liquid W with the measured temperature and pressure values, and the tracer particles S with its density corrected are allowed to flow thereinto. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for measuring a flow direction flow velocity of a low flow velocity groundwater, and more particularly to a method and an apparatus for accurately measuring the flow direction and flow velocity of a low flow velocity groundwater in a deep underground.

  When building an underground structure, it is required to understand the flow direction, flow velocity, and other flow characteristics of the surrounding groundwater in order to predict and evaluate its safety and impact on the surroundings. For example, when building a high-level radioactive waste buried disposal site (geological disposal site) in a stable geological layer (natural barrier) of several hundred to 1,000 meters underground, the radioactivity of waste leaked from groundwater is the biosphere. Therefore, it is necessary to evaluate the safety of whether or not it has attenuated to a sufficiently low level, and it is required to accurately grasp the flow characteristics of groundwater flowing through the natural barrier covering waste.

  Conventionally, as a method of investigating the flow characteristics of groundwater, multiple boreholes (observation holes) are drilled in the ground, and the flow direction and flow velocity of groundwater are determined from the groundwater level and distance between holes (porous method). Has been done. However, when investigating deep underground water, a method (single hole method) that determines the flow direction and flow velocity of groundwater with a single borehole is effective from the viewpoint of economy and workability. In the single hole method, the flow direction and flow velocity of groundwater are generally detected by tracking the three-dimensional position of the tracer thrown into the borehole, but several types of tracer types and tracer tracking methods have been developed. Has been.

  For example, in Patent Document 1, as shown in FIG. 6, a directional neutron moisture meter 41 is inserted into a measurement section partitioned by packers 11 and 12 in a borehole 2 drilled in an aquifer of the ground 1, The injection device 44 injects a tracer liquid (for example, an aqueous solution in which a boron compound having a large thermal neutron absorption cross-section is dissolved) 42 around the neutron moisture meter 41 and counts the thermal neutrons detected by the neutron moisture meter 41 according to the orientation. A method for measuring the flow rate and flow velocity of groundwater by measuring the rate with the measuring device 45 is disclosed. The counting rate of thermal neutrons detected by the neutron moisture meter 41 is reduced by the injection of the tracer liquid 41, but gradually recovers as the tracer liquid 41 is diluted by the flow of groundwater. In the measuring device 45, the flow rate of the groundwater can be obtained from the recovery rate of the count rate, and the flow direction of the groundwater can be obtained from the difference in recovery rate (plane distribution) for each direction. Further, Patent Document 2 uses distilled water as the tracer liquid 42, uses a plurality of electrode groups at predetermined intervals instead of the neutron moisture meter 41, and changes the groundwater flow direction and the change in potential difference (electrical resistance difference) between the electrodes. A method for measuring flow velocity is disclosed. A method of measuring the flow direction and flow velocity of groundwater from changes in heat quantity and specific resistance using heated water or salt water as the tracer liquid 42 has been developed.

However, the methods of Patent Documents 1 and 2 are not suitable for measuring the flow characteristics of groundwater with a low flow velocity. For example, as shown in FIG. 6, the tracer liquid 42 such as an aqueous boron solution has a property of advancing and diffusing itself. Therefore, when the flow rate of the groundwater is reduced, the diffusion rate of the tracer liquid 42 itself cannot be ignored, and the accurate groundwater Measurement of flow direction and flow velocity becomes difficult. The application range of the conventional measurement method using boron aqueous solution, heated water, distilled water, salt water, etc. is considered to be about 10 ^-7 to 10 ^-3 m / s, and it is measured when applied to a lower velocity field. The error increases. On the other hand, in geological disposal sites for high-level radioactive waste, safety assessment over an extremely long time of the order of a thousand years is required, and groundwater with extremely low flow rates (about 10 ^-10 m / s) outside the conventional measurement range is required. It is required to investigate the flow characteristics accurately. In order to accurately measure the flow characteristics of groundwater at such an extremely low flow rate, a measurement method that is not affected by the diffusion of the tracer liquid 42 is required.

