JPH0795102B2 - Method and apparatus for measuring flow velocity in holes - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] This invention excavates a deep hole in the ground when conducting a ground survey,
The present invention relates to a hole flow velocity measuring method and a measuring device in which a measurement device is suspended therein to measure the flow velocity of groundwater.

[Prior Art] Generally, in order to measure the flow velocity of groundwater, first, a boring machine is used to excavate a deep hole into a given ground, and then a yagura is provided above the excavated deep hole. After mounting a measuring device for measuring the flow velocity inside, the measuring device is hung down to a predetermined place in the hole to be measured. The measuring device suspended in the hole is fixed in the formation to be measured by a fixing mechanism associated with the measuring device. When this measuring device is fixed, groundwater passing through the strata also passes through the measuring device, so by detecting the passing groundwater with a sensor probe provided in the measuring device,
The flow velocity of groundwater at the measurement location can be measured.

Conventionally, as a measuring device for measuring the flow velocity of this type of groundwater, a device having the following configuration is known. That is, this measuring device is roughly composed of a sensor probe for measuring the flow velocity at a predetermined place in the hole in the middle, and upper and lower packers serving as the fixing mechanism, which are provided on the upper and lower parts thereof via a rod. It is a thing. The upper and lower packers are hollow bodies made of hard rubber, and are expanded by compressed air sent from the ground to be fixed by being pressed against the wall surface in the hole, thereby the upper and lower packers. The sensor probe located between the packers is also fixed. Furthermore, the sensor probe includes a tracer whose concentration changes depending on the flow of groundwater (for example, saline, distilled water,
When boron or the like) is charged, a sensor for measuring the change in concentration of the tracer is built in, and the flow rate of groundwater can be measured by measuring the change in concentration of the tracer.

[Problems to be Solved by the Invention] Meanwhile, the conventional in-hole flow velocity measuring device using the tracer has the following problems.

(1) Since the flow velocity in the hole is indirectly measured by measuring the change in the concentration of the tracer with a sensor, the true flow velocity in the hole cannot be directly measured.

(2) Since it takes a tracer, it takes time to measure.

(3) Since it is measured by the tracer, the measurement range of the flow velocity is limited.

(4) Since the tracer is put into the measurement part, the temperature and density of groundwater change, and the diffusion phenomenon of groundwater occurs, which causes a flow different from the original flow of groundwater in the hole.

The present invention has been made in view of the above circumstances, in a short time, the true flow velocity of groundwater having a wide range of flow velocity, and a hole flow velocity measuring method capable of directly measuring,
It is also an object of the present invention to provide a measuring device that realizes this.

[Means for Solving Problems] In order to solve the above problems, a first invention of the present invention is to dig a deep hole in the ground and measure a sensor at a predetermined depth in the hole. A probe is inserted, which is a hole flow velocity measuring method for measuring the flow velocity of groundwater passing through the hole,
A transmission type diffraction grating and a light source are provided in the sensor probe, and diffraction fringes are formed by passing the light from the light source through the diffraction grating, and from the scattering particles in groundwater passing through the diffraction fringe. The method for measuring the flow velocity in the hole is configured such that the scattered light is received and the flow velocity of the groundwater is measured by the intensity change of the scattered light.

A second invention is a sensor probe which is a measuring part to be inserted into a deep hole excavated in the ground in order to realize the method for measuring the flow velocity in the hole which is the first invention, and the sensor probe of the sensor probe. Attached to the upper and lower ends via rods, by the upper packer and the lower packer that fix the sensor probe at a predetermined position in the hole, in a hole flow velocity measuring device for measuring the flow velocity of groundwater passing through the hole, The sensor probe has a light source that emits a laser beam, a transmission diffraction grating located in front of the light source in the light emission direction, and a plurality of orders of diffracted light formed by the diffraction grating are converged on a predetermined portion. To form a diffraction fringe, a converging means such as a lens, and a light receiving section for receiving scattered light from the diffraction fringe are provided.

