CN-120971498-B - Soil moisture content detection method based on unsteady state heat conduction and optical fiber temperature measurement

CN120971498BCN 120971498 BCN120971498 BCN 120971498BCN-120971498-B

Abstract

The invention provides a soil moisture content detection method based on unsteady state heat conduction and optical fiber temperature measurement, which comprises the steps of heating a soil body in a target area based on an active heating method, measuring soil temperature values at each moment in different radial distances from a heating source in the heating process, substituting the soil temperature values at any moment in the heating process and the corresponding radial distances into a predetermined soil moisture content relation model to obtain the soil moisture content of the target area at the corresponding moment, which is at the position, corresponding to the radial distances from the heating source, and determining the soil moisture content of the target area according to the soil moisture content of the target area at the corresponding moment, which is at the position, corresponding to the radial distances from the heating source. The invention realizes in-situ monitoring and long-time monitoring of the soil mass in the target area in a large range by constructing the relation between the water content of the soil mass and the temperature value of the soil mass and obtaining the temperature value of the soil mass by an active heating method.

Inventors

LIU YONGLI
Liao Yingan
XIAO HENGLIN
MA QIANG
YUE RUIJIE
CHEN ZHI

Assignees

湖北工业大学
江汉大学

Dates

Publication Date: 20260508
Application Date: 20250928

Claims (9)

1. The soil body water content detection method based on unsteady state heat conduction and optical fiber temperature measurement is characterized by comprising the following steps of: Heating the soil body of a target area based on an active heating method, and measuring soil body temperature values at each moment in different radial distances from a heating source in the heating process, wherein the target area comprises a plurality of soil layers; Substituting a soil body temperature value and a corresponding radial distance thereof at any moment in a heating process into a predetermined soil body water content relation model to obtain the soil body water content of a target area at the corresponding moment, wherein the soil body water content relation model is determined according to a first relation between a thermal diffusion coefficient and the soil body temperature value, a second relation between the water content and the thermal diffusion coefficient and a soil layer corresponding to the soil body temperature value; determining the water content of the soil body in the target area according to the water content of the soil body in the target area at the corresponding moment, which is at each radial distance from the heating source; the soil body water content relation model comprises: (1); (2); wherein formula (1) characterizes the second relationship, The water content of the soil body is represented, The thermal diffusion coefficient of the soil body at the radial distance r from the heating source in the target area at the moment t is expressed, The dry soil thermal diffusion coefficient of the soil body of the target area is represented, Representing the thermal diffusivity of the soil water in the target zone, The dry soil specific heat capacity of the soil body of the target area is represented; Representing the specific heat capacity of soil water in the target area, wherein the formula (2) represents the first relation, For the empirical factor, T is the measured soil temperature value, T w is the temperature of the heating source surface, and T 0 is the initial temperature of the soil in the target zone before heating.
2. The method for detecting the water content of the soil body based on unsteady state heat conduction and optical fiber temperature measurement according to claim 1, wherein the first relation is obtained by deducting a heat conduction equation under a cylindrical coordinate system based on an unsteady state heat conduction model, and the second relation is constructed based on Hashin-SHTRIKMAN models.
3. The method for detecting the moisture content of the soil body based on unsteady state heat conduction and optical fiber temperature measurement according to claim 1, wherein before the step of heating the soil body in the target area based on the active heating method, the method further comprises: sampling soil of each soil layer in the target area to obtain soil samples of each soil layer; performing a soil baking experiment on the soil samples of each soil layer to obtain the dry soil thermal diffusion coefficient of each soil layer soil body in the target area and the dry soil specific heat capacity of each soil layer soil body in the target area; And determining a soil moisture content relation model corresponding to each soil layer of the target area based on the dry soil thermal diffusion coefficient and the dry soil specific heat capacity of the soil body of each soil layer of the target area.
4. The method for detecting soil moisture content based on unsteady state heat conduction and optical fiber temperature measurement according to claim 3, wherein the step of substituting the soil temperature value and the corresponding radial distance thereof at any moment in the heating process into a predetermined soil moisture content relation model to obtain the soil moisture content in the target area at the corresponding moment, the soil moisture content being at a position corresponding to the radial distance from the heating source specifically comprises the following steps: Determining soil layers corresponding to the measured soil temperature values according to the soil layer distribution conditions of the target area; And calling a soil moisture content relation model corresponding to each soil layer respectively, and substituting each soil temperature value and the corresponding radial distance into the soil moisture content relation model of the corresponding soil layer to obtain the soil moisture content of the soil temperature value position.
5. The method for detecting the water content of the soil body based on unsteady state heat conduction and optical fiber temperature measurement according to any one of claims 1 to 3, wherein the step of heating the soil body in the target area based on the active heating method specifically comprises the following steps: an active heating optical fiber and a plurality of temperature measuring optical fibers are distributed in a target area, wherein the plurality of temperature measuring optical fibers are used for measuring the temperature of a plurality of measuring sections which are parallel and are spaced with different radial distances from the active heating optical fibers; actively heating the optical fiber until the surface is at a preset temperature, and enabling the soil temperature of the target area to reach a steady state.
6. Soil body moisture content detecting system based on unsteady state heat conduction and optic fibre temperature measurement, characterized by comprising: The device comprises an acquisition module, a heating module and a control module, wherein the acquisition module is used for heating soil mass temperature values at each moment under different radial distances from a heating source in a heating process, the heating process is a process of heating the soil mass of a target area based on an active heating method, and the target area comprises a plurality of soil layers; The calculation module is used for substituting the soil temperature value and the corresponding radial distance thereof into a predetermined soil moisture content relation model at any moment in the heating process to obtain the soil moisture content of the position, corresponding to the radial distance from the heating source, in the target area at the corresponding moment, wherein the soil moisture content relation model is determined according to a first relation between the thermal diffusion coefficient and the soil temperature value, a second relation between the moisture content and the thermal diffusion coefficient and a soil layer corresponding to the soil temperature value; The determining module is used for determining the soil moisture content of the target area according to the soil moisture content of the target area at each radial distance position from the heating source at the corresponding moment; the soil body water content relation model comprises: (1); (2); wherein formula (1) characterizes the second relationship, The water content of the soil body is represented, The thermal diffusion coefficient of the soil body at the radial distance r from the heating source in the target area at the moment t is expressed, The dry soil thermal diffusion coefficient of the soil body of the target area is represented, Representing the thermal diffusivity of the soil water in the target zone, The dry soil specific heat capacity of the soil body of the target area is represented; Representing the specific heat capacity of soil water in the target area, wherein the formula (2) represents the first relation, For the empirical factor, T is the measured soil temperature value, T w is the temperature of the heating source surface, and T 0 is the initial temperature of the soil in the target zone before heating.
7. An electronic device comprising a memory, a processor and a computer program stored on the memory and operable on the processor, wherein the processor, when executing the program, implements the method for detecting soil moisture content based on unsteady state heat conduction and optical fiber temperature measurement as claimed in any one of claims 1 to 5.
8. A non-transitory computer readable storage medium having a computer program stored thereon, wherein the computer program when executed by a processor implements the soil moisture content detection method based on unsteady state heat conduction and optical fiber temperature measurement as claimed in any one of claims 1 to 5.
9. A computer program product comprising a computer program, characterized in that the computer program, when executed by a processor, implements the method for detecting the moisture content of a soil body based on unsteady state heat conduction and optical fiber temperature measurement according to any one of claims 1 to 5.

