A device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection technology

Abstract

A device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection technology belongs to the field of frozen soil subgrade monitoring technology. It includes an HP-FDR composite probe for acquiring soil hydrothermal parameters; a data acquisition and processing module for processing the data acquired by the HP-FDR composite probe; a power supply module connected to and supplying power to both the HP-FDR composite probe and the data acquisition and processing module; and a fixing device to fix the HP-FDR composite probe in the frozen soil subgrade. This invention solves the problems of complex operation and long time consumption in traditional frozen soil subgrade hydrothermal parameter measurement methods, achieving high-precision, in-situ, synchronous, real-time, continuous, and reliable hydrothermal parameter monitoring to meet the needs of highway construction and maintenance in frozen soil areas; it also solves the problem of asynchronous measurement of moisture and temperature, which cannot accurately reflect the coupling relationship between the two, ensuring accurate assessment of the stability of frozen soil subgrades.

Description

Technical Field

[0001] This utility model belongs to the field of frozen soil subgrade monitoring technology, specifically relating to a device for obtaining hydrothermal parameters of frozen soil subgrade in situ using thermal pulse-frequency domain reflection technology. Background Technology

[0002] The frost heave and thaw settlement process of roadbeds in permafrost regions is an extremely complex one. Under the influence of temperature changes and moisture migration, the physical and mechanical properties of permafrost undergo significant changes, thereby affecting the bearing capacity and durability of the roadbed. The hydrothermal parameters of permafrost roadbeds (such as water content, thermal conductivity, and specific heat capacity) are key indicators for assessing their engineering stability and environmental adaptability. Therefore, accurately obtaining the hydrothermal parameters of permafrost roadbeds is of great significance for road design, construction, and maintenance in permafrost regions.

[0003] Currently, traditional methods for measuring hydrothermal parameters in frozen soil subgrades typically require separate measurements of thermal and water parameters. These methods are complex, time-consuming, and fail to meet the demands of highway construction and maintenance in frozen soil regions for high-precision, synchronous, real-time, continuous, and reliable hydrothermal parameter monitoring. Moisture and temperature are two key indicators of the hydrothermal state of frozen soil subgrades; asynchronous measurements cannot accurately reflect the coupling relationship between them, which is crucial for accurately assessing the stability of frozen soil subgrades. Furthermore, while existing technologies such as thermal pulse method, frequency domain reflectance (FDR), and time domain reflectance (TDR) have been applied to the determination of hydrothermal parameters in agricultural soils, frozen soil subgrades differ significantly from ordinary soils in physical properties and environmental conditions (such as low temperature and freeze-thaw cycles), making existing technologies unsuitable for direct application to frozen soil subgrades. Utility Model Content

[0004] This invention aims to overcome the shortcomings of the prior art and provide a device for simultaneously and continuously measuring the water content and thermal characteristics of frozen soil subgrade using thermal pulse-frequency domain reflection technology. This device accurately captures the coupled changes in the hydrothermal state and provides reliable data support for highway construction and maintenance in permafrost regions.

[0005] The technical solution adopted by this utility model is:

[0006] A device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection technology, comprising:

[0007] HP-FDR composite probe is used to obtain soil hydrothermal parameters;

[0008] The data acquisition and processing module processes the data acquired by the HP-FDR composite probe.

[0009] The power supply module is connected to and supplies power to the HP-FDR composite probe and the data acquisition and processing module, respectively.

[0010] The fixing device secures the HP-FDR composite probe to the frozen soil subgrade.

[0011] Furthermore, the HP-FDR composite probe includes a cylindrical stainless steel housing, a thermal pulse generator probe, and a temperature sensor probe. The cylindrical stainless steel housing houses a thermal pulse generator control circuit, a frequency domain reflector (FDR) module, and a power distribution module. The front end of the cylindrical stainless steel housing has three composite probes: one thermal pulse generator probe located at the center of the front end, and two temperature sensor probes symmetrically distributed.

