CN114705548A - Testing device and method for thermophysical property parameters of rock and soil material in complex stress state - Google Patents
Testing device and method for thermophysical property parameters of rock and soil material in complex stress state Download PDFInfo
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- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/022—Environment of the test
- G01N2203/0222—Temperature
- G01N2203/0226—High temperature; Heating means
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
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Abstract
The invention discloses a testing device and a testing method for thermophysical parameters of rock and soil materials in a complex stress state, wherein the testing device comprises a sample assembly, a pressure chamber, an axial pressure loading assembly, a confining pressure loading assembly and a sample heating assembly; the sample heating assembly comprises a hard sample heating assembly and a soft sample heating assembly; the hard sample heating assembly comprises a heating plate, a cooling plate, a bottom heat flow sensor and a top heat flow sensor; the soft sample heating assembly comprises a double-needle heat probe; the double-needle thermal probe comprises a heating probe and a temperature probe which are arranged in parallel. The method comprises the steps of 1, preparing a sample assembly; step 2, loading confining pressure; step 3, testing thermophysical parameters in an initial state; step 4, loading the axial pressure; step 5, testing thermophysical parameters under the axial compression; and 6, regulating confining pressure. The invention can realize the heat conductivity and volumetric specific heat capacity test under different stress field conditions, and has the advantages of simple and convenient operation, rapidness, high result precision and the like.
Description
Technical Field
The invention relates to a testing technology of basic physical property parameters of porous materials in the field of civil engineering and geotechnical engineering, in particular to a testing device and a testing method of the thermal property parameters of the geotechnical materials in a complex stress state.
Background
The thermal physical property parameter of the geotechnical material is one of important design parameters of the design and construction of a thermal structure in the field of civil engineering. With the increasing consumption of fossil energy and the environmental hazards caused by the consumption, people are continuously seeking new clean energy and striving to improve the utilization efficiency of the energy. In recent years, the size and number of thermal structures in the civil engineering field have increased dramatically. In the design and construction process of the thermal structure, the measurement accuracy is required for the thermophysical parameters of the surrounding rock-soil materials, such as thermal conductivity, thermal capacity, thermal radiation and the like, and the direct influence is exerted on the heat exchange efficiency and the service performance of the thermal structure. The method has important significance for engineering practice by knowing the transfer characteristics of heat energy in the rock-soil material and accurately and effectively testing the thermophysical parameter indexes of the rock-soil material. The rock-soil material has the characteristics of porosity, medium heterogeneity, non-uniformity and the like, so that accurate measurement of thermophysical parameters of the rock-soil material under different preparation states is particularly important. The thermal conductivity and the specific heat capacity are important indexes for representing the thermal conductivity characteristics of the rock-soil material, and the transfer efficiency of heat in the rock-soil material can be directly reflected.
The testing method for the thermal conductivity/specific heat capacity of the rock-soil material is various and can be divided into two categories according to the testing principle: steady state and unsteady state processes; according to the test equipment, there may be a thermal probe method, a plate method, a water heating method, etc. The development of the testing technologies is mature so far, and the thermophysical parameters of the rock-soil material can be accurately measured. It is worth noting that, when the geotechnical materials are applied in practical engineering, the geotechnical materials are all in a certain stress field environment, for example, the roadbed filling material of roads in cold regions needs to bear the self weight of the superstructure and the load of external vehicles during the service process. The contact properties of solid phase particle media in the rock-soil material are different under different stress environments, and the overall heat conduction characteristic can be directly influenced. Therefore, a new and efficient testing device needs to be developed for measuring the thermophysical parameters of the rock-soil material in a complex stress state.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a device and a method for testing the thermal physical property parameters of the geotechnical material in the complex stress state aiming at the defects of the prior art, the device and the method for testing the thermal physical property parameters of the geotechnical material in the complex stress state can quantitatively evaluate the thermal conductivity of the geotechnical material in the complex stress environment in a thermotechnical structure, and have the advantages of simple and rapid operation, high testing precision and the like, and good social and economic benefits and engineering application prospects.
