A system and method for in-situ determination of thermoelectric parameters of rock-soil mass

Abstract

The application discloses a system and a method for in-situ determination of thermoelectric parameters of rock-soil bodies, which comprises an in-situ detection probe, a data acquisition instrument, a penetration assembly connecting the two, and a data analysis platform connected with the data acquisition instrument; the in-situ detection probe comprises a CPTU static sounding probe, a four-phase electrode resistivity probe, a heating probe inserted into a hollow cylinder of the four-phase electrode resistivity probe, and an adapter connecting the CPTU static sounding probe and the four-phase electrode resistivity probe; the four-phase electrode resistivity probe comprises a hollow metal shell, and an insulating material, a voltage electrode and a current electrode are arranged at intervals in a cylinder outer ring. In the application, the soil resistivity is first tested, then the heating wire is powered and heated, the four-phase electrode resistivity probe is used as a temperature sensor of the heating probe, and the synchronous test of the rock-soil body soil layer classification and the thermoelectric parameters is realized. The application also proposes a column heat source-parameter estimation method for the test of the thermal parameters, which significantly improves the accuracy of the test.

Description

Technical Field

[0001] This invention relates to the field of soil and rock parameter testing technology, specifically to a system and method for in-situ determination of the thermodynamic and electrical parameters of soil and rock. Background Technology

[0002] In geotechnical engineering, a comprehensive assessment of soil and rock parameters is crucial to ensure the safety, reliability, and economy of engineering designs. Soil mechanical parameters such as elastic modulus, shear strength, internal friction angle, cohesion, and unit weight are key to accurately assessing soil engineering properties and predicting its mechanical behavior under different load conditions. Soil unit weight is related to the soil's weight and bearing capacity, and is significant for calculating self-weight stress and stability analysis. Elastic modulus reflects the stiffness characteristics of soil during elastic deformation, affecting foundation settlement and structural deformation. Shear strength is an important indicator of soil's resistance to shear failure and is closely related to slope stability and foundation pit support design. The internal friction angle reflects the frictional characteristics between soil particles, affecting the soil's shear strength and stability. Cohesion mainly reflects the shear strength of cohesive soils and is related to the soil's bonding properties and overall integrity. Accurate acquisition of these mechanical parameters helps to precisely assess the bearing capacity of the foundation, soil layer classification, and soil deformation characteristics, thereby optimizing engineering design and construction plans, improving the safety, reliability, and economy of the project, and avoiding engineering accidents and losses caused by inaccurate estimation of soil parameters.

[0003] Therefore, to ensure project safety and stability, optimize design schemes, and control project costs, in-situ mechanical parameters (tested via CPTU) are crucial for assessing soil classification, bearing capacity, and stability, thus providing scientific guidance for project construction and design. Thermal parameters (thermal conductivity, specific heat capacity) are important parameters for analyzing soil heat transfer and controlling the heat exchange of the entire system in ground source heat pump technology. They directly affect the rate of heat transfer and temperature distribution characteristics in the soil. Accurate measurement is of profound significance for the rational planning of the layout and size of underground heat exchangers, improving energy efficiency, reducing operating costs, and promoting sustainable development. Accurate measurement directly affects the thermal stability and energy efficiency of geothermal systems, underground storage facilities, and building foundations.

[0004] However, the thermo-mechanical properties of underground soil are dynamically changing due to factors such as temperature variations, underground runoff, and ion erosion. Currently, many parameters are mainly obtained through indoor sampling tests or prediction using empirical formulas based on in-situ shallow test data. However, the reliability of the prediction results is relatively low. In addition, some in-situ testing equipment only integrates the testing of one parameter, and the testing instruments are complex and costly. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a system and method for in-situ determination of the thermoelectric and electrical parameters of soil and rock, aiming to offer a more efficient and comprehensive solution for testing soil and rock parameters, thereby improving testing accuracy, ease of operation, and cost-effectiveness.

[0006] According to a first aspect of the present disclosure, a system for in-situ determination of thermoelectric parameters of soil and rock is provided. The system includes an in-situ detection probe, a data acquisition instrument, a penetration assembly connecting the in-situ detection probe and the data acquisition instrument, and a data analysis platform connected to the data acquisition instrument.

[0007] The in-situ detection probe includes a CPTU static cone probe, a cylindrical four-phase resistivity probe, a heating probe inserted into the hollow cylinder of the four-phase resistivity probe, and an adapter connecting the CPTU static cone probe and the four-phase resistivity probe.

