Wall-attached in-situ rock-soil layer heat conductivity coefficient measuring device and method
Through the combined design of expansion modules and high-precision sensors, the accuracy and adaptability issues of geotechnical thermal conductivity measurements have been resolved, achieving high-precision and safe in-situ measurements, with measurement results closer to the actual state of the geotechnical layer.
Patent Information
- Application Number
- CN202510927082.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-07
- Publication Date
- 2025-10-03
AI Technical Summary
The existing method for measuring the thermal conductivity of rock and soil layers has problems such as measurement results inconsistent with the in-situ state, low measurement accuracy, poor adaptability and insufficient safety. It is especially difficult to accurately measure in environments with different hardness and water-rich environments.
The system adopts a combined design of expansion module, heating module and measurement module, uses expandable elastomer to cling to the wall of rock and soil layer, combines oxidation-resistant heating wire and high-precision temperature sensor, calculates thermal conductivity through hot wire method, and realizes automatic data processing by central controller.
It improves measurement accuracy and adaptability, reduces contact thermal resistance and human errors, expands applicable scenarios, enhances safety and data reliability, and the measurement results are closer to the actual in-situ state of the rock and soil layer.
Smart Images
Figure CN120741554A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of rock and soil thermal property testing, and particularly relates to a wall-attached in-situ rock and soil layer thermal conductivity measurement device and method. Background Art
[0002] Accurately measuring the thermal conductivity of rock and soil layers is crucial in fields such as geological engineering, geothermal energy development, and nuclear waste disposal. Traditionally, the measurement of geotechnical thermophysical parameters has primarily relied on laboratory methods, where rock and soil samples are removed and tested in a laboratory setting. However, this method has significant drawbacks: Firstly, the physical structure of rock and soil samples may change during sampling and transportation, resulting in deviations from the in-situ state. Secondly, the laboratory environment cannot fully simulate in-situ conditions such as temperature, pressure, and moisture content, further impacting measurement accuracy.
[0003] Existing in-situ measurement methods primarily include the thermal probe method and the heat pulse method. The thermal probe method involves inserting a metal probe into the soil for measurement. However, this method is less suitable for hard rock, and insufficient contact between the probe and the soil creates thermal resistance, reducing measurement accuracy. The heat pulse method requires pre-embedding a heat source and temperature sensor in the soil, which is complex and may damage the original soil structure.
[0004] In addition, existing measuring devices lack adaptability when encountering rock and soil layers of different hardness and pore sizes, making it difficult to ensure effective contact between the measuring components and the rock and soil wall. At the same time, the insulation performance is insufficient in water-rich environments, which can easily lead to measurement failure or safety accidents.
[0005] Existing equipment has only made some progress in in-situ measurements of soil thermal conductivity, but is unable to measure rock thermal conductivity. In particular, it is unclear whether rocks or soil layers exhibit different thermophysical properties in specific geological environments beyond a certain depth.
[0006] Therefore, there is an urgent need for an in-situ rock and soil layer thermal conductivity measurement device and method that can adapt to various geological conditions, has high measurement accuracy, and is easy to operate. Summary of the Invention
[0007] Purpose of the invention: The purpose of the present invention is to address the deficiencies of the existing technology and provide a wall-mounted in-situ rock and soil layer thermal conductivity measurement device and method. Compared with traditional laboratory methods, the measurement results are closer to the actual in-situ state of the rock and soil layer, and the data reliability is improved.
[0008] Technical solution: The wall-mounted in-situ rock and soil layer thermal conductivity measurement device of the present invention comprises: An expansion module, used to make the measuring device close to the wall of the rock and soil layer, the expansion module comprising an expandable elastic body, a connecting piece connected to the elastic body, and a driving piece connected to the connecting piece; a heating module disposed on the surface of the elastomer and configured to provide heat to the wall of the rock and soil layer, the heating module comprising an oxidation-resistant heating wire, a heating circuit connected to the heating wire, and a heating power supply, the oxidation-resistant heating wire being in close contact with the surface of the elastomer and maintaining contact with the surface of the elastomer as the elastomer expands or contracts; a measurement module, comprising a plurality of temperature sensors, a data transmission line, and a temperature measurement terminal, wherein the plurality of temperature sensors are evenly distributed on the surface of the elastomer and in close contact with the oxidation-resistant heating wire, and are used to measure the temperature change of the rock and soil layer wall; and A central controller is electrically connected to the expansion module, heating module and measurement module, and is used to control the working state of each module and summarize and process the measurement data; The diameter of the elastic body is not greater than 110 mm in the unexpanded state and not less than 140 mm after expansion. The central controller processes the measurement data by the following steps: The temperature changes of the rock and soil layer wall are recorded by the measurement module; Record the output power of the heating module and calculate the heat flow rate ; The thermal conductivity of the rock and soil layer is calculated according to the following formula : in, is the thermal conductivity of the elastomer and is pre-determined by the hot wire method, t1 and t2 are two different moments, and The temperatures at time t1 and t2 are respectively. t1 and t2 are two time periods selected from the middle section of the temperature rise time.
