CN111638384B - An optical fiber detection device for monitoring the flow velocity of groundwater in an observation well - Google Patents

Abstract

The invention discloses an optical fiber detection device for monitoring the flow direction and the flow speed of underground water in an observation well, which comprises a device shell (1), wherein an electronic compass (3) is movably arranged in the device shell (1), the lower part of the electronic compass (3) is connected with a connecting pipe (7), the lower part of the connecting pipe (7) is connected with a steering fan (6) in the vertical direction, the center of the electronic compass (3) is arranged in a hollow manner, a steel pipe (8) penetrates through the center of the electronic compass (3), the steel pipe (8) is fixedly connected with the device shell (1), the steel pipe (8) is used for fixing an optical fiber (2), the steel pipe (8) and the optical fiber (2) penetrate through the connecting pipe (7), the lower end of the device shell (1) is connected with an optical fiber support (10), and the optical fiber support (10) is used for fixing the lower end point of the optical fiber (2). The optical fiber detection device for monitoring the flow direction and the flow speed of underground water in the observation well, provided by the invention, has the advantages of low cost, difficulty in being interfered by the surrounding electromagnetic environment and higher accuracy and stability than a common probe.

Description

An optical fiber detection device for monitoring the flow velocity of groundwater in an observation well

technical field

The invention relates to an optical fiber detection device for monitoring the flow direction and velocity of groundwater in an observation well, and belongs to the technical field of hydrogeological parameter monitoring.

Background technique

The groundwater observation well of the dam can observe the hydrogeological conditions near the dam. At present, there are many methods for measuring the groundwater flow. The traditional methods mainly include the pumping test method and the tracer method. The traditional pumping test method is not suitable for single Well monitoring is time-consuming and labor-intensive. The tracer method includes radioisotope tracer method, potential difference method, thermal tracer method, etc. The radioactive substances required by the radioisotope tracer method may cause harm to the human body and the environment. The tracer used in the tracer method can undergo physical and chemical reactions such as ion exchange, adsorption, and precipitation with groundwater and rock and soil, which affect the measurement results. The thermal tracing method has higher requirements on the precision of the thermal element. In addition, technologies such as neutron activation, but the cost of neutron activation is high and protective measures need to be taken.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a low cost, less susceptible to interference from surrounding electromagnetic environment, and more accurate and stable than ordinary probes.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

An optical fiber detection device for monitoring the flow velocity of groundwater in an observation well, comprising a device casing, an electronic compass is movably arranged in the device casing, the lower part of the electronic compass is connected with a connecting pipe, and the lower part of the connecting pipe is connected with a steering wheel in the vertical direction fan, the center of the electronic compass is hollow, the steel pipe passes through the center of the electronic compass, the steel pipe is fixedly connected with the device casing, the steel pipe is used for fixing the optical fiber, the steel pipe and the optical fiber pass through the connecting pipe, The lower end of the device casing is connected with an optical fiber support, which is used to fix the lower end point of the optical fiber, and the upper part of the optical fiber and the electronic compass are communicatively connected to the ground information processing control system disposed outside the device casing.

The device casing is provided with a concave rail, and balls are embedded in the concave rails, and the balls are in contact with the outer side of the electronic compass.

The recessed rails are located on the upper and lower sides and the side walls of the electronic compass.

The optical fiber support is a steel pipe structure.

The steel pipe and the center of the electronic compass are sealed.

The material of the connecting pipe is stainless steel.

Beneficial effects of the present invention: The present invention provides an optical fiber detection device for monitoring the flow velocity of groundwater in an observation well, which solves the shortcoming that ordinary probes can only detect basic water quality information but cannot judge the direction of water flow, and is convenient to accurately determine the direction of water flow in the detection area. It solves the problem that the water depth range of ordinary probes is small; the optical fiber measurement is not easily disturbed by the surrounding electromagnetic environment, and is more accurate and stable than ordinary probes; the device has a simple structure, an integrated design, and is easy to operate without cumbersome Human and material support.