[Operation] In the present invention, a plurality of orders of diffracted light are generated by the light source and the transmission type diffraction grating provided in the sensor probe, and the plurality of orders of diffracted light are converged to a predetermined portion by the reflection plate. Thus, an interference fringe is formed on this predetermined portion. When the groundwater passes through the portion where the interference fringes are formed, scattered light is generated by the particles contained in the groundwater, and the intensity thereof is strong if the particles are in the bright portion of the interference fringe, and conversely in the dark portion. If it becomes weaker. The intensity change is proportional to the moving speed of particles and inversely proportional to the interval of interference fringes. Therefore, if the change in the intensity of this scattered light is detected, the moving speed of the particles can be measured, and assuming that the particle size of the particles is sufficiently small, use the moving speed of the particles as the moving speed of groundwater. You can

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a diagram for explaining a hole flow velocity measuring method which is an embodiment of the first aspect of the invention, and a symbol G is the ground to be investigated. The ground G is composed of an impermeable layer G ₁ and an aquifer G ₂ through which groundwater flows, and the ground G has a deep hole drilled vertically to penetrate the aquifer G _2. H is formed. Reference numeral B is a measurement section of the hole H in which the flow velocity of groundwater is to be measured. In the measurement section B, the hole flow velocity measuring device 1 (which is an embodiment of the second invention of the present invention is (Hereinafter simply referred to as "measuring device"). The measuring device 1 is suspended by a cable 2, and the cable 2 is fixed to a yagura section 3 installed on the ground.

FIG. 2 is a diagram showing the Yakura part 3 installed on the ground. In FIG. 2, reference numeral 4 is the Yakura main body, and reference numeral 5
Is a cable winding device. An upper / lower packer control device 6 and a signal receiving / analyzing unit 7 (hereinafter simply referred to as “analyzing unit”) are connected to the cable winding device 5 by a cable 8 and an optical fiber 9, respectively. The upper and lower packer control device 6 has a function of sending compressed air to the upper and lower packers of the measuring device 1 described later and adjusting the pressure of the compressed air. The analyzing unit 7 is composed of a photomultiplier 10, a bandpass filter 11, a digital correlator 12, and a computer 13. The cable 2 is wound around the cable winding device 5, and the cable 2 is connected to the Yakura main body 4
It is hung on a pulley 14 attached to the top of. The measuring device 1 is attached to the tip of the cable 2 as described above.
Is attached.

As shown in FIGS. 1 and 2, this measuring device 1 has
From the cylindrical sensor probe 15 that is the measurement unit, and the upper and lower ends of the sensor probe 15 attached via the upper rod 16 and the lower rod 17, the hollow cylindrical upper packer 18 and the lower packer 19 made of hard rubber. It is roughly configured.

FIG. 3 is a diagram showing the sensor probe 15. In FIG. 3, reference numeral 20 is a light source such as a laser source arranged above the sensor probe 15, and reference numeral 21 is a disc-shaped transmission type located in front of the light sources 20, 20 ,. It is a diffraction grating. In this diffraction grating 21, N slits per 1 mm are radially engraved. Also,
Reference numeral 22 is a reflecting mirror (converging means) attached to the lower portion of the sensor probe 15, and the reflecting mirror 22 is the diffraction grating.
The 0th-order diffracted light 23 and the 1st-order diffracted light 24 from 21 are located in front of the traveling direction, and the 0th-order 1st-order diffracted light 2
The light guiding direction is adjusted so that the light beams 3 and 24 converge on a predetermined crossing portion (portion) 30 below the sensor probe 15. Reference numeral 25 indicates that the light receiving direction is the 0th and 1st order diffracted light.
The light is a condenser lens (light receiving portion) directed to the intersection 30 of 23 and 24, and the light received by the condenser lens 25 is transmitted by the optical fiber 26.

4 is a view showing a cross section of the cable 2, in which the power supply cable 27 for supplying power to the light source 20 in the sensor probe 15 and the cable 8 are provided.
To the analysis unit 7 on the ground via the optical fiber 9 and the air supply tubes 28 and 29 for communicating compressed air to the upper and lower packers 18 and 19 and the light received by the condenser lens 25. The optical fiber 26 for transmission is loaded.