[0009] To further improve the above technical solution, the elastomer is an expandable rubber or an electroactive polymer; when the elastomer is an expandable rubber, the connecting member is an air duct, and the driving member is an air pump; when the elastomer is an electroactive polymer, the connecting member is a power supply circuit, and the driving member is an expansion power supply.
[0010] Furthermore, the oxidation-resistant heating wire is an iron-chromium-aluminum alloy or a nickel-chromium alloy heating wire.
[0011] Furthermore, the temperature sensor is a thermistor temperature sensor or a grating thermometer; when the temperature sensor is a thermistor temperature sensor, the data transmission line adopts a temperature transmission circuit; when the temperature sensor is a grating thermometer, the data transmission line adopts an optical fiber.
[0012] Furthermore, when the measurement accuracy of the temperature sensor is not less than 0.1°C; when the temperature sensor is a thermistor temperature sensor, the sensors are connected in parallel; when the temperature sensor is a grating thermometer, the sensors are connected in series.
[0013] Furthermore, the plurality of temperature sensors include 6 temperature sensors.
[0014] Furthermore, the outer wall of the oxidation-resistant heating wire is insulated to adapt to a water-rich environment.
[0015] The method for measuring the thermal conductivity of rock and soil layers using the above-mentioned wall-mounted in-situ rock and soil layer thermal conductivity measuring device comprises the following steps: Lowering the measuring device along the borehole to a predetermined measuring depth; Control the expansion module to make the elastic body expand and adhere closely to the wall of the rock and soil layer to be tested; While the elastomer remains in an expanded state, the measurement module is started to record temperature data; After the temperature reading stabilizes, start the heating module and continuously record the temperature change data and heat flow rate ; The thermal conductivity of the rock and soil layer is calculated according to the following formula : in, is the thermal conductivity of the elastomer, t1 and t2 are two different moments, and are the temperatures at time t1 and t2 respectively.
[0016] Furthermore, the recording frequency of the temperature data is to record a set of data every 0.25 seconds, and the average temperature measured in a set of data is taken as the temperature for calculation.
[0017] Furthermore, the thermal conductivity of the elastomer is Preliminary measurement was performed by the hot-wire method.
[0018] Beneficial effects: Compared with the prior art, the advantages of the present invention are: the expansion module of the present invention adopts an expandable elastomer design (the diameter in the unexpanded state is not more than 110mm, and after expansion is not less than 140mm), which can adapt to boreholes of different diameters and improve the versatility and adaptability of the device; the application of expandable rubber or electroactive polymer enables the measuring component to fit tightly to the wall of the rock and soil layer, significantly reducing the contact thermal resistance and improving the measurement accuracy; it supports both air pump drive and electric drive expansion mechanisms, thereby improving the reliability and operational flexibility of the device in different working environments.
[0019] The heating module in the present invention adopts oxidation-resistant iron-chromium-aluminum or nickel-chromium alloy heating wire, which has high thermal stability and long service life, and can work stably for a long time at high temperatures of 300-800℃; the heating wire is tightly attached to the surface of the elastomer and expands and contracts with it, ensuring that the heat source and the measuring surface always maintain stable contact, reducing measurement errors; the outer wall of the heating wire is provided with an insulating layer, so that the device can be safely used in water-rich environments, expanding the applicable scenarios and improving safety performance.
[0020] The measurement module in this invention uses six high-precision (accuracy up to 0.1°C) temperature sensors for evenly distributed measurement, eliminating measurement errors caused by rock and soil heterogeneity and improving data reliability. It supports two sensor types: thermistor temperature sensors (connected in parallel) and grating thermometers (connected in series), enhancing system compatibility and adaptability. The method of taking the average temperature of multiple points effectively filters out random measurement noise and improves measurement accuracy.
[0021] The central controller of the present invention uniformly manages each module, automates the measurement process, and reduces human operation errors by approximately 40%. The built-in data processing algorithm can calculate the thermal conductivity coefficient in real time, improve work efficiency, and shorten the measurement cycle. It supports data storage and export functions to facilitate subsequent analysis and processing.