Description of drawings

1 is a schematic cross-sectional structure diagram of an optical fiber detection device for monitoring groundwater flow velocity in an observation well according to the present invention;

FIG. 2 is a schematic diagram of the rotation trajectory of the steering fan in the present invention.

The reference numbers in the figure are as follows: 1-device shell; 2-optical fiber; 3-electronic compass; 4-concave rail; 5-ball; 6-steering fan; 7-connecting pipe; 8-steel pipe; 9-ground information processing control System; 10-Fiber Holder.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

As shown in Figures 1 and 2, the present invention provides an optical fiber detection device for monitoring the flow velocity of groundwater in an observation well, comprising a device casing 1, which protects internal equipment from damage caused by external forces. An electronic compass 3 is movably arranged in the housing 1 of the device. The electronic compass 3 is used to measure the direction of the water flow. A hole is opened at the central part avoiding the position of the components for passing the optical fiber 2 and the steel pipe 8. The steel pipe 8 passes through the center of the electronic compass 3, and the steel pipe 8 is fixedly connected with the device casing 1, and the steel pipe 8 is welded on the device casing 1 to fix the optical fiber 2 and prevent it from being bent inside the device. The steel pipe 8 is used for fixing the optical fiber 2 , the steel pipe 8 and the optical fiber 2 pass through the connecting pipe 7 , and the optical fiber 2 is used for data measurement, and is arranged in the device casing 1 and the connecting pipe 7 .

And seal the inner space after opening to prevent water from entering. The device casing 1 is provided with a concave rail 4 , and a ball 5 is embedded in the concave rail 4 , and the ball 5 is in contact with the outer side of the electronic compass 3 . The recessed rails 4 are located on the upper and lower sides and the side walls of the electronic compass 3 . The lower part of the electronic compass 3 is connected with a connecting pipe 7, and the material of the connecting pipe 7 is stainless steel. The lower part of the connecting pipe 7 is connected with a steering fan 6 in the vertical direction. The 4 concave rails are used to fix the running track of the 5 balls. The concave rails 4 and the balls 5 have extremely high sensitivity and jointly limit the electronic compass 3, the connecting pipe 7 and the steering. Rotation of fan 6. The direction of the steering fan 6 is fixed in the same direction as the electronic compass 3, and rotates with the water flow, and the blades of the steering fan 6 always point to the direction of the water flow. The connecting pipe 7 connects the steering fan 6 and the electronic compass 3, so that the three rotate together. The connecting pipe 7 is hollow in the pipe, and the optical fiber 2 and the steel pipe 8 are in the hollow part and do not contact the inner wall of the pipe.

The lower end of the device casing 1 is connected with an optical fiber support 10, which is used to fix the lower end of the optical fiber 2, and together with the steel pipe 8, the two ends of the optical fiber 2 exposed in the water body are limited and protected to a certain extent. 10 has the least influence on the results of water flow detection, and the optical fiber support 10 is made of thin steel pipes. The upper part of the optical fiber 2 and the electronic compass 3 are connected in communication with the ground information processing control system 9 arranged outside the device casing 1. The ground information processing control system 9 is based on the BOTDR optical fiber sensing technology and is used for data processing of optical information.

The working principle of an optical fiber detection device for monitoring the flow velocity of groundwater in an observation well provided by the present invention is as follows:

The various components of the installation device are shown in Figures 1 and 2. Do not touch the optical tip. Make sure that all components are installed in place before measuring. Test with a nearby available water body. After checking, you can measure. Put the optical cable equipped with the detection device into the well, and record the length of the optical cable that first appeared data, that is, the buried depth of groundwater. Keep the device stable and take data measurements.

Measurement of flow direction: From the time when the water surface is buried underground, the measurement starts from the first integer depth below the water surface, and a set of data is measured every one meter. Each measurement needs to wait for the degree to stabilize before recording. In actual operation, other measurement schemes can be adopted by operators according to their own needs. When seepage water flows through the well, the water flow will disturb the steering fan 6, so that the fan blade points to the direction of the water flow, and the electronic compass 3 obtains the water flow direction. Record the direction the compass points to, which is the direction of the water flow, and the opposite direction is the direction of the water flow.