[0008] The four-phase resistivity probe includes a hollow metal shell, an outer cylindrical ring with insulating material, voltage electrodes and current electrodes spaced apart;

[0009] The penetration assembly includes a tracked CPTU penetration truck and a retractable connecting probe that connects the in-situ detection probe to the tracked CPTU penetration truck. The tracked CPTU penetration truck is equipped with an adjustable support structure to fix and guide the retractable connecting probe. A cable is led out from the in-situ detection probe, passes through the retractable connecting probe, and connects to the data acquisition instrument.

[0010] A further technical solution of the present invention is as follows: The CPTU static cone penetration probe includes an integrated cone tip probe and a cylinder. The cone tip probe is equipped with a filter, and a pressure sensor is provided above the filter. The cylinder has a hollow inner ring, and an inclinometer is provided inside the hollow inner ring. Between the inner ring and the outer ring of the cylinder, there is a cone sensor, a friction sleeve, a water seal ring, a soil seal ring, and a pressure-sensitive connector. The cables connecting the various sensors extend out through the hollow inner ring. The pressure-sensitive connector is the connection interface between the cable and the CPTU static cone penetration probe end of the adapter.

[0011] A further technical solution of the present invention is as follows: the heating probe has a hollow shaft structure, the heating wire is placed between the outer shell and the inner wall shell of the heating probe, and is filled with backfill material.

[0012] A further technical solution of the present invention is as follows: the diameter of the four-phase resistivity probe is larger than that of the CPTU static cone probe, and the cable leading out from the CPTU static cone probe extends through the hollow shaft of the heating probe and is led out together with the cable of the heating probe to connect to the data acquisition instrument.

[0013] The present invention further provides a method for measuring the above-mentioned in-situ thermoelectric parameters of soil and rock. During the test, the resistivity of the soil is measured first, and then the resistance heating wire is heated by electricity. A four-phase resistivity probe is used as the temperature sensor of the heating probe.

[0014] A further technical solution of the present invention is that the resistance heating wire is a nickel-chromium alloy wire.

[0015] A further technical solution of the present invention is as follows: the four-phase resistivity probe obtains the resistance of the soil being measured by testing the voltage drop between the two electrodes under constant current, and further obtains the soil porosity, soil moisture content, and mass moisture content, wherein the soil porosity... , The bonding coefficient is denoted as . For soil properties, The resistivity of pore water Soil resistivity; soil moisture content , Saturation index; Moisture content (by mass) , For the density of water, This represents the density of soil particles.

[0016] A further technical solution of the present invention is: based on pore pressure parameters Classify the penetrating soil layers. , This represents the pore pressure test value between the cone-tip probe and the cylinder. The static pore pressure; The cone tip resistance is corrected for area. To calculate the total overburden pressure, the following soil mechanical parameters were obtained: unit weight Compression modulus , For coefficients, For cone tip resistance; undrained shear strength , Shear strength coefficient; effective internal friction angle Relative density of sandy soil , Indicates effective stress.

[0017] A further technical solution of the present invention is as follows: obtaining the thermal conductivity parameters of soil includes the following steps:

[0018] Step 1: Obtain the initial resistivity of the soil using the CPTU static cone penetration test probe, and determine the soil temperature at that moment using the relationship between resistivity and temperature. , For temperature response, This represents the resistivity at a standard temperature of 25°C, where 25°C is used in this context. It is the thermoelectric constant;

[0019] Step 2: Start heating the alloy wire by applying electricity, record the heating time, and at the same time test the real-time resistivity of the outer soil and calculate the real-time temperature.

[0020] Step 3: Set and fix the initial value of soil heat capacity, the initial effective volumetric heat capacity of the soil and rock mass. Calculated based on porosity ratio n is the soil porosity. , These are the volumetric heat capacities of soil and water, respectively.

[0021] Step 4: Generate random values ​​of the input soil thermal conductivity within the range of thermal conductivity based on the Monte Carlo algorithm. Based on random values ​​of soil thermal conductivity The soil temperature at position i at time j is calculated using a finite-length column heat source analytical model based on temperature response analytical theory. ;

[0022] Step 5: Based on the calculated soil temperature and the results of the test Repeated calculation Until the minimum is calculated value, obtain the minimum The value corresponds to the optimal soil thermal conductivity. , The bonding coefficient;

[0023] Step 6: Fix the optimal soil thermal conductivity ;

[0024] Step 7: Generate random values ​​of the input soil heat capacity within the thermal conductivity range based on the Monte Carlo algorithm. And fix the optimal thermal conductivity of the soil Random value of soil specific heat capacity Calculations based on the analytical model of a finite-length column heat source using temperature response analytical theory j Time of the first i Soil temperature at each location ;

[0025] Step 8: Based on the calculated soil temperature and the results of the test Repeated calculation Until the minimum is calculated value, obtain the minimum The optimal soil specific heat capacity corresponding to the value .