[0022] The present invention is based on the principle of the hot-wire method and takes into account the thermal conductivity characteristics of the material interface, thereby improving measurement accuracy. It adopts high-frequency data acquisition (one set every 0.25 seconds) to capture the details of temperature changes and improve calculation accuracy. By pre-determining the thermal conductivity of the elastomer and combining it with the interface heat flux distribution formula, the thermal conductivity of the rock and soil layer can be accurately derived, eliminating the influence of interfacial thermal resistance and reducing measurement errors.
[0023] The modular design facilitates maintenance and upgrades, and each component can be replaced individually, reducing maintenance costs. The overall structure is compact (the diameter in the unexpanded state is no more than 110mm), making it easy to operate and transport in confined spaces. It is applicable over a wide depth range. Compared with traditional laboratory methods, the measurement results are closer to the actual in-situ state of the rock and soil layer, and data reliability is improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION
[0025] The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the embodiments.
[0026] Example 1: Figure 1The wall-mounted in-situ rock and soil thermal property parameter measurement device shown includes an expansion module, a heating module and a measurement module. Each module is connected to a central controller 6. The central controller 6 can open or close each module separately, and summarize and process the measurement data. Through automatic data processing, the thermal conductivity coefficient of the rock or soil layer is obtained.
[0027] The expansion module includes an expandable elastomer 1, a connector connected to the elastomer 1, and a driver connected to the connector. The elastomer 1 is made of expandable rubber or electroactive polymer. When the elastic member 1 is expandable rubber, the connector 2 and the driver 3 are the air guide tube and air pump respectively. When the elastic member 1 is electroactive polymer, the connector 2 and the driver 3 are the power supply circuit and the expansion power supply respectively. The diameter of the expandable rubber or electroactive polymer should not exceed 110mm and should not be less than 140mm after expansion. The thermal conductivity should be measured in the laboratory in advance. The measurement method can refer to the method specified in the specification "Determination of thermal conductivity of non-metallic solid materials - Hot wire method (GB_T 10297-2015)".
[0028] The heating module includes an oxidation-resistant heating wire 7 (generally iron-chromium-aluminum or nickel-chromium electric heating alloy), a heating circuit 8, and a heating power supply 9. The oxidation-resistant heating wire 7 is in close contact with the expandable rubber or electroactive polymer and remains in close contact with its surface as the expandable rubber or electroactive polymer expands or contracts. Because the experiment may be conducted in a water-rich environment, the oxidation-resistant heating wire 7 needs to be insulated from the outer wall.
[0029] The measurement module includes six temperature sensors (4, 12, 13, 14, 15, and 16), a data transmission line 10, and a temperature measurement terminal 5. The temperature sensors are either thermistors or grating thermometers. When using thermistors, the data transmission line 10 utilizes a temperature transmission circuit. When using grating thermometers, the transmission channel utilizes an optical fiber. The six temperature sensors (4, 12, 13, 14, 15, and 16) are evenly distributed on the surface of the expanded rubber or electroactive polymer 1 and in close contact with the oxidation-resistant heating wire 7. The temperature sensors are either thermistors or grating thermometers, with an accuracy of 0.1°C. Thermistors are connected in parallel, while grating thermometers are connected in series.
[0030] Example 2: The thermal physical property parameter measurement device for rock and soil layer provided in Example 1 is used to measure the thermal physical property parameter of rock and soil layer, including the following steps: 1. After cleaning the borehole, lower the device along the borehole to the depth required for measurement. 2. Open the expansion module and inflate or energize it so that the expansion rubber or electroactive polymer 1 is in close contact with the rock or soil layer to be measured. The oxidation-resistant heating wire 7 is then tightly fitted between the expansion rubber or electroactive polymer 1 and the target object to be measured. 3. Keep the expansion rubber or electroactive polymer 1 in an expanded state, turn on the measurement module, and accurately record a set of temperature sensors (thermistor temperature sensor or grating thermometer). Generally, a set of data is recorded every 0.25 seconds. A set of temperature sensors consists of 6. After the system records a stable temperature, turn on the heating module and continue to record the temperature data until the data is stable and no longer increases. At the same time, record the output power of the heating module, that is, the heat flow rate. ; 4. The digital average value measured by a group of 6 temperature sensors is used as the temperature for calculation; 5. The logarithm of temperature increase and time conforms to the relationship: Where: Indicates warming, represents the heat flow rate, represents the thermal conductivity of the material, represents the thermal diffusion coefficient, R is the distance between the temperature measurement point and the line heat source, A =0.57726 is Euler's constant, ; When the temperature measurement point is close to the heat source, the surface temperature change of the semi-infinite object conforms to the relationship: (1) Where: represents the temperature at time t2, q is the heat flow rate, is the thermal conductivity; When two different materials are bonded together, material 1 and material 2 share the total heat flow rate of the line heat source. ,and , the energy distribution conforms to the following relationship: (2) therefore, (3) Therefore, the thermal conductivity of unknown material 2 can be expressed using the thermal conductivity of known material 1 as follows: (4) As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to it in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims.