In order to solve the technical problems, the invention adopts the technical scheme that:
the testing device for the thermophysical parameters of the rock and soil materials in the complex stress state comprises a sample assembly, a pressure chamber, an axial pressure loading assembly, a confining pressure loading assembly and a sample heating assembly.
The sample assembly comprises a rock-soil sample, a sample support, a sample cap and a latex film; the sample support is coaxially arranged at the bottom of the rock-soil sample, the sample cap is coaxially arranged at the top of the rock-soil sample, and the latex film can be integrally sealed and coated on the rock-soil sample, the sample support and the sample cap.
The pressure chamber is a sealed chamber coaxially arranged at the periphery of the sample assembly.
The axial compression loading assembly is used for applying axial pressure to the sample assembly.
And the confining pressure loading assembly is used for applying confining pressure to the sample assembly.
The sample heating assembly includes a hard sample heating assembly and a soft sample heating assembly.
The rigid sample heating assembly includes a heating plate, a cooling plate, a bottom heat flow sensor, and a top heat flow sensor.
The hot plate sets up at sample support top, and the cooling plate setting is in sample cap bottom, and bottom heat flow sensor is used for detecting ground sample top temperature, and top heat flow sensor is used for detecting ground sample bottom temperature.
The soft sample heating assembly comprises a double-needle heat probe, the bottom of the double-needle heat probe is detachably arranged on a sample support or a heating plate, and the top of the double-needle heat probe can extend into the sample; the double-needle thermal probe comprises a heating probe and a temperature probe which are arranged in parallel.
The sample subassembly still includes adiabatic film, and the coaxial integral type cladding of adiabatic film is in ground sample, sample support and sample cap periphery, and the latex film cladding is in adiabatic film periphery.
The heat conductivity K range of the double-needle heat probe is 0.02W/(m.K) to 2.00W/(m.K), and the range of the volume specific heat capacity c is 0.5MJ/m3To 4.0MJ/m3The measurement error should be less than + -10%.
The axial compression loading assembly comprises a reaction frame and a force transmission guide rod, and the force transmission guide rod is installed at the top of the reaction frame and can be lifted.
The axial compression loading assembly further comprises a displacement sensor, and the displacement sensor can detect the axial displacement of the sample assembly.
A method for testing the thermophysical parameters of rock-soil materials under a complex stress state comprises the following steps.
A. when the rock-soil sample is a soft rock-soil sample, the initial state thermophysical property parameters comprise initial thermal conductivity k0-1And initial volumetric specific heat capacity c0-1(ii) a Wherein the initial thermal conductivity k0-1And initial volumetric specific heat capacity c0-1All are obtained by adopting a double-needle heat probe for testing.
B. When the rock-soil sample is a hard rock-soil sample, the initial state thermophysical property parameter comprises initial thermal conductivity k0-2Initial thermal conductivity k0-2The test sample is obtained by adopting a hard sample heating assembly.
in the formula, FaThe applied upper stage axial load; fbFor applying the next axial load。
And 6, adjusting the set pressure value of the confining pressure applied to the rock-soil sample in the step 2, and repeating the steps 3 to 5, thereby obtaining the thermophysical property parameter tests under different confining pressures.
In step 3A, a double-needle thermal probe is adopted to test the initial thermal conductivity k0-1The method specifically comprises the following steps:
step 3A1, heating a rock soil sample: actively heating the rock soil sample by adopting a heating probe, wherein the total heating time is thIn seconds.
Step 3a2, recording the temperature change start time: in the heating process of the step 3A1, the heating probe also monitors the temperature of the rock-soil sample in real time and records the start time t of the temperature change of the rock-soil sample1And an end time t2The units are seconds; wherein, 0 < t1＜t2＜th，t1Corresponding rock-soil sample temperature is theta1，t2Corresponding rock-soil sample temperature is theta2。
Step 3A3, calculating the temperature change delta theta of the sample, wherein the specific calculation formula is as follows: Δ θ ═ θ1-θ2。
Step 3A4, calculating initial thermal conductivity k0-1The specific calculation formula is as follows:
wherein Q is the heat energy input into the rock soil sample by the heating probe with unit length.
