Point heat source mobile distributed seepage monitoring system and its monitoring method

A monitoring system and distributed technology, applied in measurement devices, permeability/surface area analysis, suspension and porous material analysis, etc., can solve problems such as affecting the monitoring accuracy, unable to eliminate the effect of seepage direction, and increasing measuring points, etc. Spatial resolution problem, meeting long-term monitoring needs, and avoiding the effect of failure

Active Publication Date: 2020-04-28
SICHUAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] (1) This technology uses a distributed optical fiber temperature measurement system based on Raman scattering, which has a low spatial resolution of about 1m, and the measured temperature is the average temperature within a range of 1m, with low accuracy;
[0008] (2) The heating method adopts resistance wire heating. The monitoring line of the earth-rock dam is long, and the resistance value of the resistance wire matched with the monitoring line is relatively large. To reach the predetermined heating temperature, a higher voltage and a longer heating time are often required ;
[0009] (3) The resistance value of the resistance wire will change with the change of temperature, therefore, it is difficult to ensure the stability of the heating power;
[0010] (4) There is a hidden danger of electric leakage when the cable is buried in wet soil for a long time;
[0011] (5) The heat source in the monitoring system is a linear heat source, which cannot eliminate the influence of the seepage direction on the monitoring results
This technology directly penetrates the fiber grating sensing string into the heating pipeline, and the two ends are sealed with hot melt adhesive. The position of the measuring point is fixed, but the position of the seepage is uncertain. When there is no measuring point near the seepage area , it will affect the identification accuracy of the seepage state
The monitoring range of earth-rock dams is large. To ensure spatial resolution and avoid missed judgments, it is necessary to increase the number of measuring points, thereby increasing monitoring costs.
[0016] (2) As the length of the monitoring line increases, the heating effect will weaken, thereby affecting the monitoring accuracy
[0017] (3) The heat source in the monitoring system is a linear heat source, which cannot eliminate the influence of the seepage direction on the monitoring results

Method used

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  • Point heat source mobile distributed seepage monitoring system and its monitoring method
  • Point heat source mobile distributed seepage monitoring system and its monitoring method
  • Point heat source mobile distributed seepage monitoring system and its monitoring method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0063] In order to verify the effectiveness of the point heat source seepage monitoring system developed by the present invention, a Figure 9The test model shown (H1=100mm, H2=600mm, H3=600mm, B=300mm, L=800mm), under the influence of dual factors of seepage velocity and seepage direction, the calibration test was carried out. The shell of the model box is spliced ​​by 3mm thick steel plates, and a square steel pipe frame is set outside the box as a lateral support. There are 4 drain pipes at the bottom of the box, and valves are installed on the drain pipes to control the flow. Embed 4 monitoring pipes 7 (PE-RT pipes, outer diameter 20mm, wall thickness 2mm) in the box, the axis and the infiltration direction (from top to bottom) are respectively 90°, 70°, 50°, 30° °. First, lay 10cm-thick gravel at the bottom of the box as a reverse filter layer, and then fill in river sand to the design elevation. Before filling the river sand, put a steel bar in the monitoring pipe 7 i...

Embodiment 2

[0069] On the basis of Example 1, using Figure 8 In the improved scheme shown, pure water is poured into the monitoring pipe 7 to carry out calibration tests at different seepage velocities. Each working condition ln(λ-λ θ ) vs. time curve, see Figure 11 . It can be seen that as the seepage velocity increases, the temperature drops faster, and ln(λ-λ θ ) has a strong correlation with the seepage velocity. According to ln(λ-λ θ ) time history curve, and divide it into three stages: rapid cooling period (0-200s), transitional period (200s-300s), and slow cooling period (300s-temperature stable). In the fast cooling section and the slow cooling section, ln(λ-λ θ ) time history curve is approximately linear, using the data from 50s to 200s and 300s to 600s respectively to fit ln(λ-λ θ ) The slope ξ of the time history curve in these two periods v1 and ξ v2 , as shown in Table 2. ξ v1 and ξ v2 The absolute values ​​of both increase with the increase of the seepage vel...

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Abstract

The invention discloses a point heat source mobile distributed seepage monitoring system and a monitoring method thereof. The monitoring system includes a sensing heating element, a monitoring tube, a voltage stabilized power supply, an optical fiber grating demodulator, a notebook computer, an armored optical cable and a wire. The armored optical cable connects the sensing elements in the sensing heating element in series, and the armored optical cable is connected with the fiber grating demodulator, and the wavelength division multiplexing technology is used for simultaneous measurement of multiple measuring points; the fiber grating demodulator is connected with the laptop; The wires connect the heating elements in the sensing heating elements in series, and the two ends of the wires are connected with a voltage-stabilized power supply to form a closed circuit for electrification and heating; the sensing heating elements are penetrated into the monitoring tube. The invention has the advantages of: building a point heat source heating system, avoiding the influence of seepage monitoring results by the seepage direction; moving distributed monitoring, solving the spatial resolution problem of the fiber grating quasi-distributed sensing system; Remove for repair or replacement.

Description

technical field [0001] The invention relates to the technical field of geotechnical engineering seepage monitoring, in particular to an optical fiber grating point heat source moving distributed seepage monitoring system and a monitoring method thereof. Background technique [0002] Seepage problems exist in many geotechnical projects. Seepage will affect the stability of rock and soil mass and directly threaten the safety of the project. The well-known failure of the Teton Dam in the United States was caused by seepage damage. [1] . Seepage is concealed, random in space and time, and most of the prevention and control of seepage needs to be supplemented by certain monitoring methods. Therefore, seepage monitoring is an important monitoring content in the field of geotechnical engineering. [0003] Seepage monitoring methods are diverse, including: (1) Conventional monitoring methods. This type of method has a long history, with many engineering applications and experience...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N15/08
Inventor 陈江方晓熊峰
Owner SICHUAN UNIV
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