[0026] The present disclosure provides a system and method for in-situ determination of thermoelectric parameters of soil and rock masses, which, compared with existing technologies, have the following advantages:

[0027] (1) Multifunctional Integrated Testing Capability: The in-situ testing equipment of this invention integrates a CPTU static cone penetration probe, a four-phase resistivity probe, and a thermal conductivity probe, enabling simultaneous testing of the mechanical, electrical, and thermal parameters of soil and rock. This integrated design reduces the need for multiple independent testing devices, providing a more efficient and comprehensive solution for testing soil and rock parameters. Traditional technologies typically require the use of separate equipment and multiple sensors for thermal and electrical testing, which not only increases testing costs and complexity but may also lead to data synchronization and consistency issues. This invention, through its integrated design, reduces reliance on individual thermal and electrical testing equipment and simplifies the testing process.

[0028] (2) Innovative Application of Resistivity Probe: The four-phase resistivity probe in this invention can not only measure soil resistivity, but also has the significant advantage of predicting soil moisture content based on changes in soil resistivity, further improving the efficiency and value of the test. It also innovatively utilizes the relationship between resistivity and temperature as a temperature sensor for the heating probe, thus eliminating the need for additional temperature measurement sensor equipment. This typically requires a separate sensor and testing steps in traditional testing methods.

[0029] (3) Improved testing accuracy and efficiency: The in-situ testing equipment of this invention provides a solution for in-situ underground testing of soil thermo-mechanical properties, effectively overcoming the challenges of traditional indoor testing methods due to disturbances during sampling, differences between samples and in-situ environmental conditions, and discontinuities in testing conditions. It also avoids potential errors during sampling and testing, providing more accurate and real-time data. Through the series connection of the CPTU probe and the resistivity probe, this invention enables the testing of multiple physical properties of soil and rock during a single penetration test, reducing multiple disturbances to the soil and testing time. Furthermore, due to the integrated design of the test probes, different parameters can be measured more accurately and simultaneously, further improving the accuracy and reliability of the test results. In addition, traditional in-situ soil thermal conductivity parameter testing methods currently mainly include the thermal response test of vertical buried pipes for ground source heat pumps and the temperature dissipation process parameter fitting method for static cone penetration tests. This method is based on the theory of infinitely long line heat sources and requires a long time to form a stable heat flow. In-situ testing instruments for thermal conductivity parameters in deep soil and rock masses require significant rigidity and length-to-diameter ratios to penetrate and detect the thermal conductivity. However, the assumption of an infinitely long heat source simplifies the actual model and introduces errors in the calculations. Parameter identification is a back-calculation method that compares heat source test results with a heat transfer analytical model. It uses a parameter iteration algorithm to minimize the objective function of the heat transfer model to estimate the soil's thermal properties. The finite-length column heat source model considers the size of the heat source and longitudinal heat transfer, allowing for the acquisition of temperature response patterns and spatiotemporal variations at surrounding measuring points. Furthermore, it can be applied to situations involving groundwater seepage. This invention improves upon the traditional infinitely long heat source theory by establishing a finite-length column heat source theoretical model for temperature response analysis, and applies a parameter estimation iterative method to obtain the thermal conductivity parameters.

[0030] (4) Ease of Operation and Cost-Effectiveness: The combination of the data acquisition instrument and the data analysis cloud platform of this invention enables real-time data synchronization and efficient processing. It can be flexibly deployed in various environments, without being limited by geographical location or site conditions, thus increasing work flexibility. The integrated design reduces the need for multiple independent testing devices, lowering equipment costs and maintenance expenses. At the same time, efficient data processing reduces manpower requirements, further improving cost-effectiveness.

[0031] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention:

[0033] Figure 1 This is a system structure diagram of in-situ measurement of thermoelectric parameters of rock and soil in an embodiment of the present invention;

[0034] Figure 2 This is a structural diagram of the in-situ detection probe in an embodiment of the present invention;

[0035] Figure 3 This is a structural diagram of the CPTU static cone penetration probe in an embodiment of the present invention;

[0036] Figure 4 This is a structural diagram of the four-phase resistivity probe in an embodiment of the present invention;

[0037] Figure 5 This is a structural diagram of the heating probe in an embodiment of the present invention;

[0038] Figure 6 This is a cross-sectional view of the heating probe in an embodiment of the present invention;

[0039] Figure 7 This is a schematic diagram of a finite-length column heat source model in an embodiment of the present invention. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the drawings, not the entire structure.