Claims
1. A wall-mounted in-situ rock and soil layer thermal conductivity measurement device, characterized in that: include: An expansion module, used to make the measuring device close to the wall of the rock and soil layer, the expansion module comprising an expandable elastic body, a connecting piece connected to the elastic body, and a driving piece connected to the connecting piece; a heating module disposed on the surface of the elastomer and configured to provide heat to the wall of the rock and soil layer, the heating module comprising an oxidation-resistant heating wire, a heating circuit connected to the heating wire, and a heating power supply, the oxidation-resistant heating wire being in close contact with the surface of the elastomer and maintaining contact with the surface of the elastomer as the elastomer expands or contracts; a measurement module comprising a plurality of temperature sensors, a data transmission line and a temperature measurement terminal, wherein the plurality of temperature sensors are evenly distributed on the surface of the elastomer and in close contact with the oxidation-resistant heating wire, and are used to measure the temperature change of the rock and soil layer wall; as well as A central controller is electrically connected to the expansion module, heating module and measurement module, and is used to control the working state of each module and summarize and process the measurement data; The diameter of the elastic body is not greater than 110 mm in the unexpanded state and not less than 140 mm after expansion. The central controller processes the measurement data by the following steps: The temperature changes of the rock and soil layer wall are recorded by the measurement module; Record the output power of the heating module and calculate the heat flow rate; The thermal conductivity of the rock and soil layer is calculated according to the following formula : in, is the thermal conductivity of the elastomer and is pre-determined by the hot wire method, t1 and t2 are two different moments, and are the temperatures at time t1 and t2 respectively.
2. The wall-mounted in-situ rock and soil layer thermal conductivity measuring device according to claim 1, characterized in that: The elastomer is an expandable rubber or an electroactive polymer; when the elastomer is an expandable rubber, the connecting member is an air duct and the driving member is an air pump; when the elastomer is an electroactive polymer, the connecting member is a power supply circuit and the driving member is an expansion power supply.
3. The wall-mounted in-situ rock and soil layer thermal conductivity measuring device according to claim 1, characterized in that: The oxidation-resistant heating wire is an iron-chromium-aluminum alloy or a nickel-chromium alloy heating wire.
4. The wall-mounted in-situ rock and soil layer thermal conductivity measuring device according to claim 1, characterized in that: The temperature sensor is a thermistor temperature sensor or a grating thermometer; when the temperature sensor is a thermistor temperature sensor, the data transmission line adopts a temperature transmission circuit; when the temperature sensor is a grating thermometer, the data transmission line adopts an optical fiber.
5. The wall-mounted in-situ rock and soil layer thermal conductivity measuring device according to claim 4, characterized in that: When the measurement accuracy of the temperature sensor is not less than 0.1°C; when the temperature sensor is a thermistor temperature sensor, each sensor is connected in parallel; when the temperature sensor is a grating thermometer, each sensor is connected in series.
6. The wall-attached in-situ rock and soil layer thermal conductivity measuring device according to claim 1, characterized in that: The plurality of temperature sensors includes six temperature sensors.
7. The wall-mounted in-situ rock and soil layer thermal conductivity measuring device according to claim 1, characterized in that: The outer wall of the oxidation-resistant heating wire is insulated to adapt to a water-rich environment.
8. A method for measuring thermal conductivity of rock and soil layers using the wall-attached in-situ rock and soil layer thermal conductivity measuring device according to claim 1, characterized in that: The following steps are involved: Lowering the measuring device along the borehole to a predetermined measuring depth; Control the expansion module to make the elastic body expand and adhere closely to the wall of the rock and soil layer to be tested; While the elastomer remains in an expanded state, the measurement module is started to record temperature data; After the temperature reading stabilizes, start the heating module and continuously record the temperature change data and heat flow rate ; The thermal conductivity of the rock and soil layer is calculated according to the following formula : in, is the thermal conductivity of the elastomer, t1 and t2 are two different moments, and are the temperatures at time t1 and t2 respectively.
9. The method for measuring thermal conductivity of rock and soil layers according to claim 8, characterized in that: The temperature data is recorded at a frequency of one set of data every 0.25 seconds, and the average temperature value of one set of data is taken as the temperature for calculation.
10. The method for measuring thermal conductivity of rock and soil layers according to claim 8, characterized in that: The thermal conductivity of the elastomer Preliminary measurement was performed by the hot-wire method.