[0012] The thermal pulse generator control circuit uses a high-temperature shielded wire to connect to the thermal pulse generator. The thermal pulse generator uses a nickel-chromium alloy resistance wire, spirally arranged inside the thermal pulse generator probe, for emitting thermal pulses. A wire connects the thermal pulse generator to the data acquisition and processing module. The temperature sensor is an NTC thermistor, installed inside the temperature sensor probe, and a wire connects the temperature sensor to the data acquisition and processing module. The frequency domain reflector (FDR) module reuses a single temperature sensor probe as the center electrode and the thermal pulse generator probe as the outer electrode for transmitting and receiving signals. The FDR module integrates a preamplifier and a filter circuit board, fixed inside the front end of the probe housing, and connects the thermal pulse generator probe and the temperature sensor probe via a short shielded wire. A coaxial cable connects it to the data acquisition and processing module. The power distribution module includes power supply circuits for the preamplifier and filter circuit board, the thermal pulse generator control circuit, and the temperature sensor, providing power to each component. The signal lines at the rear of the cylindrical stainless steel housing include wires for the thermal pulse generator and temperature sensor, and a coaxial cable for the frequency domain reflector (FDR) module, used to connect to the data acquisition and processing module; one end of the power line at the rear of the cylindrical stainless steel housing is connected to the power distribution module for power supply, and the other end is connected to the power module.

[0013] Furthermore, the probe material of the thermal pulse generator is stainless steel, and epoxy resin is injected into the interior of the thermal pulse generator probe.

[0014] Furthermore, the temperature sensor probe is made of stainless steel, and the interior of the temperature sensor probe is filled with thermally conductive silicone.

[0015] Furthermore, the frequency domain reflector (FDR) module reuses a temperature sensor probe as the central electrode and a thermal pulse generator probe as the outer electrode for transmitting and receiving signals.

[0016] Furthermore, the power distribution module includes a power supply circuit for the preamplifier and filter circuit board, a power supply circuit for the thermal pulse generator control circuit, and a power supply circuit for the temperature sensor, providing power to each component.

[0017] Furthermore, the power module includes a solar panel, a pole, and a concrete well; the solar panel is fixed to the concrete well via the pole, and the concrete well is buried in the soil.

[0018] Furthermore, both the data acquisition and processing module and the power supply module are installed inside the concrete well.

[0019] Furthermore, the fixing device is a wooden pole, which is installed within the frozen soil roadbed.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention solves the problems of complex operation and long time consumption in traditional methods for measuring hydrothermal parameters of frozen soil subgrades, and achieves high-precision, synchronous, real-time continuous and reliable monitoring of hydrothermal parameters to meet the needs of highway construction and maintenance in frozen soil areas; it also solves the problem that asynchronous measurement of moisture and temperature cannot accurately reflect the coupling relationship between the two, ensuring that the stability of frozen soil subgrades can be accurately assessed.

[0022] Meanwhile, this invention overcomes the significant differences between frozen soil roadbeds and ordinary soil in terms of physical properties and environmental conditions (such as low temperature and freeze-thaw cycles).

[0023] This invention is applicable to frozen soil roadbeds, rather than directly using existing hydrothermal parameter measurement techniques applicable to agricultural soils. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0025] Figure 2 This is a schematic diagram of the HP-FDR composite probe structure of this utility model;

[0026] The components include: 1. HP-FDR composite probe; 101. Thermal pulse generator control circuit; 102. Thermal pulse generator; 103. Thermal pulse generator probe; 104. Temperature sensor; 105. Temperature sensor probe; 106. Frequency domain reflection module; 1061. Preamplifier and filter circuit board; 107. Power distribution module; 1071. Power supply circuit for preamplifier and filter circuit board; 1072. Power supply circuit for thermal pulse generator control circuit; 1073. Power supply circuit for temperature sensor; 108. Signal line; 109. Power line; 2. Data acquisition and processing module; 3. Power module; 301. Solar panel; 302. Pole; 303. Concrete well; 4. Fixing device; 5. Roadbed; 6. Soil. Detailed Implementation