Next, with reference to FIG. 1 to FIG. 4, an explanation will be given on the method for measuring the flow velocity in the hole which is one embodiment of the first invention of the present invention.

First, as shown in FIG. 1, a hole H reaching the aquifers G ₂ and G ₂ to be measured in the ground G to be investigated is excavated by an excavator (not shown).

Next, the cable 2 wound around the cable winding device 5 is unwound into the excavated hole H, and the measuring device 1 is suspended from the Yakura main body 4. This suspended measuring device 1
When reaches the measurement section B, the winding device 5 is stopped from feeding and the measurement apparatus 1 is stopped at a predetermined position in the measurement section B. When the measuring device 1 stops at a predetermined position in the measuring section B, the above-mentioned vertical packer control device 6 on the ground is driven, and compressed air whose air pressure is adjusted is supplied through the air supply tubes 28 and 29 in the cable 2. Supply to the upper packer 18 and the lower packer 19. When compressed air is supplied,
These upper packer 18 and lower packer 19 expand,
It becomes immovable by pressing itself against the wall surface of the hole H, and is fixed at that position. Therefore, the sensor probe 15 located in the middle of the upper and lower packers 18, 19
Is also fixed in that position.

When the sensor probe 15 is fixed in the measurement section B, the light source 20 in the sensor probe 15 is driven to emit light such as laser light toward the transmissive diffraction grating 21. The emitted light is diffracted by passing through the diffraction grating 21, and 0th, 1st, ... Then, of these diffracted lights of multiple orders, the 0th-order diffracted lights 23 and 1
The second-order diffracted light 24 is converged by the reflecting mirror 22 onto a predetermined crossing portion 30, and the crossing of the 0th-order and first-order diffracted light rays 23 and 24 produces diffraction fringes at the crossing portion 30. Where this crossover 30
Is the measurement part for measuring the flow velocity of groundwater.

When particles in groundwater in the interference fringes pass, scattered light is generated. The generated scattered light is received by the condenser lens 25, transmitted through the optical fiber 26 to the analysis unit 7 on the ground, analyzed and recorded, whereby the flow velocity of groundwater can be measured.

Here, regarding the analysis process performed by the analysis unit 7,
The principle will be explained. In other words, this is the so-called Laser Doppler Veloci
This is based on the principle of the meter). If the laser beam emitted from the laser source is split into two beams of equal intensity and these are crossed to one point using a lens, this crossing part The wavelength λ of the laser light is
And the beam crossing angle θ causes interference fringes whose spacing d _F is determined. The distance d _F between the interference fringes is d _F =
It is represented by (λ / 2) sin (θ / 2). When fine particles (diameter several μm) pass through this measurement portion, the intensity of light scattered by the particles becomes strong if the particles are in the bright part of the interference fringes, and weaker if they are in the dark part. The rate of change is proportional to the moving velocity V of the particles and inversely proportional to the spacing d _{F of the} interference fringes. Therefore, by converging this scattered light with a lens or the like, converting it into an electric signal with a photoelectric converter such as _Photomul, and measuring the period t _d of the signal (Doppler signal) or the frequency f _d , The moving speed V of particles can be measured. Considering the case where a particle passes perpendicularly to the surface on which interference fringes are formed, the moving speed V of this particle is as follows: V = d _F / t _d = d _F · f _d = {(λ / 2) sin (Θ / 2)} · f _d . This is only measuring the velocity of particles, not the velocity of fluid, that is, groundwater. However, if the particle diameter is small enough, it can be considered that the particle moves following the fluid.
There is no problem even if the moving speed V of the particles is directly used as the moving speed of the fluid.

The groundwater flow velocity can be measured based on the above principle. Then, when the flow velocity measurement in the measurement section B is completed, the air in the upper and lower packers 18, 19 is loosened, the measuring device 1 is moved to the depth of the next measurement section, and the measurement is repeated.

