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Fiber grating-based soil matrix suction monitoring device and method

A technology of matrix suction and fiber grating, applied in measuring devices, using optical devices, soil material testing, etc., can solve the problems of inability to monitor in real time, slow response speed, complicated operation, etc., and achieve good waterproof performance, fast response speed, and easy operation Effects in simple steps

Active Publication Date: 2021-06-15
NANJING UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Compared with the traditional method of monitoring soil matrix suction, this method has the advantages of good stability, fast response, good water resistance, simple operation, and real-time monitoring. It is suitable for indoor and field in-situ monitoring experiments and solves the problem of traditional monitoring of soil matrix. Poor suction stability, slow response, poor water resistance, complicated operation, unable to monitor in real time, etc.

Method used

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  • Fiber grating-based soil matrix suction monitoring device and method
  • Fiber grating-based soil matrix suction monitoring device and method
  • Fiber grating-based soil matrix suction monitoring device and method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0071] The application of the device and method of the present invention requires the calibration experiment of soil matrix suction and FBG-1 strain value. The experiment is carried out under constant temperature indoors, and the soil type for calibration is clay. Specific steps are as follows:

[0072] Step 1: place the electronic soil tensiometer and the device of the present invention on the same layer of dried soil, and record the temperature T measured by FBG-2 as the calibration experiment temperature;

[0073] Step 2: When the matrix suction of the electronic soil tensiometer and the strain value ε of FBG-1 0 Record it when it reaches stability;

[0074] Step 3: Add water to make the soil saturated, and also record the matrix suction when it is stable and the strain value ε of FBG-1 b ;

[0075] Step 4: Under the action of water release and evaporation, continuously record several groups of stable matrix suction and FBG-1 strain value ε n (n=1, 2, 3...);

[0...

Embodiment 2

[0078] The field monitoring experiment of soil matrix suction is carried out by applying the method and device of the present invention. The experiment site is the back hill of Xianlin Campus of Nanjing University, and the soil type of the site is clay.

[0079]Step 1: Add an appropriate amount of water to the clay stick and make it upright, let the water soak the clay head, when you see water dripping from the surface of the clay head, it means that the clay head has reached saturation, then cover the rubber threaded cap, Make the inside of the clay rod airtight, and then bury the clay rod at a certain depth in the soil;

[0080] Step 2: Stand still for a period of time until the clay rod and the soil reach the water potential equilibrium, then turn on the fiber grating demodulator for monitoring;

[0081] Step 3: As the suction of the soil matrix changes, the displacement of the piston in the strain sensor will change, which will cause strain on the elastic steel sheet and t...

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Abstract

The invention discloses a fiber grating-based soil matrix suction monitoring device and method. The device comprises a pottery clay rod, a strain sensor, a fiber grating demodulator and a computer. The pottery clay rod in a saturated state is buried in soil, after the pottery clay rod and the soil reach water potential balance, the fiber grating demodulator is started, the piston provided with the strain sensor can move along with the change of the matrix suction of the soil, so that the elastic steel sheet and the FBG-1 adhered to the elastic steel sheet generate strain, the wavelength of the FBG-1 is changed, receiving by the fiber grating demodulator is carried out, the FBG-2 performs temperature compensation on the elastic steel sheet and the FBG-1 so as to obtain a strain value of the FBG-1 after temperature influence is eliminated, the function relation between the soil matrix suction and the strain value of the FBG-1 is established through an electronic soil tensiometer calibration experiment so as to obtain the soil matrix suction corresponding to the strain value of the FBG-1, and the purpose of monitoring the soil matrix suction is achieved.

Description

Technical field: [0001] The invention discloses a soil matrix suction monitoring device and method based on an optical fiber grating, and relates to the technical field of soil matrix suction monitoring. Background technique: [0002] Soil matrix suction is a key parameter determining the properties of unsaturated soils, and it is also one of the most difficult soil physical parameters to measure. Soil matrix suction mainly exists at the water-air interface in unsaturated soil, and it increases continuously with the decrease of soil moisture content. Soil-water characteristic curve (SWCC) is often used to describe the relationship between unsaturated soil matrix suction and water content. rate relationship. Soil matric suction is of great significance for studying soil permeability coefficient, shear strength and analyzing the stability of geotechnical structures such as slopes and unsupported foundation pits. [0003] At present, the methods for measuring the suction of s...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N33/24G01B11/16
CPCG01N33/24G01B11/165
Inventor 李杰朱鸿鹄王家琛程刚刘喜凤刘天翔刘威
Owner NANJING UNIV
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