  On the other hand, Patent Documents 3 and 4 disclose a method of measuring the flow direction and flow velocity of groundwater by tracking the three-dimensional position of the tracer particles introduced into the groundwater with an ultrasonic sensor or an optical imaging device. For example, as shown in FIG. 5, the measurement section 3 is formed by the packers 11 and 12 suspended in the boring hole 2 by the suspension device 60, and the current plate 53 and the plurality of ultrasonic waves are formed in the measurement section 3 by the support member 52. The measuring unit 51 (see FIG. 5B) to which the sensor 55 or the optical imaging device 58 is attached is suspended, and the groundwater G in the measuring section 3 is approximately equivalent to the groundwater G through the tracer introduction pipe 54. Tracer particles S having a specific gravity are supplied. Ultrasonic waves are transmitted from the plurality of ultrasonic sensors 55 to the tracer particles S flowing along the flow of the groundwater G at regular intervals to detect reflected waves (ultrasonic echoes), and the detected data is transmitted to the signal transmission unit 61 and The data is transmitted to the measuring device 62 via the transmission line 63, and the measuring device 62 measures the three-dimensional continuous movement position of the tracer particles S from the detection data and the sound velocity in the groundwater G. Measure flow direction and flow velocity. Image data of the tracer particles S taken by the optical imaging device 58 photographed through the transparent window 59 of the rectifying plate 53 is transmitted to the measuring device 62, and the three-dimensional continuous movement position of the tracer particles S is measured from the image data. It is also possible.

  As the tracer particle S, Patent Document 3 proposes agglomerated protein of milk, eslene particles mixed with a fluorescent paint, and the like. Patent Document 4 discloses a variable density type in which a vapor-deposited coating layer of a metal having a specific gravity greater than 1 is formed on the surface of an inner sphere having a particle size of about 100 to several hundreds of μm made of polyethylene or polypropylene having a specific gravity smaller than 1. It has been proposed to use artificial tracer particles S. According to such a method of tracking the three-dimensional position of the tracer particles S, the diffusion speed that has become a problem in the tracer liquid 42 in FIG. 6 can be ignored, and the flow direction and flow speed of groundwater with a very low flow rate can be accurately determined. It can be expected to measure.

JP-A-6-273538 Japanese Patent Publication No. 2-046904 JP 2001-183471 A JP 2002-107370 A

  However, the methods of Patent Documents 3 and 4 have a problem that it is difficult to make the density of the tracer particles S exactly match the density of the groundwater G in the measurement section 3. When the density of the tracer particles S is different from the density of the groundwater G, the tracer particles S gradually fall or float in the groundwater G, and the precise measurement of the flow direction and flow velocity of the groundwater G, particularly the measurement of the vertical flow direction and flow velocity, is possible. become unable. In order to improve the measurement accuracy in Patent Documents 3 and 4, it is considered that measuring the flow characteristics of groundwater G at an extremely low flow rate requires about 2 to 3 days. Therefore, it is necessary to keep the distance of falling or flying down small.

Figure 4 shows the relationship between the density difference (g / cm ³ ) between the tracer particles S that fall or float 3 mm in 3 days and the groundwater G and the particle size (μm) of the tracer particles S based on Stokes' law. The graph is shown. As can be seen from the figure, it is effective to reduce the particle size of the tracer particles S in order to keep the tracer particles S falling or floating in the groundwater G to a small distance. However, according to the experiments by the present inventors, when the particle size of the tracer particles S becomes 100 μm or less, the particles are charged and the tracer particles S repel each other and cause measurement errors. It is not desirable that the diameter be 100 μm or less. As shown in FIG. 4, in order to keep the tracer particle S having a particle size of about 100 to 150 μm in the measurement period to a drop or lift distance of 3 mm or less, the density difference between the tracer particle S and the groundwater G is 1.0 × 10 ^−6. Although it is necessary to set it as about g / cm < ³ > or less, it is very difficult to suppress the preparation precision of such a fine particle in the range of density 1.0 * 10 < ^-6 > g / cm < ³ > or less.