Therefore, the measuring method and the measuring apparatus 1 according to the embodiment shown above
According to the method, the flow velocity of groundwater can be directly measured, the measurement time can be shortened significantly, and the measurement range of the flow velocity is V = 1 × 10 ⁻⁶ cm / sec to ¹ × 10 ⁰ cm / sec. And a wide range of measurement becomes possible. If the particle size distribution of particles in groundwater is assumed to be broad to some extent and the influence of Brownian motion is removed by the bandpass filter 11 provided in the analysis unit 7, the true groundwater flow velocity can be obtained. further,
This measuring method and measuring device is provided with the sensor probe 15
Since there is no need to use a tracer for the measurement, there is no possibility of causing a phenomenon that disturbs the groundwater velocity such as density change or diffusion phenomenon in the groundwater to be measured. Since the measuring device 1 can be made smaller in diameter than conventional measuring devices, it can be applied to deep holes having a smaller diameter.

Particularly, in this embodiment, by adjusting the position of the reflecting mirror 22 and the like,
The intersection 30 of the diffracted lights 23 and 24 can be located at an arbitrary position, and the surface on which the interference fringes formed by the intersection 30 are formed can be turned in an arbitrary direction. Therefore, by arranging the surface on which the interference fringes are formed so as to be orthogonal to the axis of the sensor probe 15, for example,
It becomes possible to measure the flow velocity of groundwater in one defined direction. In addition, as in this embodiment, the light source 20 is
By equipping them individually and making the formation planes of the interference fringes generated by the light source 20 the same, and making the directions of the fringes orthogonal to each other, it becomes possible to directly measure the X component and the Y component of the groundwater flow velocity. The absolute value of the flow velocity can be measured.

Next, FIG. 5 is a view showing an in-hole flow velocity measuring device according to another embodiment of the present invention. In the following explanation,
The same components as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The difference between the measuring device 1 shown in FIG. 5 and the measuring device of the above embodiment is that the transmission diffraction grating 21 in the sensor probe 15 is
The point is that it is rotatably attached to the center of rotation. That is, the rotating shaft 31 is provided at the center of rotation of the diffraction grating 21, and the rotating shaft 31 is connected to the motor 32. Therefore, by driving the motor 32, the diffraction grating 21 is rotated in a predetermined direction and at a predetermined speed. Further, in this embodiment, only one light source 20 is provided above the sensor probe 15, and
One light emitted from the light source 20 is branched into a predetermined number (two in the illustrated example) by a beam splitter 33 provided in front of the light, and the diffraction grating 21 is reflected by the reflecting mirrors 34, 34, ....
Is guided to.

The method for measuring the flow velocity of groundwater with this measuring device 1 is
The measurement method is the same as that of the above-described embodiment, and according to this method, the flow velocity of groundwater passing through the hole H can be measured as in the above-mentioned embodiment. Here, during measurement of the flow velocity of groundwater, if the motor 32 is driven and the diffraction grating 21 is rotated in one direction at a predetermined speed, not only the flow velocity of groundwater but also its flow direction can be measured. .

To explain this principle step by step, when the diffraction grating 21 rotates in one direction at a predetermined speed as described above, the frequency f ₀ of the _0th-order diffracted light 23 does not change, but the frequency of the 1st-order diffracted light 24 f ₁ is shifted by Δf. This shift amount Δf is
If the slit width of the diffraction grating 21 is p ₀ and the rotation speed is υ,
The quantity is given by the following formula.

Δf = f ₁ −f ₀ = υ / 2p ₀ = πDr / 2p ₀ Here, D is the diameter of the diffraction grating 21, and r is the rotation speed of the diffraction grating 21. Therefore, the 0th-order diffracted light 23 and the 1st-order diffracted light
The bright and dark portions of the interference fringes formed on the crossing portions 30 of 24 also move in a fixed direction with this frequency shift Δf. Such interference during fringes, if the particles suspended within the groundwater has passed, although as described above the scattered light is generated, the frequency fd 'is an amount obtained by adding the frequency shift Δf to the frequency f _d. Since the frequency shift Δf and the moving direction of the interference fringes can be known in advance, if the positive or negative of the frequency change f _d ′ −f _d due to the rotation of the diffraction grating 21 is detected, the flow direction of the particles, and thus the groundwater. The flow direction of can be measured.