[0027] This invention aims to provide a device for simultaneously acquiring the moisture content, thermal conductivity, and specific heat capacity of frozen soil subgrade based on thermal pulse-frequency domain reflection (HP-FDR) technology. This solves the problems of cumbersome installation, asynchronous measurements, and poor data accuracy caused by the dispersed equipment in existing technologies for acquiring hydrothermal parameters of frozen soil subgrades. By organically integrating thermal pulse technology and frequency domain reflection technology, it achieves simultaneous and accurate simultaneous measurement of hydrothermal parameters such as moisture content, thermal conductivity, and thermal diffusivity of frozen soil subgrades, greatly improving monitoring efficiency. It eliminates the inconvenience and errors of traditional manual measurement, enhances the objectivity of data, and provides timely, reliable, and comprehensive data support for the design, construction, and long-term maintenance of frozen soil subgrade-related projects, effectively improving the timeliness and relevance of engineering operations. To make the above-mentioned objectives, features, and advantages of this invention more apparent and understandable, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1 As shown, a device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection technology includes...

[0029] HP-FDR composite probe 1 (thermal pulse-frequency domain reflection) is used to obtain the hydrothermal parameters of soil 6, including temperature, thermal conductivity, thermal diffusivity, specific heat capacity, and water content;

[0030] Data acquisition and processing module 2 processes the temperature data and frequency domain reflection signal data acquired by HP-FDR composite probe 1;

[0031] Power module 3 is powered by a solar panel. It is connected to and powers both the HP-FDR composite probe 1 and the data acquisition and processing module 2.

[0032] The fixing device 4 uses a wooden pole to fix the HP-FDR composite probe 1 in the frozen soil subgrade 5, ensuring that the HP-FDR composite probe 1 is in full contact with the soil 6.

[0033] The HP-FDR composite probe 1, data acquisition and processing module 2, and power supply module 3 work together to achieve in-situ, high-precision, and synchronous measurement of hydrothermal parameters of frozen soil subgrade.

[0034] like Figure 2 As shown, the HP-FDR composite probe 1 includes a cylindrical stainless steel housing, a thermal pulse generator control circuit 101, a thermal pulse generator 102, a thermal pulse generator probe 103, a temperature sensor 104, a temperature sensor probe 105, a frequency domain reflectance module 106 (FDR), a preamplifier and filter circuit board 1061, a power distribution module 107, a power supply circuit 1071 for the preamplifier and filter circuit board, a power supply circuit 1072 for the thermal pulse generator control circuit, a power supply circuit 1073 for the temperature sensor, a signal line 108, and a power line 109.

[0035] The cylindrical stainless steel housing houses a thermal pulse generator control circuit 101, a frequency domain reflector (FDR) module 106, and a power distribution module 107. Three composite probes arranged in an isosceles triangle are located at the front end of the cylindrical stainless steel housing: a thermal pulse generator probe 103, located at the center of the front end, made of stainless steel and internally filled with epoxy resin; and two temperature sensor probes 105, symmetrically distributed, also made of stainless steel and internally filled with thermally conductive silicone.

[0036] The thermal pulse generator control circuit 101 is connected to the thermal pulse generator 102 using a high-temperature shielded wire. The thermal pulse generator 102 uses a nickel-chromium alloy resistance wire, which is spirally arranged inside the thermal pulse generator probe 103 to emit thermal pulses. The thermal pulse generator 102 is connected to the data acquisition and processing module 2 using a wire.

[0037] The temperature sensor 104 is an NTC thermistor, which is suitable for the low-temperature environment of frozen soil roadbed. It is installed inside the temperature sensor probe 105 to monitor the temperature change during the propagation of heat pulse in real time. The temperature sensor 104 is connected to the data acquisition and processing module 2 using wires.