[0041] Before discussing the exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the steps as sequential processes, many of these steps can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the steps can be rearranged. The process can be terminated when its operation is complete, but may also have additional steps not included in the figures. The process can correspond to a method, function, procedure, subroutine, subroutine, etc.

[0042] The present invention aims to overcome the deficiencies in the prior art and provide a system for in-situ measurement of thermoelectric parameters of rock and soil, such as... Figure 1As shown, the system includes an in-situ detection probe 1, a data acquisition unit 4, a penetration assembly connecting the in-situ detection probe 1 and the data acquisition unit 4, and a data analysis platform 5 connected to the data acquisition unit 4; wherein, the in-situ detection probe 1 includes a CPTU static cone penetrometer 11, a cylindrical four-phase resistivity probe 12, a heating probe 13 inserted into the hollow cylinder of the four-phase resistivity probe 12, and an adapter 14 connecting the CPTU static cone penetrometer 11 and the four-phase resistivity probe; the four-phase resistivity probe 12 includes The hollow metal shell 121 and the cylindrical outer ring are provided with insulating material 122, voltage electrode 123 and current electrode 124 at intervals; the penetration assembly includes a tracked CPTU penetration truck 3 and a telescopic connecting probe 2 that connects the in-situ detection probe 1 to the tracked CPTU penetration truck 3. The tracked CPTU penetration truck 3 is equipped with an adjustable support structure to fix and guide the telescopic connecting probe 2. A signal transmission cable 119 is led out from the in-situ detection probe 1, passes through the telescopic connecting probe 2 and is connected to the data acquisition instrument 4.

[0043] The CPTU static cone penetration probe 11 includes an integrated cone tip probe 111 and a cylinder (not shown). The cone tip probe 111 contains a filter, and a pressure sensor 113 is located above the filter. The cylinder has a hollow inner ring, and an inclinometer is located inside the hollow inner ring. Between the inner ring and the outer ring of the cylinder are a cone sensor, a friction sleeve, a water seal ring, a soil seal ring, and a pressure-sensitive connector. The cables connecting the various sensors extend out through the hollow inner ring. The pressure-sensitive connector is the connection interface between the cables and the CPTU static cone penetration probe end of the adapter.

[0044] The heating probe has a hollow shaft structure. The heating wire is placed between the outer shell and the inner wall shell of the heating probe and is filled with backfill material. The thermal conductivity of the backfill material between the heating wire and the inner wall shell is lower than that between the heating wire and the outer shell of the heating probe.

[0045] The diameter of the four-phase resistivity probe is larger than that of the CPTU static cone probe. The cable leading from the CPTU static cone probe extends through the hollow shaft of the heating probe and is led out together with the cable of the heating probe to connect to the data acquisition instrument.

[0046] Specifically, the in-situ detection probe 1 is connected to the connecting probe 2 through a dedicated interface to ensure accurate transmission of penetration force and allow the probe to be connected during the penetration process.

[0047] The penetration vehicle 3 serves as the supporting foundation for the entire system. An adjustable support structure is installed on it to fix and guide the connection 2, ensuring the vertical penetration of the in-situ detection probe 1. At the same time, the jack penetration power device integrated in the penetration vehicle 3 is responsible for providing the necessary penetration force, which is transmitted to the in-situ detection probe 1 through the probe rod 2, achieving stable penetration of the rock and soil mass.

[0048] The in-situ detection probe 1 has a built-in sensor for collecting the thermodynamic and electrical parameters of the soil, including strain and voltage and current data, which are transmitted to the data acquisition instrument 4 through the wire embedded in the hollow shaft of the probe rod 2.

[0049] The data acquisition unit 4 receives data from the in-situ detection probe 1, performs analog-to-digital conversion and preliminary processing, such as signal amplification, filtering and digitization, to ensure data quality.

[0050] The data acquisition device 4 synchronizes the data to the data analysis system 5 in real time via a wireless network. In the data analysis system 5, the data undergoes further processing and analysis to assess the thermo-mechanical properties of the soil and rock mass.

[0051] like Figure 2 As shown, the CPTU static cone penetrometer 11, the four-phase resistivity probe 12, the heating probe 13, and the adapter 14 are included. The CPTU static cone penetrometer 11 and the four-phase resistivity probe 12 are connected in series via the adapter 14. Preferably, the four-phase resistivity probe 12 is a hollow cylindrical structure, with the heating probe positioned inside.