In particular, also in this embodiment, as in the case of the above-mentioned embodiment, the X-component and the Y-component of the groundwater flow velocity can be directly measured if the interference fringes generated by the light source 20 are made to be the same and the directions of the fringes are made orthogonal to each other. Therefore, the absolute value of the groundwater flow velocity and the flow direction can be measured.

The method and apparatus for measuring the flow velocity in the hole according to the present invention are not limited to the above-mentioned embodiment, and can be appropriately changed depending on the construction conditions. For example, the packers 18 and 19 may be mechanical packers, air packers, or the like depending on the properties of the ground G. Further, the converging means for converging the 0th-order and 1st-order diffracted lights 23, 24 are not limited to the reflecting mirror 22 as described above, and may be appropriately selected from known means such as a lens and a prism.

"Effects of the Invention" As described in detail above, the present invention provides a transmission type diffraction grating in a sensor probe of an in-hole flow velocity measuring device, and forms an interference fringe using diffracted light obtained by this diffraction grating, Since the flow velocity of groundwater in the hole is measured from the intensity change of the scattered light of the particles passing through the interference fringes, the following excellent effects are obtained.

(1) The true flow velocity of groundwater in the hole can be measured.

(2) The measurement time can be shortened.

(3) The flow velocity measurement range is V = 1 × 10 ⁻⁶ cm / sec to 1 × 10
^It can measure a wide range of ⁰ cm / sec.

(4) Since a tracer is not used for the sensor probe, the density change and diffusion phenomenon of groundwater to be measured hardly occur.

(5) Further, since this measuring device can be made smaller in diameter than the conventional measuring device, it can be applied to a deep hole having a smaller diameter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 4 are views for explaining a hole flow velocity measuring method which is an embodiment of the first invention of the present invention, and FIG. Second schematic diagram for explaining the whole
The figure is a front view showing the Yakura part, and FIG. 3 is the second part of the present invention.
FIG. 4 is a perspective view showing a sensor probe part of an in-hole flow velocity measuring apparatus as an embodiment of the invention of FIG. 4, FIG. 4 is a sectional view of a cable, and FIG. 5 is another embodiment of the second invention of the present invention. It is a perspective view showing a sensor probe part of an in-hole flow velocity measuring device. G ... Ground, H ... Deep hole, 1 ... Measuring device, 15 ... Sensor probe, 16 ... Upper rod, 17 ... Lower rod, 18 ... Upper packer, 19 ... Lower packer, 20 ... Light source, 21 ... Diffraction grating, 22 ... Reflecting mirror (converging means), 25 ... Condensing lens (light receiving section).

Claims (2)

[Claims] 1. A method for measuring the flow velocity in a hole, which comprises digging a deep hole in the ground, inserting a sensor probe as a measuring unit at a predetermined depth in the hole, and measuring the flow velocity of groundwater passing through the hole. Therefore, a transmission type diffraction grating and a light source are provided in the sensor probe, and light from this light source is passed through the diffraction grating to form diffraction fringes, and scattering in groundwater passing through the diffraction fringes. A method for measuring the flow velocity in a hole, which comprises receiving scattered light from particles and measuring the flow velocity of the groundwater by changing the intensity of the scattered light. 2. A sensor probe, which is a measuring section to be inserted into a deep hole excavated in the ground, and is attached to the upper and lower ends of the sensor probe via rods, and the sensor probe is placed at a predetermined position in the hole. A hole flow velocity measuring device for measuring the flow velocity of groundwater passing through the hole by an upper packer and a lower packer that are fixed, wherein the sensor probe emits a laser beam or the like and a light emission of this light source. A transmission type diffraction grating located in the front direction, a converging means for converging a plurality of orders of diffracted light formed by the diffraction grating into a predetermined portion to form a diffraction fringe, and a scattered light from the diffraction fringe. And a light receiving section for receiving the light.