In step 3A, a double-needle thermal probe is adopted to test the initial volumetric specific heat capacity c0-1The method comprises the following steps:
step 3A5, calculating thermal diffusivity D: according to the difference of the current test time t of the temperature probe, selecting the following formula (2) to calculate and obtain the thermal diffusivity D; wherein, the unit of the current test time t is second, and the formula (2) is:
where Δ T is the temperature change measured by the temperature probe, r is the distance between the heating probe and the temperature probe, and Ei is the exponential integral.
Step 3A6, calculating initial volume specific heat capacity c0-1The specific calculation formula is as follows:
wherein rho is the density of the rock-soil sample.
In step 3B, the initial thermal conductivity k is tested by adopting a hard sample heating assembly0-2The method comprises the following steps:
step 3B1, heating the rock soil sample: heating the rock soil sample by adopting a heating plate; the heat generated by heating is gradually transferred from the bottom of the rock-soil sample to the top of the rock-soil sample and the cooling plate; wherein, within the set time T, the input heat energy of the heating plate is equal to the heat flux q passing through the rock-soil sample under the steady state condition.
Step 3B2, calculating the temperature gradient: in the heating process of the step 3B1, the bottom heat flow sensor and the top heat flow sensor respectively monitor the temperatures of the bottom and the top of the rock-soil sample in real time; wherein, in a set time T, when the rock-soil sample is in a steady state condition, the temperature monitored by the bottom heat flow sensor is set to be K1The temperature monitored by the top heat flow sensor is K2And the temperature gradient delta K of the upper and lower surfaces of the rock-soil sample is equal to K1-K2。
Step 3B3, calculating initial thermal conductivity k0-2The specific calculation formula is as follows:
wherein L is the height of the rock-soil sample.
And 3B4, stopping heating the heating plate, and gradually cooling the rock-soil sample to the initial temperature.
The invention has the following beneficial effects:
1. the testing device is used for testing thermophysical parameters according to the environmental characteristics of the geotechnical materials, has the advantages of simple and rapid operation, high precision of test results and the like, and has good engineering application prospect and social and economic benefits.
2. The rock-soil material can realize the tests of thermal conductivity and volume specific heat capacity under different stress field conditions, and the characteristics of mutual coupling of mechanical property and thermal property of the sample are determined while the compression characteristic parameters and the strength characteristic parameters of the sample are obtained.
3. The heat conductivity of the double-pin heat probe test can be mutually checked with the heat conductivity of the heating plate/cooling plate test, so that the high accuracy of the test result of the device is ensured.
Drawings
FIG. 1 shows a schematic structural diagram of a testing device for testing the thermophysical parameters of the geotechnical material in a complex stress state.
Fig. 2 shows a graph of the temperature monitored by the temperature probe in the dual-needle thermal probe in the example with time.
FIG. 3 shows a schematic diagram of calculating the thermal conductivity of the geotechnical material by using the dual-needle thermal probe in the embodiment.
Figure 4 shows a graph of the temperature of the top heat flow sensor and the bottom heat flow sensor over time in an example embodiment.
Fig. 5 shows a graph of heat flux over time in the examples.
Among them are:
1. a pressure chamber; 2. a stainless steel top cover; 3. a rigid base; 4. a screw; 5. a force transfer guide bar; 6. an exhaust valve; 7. a displacement sensor; 8. a chamber water injection pipe; 9. a pressure controller; 10. rock and soil samples; 11. a top heat flow sensor; 12. a cooling plate; 13. a sample cap; 14. a bottom heat flow sensor; 15. a dual needle thermal probe; 16. heating plates; 17. a sample support; 18. a heat insulating film; 19. a latex film; 20. a top water stop rubber ring; 21. a bottom water stop rubber ring; 22. a data acquisition line; 23. a data acquisition instrument; 24. a heating cable; 25. a heating power supply; 26. a data cable; 27. and a control host.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific preferred embodiments.