  In order to solve this problem, a method of preparing a large number of tracer particles S having different densities, measuring the density of the groundwater G in the measurement section 3, and selecting the tracer particles S according to the measured density of the groundwater G is also considered. It is done. However, since the density of the groundwater G changes due to the influence of temperature and pressure at each depth, the groundwater G is kept at the original temperature and pressure state in order to measure the density of the groundwater G in the measurement section 3. It is necessary to measure water as it is. Such in-situ measurement of the density of groundwater G is not only troublesome but also tends to cause measurement errors. Therefore, in the method of selecting the tracer particles S according to the measured density of the groundwater G, it is difficult to precisely match the density of the groundwater G and the density of the tracer particles S. Currently, it is very difficult to measure.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus capable of accurately and easily measuring the flow direction and flow velocity of groundwater having a low flow velocity.

  Referring to the embodiment of FIG. 1, the flow velocity measurement method of low flow velocity groundwater according to the present invention forms a measurement section 3 partitioned by packer pairs 11 and 12 at a low flow velocity in the underground borehole 2. Then, after replacing the ground water G in the measurement section 3 with the liquid W having a predetermined density, the tracer particles S having the same density as the liquid W are caused to flow into the measurement section 3 and supported by the packer pair 11 or 12; The floating three-dimensional position of the tracer particle S is continuously detected by 30b, and the flow direction and the flow velocity of the groundwater G are measured from the change over time of the detected value of the floating three-dimensional position.

  Referring to the embodiment of FIG. 2, the low-flow-rate groundwater flow velocity measuring apparatus according to the present invention is a packer that forms a measurement section 3 partitioned from the adjacent depth by the low-flow-rate groundwater depth in the underground borehole 2. Pair 11, 12, a water absorption path 18 that absorbs groundwater G from the site near one packer 12 (or 11) in the measurement section 3, and a liquid of a predetermined density in the site near the other packer 11 (or 12) in the measurement section 3 Position detection sensor 30a for detecting the three-dimensional position of a suspended substance at a predetermined detection portion 33 (see FIG. 2B) in the measurement section 3 supported by an infeed path 17 for feeding W, a packer pair 11 or 12 30b, an inflow path 21 for allowing the tracer particles S having the same density as the liquid W to flow into the predetermined detection site 33 in the measurement section 3, and a detection value signal of the floating three-dimensional position of the tracer particles S by the position detection sensors 30a and 30b. A transmission device 34 for transmission is provided.

  Preferably, a storage tank 20 for storing the tracer particles S together with the liquid W is provided in the inflow channel 21 into the measurement section 3 for the tracer particles S, and the tracer particles S floating in the storage tank 20 are selectively placed in the measurement section 3. To flow into. In this case, a pair of flow passages 21 and 22 are provided between the storage tank 20 and the measurement space 3 so that the opening on the measurement space 3 side faces each other, one of which serves as the inflow passage 21 for the tracer particles S, and the other is the tracer particles. The S recovery path 22 can be used. More preferably, a measurement sensor 27 for measuring the temperature and pressure in the measurement section 3 and a supply for correcting the density of the liquid W by the measurement value of the measurement sensor 27 and supplying the corrected tracer particles S to the inflow passage 21 Means 7 (see FIG. 1) are provided.

  The low flow velocity groundwater flow direction velocity measurement method and apparatus according to the present invention replaces the groundwater G in the measurement section 3 in the underground borehole 2 with the liquid W having a predetermined density, and then the tracer particles S having the same density as the liquid W. The flow direction and flow velocity of the groundwater G are measured by continuously detecting the three-dimensional floating position of the tracer particles S in the liquid W by the position detection sensors 30a and 30b. Has a remarkable effect.

(B) Since the tracer particles are allowed to flow after the measurement section is replaced with a liquid of known density, the liquid density and the tracer particle density in the measurement section can be matched exactly, 10 ^-5 to 10 ^-10 m It is possible to accurately measure the flow characteristics of groundwater with a low flow rate of / s.
(B) In addition, it is not necessary to strictly measure the density of groundwater in the measurement section, and the precise flow direction and flow velocity of groundwater can be ascertained by a simple operation consisting of feeding a liquid of a predetermined density and inflow of tracer particles. Can do.
(C) The same liquid and / or tracer particles can be applied to the measurement of groundwater at any depth, but different tracer particles may be selected depending on the depth.