[0038] The frequency domain reflectance module 106 (FDR) uses a temperature sensor probe 105 as the center electrode (receiving signal) and a thermal pulse generator probe 103 as the outer electrode (transmitting signal) for both transmitting and receiving signals. The FDR integrates a preamplifier and filter circuit board 1061, fixed inside the front end of the probe housing. It connects the thermal pulse generator probe 103 and the temperature sensor probe 105 via a short shielded cable to amplify and process the received reflected signal, effectively reducing signal loss and interference during transmission. The FDR is connected to the data acquisition and processing module 2 via a coaxial cable.

[0039] The power distribution module 107 includes a power supply circuit 1071 for a preamplifier and a filter circuit board, which is connected to the preamplifier and filter circuit board 1061 to supply power to it.

[0040] The power supply circuit 1072 of the heat pulse generator control circuit is connected to the heat pulse generator 102 and supplies it with power;

[0041] The temperature sensor power supply circuit 1073 is connected to the temperature sensor 104 to supply power to it.

[0042] The signal line 108 at the rear end of the cylindrical stainless steel housing includes wires for the thermal pulse generator 102 and the temperature sensor 104, and a coaxial cable for the frequency domain reflection module 106 (FDR), used to connect to the data acquisition and processing module 2; the power line 109 at the rear end of the cylindrical stainless steel housing outputs a 12V regulated power supply, one end of which is connected to the power distribution module 107 for power supply, and the other end is connected to the power module 3; the signal line 108 and the power line 109 are laid along the wire grooves on the inner wall of the housing.

[0043] Figure 1 This is a schematic diagram of the overall structure of the device for obtaining hydrothermal parameters of frozen soil subgrade in situ using thermal pulse-frequency domain reflection technology provided by this utility model. It includes an HP-FDR composite probe 1, a data acquisition and processing module 2, a power supply module 3, an installation and fixing device 4, a frozen soil subgrade 5, and soil 6.

[0044] In this embodiment, the HP-FDR composite probe 1 is buried in the frozen soil subgrade at specific intervals and mounted on the wooden pole of the fixing device 4 to ensure full contact between the HP-FDR composite probe 1 and the soil 6. In this embodiment, the frozen soil subgrade 5 is 12m wide, 5m high, and 10m thick. In this implementation, HP-FDR composite probes 1 are deployed along the centerline of the frozen soil subgrade 5 and at the soil shoulder 5.5m away from the centerline, with one probe every 1m in the depth direction. Denser measuring points are deployed on the surface of the frozen soil subgrade 5 and below its bottom, with a spacing of 0.5m between the measuring points in the densified area. The determination of the measuring point spacing needs to be initially set considering factors such as frozen soil characteristics and measurement accuracy requirements, and can be fine-tuned and optimized during actual operation.

[0045] Data acquisition and processing module 2 acquires temperature data and frequency domain reflection signal data of the frozen soil subgrade monitored by HP-FDR composite probe 1, processes and analyzes the signals, and finally obtains the hydrothermal parameters of the frozen soil subgrade, storing and displaying the data. Meanwhile, to ensure data security, data is regularly backed up to a remote server to prevent data loss due to local equipment failure.

[0046] Power module 3 is powered by solar panel 301, supplying power to HP-FDR composite probe 1 and data acquisition and processing module 2. Solar panel 301 is fixed to concrete well pool 303 by main support pole 302, and concrete well pool 303 is buried in soil 6. Data acquisition and processing module 2 and power module 3 are protected within concrete well pool 303, effectively resisting external mechanical impacts, animal damage, and erosion from harsh weather, facilitating regular equipment inspection, maintenance, and upgrades by staff.

[0047] The measurement process of the device for obtaining hydrothermal parameters of frozen soil subgrade in situ using thermal pulse-frequency domain reflection technology provided by this utility model is described below.

[0048] like Figure 1 As shown, an HP-FDR composite probe 1 is installed in the frozen soil subgrade, and a thermal pulse generator probe 103 emits thermal pulse signals to the frozen soil subgrade 5 to record the heating time of the resistance wire. ,Voltage Voltage sampling of series resistors Calculate the heat of the thermal pulse .