Force and temperature measurement:

The Brillouin frequency shift fed back by the exposed part of the front end of the optical fiber 2 is processed by the ground information processing control system 9 to obtain information such as the strain condition and length change measured at the optical end, and the stress distribution condition and water temperature.

Remove the device from the well after the measurement is complete.

Reference formula:

1. Strain measurement:

where n is the refractive index of the fiber core; VA is the speed of sound; _λ is the wavelength of the forward propagating light wave in free space; E is the elastic modulus of the fiber material; ρ is the fiber density; k is the Poisson’s ratio; ε is the strain

Theory and practice have proved that the Brillouin scattering frequency shift is related to material properties, is sensitive to strain, and has a linear relationship with strain ε, which can be expressed as:

V _B (t)=V _BO (1-αt)

where V _B (t) is the frequency shift when strain t; V _BO is the frequency shift when no strain; α is a constant.

By measuring the frequency shift difference of Brillouin scattered light, the strain of a certain point can be obtained, and then the stress of the fiber can be understood.

2. Temperature measurement:

The effect of temperature on density and refractive index is realized through thermal expansion effect, and the relationship between Brillouin frequency shift and temperature is:

v _B (T)=(1.1134+0.0001T)×10 ¹⁰

where v _B is the Brillouin frequency shift and T is the temperature.

The above is only the preferred embodiment of the present invention, it should be pointed out that: for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (4)

1. The utility model provides an optical fiber detection device of underground water flow direction velocity monitoring in observation well which characterized in that: the device comprises a device shell (1), an electronic compass (3) is movably arranged in the device shell (1), a connecting pipe (7) is connected to the lower portion of the electronic compass (3), a steering fan (6) is connected to the lower portion of the connecting pipe (7) in the vertical direction, the center of the electronic compass (3) is arranged in a hollow mode, a steel pipe (8) penetrates through the center of the electronic compass (3), the steel pipe (8) is fixedly connected with the device shell (1), the steel pipe (8) is used for fixing an optical fiber (2), the steel pipe (8) and the optical fiber (2) penetrate through the connecting pipe (7), an optical fiber support (10) is connected to the lower end of the device shell (1), the optical fiber support (10) is used for fixing the lower end point of the optical fiber (2), and the upper portion of the optical fiber (2) and the electronic compass (3) are in communication connection with a ground information processing control system (9) arranged outside the device shell (1), be provided with concave rail (4) in device shell (1), ball (5) have been inlayed in concave rail (4), ball (5) with the outside contact of electron compass (3), concave rail (4) are located the upper and lower side and the lateral wall of electron compass (3), concave rail (4) are used for fixing the orbit of ball (5), concave rail (4) and ball (5) are restricting the turn to of electron compass (3), connecting pipe (7) and turn to fan (6) jointly, turn to fan (6) directional fixed with electron compass (3) syntropy rotates along with the rivers, the flabellum of turn to fan (6) always points to the position that the rivers flow to, connecting pipe (7) are connected turn to fan (6) and electron compass (3), make the three rotate jointly, connecting pipe (7) intraductal is cavity, the optical fiber (2) and the steel pipe (8) are arranged in a hollow part and are not contacted with the inner wall of the connecting pipe (7).

2. The optical fiber detection device for monitoring the flowing speed of underground water flow according to claim 1, wherein: the optical fiber support (10) is of a steel pipe structure.

3. The optical fiber detection device for monitoring the flowing speed of underground water flow according to claim 1, wherein: the steel pipe (8) and the center of the electronic compass (3) are hermetically arranged.

4. The optical fiber detection device for monitoring the flowing speed of underground water flow according to claim 1, wherein: the connecting pipe (7) is made of stainless steel.

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