(D) Since the density of the liquid to be replaced can vary depending on the temperature and pressure in the measurement section, the liquid density can be corrected by measuring the temperature and pressure in the measurement section as necessary. The optimum tracer particles can be selected according to the conditions.
(E) A storage tank for storing the tracer particles together with the liquid is provided, and the tracer particles floating in the storage tank are selectively introduced into the measurement section, thereby further stricter the liquid density and the tracer particle density in the measurement section. Can match.
(F) When a large amount of tracer particles are introduced into the measurement section, there is a concern about clogging of rock cracks around the borehole, but it is not necessary by providing a pair of channels facing the opening in the measurement space from the storage tank Tracer particles can be recovered.

FIG. 1 shows an embodiment in which a flow direction flow velocity measuring device 10 of the present invention is applied to a measurement section 3 in a borehole 2 excavated in the ground 1 at a depth of about several hundred to 1,000 m. The present invention can be applied to the measurement section 3 having a low flow velocity in which the groundwater flow is very slow and the number of days in which the groundwater G in the measurement section 3 is completely replaced (hereinafter sometimes referred to as a replacement period) is larger than the measurement period. . If the replacement period is longer than the measurement period, even if the groundwater G in the measurement section 3 is replaced with the liquid W having a predetermined density, the influence on the measurement of the flow direction and the flow velocity of the groundwater G at the depth can be suppressed. The measuring device 10 of the present invention can be expected to be applied to a low flow velocity field of about 10 ⁻⁵ to 10 ⁻¹⁰ m / s, for example.

For example, assuming that the radius R of the measurement section 3 in the borehole 2 is 50 mm (= 0.05 m) and the groundwater G in the measurement section 3 flows in the horizontal direction, the flow velocity of the groundwater G is calculated according to equation (3). When v is 10 ⁻⁷ m / s, the replacement period in the measurement section 3 is about 5.8 days, and when the flow velocity v is 10 ⁻⁸ m / s, the replacement period is about 58 days. When the present invention is applied to such a measurement section 3, a measurement period of 2 to 3 days or more can be secured. When the flow velocity v of the groundwater G is larger than 10 ⁻⁷ m / s, the replacement period can be made longer than the measurement period by increasing the diameter of the borehole 2.

[Equation 1]
Measurement section volume Q = πR ² H (m ³ ) ……………………………………… (1)
The amount of groundwater q to be replaced in one day of the measurement section
= Surface area of measurement section (m ² ) x (1/2) x flow velocity v (m / s)
= ΠRH × v × (60 × 60 × 24) …………………………… (2)
Replacement period = Q / q = R / (v × (60 × 60 × 24)) …………………… (3)

  FIG. 2 shows an example of the measuring device 10 of the present invention inserted into the boring hole 2. The measuring device 10 in the illustrated example includes a pair of packers 11 and 12 that form a measurement section 3 in the borehole 2, a water absorption path 18 that absorbs groundwater G from the vicinity of one packer 12 in the measurement section 3, and a measurement. A feed path 17 for feeding a liquid W having a predetermined density into the vicinity of the other packer 11 in the section 3, and a tracer having the same density as the liquid W in a predetermined section 33 (see FIG. 5B) of the measurement section 3. And an inflow passage 21 through which the particles S flow. The packer pairs 11 and 12 are held at a predetermined interval by the coupling member 13, and are a suspension device 60 (see FIG. 5) provided on the ground 1 and a packer control device 43 (see FIG. 6) for controlling expansion / contraction. Connected. An example of the packer pairs 11 and 12 is a water-impervious packer or a mechanical packer that expands and contracts by injecting and collecting a liquid (water or the like) or a gas (air or the like).

  The upper ends of the inflow path 17 and the water intake path 18 of the measuring device 10 are connected to the supply device 7 on the ground 1 via the supply path 14 and the discharge path 15 (see FIG. 1), respectively. The lower ends of 18 are opened at portions separated in the vertical direction and the horizontal direction in the measurement section 3, respectively. Although the measurement section 3 in the deep underground is high-pressure, the supply device 7 makes the lower end of the water absorption path 18 a relatively low-pressure water absorption section, so that the ground water G is absorbed through the water absorption path 18 and at the same time the inlet path 17 Then, the liquid W can be fed through the groundwater G, and the groundwater G in the region between the lower end port of the inflow channel 17 and the lower end port of the water absorption channel 18 in the measurement section 3 can be replaced with the liquid W having a predetermined density. An example of the liquid W is water whose density has been measured in advance.