[0049]

[0050] Furthermore, heat diffuses through the soil 6 via thermal conduction, causing a temperature change around the temperature sensor probe 105. The voltage sampling of the thermistor is recorded in real time by the data acquisition and processing module 2. The sampling frequency is 1Hz, and the temperature-resistance relationship is described by the Steinhart-Hart equation. Transient temperature changes were captured. For temperature, For thermistors at temperature The resistance value at that time, is the material constant of the thermistor.

[0051] Furthermore, a temperature-time curve (temperature response curve) is plotted, and the thermal conductivity of the soil is calculated using the heat conduction equation. and thermal diffusivity Specific heat capacity The formula is as follows:

[0052]

[0053]

[0054]

[0055] in, The total heat of the heat pulse (J). The distance (m) between the temperature sensor probe and the thermal pulse generator probe. The change in temperature (°C) The time (in seconds) for the temperature to reach its maximum value. This represents the soil density.

[0056] Furthermore, a 100MHz high-frequency electromagnetic wave signal is emitted into the frozen soil subgrade via the frequency domain reflection module 106 (FDR). The signal propagates and is reflected within the soil. The reflected signal is received by the data acquisition and processing module 2, which records the amplitude and phase changes, performs frequency domain analysis, and calculates the dielectric constant. The moisture content is calculated using the relationship between dielectric constant and water content (Topp equation). The calculation formula is as follows:

[0057]

[0058] Thus, soil hydrothermal parameters, including temperature, thermal conductivity, thermal diffusivity, specific heat capacity, and moisture content, are obtained. All measured data are stored in a computer database, providing long-term data support for subsequent engineering construction and maintenance. The above embodiments can be modified in several ways without departing from the scope of this utility model. Therefore, the above description should be considered illustrative and not intended to limit the scope of protection of this utility model.

[0059] This invention provides a device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection (FDR) technology. The HP-FDR composite probe 1 is fixed to the frozen soil subgrade 5 by a wooden rod and emits thermal pulses into the subgrade 5. Based on the propagation and reflection of the thermal pulses in the soil, combined with real-time temperature data fed back by an NTC thermistor, thermal parameters such as thermal conductivity and thermal diffusivity of the soil are calculated more accurately. Simultaneously, the FDR module emits electromagnetic wave signals of different frequencies. Based on the reflection and attenuation characteristics of the signals in the soil, moisture parameters such as water content and dielectric constant of the soil are obtained. The data acquisition and processing module 2 coordinates the work of each module, processes and analyzes the received signals, and finally obtains accurate hydrothermal parameters of the frozen soil subgrade 5.

[0060] Unlike traditional methods that cannot monitor in real time, the measurement system constructed in this invention enables real-time continuous monitoring of hydrothermal parameters of frozen soil subgrades. Thermal pulse-frequency domain reflection technology can sensitively detect subtle thermal and electromagnetic changes in frozen soil. With the aid of precise mathematical models and algorithms, as well as the aforementioned calculation formulas, the measurement accuracy of hydrothermal parameters is greatly improved. The use of an embedded measuring device minimizes the impact on the structure and physical properties of the frozen soil subgrade, ensuring the authenticity and reliability of the measurement data. Simultaneously, a specialized multi-parameter coupling analysis algorithm has been developed to deeply analyze the interrelationships between hydrothermal parameters and accurately capture the coupled changes in hydrothermal states. This algorithm not only considers physical processes such as heat conduction and moisture migration but also incorporates the physicochemical properties of frozen soil. Through learning and optimization from a large amount of experimental data, it can accurately predict the hydrothermal change trends of frozen soil subgrades under different conditions, providing strong data support for long-term stability monitoring of the project.

[0061] It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this utility model.