[0052] The CPTU static cone penetration probe 11, under the penetrating force of the connecting probe rod 2 and the penetration vehicle 3, is vertically penetrated into the underground rock and soil mass to the designated location.

[0053] According to the CPTU static cone penetration test, the pore water pressure, sidewall resistance and cone tip resistance of the soil and rock can be obtained, and then the mechanical parameters such as the weight, relative density, compression modulus, shear strength, consolidation and permeability coefficient of the soil and rock can be obtained, and the soil layers can be classified.

[0054] The resistivity of the soil and rock mass is obtained by energizing the voltage electrode 123 and the current electrode 124 of the four-phase resistivity electrode, and then parameters such as the water content and temperature of the soil and rock mass are obtained.

[0055] Heating alloy wire 132 is energized to achieve heating. The relationship between resistivity and temperature is used as a sensor to test the soil temperature, thereby obtaining the heating time and heating temperature, and then calculating the thermal conductivity parameters of the soil and rock.

[0056] The CPTU continued to penetrate downwards, repeating the above tests on the thermo-electrical parameters of the underlying rock and soil.

[0057] like Figure 3 As shown, the CPTU static cone penetration probe 11 for in-situ testing of soil and rock mechanical parameters includes a cone tip probe 111, a filter 112, a pressure sensor 113, a soil sealing ring 114, a water sealing ring 115, a cone sensor 116, a friction sleeve 117, an inclinometer 118, a signal transmission cable 119, a pressure-sensitive connector 1110, and a probe rod 1111.

[0058] The CPTU static cone penetration test probe 11, used for in-situ testing of soil and rock mechanical parameters, is controlled by the jack power unit of the penetration vehicle 3 to achieve precise penetration depth and speed. Pressure sensor 113 and cone sensor 116 measure the cone tip resistance and sidewall friction during penetration in real time and transmit the data to the data acquisition instrument 4 via signal transmission cable 119. Inclinometer 118 monitors the probe's tilt and direction changes during penetration to ensure vertical penetration and sends data to the data acquisition instrument 4 via signal transmission cable 119. The data acquisition instrument 4 receives and initially processes the data from probe 11, and then performs in-depth analysis through data analysis system 5 to determine the soil mechanical parameters.

[0059] The cone-shaped probe 111 is tightly connected to a specially designed filter 112. The filter 112 is designed to allow groundwater to flow freely while preventing soil particles from entering the probe, ensuring that the pressure sensor 113 accurately measures the penetration resistance of the soil to the probe.

[0060] The pressure sensor 113 is installed at the bottom center of the cone tip probe 111 to measure the cone tip resistance, that is, the resistance of the soil to the probe penetration.

[0061] Soil sealing ring 114 and water sealing ring 115 are respectively set between cone tip probe 111 and friction sleeve 117 to ensure the sealing of probe during penetration and prevent soil and water from entering the probe and affecting measurement accuracy.

[0062] The cone sensor 116 surrounds the cone tip probe 111 and fits tightly with the friction sleeve 117 to measure the sidewall friction, that is, the resistance of the soil to the side of the probe.

[0063] The friction sleeve 117 not only provides support for the cone sensor 116, but also allows the cone tip probe 111 to move along the axis of the probe rod 1111, ensuring the stability of the probe during the penetration process.

[0064] The inclinometer 118 is installed on the upper part of the cone tip probe 111 and fixed by the friction sleeve 117. It monitors the tilt angle and direction of the probe in real time to ensure that the probe penetrates the soil vertically. Its data is transmitted through the signal transmission cable 119.

[0065] The signal transmission cable 119 connects all sensors, inclinometer 118 and pressure-sensitive connector 1110, and is responsible for transmitting measurement data from probe 11 to the ground acquisition instrument 4.

[0066] The pressure-sensitive connector 1110 serves as the connection interface between the signal transmission cable 119 and the probe 1111, ensuring the stability and accuracy of the signal during transmission.

[0067] As an extension of the probe 11, the probe rod 1111 not only bears the force during the penetration process, but also helps the probe reach the required test depth through its length.

[0068] like Figure 4 As shown, the four-phase resistivity probe 12 is a hollow cylindrical structure, consisting of a metal shell 121, voltage electrodes 123, current electrodes 124, insulating material 122, and an internal resistance system.

[0069] An insulating material 122 is placed in the middle of the hollow cylindrical metal shell 121. Two voltage electrodes 123 are in the middle, two current electrodes 124 are on both sides, and four copper electrodes are arranged at equal intervals and connected to a power supply, voltage and current testing device.