  The upper end of the inflow channel 21 of the measuring device 10 is connected to the supply device 7 on the ground 1 via the supply channel 14 (see FIG. 1), and the lower end of the inflow channel 21 is the inlet channel 17 and the water absorption channel in the measurement section 3. An opening is made at a predetermined portion 33 between the two. As shown in FIG. 5B, it is desirable that the predetermined portion 33 that opens the lower end of the inflow passage 21 coincides with a focal range (detection portion) of the position detection sensor 30 described later. The measuring device 10 in the illustrated example has an opening facing the lower end of the inflow passage 21 and has a recovery path 22 for recovering the liquid W from the predetermined portion 33 of the measurement section 3, and the upper end of the recovery path 22 is connected to the discharge path 15. The tracer particles S flow into the predetermined portion 33 of the measurement section 3 from the supply device 7 through the inflow passage 21 by connecting to the supply device 7 via the supply device 7 and setting the lower end of the recovery passage 22 to the low pressure portion. Let However, the recovery path 22 is not essential for the present invention, and instead of the recovery path 22, the tracer particles S can be allowed to flow in by using the lower end port of the water absorption path 18 as a low pressure portion.

  As an example of the tracer particle S, a resin sphere having a particle size of about 100 to 150 μm having a specific gravity smaller than 1 is coated with an organic material having a specific gravity larger than 1, and the same density ( Specific gravity). However, it is also possible to use tracer particles S having a particle size of about 100 to 150 μm prepared using a single material having the same density as the liquid W.

  The measuring device 10 in the illustrated example is provided with a storage tank 20 that stores the tracer particles S together with the liquid W at the intersection of the inflow path 21 and the recovery path 22. The predetermined portion 33 is communicated with the on-off valve V5 (see FIG. 1). Further, the storage tank 20 and the predetermined portion 33 of the measurement section 3 are communicated with each other via the on-off valve V6 by the recovery path 22, and the storage tank 20 and the discharge path 15 are connected by the communication path 23 (see FIG. 1). Since the tracer particles S are fine particles having a particle diameter of about 100 to 150 μm, it is difficult to prepare all of them at the same density as the liquid W. However, the tracer particles S supplied from the supply device 7 are once stored in the storage tank 20 together with the liquid W. By storing and flowing the tracer particles S from the liquid phase part of the storage tank 20 into the measurement section 3, only the tracer particles S having the same density as the liquid W floating in the liquid phase part of the storage tank 20 are selectively introduced. Can be made. Further, by storing the tracer particles S together with the liquid W in the storage tank 20 in the vicinity of the measurement section 3 as in the illustrated example, the optimum tracer particles for the density of the liquid W that changes according to the temperature and pressure in the measurement section 3. Can be selected. However, as will be described later, in the present invention, it is possible to select the tracer particles S according to the temperature and pressure measured values in the measurement section 3 in the supply device 7, and the storage tank 20 is not essential to the present invention. .

  In the illustrated example, since the single supply path 14 is shared by the inflow path 21 and the inflow path 17, the supply path 14 and the inflow path are connected via a three-way valve A1 (open / close valves V1 and V2) as shown in FIG. 21 and the inlet / outlet path 17 are connected, but if a plurality of supply paths 14 are provided, the three-way valve A1 can be omitted. Further, since the single discharge path 15 is shared by the recovery path 22 (communication path 23) and the water absorption path 18, the discharge path 15 and the recovery path 22 (communication path 23) via the three-way valve A2 (open / close valves V3 and V4). ) And the water absorption path 18 are connected, but as described above, the recovery path 22 can be omitted, and the three-way valve A2 can also be omitted.

  Furthermore, the measuring apparatus 10 in the illustrated example includes position detection sensors 30a and 30b that detect the three-dimensional position of the tracer particle S that has flowed into the predetermined portion 33 of the measurement section 3, and the three-dimensional shape of the tracer particle S by the position detection sensors 30a and 30b. And a signal transmission device 34 for transmitting the position detection value signal to the signal processing device 8 on the ground 1 via the signal transmission path 16. The position detection sensors 30a and 30b and the signal transmission device 34 are connected by a signal cable 39. One example of the position detection sensors 30a and 30b is a plurality of array-type ultrasonic sensors arranged in directions orthogonal to each other so as to face the inflow portion 33 of the tracer particle S as shown in FIG. A similar optical imaging device 58 is provided.

