JPH083535B2 - Tracer release method for groundwater flow measurement - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tracer discharge method when measuring the flow direction and flow velocity of groundwater in a borehole by direct observation of the tracer, and more specifically, to a method of pressurizing the groundwater. Form the water surface of groundwater in contact with the gas, supply the same pressurized gas to both sides of the tracer discharge part to maintain the pressure balance, and after forming the underwater water surface, slightly pressurize the rear part of the tracer discharge part to form a tracer on the underwater surface. The present invention relates to a tracer discharge method for measuring the flow of groundwater discharged.

[Prior Art] In recent years, it has become necessary to accurately grasp the flow state of groundwater in relation to problems such as groundwater pollution. In order to deal with these demands, several single-hole type measurement methods for directly measuring the flow direction and velocity of groundwater at one point have been proposed.One of them is the movement of a tracer released into groundwater with a TV camera or the like. There is a method of directly observing the flow of groundwater by taking a picture.

As the tracer, a plastic particle having a density almost equal to that of groundwater, a liquid tracer, or the like is used.

[Problems to be Solved by the Invention] The method of directly observing the movement of the tracer has an advantage that the measurement operation is relatively simple and easy. However, in order to carry out accurate observations, it is necessary to have an observation technology that accurately reflects the flow state of groundwater as well as a technology that emits an extremely small amount of tracer so as not to disturb the flow of groundwater. However, these points have not been sufficiently solved by the prior art.

As a means for solving the former problem, the present inventor has stated that "a transparent plate and an observation section having a collar surrounding the transparent plate and projecting downward are installed in groundwater in a well, and a pressurized gas is supplied into the observation section. Then, the gas was stored up to the lower end of the collar to form the water surface of groundwater, and a tracer was discharged to the water surface to observe the movement of the tracer.

The object of the present invention is premised on the groundwater flow measurement forming the underwater water surface as described above, regardless of the depth of the water,
It is an object of the present invention to provide a tracer discharging method capable of discharging a trace amount of tracer slowly without disturbing the measurement field.

[Means for Solving Problems] In the present invention, an observation part having a transparent plate and a collar surrounding the transparent plate and projecting downward is installed in groundwater in a well, and pressurized gas is supplied into the observation part. A gas is stored to the lower end of the collar to form the water surface of groundwater, and a tracer is discharged to the water surface to observe the movement of the tracer. In this method, the tracer is discharged to the underwater water surface.

In order to achieve the above-mentioned object, the method of the present invention, during formation of the water surface of groundwater, maintains a pressure balance by applying a pressurized gas to both the front side and the rear side of the tracer discharge part at the same time in the observation part, and thereafter, The tracer is configured to be discharged by slightly pressurizing the rear side than the front side.

[Operation] Since the observation part is installed in groundwater, water pressure is applied in proportion to its depth, and the tracer cannot be discharged unless a pressure that can counteract it is applied. However, if the pressure applied at this time is too high, the tracer or tracer and carrier will be released in large amounts and suddenly, disturbing the measurement field. Conversely, if the groundwater pressure is higher, the tracer will flow backward and at the same time The water surface fluctuates, and the measurement field is also disturbed. Therefore, when discharging the tracer, the water pressure and the discharge gas pressure must be balanced.

In the present invention, the same pressurized gas is applied to both the front side and the rear side of the tracer discharge part, so that the pressure balance is always maintained even if the pressure changes. Ground gas in the observation part was pushed out by the pressurized gas to form a gas storage space, and then a very small amount of tracer was slowly formed by making the rear side of the tracer discharge part slightly higher than the tip side. Can be released underwater.

[Embodiment] FIG. 1 is an explanatory view showing a preferred embodiment of a tracer releasing method in groundwater flow measurement according to the present invention.

The groundwater flow measurement is performed by observing the movement of the released tracer, using a transparent plate 10 made of glass or the like and an observation unit 14 having a collar 12 surrounding the periphery and protruding downward. Actually, the observation unit 14 is attached to the lower portion of a cylinder in which various devices such as the television camera 16 are incorporated, is suspended from the surface of the earth into the boring hole, and is installed in the groundwater.

A tubular body 18 having a lower end opened through the center of the transparent plate 10 is mounted in a liquid-tight manner, and a gas supply pipe is provided above the tubular body 18.
20 and the tracer discharge pipe 22 are connected. The gas supply pipe 20 is provided with a valve 24. The tracer discharge pipe 22 is also provided with a valve 26 and connected to the tracer reservoir 28. The tracer reservoir 28 is divided into a gas space and a liquid space by a diaphragm 30, and the gas space side is connected to the gas supply pipe 20 and guided to the ground. A gas cylinder 34 having a valve 32 and an air cylinder 38 having a valve 36 are connected to the gas supply pipe 20.