In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part", etc. indicate orientations or positional relationships based on those shown in the drawings, only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, "first", "second", etc. do not represent an important degree of the component, and thus, are not to be construed as limiting the present invention. The specific dimensions used in the present example are only for illustrating the technical solution and do not limit the scope of protection of the present invention.
As shown in figure 1, the testing device for the thermophysical parameters of the geotechnical material in the complex stress state comprises a sample assembly, a pressure chamber 1, an axial pressure loading assembly, a confining pressure loading assembly, a sample heating assembly, a data acquisition instrument 23 and a control host 27.
The sample assembly comprises a rock soil sample 10, a sample support 17, a sample cap 13, a heat insulation film 18, a latex film 19, a top water stop rubber ring 20 and a bottom water stop rubber ring 21.
The shape of the geotechnical test sample is preferably cylindrical, the diameter is preferably 38mm to 50mm, the height is preferably 76mm to 100mm, and the height-diameter ratio is preferably 1.5 to 2.
The sample support is coaxially arranged at the bottom of the rock-soil sample, and the sample cap is coaxially arranged at the top of the rock-soil sample. The diameters of the sample cap and the sample support are the same as the diameter of the rock-soil sample, and the mass range of the sample cap is preferably 50g to 100 g.
The coaxial integral type cladding of adiabatic film is in ground sample, sample support and sample cap periphery, and the latex film cladding is in adiabatic film periphery. Among them, the thermal conductivity of the heat insulating film is preferably less than 0.01W/(m.K).
The pressure chamber is a sealed chamber coaxially arranged on the periphery of the sample assembly, and an exhaust valve 6 is arranged at the top of the pressure chamber. In the embodiment, the pressure chamber is preferably made of transparent toughened glass material, the inner diameter is preferably 200mm, the height is preferably 400mm, and the maximum confining pressure borne by the pressure chamber is 10 MPa.
The axial compression loading assembly is used for applying axial pressure to the sample assembly.
The axial compression loading assembly comprises a reaction frame, a force transmission guide rod 5 and a displacement sensor 7.
The reaction frame comprises a rigid base 3, a stainless steel top cover 2 and a plurality of screw rods 4 for connecting the rigid base 3 and the stainless steel top cover 2.
The force transmission guide rod is arranged at the top of the reaction frame and can be lifted. The bottom of the force transfer guide rod can be contacted with the top of a sample cap in the sample assembly. The axial force exerted by the force transmission guide rod is preferably 5kN at the most.
The displacement sensor can detect the axial displacement of the sample assembly, and the precision of the displacement sensor is preferably more than 0.01 mm.
And the confining pressure loading assembly is used for applying confining pressure to the sample assembly. The confining pressure loading assembly comprises a chamber water injection pipe 8 and a pressure controller 9. The chamber water injection pipe is used for injecting pressurized water into the pressure chamber on the periphery of the rock-soil sample, and the pressure controller is arranged on the chamber water injection pipe 8 and used for pressurization.
The sample heating assembly comprises a hard sample heating assembly, a soft sample heating assembly and a heating power supply 25.
The rigid sample heating assembly includes a heating plate 16, a cooling plate 12, a bottom heat flow sensor 14, and a top heat flow sensor 11.
The heating plate is arranged on the top of the sample support and is connected with a heating power supply 24 through a heating cable 24. The maximum heating temperature of the heating plate is preferably 70 ℃, and the time from the start of heating to the maximum heating temperature by turning on the heating power should be more than 30 min.
The cooling plate sets up in sample cap bottom, and bottom heat flow sensor is used for detecting ground sample top temperature, and top heat flow sensor is used for detecting ground sample bottom temperature. The diameter of the top heat flow sensor and the bottom heat flow sensor is preferably the same as the diameter of the geotechnical sample. The top and bottom heat flow sensors preferably have the following composition: 1 polycarbonate disc with the thickness of 1mm is arranged in the middle of 2 aluminum plates with the thickness of 4mm, holes are drilled in the centers of the aluminum discs, and thermocouples are inserted into the center holes and used for monitoring the temperature change of the aluminum discs.