[0070] like Figure 5 As shown, the heating probe 13 is mainly composed of a metal shell 121, a heating alloy wire 132, and a filling material 131.

[0071] The heating probe 13 has a circular structure, its size fitting perfectly within the four-phase resistivity probe 12 and the metal casing 121. The interior of the heating probe is also hollow, with a hollow shaft 133 serving as the power supply cable for the heating alloy wire 132, the voltage electrode 123 of the four-phase resistivity probe 12, and the current electrode 124. It also functions as the sensor cable for the CPTU resistivity probe 11. The inner shell 134 of the heating probe 13 is made of a heat-resistant, hard material with poor thermal conductivity. The inner shell 134 and the metal casing 121 are internally composed of a ring-shaped structure consisting of the heating alloy wire 132 and a filler material 131. The heating alloy wire 132 is made of nickel-chromium alloy wire. The space between the heating alloy wire 132 and the metal casing is filled with a first filler material 1312, which has excellent thermal conductivity, while the space between the heating alloy wire 132 and the inner shell is filled with a second filler material 1311, which has extremely poor thermal conductivity. The purpose of this is to transfer heat outwards.

[0072] Another embodiment is a method for measuring the above-mentioned in-situ thermoelectric parameters of soil and rock. During the test, the resistivity of the soil is measured first, and then the resistance heating wire is heated by electricity. A four-phase resistivity probe is used as the temperature sensor of the heating probe.

[0073] A four-phase resistivity probe obtains the soil resistance by measuring the voltage drop between two electrodes under constant current, and further obtains the soil porosity, soil moisture content, and mass moisture content, among which soil porosity... , The bonding coefficient; Porosity For soil properties, The resistivity of pore water Soil resistivity; soil moisture content , Saturation index; Moisture content (by mass) , For the density of water, This represents the density of soil particles.

[0074] Based on pore pressure parameters (Based on relevant standards or soil classification maps) classify the penetrating soil layers. , This represents the pore pressure test value between the cone-tip probe and the cylinder. The static pore pressure; The cone tip resistance is corrected for area. To calculate the total overburden pressure, the following soil mechanical parameters were obtained: unit weight Compression modulus , For coefficients, For cone tip resistance; undrained shear strength , Shear strength coefficient; effective internal friction angle Relative density of sandy soil , Indicates effective stress.

[0075] Obtaining the thermal conductivity parameters of soil includes the following steps:

[0076] Step 1: Obtain the initial resistivity of the soil using the CPTU static cone penetration test probe, and determine the soil temperature at that moment using the relationship between resistivity and temperature. , For temperature response, This represents the resistivity at a standard temperature of 25°C, where 25°C is used in this context. C TE It is the thermoelectric constant;

[0077] Step 2: Start heating the alloy wire by applying electricity, record the heating time, and at the same time test the real-time resistivity of the outer soil and calculate the real-time temperature.

[0078] Step 3: Calculate the thermal parameters using the finite-length column heat source analytical model and parameter estimation method. Specifically, set and fix the initial value of the soil's heat capacity and the initial effective volumetric heat capacity of the soil / rock mass. Calculated based on porosity ratio n is the soil porosity. , These are the volumetric heat capacities of soil and water, respectively.

[0079] Step 4: Generate random values ​​of the input soil thermal conductivity within the range of thermal conductivity based on the Monte Carlo algorithm. Based on random values ​​of soil thermal conductivity The soil temperature at position i at time j is calculated using a finite-length column heat source analytical model based on temperature response analytical theory. ;

[0080] Step 5: Based on the calculated soil temperature and the results of the test Repeated calculation Until the minimum is calculated value, obtain the minimum The value corresponds to the optimal soil thermal conductivity. , The bonding coefficient;

[0081] Step 6: Fix the optimal soil thermal conductivity ;

[0082] Step 7: Generate random values ​​of the input soil heat capacity within the thermal conductivity range based on the Monte Carlo algorithm. And fix the optimal thermal conductivity of the soil Random value of soil specific heat capacity Calculations based on the analytical model of a finite-length column heat source using temperature response analytical theory j Time of the first i Soil temperature at each location ;

[0083] Step 8: Based on the calculated soil temperature and the results of the test Repeated calculation Until the minimum is calculated value, obtain the minimum The optimal soil specific heat capacity corresponding to the value .