Description

Soil moisture content detection method based on unsteady state heat conduction and optical fiber temperature measurement Technical Field The invention relates to the technical field of soil moisture field monitoring, in particular to a soil moisture content detection method based on unsteady state heat conduction and optical fiber temperature measurement. Background The water content is used as a core index for representing the water state of the soil body, the accurate measurement of the water content is important for researching the ecological characteristics and engineering performance of the soil and exploring the water migration and storage mechanism, and the water content is a basis for developing related researches in the fields of geology, geotechnical engineering, agricultural ecological environment and the like. At present, the soil moisture content measuring method based on the optical fiber technology is widely applied in the field due to the advantages of strong anti-interference performance, distributed monitoring, good durability and the like. In the prior art, a core thought of calculating the water content of a soil body by utilizing an optical fiber is to establish a quantitative relation between a temperature characteristic value (or an optical signal characteristic value) and the water content through laboratory calibration, specifically, a technician needs to configure soil body samples with different water contents in a laboratory, embed an optical fiber sensor (such as an active heating optical fiber, a distributed optical fiber temperature measuring system and the like) into the samples, obtain a calibration formula of the characteristic value and the water content through fitting by measuring characteristic values such as temperature change, optical power attenuation or Brillouin frequency shift and the like of the optical fiber under different water contents, and then apply the formula to on-site soil body measurement and reversely push the water content through the optical fiber actual measurement characteristic value. However, the prior art has obvious defects that on one hand, the laboratory calibration process is complicated, a large number of soil samples with different water contents and even different dry densities are required to be prepared, the calibration operation is influenced by factors such as uniformity of soil samples, experimental environment temperature and the like, time and labor are consumed, on the other hand, the suitability of a formula established by laboratory calibration and on-site soil is poor, the quality, pore structure and mineral composition of the on-site soil are often different from those of the laboratory samples, so that the calibration formula is deviated in practical application, the measurement precision is reduced, and in addition, the traditional method excessively depends on the laboratory calibration result, lacks a simplified model with strong universality, is difficult to quickly adapt to the measurement requirements of soil bodies with different areas and different types, and limits the popularization and application of the optical fiber technology in quick monitoring of the water contents. Disclosure of Invention The invention provides a soil moisture content detection method based on unsteady state heat conduction and optical fiber temperature measurement, which is used for solving the defect that the soil moisture content measurement method based on optical fibers in the prior art lacks universality and realizing an accurate, efficient and convenient soil moisture content detection method based on unsteady state heat conduction and optical fiber temperature measurement. The invention provides a soil body water content detection method based on unsteady state heat conduction and optical fiber temperature measurement, which comprises the following steps: Heating the soil body of a target area based on an active heating method, and measuring soil body temperature values at each moment in different radial distances from a heating source in the heating process, wherein the target area comprises a plurality of soil layers; Substituting a soil body temperature value and a corresponding radial distance thereof at any moment in a heating process into a predetermined soil body water content relation model to obtain the soil body water content of a target area at the corresponding moment, wherein the soil body water content relation model is determined according to a first relation between a thermal diffusion coefficient and the soil body temperature value, a second relation between the water content and the thermal diffusion coefficient and a soil layer corresponding to the soil body temperature value; And determining the water content of the soil body in the target area according to the water content of the soil body in the target area at the corresponding moment, which is at each radial distance from the heating source. According to the s