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A fiber grating-based soil suction monitoring device and method

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

Active Publication Date: 2022-02-22
NANJING UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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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.

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  • A fiber grating-based soil suction monitoring device and method
  • A fiber grating-based soil suction monitoring device and method
  • A fiber grating-based soil 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 soil matrix suction monitoring device and method based on optical fiber gratings. Including clay rod, strain sensor, fiber grating interrogator, computer. Embed the saturated clay rod in the soil, and turn on the fiber grating demodulator after the clay rod and the soil reach the water potential equilibrium, and the piston equipped with the strain sensor will move with the change of the suction of the soil matrix, causing the elastic steel sheet and sticky The FBG‑1 attached to the elastic steel sheet produces strain, which causes the wavelength of FBG‑1 to change, and is received by the fiber grating demodulator. FBG‑2 performs temperature compensation on the elastic steel sheet and FBG‑1, thereby eliminating the influence of temperature After the final FBG-1 strain value, the functional relationship between the soil matrix suction and the FBG-1 strain value established by the electronic soil tensiometer calibration experiment, the soil matrix suction corresponding to the FBG-1 strain value is obtained, and the monitoring of the soil matrix suction is realized. the goal of.

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 Patents(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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