As shown enlarged in the tracer discharge pipe 22, there is an extremely small amount (for example, about 0.1 cc) of the tracer 40 made of a material (for example, plastic floating particles) having a density similar to or slightly lower than that of groundwater. A plurality of carriers (water) 42 are charged in advance through air 44.

The present invention is carried out as follows. First all valves 24,26,3
With 2, 36 closed, the observation room 14 is lowered to a predetermined depth in the well and installed so that the lower end edge of the collar 12 is horizontal. Then, the valves 24, 32, 36 are opened, the pressurized gas from the gas cylinder 34 is supplied into the observation section 14 to expel the groundwater therein, and the gas is stored up to the lower end of the collar 12 to form the groundwater level 46. The observation section 14 is held as it is, and the agitation of the groundwater is stopped and the original quiet state is waited for. In this state, the pressure of the pressurized gas reaches the diaphragm 30 of the tracer reservoir 28, so that the tip side and the rear side (diaphragm side) of the tracer discharge part and the inside 38a of the air cylinder 38 are all at the same pressure. Yes Pressure balance is maintained.

To release the tracer, the valves 24 and 32 are closed and the valve 26 is opened, and the handle 48 of the air cylinder 38 is operated to further gradually pressurize. As a result, the rear side of the tracer discharge part, that is, the diaphragm 30, has a pressure slightly higher than that of the tip side of the tracer discharge pipe 22, and the tracer 40 can be discharged slowly onto the water surface 46 (see FIG. 2).

Floating particles used as a tracer should be approximately equal to or slightly smaller than the density of groundwater. This is because if it is extremely light, the particles float above the surface of the water, are affected by the surface tension, and may not faithfully reflect the groundwater flow. As shown in Fig. 2, if the density is similar to that of groundwater, the influence on the surface tension is small and more accurate observation data can be obtained. Since it is difficult to release the plastic particles that are the tracer 40 by themselves, as shown in FIG.
42) Charge the tracer discharge pipe 22 while immersed in
It is desirable to release it together with the water. When the tracer is a liquid, it is constructed so that a trace amount of the tracer liquid is partitioned with air and discharged one by one.

In the case of solid tracers, it is often difficult to obtain levitation particles that are approximately equal to the density of groundwater. Therefore, as shown in FIGS. 3 and 4, a tracer 50 having a dumbbell structure in which slightly light particles 52 and slightly heavy particles 54 are connected by a filament 56 is preferable. Those particles are about 1 mm in diameter
And the total length is about 1 cm.
Very favorable results were obtained with the structure in which the surface was slightly seen through from 6. Even in the case of such a tracer having a dumbbell structure, it can be contained in a very small amount of carrier 42 and charged in the tracer discharge pipe 22.

The movement of the tracers 40, 50 released on the water surface 46 is transparent plate 1
The flow direction and the flow velocity are measured by observing through 0 through the TV camera 16 or the like and tracking the movement. Besides a television camera, a still camera, a fiberscope, etc. can be used.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a configuration.
Although the diaphragm is incorporated in the tracer reservoir in the above embodiment, the liquid may be directly pressurized without using the diaphragm, or the tracer reservoir may not be used.

In the pressurized gas system, a gas cylinder and an air cylinder are arranged in parallel, but a gas cylinder alone may be used as long as a finely adjustable structure is provided.

[Advantages of the Invention] As described above, the present invention applies a pressurized gas to both the front side and the rear side of the tracer discharge section at the same time as the inside of the observation section at the time of forming the water surface of groundwater to maintain the pressure balance, and thereafter to the rear side Since it was configured to discharge the tracer by slightly pressurizing it from the tip side, the balance between the water pressure and the discharge gas pressure is maintained accurately regardless of the installation depth of the observation part, and the tracer flows backward or the tracer There is no inconvenience that a large amount is released and disturbs the measurement field, and there is an effect that the tracer can be slowly released onto the water surface formed in the observation part in a very small amount.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a tracer releasing method in groundwater flow measurement according to the present invention, FIG. 2 is an explanatory view showing a state in which the tracer is released by it, and FIG. 3 is another example of the tracer. FIG. 4 is an explanatory diagram showing the floating state on the water table. 10 …… transparent plate, 12 …… color, 14 …… observer, 20 …… gas supply pipe, 22 …… tracer discharge pipe, 24,26,32,36 ……
Valve, 28 ... Tracer reservoir, 34 ... Gas cylinder, 38 ... Air cylinder.

Claims (1)

[Claims] 1. A transparent plate and an observation section having a collar surrounding the transparent plate and projecting downward are installed in groundwater in a well, and pressurized gas is supplied into the observation section to store gas up to the lower end of the collar to store groundwater. In the method of measuring groundwater flow, which forms a water surface of the ground and discharges the tracer to observe the movement of the tracer. To maintain the pressure balance and then slightly pressurize the rear side from the front side to discharge the tracer.