Claims

1. A device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection technology, characterized in that: include HP-FDR composite probe (1) is used to obtain hydrothermal parameters of soil (6); The data acquisition and processing module (2) processes the data acquired by the HP-FDR composite probe (1); The power supply module (3) is connected to the HP-FDR composite probe (1) and the data acquisition and processing module (2) respectively and provides them with power. Fixing device (4) to fix HP-FDR composite probe (1) in frozen soil subgrade (5).

2. The device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection technology according to claim 1, characterized in that: The HP-FDR composite probe (1) includes a cylindrical stainless steel shell, a thermal pulse generator probe (103), and two temperature sensor probes (105). The cylindrical stainless steel housing contains a thermal pulse generator control circuit (101), a frequency domain reflection module (106), and a power distribution module (107); the front end of the cylindrical stainless steel housing is provided with three composite probes, including a thermal pulse generator probe (103) located at the center of the front end, and two temperature sensor probes (105) symmetrically distributed. The thermal pulse generator control circuit (101) is connected to the thermal pulse generator (102). The thermal pulse generator (102) uses a nickel-chromium alloy resistance wire, which is spirally arranged inside the thermal pulse generator probe (103) to emit thermal pulses. The thermal pulse generator (102) is connected to the data acquisition and processing module (2) using wires. The temperature sensor (104) is an NTC thermistor, which is installed inside the temperature sensor probe (105). The temperature sensor (104) is connected to the data acquisition and processing module (2) by wires. The frequency domain reflection module (106) uses a temperature sensor probe (105) as the center electrode to receive signals and a thermal pulse generator probe (103) as the outer electrode to transmit and receive signals. The frequency domain reflection module (106) integrates a preamplifier and a filter circuit board (1061), which is fixed in a cylindrical stainless steel shell and connects the thermal pulse generator probe (103) and the temperature sensor probe (105). It is connected to the data acquisition and processing module (2) by a coaxial cable. The power distribution module (107) supplies power to the preamplifier and filter circuit board (1061), the thermal pulse generator (102), and the temperature sensor (104); The signal line (108) at the rear end of the cylindrical stainless steel housing includes wires for the thermal pulse generator (102) and temperature sensor (104), and a coaxial cable for the frequency domain reflection module (106), which is used to connect the data acquisition and processing module (2); one end of the power line (109) at the rear end of the cylindrical stainless steel housing is connected to the power distribution module (107) for power supply, and the other end is connected to the power module (3).

3. The device for obtaining hydrothermal parameters of frozen soil subgrade in situ using thermal pulse-frequency domain reflection technology according to claim 2, characterized in that: The power distribution module (107) includes a power supply circuit (1071) for the preamplifier and filter circuit board, which is connected to the preamplifier and filter circuit board (1061) to supply power to them; The power supply circuit (1072) of the heat pulse generator control circuit is connected to the heat pulse generator (102) to supply power to it; The temperature sensor power supply circuit (1073) is connected to the temperature sensor (104) to supply power to it.

4. The device for obtaining hydrothermal parameters of frozen soil subgrade in situ using thermal pulse-frequency domain reflection technology according to claim 2, characterized in that: The heat pulse generator probe (103) is made of stainless steel, and epoxy resin is injected into the interior of the heat pulse generator probe (103).

5. The device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection technology according to claim 2, characterized in that: The temperature sensor probe (105) is made of stainless steel and is filled with thermally conductive silicone.

6. The device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection technology according to claim 1, characterized in that: The power module (3) includes a solar panel (301), a pole (302) and a concrete well (303); the solar panel (301) is fixed on the concrete well (303) by the pole (302), and the concrete well (303) is buried in the soil (6).

7. The device for obtaining hydrothermal parameters of frozen soil subgrade in situ using thermal pulse-frequency domain reflection technology according to claim 1, characterized in that: The data acquisition and processing module (2) and the power supply module (3) are both located inside the concrete well pool (303).

8. The device for in-situ acquisition of hydrothermal parameters of frozen soil subgrade using thermal pulse-frequency domain reflection technology according to claim 1, characterized in that: The fixing device (4) is made of wooden poles and is installed in the frozen soil roadbed (5).

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