The soft sample heating assembly comprises a double-needle heat probe 11, the bottom of the double-needle heat probe is detachably arranged on a sample support or a heating plate, and the top of the double-needle heat probe can extend into the sample; the double-needle thermal probe comprises a heating probe and a temperature probe which are arranged in parallel. The heating probe is connected to a heating power supply 25.
The diameter of the single needle of the double-needle heat probe is preferably 3.0mm, the length of the double-needle heat probe is preferably 60mm, and the distance between the double needles is preferably 10 mm.
The thermal conductivity K range of the double-needle thermal probe is preferably 0.02W/(m.K) to 2.00W/(m.K), and the range of the volume specific heat capacity c is preferably 0.5MJ/m3To 4.0MJ/m3The measurement error should be less than + -10%.
The data acquisition instrument is connected with the double-needle thermal probe and each sensor through a data acquisition line 22. The acquisition frequency of the data acquisition instrument is preferably 1 Hz.
The data acquisition instrument is also connected with the control host through a data cable 26. The control host can also be directly connected with the dual-pin thermal probe 11 and the like through a data cable 26.
A method for testing the thermophysical parameters of rock-soil materials under a complex stress state comprises the following steps.
The specific loading mode is preferably as follows: the pressure cavity is fixed on the rigid base through a screw rod, the position of the force transmission guide rod is adjusted to enable the pressure cavity to be close to but not in contact with the sample cap, the exhaust valve and the cavity water injection pipe are opened simultaneously, water is slowly injected into the pressure cavity through the cavity water injection pipe, after the pressure cavity is completely filled with water, the exhaust valve is closed, and the target confining pressure is adjusted through the pressure controller.
Checking the verticality of the sample and whether the side latex film has a bulge phenomenon, adjusting the position of the force transmission guide rod to enable the sample to be just in contact with the sample cap, opening the control host, heating the rock-soil sample loaded with the set pressure confining pressure in the step 2, and testing to obtain initial state thermophysical property parameters, wherein the specific calculation method comprises the following steps of:
A. when the rock-soil sample is a soft rock-soil sample, the initial state thermophysical property parameters comprise initial thermal conductivity k0-1And initial volumetric specific heat capacity c0-1(ii) a Wherein the initial thermal conductivity k0-1And initial volumetric specific heat capacity c0-1All are obtained by adopting a double-needle heat probe for testing.
As shown in FIGS. 2 and 3, the initial thermal conductivity k was measured using a two-pin thermal probe0-1The method specifically comprises the following steps:
step 3A1, heating the rock-soil sample: actively heating the rock soil sample by adopting a heating probe, wherein the total heating time is thIn seconds.
Step 3a2, recording the temperature change start time: in the heating process of the step 3A1, the heating probe also monitors the temperature of the rock-soil sample in real time and records the start time t of the temperature change of the rock-soil sample1And an end time t2The units are seconds; wherein, 0 < t1＜t2＜th，t1Corresponding rock-soil sample temperature is theta1，t2Corresponding rock-soil sample temperature is theta2。
Step 3A3, calculating the temperature change delta theta of the sample, wherein the specific calculation formula is as follows: Δ θ ═ θ1-θ2。
Step 3A4, calculating initial thermal conductivity k0-1The specific calculation formula is as follows:
wherein Q is the heat energy input into the rock soil sample by the heating probe with unit length.
Step 3A5, calculating thermal diffusivity D: according to the difference of the current test time t of the temperature probe, selecting the following formula (2) to calculate and obtain the thermal diffusivity D; wherein, the unit of the current test time t is second, and the formula (2) is:
where Δ T is the temperature change measured by the temperature probe, r is the distance between the heating probe and the temperature probe, and Ei is the exponential integral.
Step 3A6, calculating initial volume specific heat capacity c0-1The specific calculation formula is as follows:
wherein rho is the density of the rock-soil sample.