[0084] Furthermore, the power is turned on, and the resistivity is calculated based on the test data from voltage electrode 123 and current electrode 124. The resistivity of the soil is determined by testing its resistance, which is obtained by measuring the voltage drop between the two electrodes under constant current, according to Ohm's law:

[0085] ,

[0086] Vertical resistivity of the sample for:

[0087] ,

[0088] In the formula, The height of the sample; This is the cross-sectional area of ​​the sample; It is the electrical constant; This is the voltage drop across the voltage divider resistor.

[0089] Furthermore, the conductivity can be calculated, and the relationship between the resistivity and conductivity of soil is as follows:

[0090] ,

[0091] Furthermore, the soil porosity (saturated soil) can be predicted using Archie's first formula:

[0092] ,

[0093] In the formula, For soil resistivity, ; The resistivity of pore water ; These are soil properties; The bonding coefficient; Porosity.

[0094] Furthermore, the soil moisture content (for unsaturated soil) can be predicted using the Keller and Frischknecht formulas:

[0095] , ,

[0096] In the formula, For saturation, The saturation index. For the density of water, ρ is the density of soil particles, and w is the mass moisture content.

[0097] First, the initial resistivity of the soil is obtained using the CPTU probe. Then, the temperature of the soil at that moment can be determined by measuring the relationship between resistivity and temperature.

[0098] ,

[0099] Furthermore, the heating alloy wire 132 is energized and heated, the heating time is recorded, the real-time resistivity of the outer soil is tested, and the real-time temperature is calculated.

[0100] Furthermore, such as Figure 7 This is a schematic diagram of the heat transfer physical model of a finite-length column heat source testing instrument in soil. For the test area V, the control equation is established. Combining the energy equation and Fourier's law, the heat conduction control equation of the heat source of the testing instrument is established, as shown in equation (1):

[0101] (1)

[0102] In the formula: T is the temperature variable; λ is the thermal conductivity, W / (m·℃); Let α be the thermal diffusivity, α = λ / ρc, and m be the thermal diffusivity. 2 / s; ρ is the soil density, kg / m³ 3 c represents the specific heat capacity of the soil, J / kg·℃; This refers to the distributed heat source term, which is the heat source intensity of the testing instrument per unit time and volume, expressed in W / m³. 3 ; q l The heat source intensity density, W / m 2 , Indicates time t The coordinates of the measuring point of the thermal probe in the cylindrical coordinate system can be used to further solve the thermal parameters of the soil based on the theory of heat transfer process of the cylindrical heat source by observing the transient temperature changes at the measuring point.

[0103] At the Earth's surface, heat transfer occurs between the soil and rock mass and the air via convection; therefore, a third-type boundary is used at the surface. Except for the boundary between the surface and the air for heat transfer, all other boundaries are adiabatic. Furthermore, assuming an initial temperature of T0,

[0104] By using the Green's function method to solve the governing equation (1), the internal heat source term can be... If we consider it as the integral superposition of instantaneous heat sources, then the solution to equation (1) can be expressed as: (2)

[0105] In the formula: In Green's function form:

[0106] (3)

[0107] The unit step function has the following value:

[0108] (4)

[0109] Furthermore, the Green's function form of the analytical solution of the instantaneous unit cylindrical heat source theoretical model is obtained as follows:

[0110] (5)

[0111] In the formula: ε, η, ν, β are constants, and satisfy the following conditions: ,at the same time , , The first type of Bessel function of order v has an eigenvalue sequence denoted as βm, where m = 1, 2, 3, ...

[0112] To determine the coefficients in equation (5), the initial conditions are substituted into equation (5), and the characteristic function is used. and By performing operations on the orthogonality relation, we can obtain:

[0113] (6)

[0114] In the formula:

[0115] (7)

[0116] (8)

[0117] (9)

[0118] Furthermore, the Green's function for a single instantaneous annular heat source is defined in [0,t] and at the length of the cylindrical heat source [...]. H a , H b Integral (when) (When the heat source is a line), the length can be obtained as l c The temperature response results of the column heat source in the soil and rock medium layer.

[0119] (10)

[0120] In this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a step or method that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such a step or method.