  The position detection sensor 30 in FIG. 2C is an example of an array type ultrasonic sensor in which a large number of piezoelectric vibrators 31 and 32 are arranged in a plane at predetermined positions on the surface. Based on a transmission command from the control unit 37 of the signal transmission device 34, a high voltage pulse is applied to any one of the piezoelectric vibrators 31 selected by the transmission unit 35, and ultrasonic waves are directed from the piezoelectric vibrator 31 toward the predetermined portion 33. To send. The transmitted ultrasonic wave is reflected by the tracer particle S, but the reflected wave is received by any of the piezoelectric vibrators 32 selected by the receiving unit 36, and the received signal is converted into a digital signal and input to the signal processing unit 38. To do. In the signal processing unit 38, a plurality of receptions are assumed, assuming an ellipsoid with a distance corresponding to a time difference (transmission time of ultrasonic waves) between the transmission and reception times with the position of the transmission piezoelectric transducer 31 and the reception piezoelectric transducer 32 as a focal point. The three-dimensional position of the tracer particle S is detected as the intersection position of the ellipsoids corresponding to the piezoelectric vibrator 32. The three-dimensional position of the tracer particle S detected by the signal processing unit 38 is transmitted to the signal processing device 8 through the signal transmission path 16 and is displayed on the output device 9 as an image, for example (see FIG. 1).

  When measuring the flow direction and flow velocity of the groundwater G using the measuring device 10 of FIG. 2, first, as shown in FIG. 1, the measuring device 10 in a state where the packers 11 and 12 are contracted is used as a measurement target in the borehole 2. The measurement section 3 is formed by extending the packers 11 and 12 by suspending them to the groundwater depth. Next, as shown in FIG. 3 (A), the on-off valve V1 of the three-way valve A1 is opened and the on-off valve V2 is closed to connect the supply path 14 and the inflow path 17 and the on-off valve of the three-way valve A2. The discharge path 15 and the suction path 18 are connected by opening V3 and closing the on-off valve V4. In this state, the supply device 7 is driven to feed the liquid W having a predetermined density stored in the liquid tank 5 into the measurement section 3, and the ground water G in the measurement section 3 is replaced with the liquid W. It is desirable that the feeding of the liquid W proceeds as slowly as possible so as not to cause a disturbance in the measurement section 3.

  After replacing the measurement section 3 with the liquid W, as shown in FIG. 3B, the supply path 14 and the storage tank 20 are connected by closing the on-off valves V1 and V5 and opening the on-off valve V2. The discharge path 15 and the storage tank 20 are connected by closing the on-off valves V3 and V6 and opening the on-off valve V4. In this state, the tracer particles S stored in the tracer tank 6 from the supply device 7 are supplied to the storage tank 20 together with the liquid W, and the tracer particles S are temporarily stored in the storage tank 20 together with the liquid W. Further, as shown in FIG. 3C, the open / close valve V2 is closed and the open / close valve V5 is opened to connect the storage tank 20 and the inflow passage 21, and the open / close valve V4 is closed and the open / close valve V6 is opened. By doing so, the storage tank 20 and the recovery path 22 are connected. By driving the inflow device 24 in this state, the tracer particles S floating in the liquid phase portion of the storage tank 20 are caused to flow together with the liquid W into the predetermined portion 33 of the measurement section 3. The inflow device 24 is, for example, a suitable piston or a small pump having a lower end port of the recovery path 22 as a low pressure portion.

  After flowing the tracer particle S into the measurement section 3, the position detection sensors 30a and 30b continuously detect the three-dimensional position of the tracer particle S, and transmit a detection signal of the three-dimensional position to the signal processing device 8, In the signal processing device 8, the flow direction and flow velocity of the groundwater G are measured from the temporal change of the three-dimensional position of the tracer particles S. According to the measurement method of the present invention, the density of the liquid W in the measurement section 3 and the density of the tracer particles S can be matched exactly, and even when the flow velocity v of the groundwater G is extremely low, the flow velocity v is accurately determined. It becomes possible to measure. In addition, it is not necessary to measure the density of the groundwater G in the measurement section 3, and if the tracer particles S having the same density as the liquid W are prepared, the liquid W is fed in and the tracer particles S are flowed in relatively easily. It is possible to grasp the flow direction and flow velocity of the groundwater G at various depths with a simple operation.