Using step 3A5 and step 3A6 described above, it was possible to test the initial volumetric specific heat capacity c0-1。
B. When the rock-soil sample is a hard rock-soil sample, the initial state thermophysical property parameter comprises initial thermal conductivity k0-2Initial thermal conductivity k0-2The test sample is obtained by adopting a hard sample heating assembly.
As shown in fig. 4 and 5, the initial thermal conductivity k was measured using a rigid sample heating assembly0-2The method of (4), comprising the following steps.
Step 3B1, heating the rock soil sample: heating the rock soil sample by adopting a heating plate; the heat generated by heating is gradually transferred from the bottom of the rock-soil sample to the top of the rock-soil sample and the cooling plate; wherein, within the set time T, the input heat energy of the heating plate is equal to the heat flux q passing through the rock-soil sample under the steady state condition.
In this embodiment, the time from turning on the heating power supply (25) to the heating of the heating plate to the maximum heating temperature should be longer than 30 min.
Step 3B2, calculating the temperature gradient: in the heating process of the step 3B1, the bottom heat flow sensor and the top heat flow sensor respectively monitor the temperatures of the bottom and the top of the rock-soil sample in real time; wherein, in the set time T, when the rock-soil sample is in a steady state condition, the bottom heat is setThe temperature monitored by the flow sensor is K1The temperature monitored by the top heat flow sensor is K2And the temperature gradient delta K of the upper and lower surfaces of the rock-soil sample is equal to K1-K2。
Step 3B3, calculating initial thermal conductivity k0-2The specific calculation formula is as follows:
wherein L is the height of the rock soil sample.
And 3B4, stopping heating the heating plate, and gradually cooling the rock-soil sample to the initial temperature.
in the formula, FaThe applied upper stage axial load; fbThe next stage of axial load is applied.
The axial pressure loading assembly applies axial load through the force transmission guide rod, and the load rate is lower than 1 mm/min.
In the embodiment, the displacement sensor records the axial deformation of the sample, and can be used for calculating the strain and the porosity so as to research the characteristic of mutual coupling of the mechanical property and the thermal property of the rock-soil sample.
And 6, adjusting the set pressure value of the confining pressure applied to the rock-soil sample in the step 2, and repeating the steps 3 to 5, thereby obtaining the thermophysical property parameter tests under different confining pressures.
Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the details of the embodiments, and various equivalent modifications can be made within the technical spirit of the present invention, and the scope of the present invention is also within the scope of the present invention.
Claims (10)
1. The utility model provides a testing arrangement of geotechnical material thermophysical property parameter under complicated stress state which characterized in that: the device comprises a sample assembly, a pressure chamber, an axial compression loading assembly, a confining pressure loading assembly and a sample heating assembly;
the sample assembly comprises a rock-soil sample, a sample support, a sample cap and a latex film; the sample support is coaxially arranged at the bottom of the rock-soil sample, the sample cap is coaxially arranged at the top of the rock-soil sample, and the emulsion film can integrally and hermetically coat the rock-soil sample, the sample support and the sample cap;
the pressure chamber is a sealing chamber coaxially arranged on the periphery of the sample assembly;
the axial pressure loading assembly is used for applying axial pressure to the sample assembly;
the confining pressure loading assembly is used for applying confining pressure to the sample assembly;
the sample heating assembly comprises a hard sample heating assembly and a soft sample heating assembly;
the hard sample heating assembly comprises a heating plate, a cooling plate, a bottom heat flow sensor and a top heat flow sensor;
the heating plate is arranged at the top of the sample support, the cooling plate is arranged at the bottom of the sample cap, the bottom heat flow sensor is used for detecting the top temperature of the rock-soil sample, and the top heat flow sensor is used for detecting the bottom temperature of the rock-soil sample;
the soft sample heating assembly comprises a double-needle heat probe, the bottom of the double-needle heat probe is detachably arranged on a sample support or a heating plate, and the top of the double-needle heat probe can extend into the sample; the double-needle thermal probe comprises a heating probe and a temperature probe which are arranged in parallel.
2. The testing device for the thermophysical parameters of the geotechnical material under the complex stress state according to claim 1, and is characterized in that: the sample subassembly still includes adiabatic film, and the coaxial integral type cladding of adiabatic film is in ground sample, sample support and sample cap periphery, and the latex film cladding is in adiabatic film periphery.