[0121] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for measuring the thermoelectric parameters of rock and soil using an in-situ measurement system, characterized in that, During the test, the soil resistivity is measured first, and then the resistance heating wire is heated by electricity. A cylindrical four-phase resistivity probe is used as the temperature sensor of the heating probe. Obtaining the thermal conductivity parameters of soil includes the following steps: Step 1: Obtain the initial resistivity of the soil using a cylindrical four-phase resistivity probe, and determine the soil temperature at that moment using the relationship between resistivity and temperature. , For temperature response, Represents the resistivity at a standard temperature of 25°C. It is the thermoelectric constant; Step 2: Start heating the alloy wire by applying electricity, record the heating time, and at the same time test the real-time resistivity of the outer soil and calculate the real-time temperature. Step 3: Set and fix the initial value of soil heat capacity, the initial effective volumetric heat capacity of the soil and rock mass. Calculated based on porosity ratio , The porosity of the soil. , These are the volumetric heat capacities of soil and water, respectively. Step 4: Generate random values ​​of the input soil thermal conductivity within the range of thermal conductivity based on the Monte Carlo algorithm. Based on random values ​​of soil thermal conductivity The soil temperature at position i at time j is calculated using a finite-length column heat source analytical model based on temperature response analytical theory. ; Step 5: Based on the calculated soil temperature and the results of the test Repeated calculation Until the smallest is calculated value, obtain the minimum The value corresponds to the optimal soil thermal conductivity. , The bonding coefficient; Step 6: Fix the optimal soil thermal conductivity ; Step 7: Generate random values ​​of the input soil heat capacity within the thermal conductivity range based on the Monte Carlo algorithm. And fix the optimal thermal conductivity of the soil Random value of soil specific heat capacity Calculations based on the analytical model of a finite-length column heat source using temperature response analytical theory j Time of the first i Soil temperature at each location ; Step 8: Based on the calculated soil temperature and the results of the test Repeated calculation Until the smallest is calculated value, obtain the minimum The optimal soil specific heat capacity corresponding to the value ; The system includes an in-situ detection probe, a data acquisition instrument, a penetration component connecting the in-situ detection probe and the data acquisition instrument, and a data analysis platform connected to the data acquisition instrument. The in-situ detection probe includes a CPTU static cone probe, a cylindrical four-phase resistivity probe, a heating probe inserted into a hollow cylinder of the cylindrical four-phase resistivity probe, and an adapter connecting the CPTU static cone probe and the cylindrical four-phase resistivity probe. The cylindrical four-phase resistivity probe includes a hollow metal shell, an outer ring of the cylinder with insulating material, voltage electrodes and current electrodes spaced apart; The penetration assembly includes a tracked CPTU penetration truck and a retractable connecting probe that connects the in-situ detection probe to the tracked CPTU penetration truck. The tracked CPTU penetration truck is equipped with an adjustable support structure to fix and guide the retractable connecting probe. A cable is led out from the in-situ detection probe, passes through the retractable connecting probe, and connects to the data acquisition instrument.

2. The method for determination according to claim 1, characterized in that, The CPTU static cone penetration probe includes an integrated cone tip probe and a cylinder. The cone tip probe contains a filter, and a pressure sensor is located above the filter. The cylinder has a hollow inner ring, within which an inclinometer is located. Between the inner ring and the outer ring of the cylinder are a cone sensor, a friction sleeve, a water seal ring, a soil seal ring, and a pressure-sensitive connector. Cables connecting the various sensors extend through the hollow inner ring. The pressure-sensitive connector is the connection interface between the cable and the CPTU static cone penetration probe end of the adapter.

3. The method for determination according to claim 1, characterized in that, The heating probe has a hollow shaft structure, with the heating wire placed between the outer shell and the inner wall shell of the heating probe and filled with backfill material.

4. The method for determination according to claim 1, characterized in that, The diameter of the cylindrical four-phase resistivity probe is larger than that of the CPTU static cone probe. The cable leading from the CPTU static cone probe extends through the hollow shaft of the heating probe and is led out together with the cable of the heating probe to connect to the data acquisition instrument.

5. The method for determination according to claim 1, characterized in that, The resistance heating wire is a nickel-chromium alloy wire.

6. The method for determination according to claim 1, characterized in that, The cylindrical four-phase resistivity probe obtains the soil resistance by measuring the voltage drop between the two electrodes under constant current, and further obtains the soil porosity, soil moisture content, and mass moisture content, where soil porosity... , The bonding coefficient is the open bonding coefficient. Second root, For soil properties, The resistivity of pore water Soil resistivity; soil moisture content , This is the saturation index, here it is open. Second root; Moisture content , For the density of water, This represents the density of soil particles.

7. The method for determination according to claim 1, characterized in that, Based on pore pressure parameters Classify the penetrating soil layers. , This represents the pore pressure test value between the cone-tip probe and the cylinder. The static pore pressure; The cone tip resistance is corrected for area. To calculate the total overburden pressure, the following soil mechanical parameters were obtained: unit weight Compression modulus , For coefficients, For cone tip resistance; undrained shear strength , Shear strength coefficient; effective internal friction angle Relative density of sandy soil , This represents the effective stress.

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