  Thus, it is possible to achieve the “method and apparatus capable of accurately and easily measuring the flow direction and flow velocity of groundwater having a low flow velocity”, which is an object of the present invention.

  FIG. 3D shows a process of collecting unnecessary tracer particles S floating in the measurement section 3 after the measurement of the flow direction and flow velocity of the groundwater G is completed. In this case, open the on-off valve V1 and close the on-off valve V2 to connect the supply path 14 and the feed-in path 17 and close the on-off valves V3 and V5 to open the on-off valves V4 and V6. Thus, the discharge path 15 and the recovery path 22 are connected. In this state, the supply device 7 is driven to feed the liquid W having a predetermined density stored in the liquid tank 5 into the measurement section 3, and unnecessary tracer particles S are recovered in the storage tank 20 via the recovery path 22. If necessary, open / close valve V3 is opened and open / close valve V4 is closed as shown in FIG. 5A to connect discharge passage 15 and suction passage 18 and to remove unnecessary tracer particles S via suction passage 18. It is also possible to discharge from the measurement section 3. When a large amount of tracer particles S are introduced into the measurement section 3, the tracer particles S may enter a rock crack around the borehole 2 and clogging may occur. However, unnecessary tracer particles S as shown in the illustrated example. By collecting the clogging, clogging and the like can be minimized even when a large amount of the tracer particles S is introduced.

  1 and 2 includes a measurement sensor 27 for measuring the temperature and pressure in the measurement section 3, and transmits the measurement value of the measurement sensor 27 to the signal processing device 8 via the signal transmission path 16. The signal processor 8 corrects the density of the liquid W in the measurement section 3 based on the measurement value of the measurement sensor 27, and the tracer selection means 7 a of the supply device 7 selectively selects the corrected tracer particles S in the inflow channel 21. Supply. In the present invention, the liquid W whose density is known in advance is used. However, since the density of the liquid W changes according to the depth of the measurement section 3, that is, temperature, pressure, and the like, the change in density can cause a measurement error. However, by calibrating the relationship between the density of the liquid W and the temperature and pressure in advance, the density of the liquid W in the measurement section 3 can be easily corrected by the measured value of the temperature / pressure measurement sensor 27. Therefore, by preparing a plurality of tracer particles S having different densities, selecting the corrected tracer particles S and allowing them to flow into the measurement section 3, measurement errors due to the density change of the liquid W can be made relatively easy. Can be avoided. Further, by combining the selection of the tracer particles S by the measurement values of the temperature / pressure measurement sensor 27 and the selection of the tracer particles S by the storage tank 20 described above, the accuracy of measuring the flow direction and the flow velocity of the groundwater G can be further improved. Can be expected.

It is a schematic explanatory drawing which shows the structure of one Example of this invention apparatus. It is a perspective view which shows the structure of one Example of this invention apparatus. It is explanatory drawing which shows the procedure of this invention method. It is a graph which shows the relationship of the density difference of a groundwater density and tracer particle density in case the tracer particle | grains of a different particle size fall 3 mm in 3 days in groundwater. It is explanatory drawing of an example of the conventional flow velocity and flow direction measuring apparatus of groundwater. It is explanatory drawing of another example of the conventional flow velocity and flow direction measuring apparatus of groundwater.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ground (bedrock) 2 ... Boring hole 3 ... Measurement area 5 ... Liquid tank 6 ... Tracer tank 7 ... Supply apparatus 7a ... Tracer selection means 8 ... Signal processing apparatus 9 ... Output apparatus
10 ... Flow direction flow velocity measuring device 11 ... Upper packer
12… Lower packer 13… Coupling member
14 ... Supply path 15 ... Discharge path
16 ... Signal transmission line 17 ... In / out path
18 ... Water absorption channel
20 ... Reservoir 21 ... Inlet channel
22 ... Recovery path 23 ... Communication path
24 ... Inflow device
27 ... Temperature / pressure sensor
30 ... Position detection sensor (ultrasonic sensor)
31 ... Transmission piezoelectric vibrator 32 ... Reception piezoelectric vibrator
33 ... Sensor detection part (focal range)
34… Signal transmission device 35… Transmitter
36 ... Receiving unit 37 ... Control unit
38 ... Signal processing unit 39 ... Signal cable
41 ... neutron moisture meter 42 ... tracer solution (boric acid aqueous solution)
43 ... Packer control device 44 ... Tracer liquid injection device
45 ... Measuring equipment
51… Measurement part 52… Support member
53 ... Rectifying plate 54 ... Tracer introduction pipe
55 ... Ultrasonic sensor 56 ... Coaxial cable
57 ... Reference reflector 58 ... Optical imaging device
59… Transparent window 60… Hanging device
61 ... Signal transmission unit 62 ... Measurement device
63 ... Transmission line G ... Groundwater S ... Tracer particles W ... Liquid with a predetermined density

Claims (10)

  Forming a measurement section partitioned by a packer pair at a low flow velocity groundwater depth in the underground borehole, replacing the groundwater in the measurement section with a liquid of a predetermined density, and then moving tracer particles with the same density into the measurement section Inflow, the position detection sensor supported by the packer pair continuously detects the floating three-dimensional position of the tracer particles, and measures the flow direction and flow velocity of groundwater from the change over time of the detected value of the floating three-dimensional position. This is a low-flow-rate groundwater flow direction flow velocity measurement method.   2. The measurement method according to claim 1, wherein a storage tank for storing the tracer particles together with the liquid is provided in an inflow path into the measurement section for the tracer particles, and the tracer particles floating in the storage tank are selectively included in the measurement section. A method for measuring the flow velocity of low-flow groundwater flowing into the ground.   3. The measurement method according to claim 2, wherein a pair of flow paths are provided between the storage tank and the measurement space so that the openings on the measurement space side face each other, and the tracer particles introduced from one of the flow paths into the measurement section are A method for measuring the flow direction flow velocity of low flow velocity groundwater collected in a storage tank via the other side of the flow path.   4. The measurement method according to claim 1, wherein the temperature and pressure in the measurement section are measured, the density of the liquid is corrected by the measured values of temperature and pressure, and the tracer particles having the corrected density are introduced. A method for measuring the flow velocity of low-flowing groundwater. 5. The flow direction flow velocity measurement method according to claim 1, wherein a flow velocity of the groundwater is 10 ⁻⁵ to 10 ⁻¹⁰ m / s.   The packer pair that forms a measurement section partitioned from the adjacent depth by the low flow velocity groundwater depth in the underground borehole, the water absorption path that absorbs groundwater from one packer vicinity part in the measurement section, the other in the measurement section An inflow path for injecting a liquid of a predetermined density into a portion near the packer, a position detection sensor that is supported by the packer pair and detects a three-dimensional position of a suspended matter at a predetermined detection portion in the measurement section, Low-flow-rate groundwater flow velocity measurement comprising an inflow path through which tracer particles having the same density as the liquid flow into a predetermined detection site, and a signal transmission device that transmits a detection value signal of the floating three-dimensional position of the tracer particles by the sensor apparatus.   The measuring device according to claim 6, wherein a storage tank for storing the tracer particles together with the liquid is provided in the inflow path, and the tracer particles floating in the storage tank are selectively allowed to flow into the measurement section by the inflow path. Flow velocity measurement device for groundwater flow direction.   8. The measurement apparatus according to claim 7, wherein a pair of flow paths are provided between the storage tank and a predetermined detection site in the measurement space so that the opening on the measurement space side faces each other, and one of the flow paths is used as an inflow path for tracer particles. A flow direction flow velocity measuring device for low flow velocity groundwater in which the other of the flow paths is used as a tracer particle recovery path.   9. The measurement device according to claim 6, wherein the measurement sensor that measures the temperature and pressure in the measurement section, and the density of the liquid is corrected by the measurement value of the measurement sensor, and the tracer particles having the corrected density are obtained. A low flow velocity groundwater flow direction flow velocity measuring device provided with supply means for supplying to the inflow channel.   10. The flow direction flow velocity measurement device according to claim 6, wherein the position detection sensors are a plurality of array type ultrasonic sensors arranged in directions orthogonal to each other.

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