3. The testing device for the thermophysical parameters of the geotechnical material under the complex stress state according to claim 1, and is characterized in that: the heat conductivity K range of the double-needle heat probe is 0.02W/(m.K) to 2.00W/(m.K), and the range of the volume specific heat capacity c is 0.5MJ/m3To 4.0MJ/m3The measurement error should be less than + -10%.
4. The testing device for the thermophysical parameters of the geotechnical material under the complex stress state according to claim 1, wherein: the axial compression loading assembly comprises a reaction frame and a force transmission guide rod, and the force transmission guide rod is installed at the top of the reaction frame and can be lifted.
5. The testing device for the thermophysical parameters of the geotechnical material under the complex stress state according to claim 4, and is characterized in that: the axial compression loading assembly further comprises a displacement sensor, and the displacement sensor can detect the axial displacement of the sample assembly.
6. A method for testing the thermophysical parameters of rock-soil materials in a complex stress state is characterized by comprising the following steps: the method comprises the following steps:
step 1, preparing a sample assembly, which specifically comprises the following steps:
step 11, preparing rock soil samples: according to the physical properties of the rock-soil material to be simulated, adding a set dose of additive and water into undisturbed soil, and forming or compacting to form a rock-soil sample with a set size; dividing rock and soil samples into hard rock and soil samples and soft rock and soil samples according to the strength of the rock and soil samples; the strength of the hard rock-soil sample is greater than that of the soft rock-soil sample;
step 12, installing a sample heating assembly: a heating plate and a bottom heat flow sensor are sequentially laid on the top of the sample support from bottom to top, and a cooling plate and a top heat flow sensor are sequentially arranged on the bottom of the sample cap; the double-needle thermal probe is selected to be installed or not according to the type of a rock-soil sample, and when the rock-soil sample is a soft rock-soil sample, the bottom of the double-needle thermal probe is detachably installed on a sample support or a heating plate; otherwise, the double-needle heat probe is not installed;
step 13, mounting rock and soil samples: placing the rock-soil sample prepared in the step 11 on the top of the sample support in the step 12, and when the rock-soil sample is a soft rock-soil sample, extending the top of the double-needle thermal probe into the soft rock-soil sample; then, placing the sample cap in the step 12 on the top of the rock-soil sample;
step 14, coating rock soil samples: sequentially coating the heat insulation film and the latex film on the periphery of the rock and soil sample which is mounted in the step 13 from inside to outside;
step 2, loading confining pressure: placing the rock-soil sample prepared in the step 1 in the center of the bottom of a pressure chamber, and applying confining pressure with set pressure to the rock-soil sample in a manner of injecting water into the pressure chamber;
step 3, testing the thermophysical property parameters of the initial state: heating and testing the rock-soil sample loaded with the set pressure confining pressure in the step 2 to obtain initial state thermophysical property parameters, wherein the specific calculation method comprises the following steps:
A. when the rock-soil sample is a soft rock-soil sample, the initial state thermophysical property parameter comprises initial thermal conductivity k0-1And initial volumetric specific heat capacity c0-1(ii) a Wherein the initial thermal conductivity k0-1And initial volumetric specific heat capacity c0-1All the materials are obtained by adopting a double-needle thermal probe test;
B. when the rock-soil sample is a hard rock-soil sample, the initial state thermophysical property parameter comprises initial thermal conductivity k0-2Initial thermal conductivity k0-2Testing by adopting a hard sample heating assembly;
step 4, loading axial pressure: applying equal-gradient d-step axial pressure on the rock-soil sample which is subjected to the initial state thermophysical parameter test and is restored to the temperature before heating by adopting an axial pressure loading assembly until the required maximum axial load is reached; wherein, the calculation formula of the gradient d is as follows:
in the formula, FaThe applied upper stage axial load; fbThe next stage of axial load is applied;
step 5, testing thermophysical parameters under the axial compression: after each stage of axial compression loading in the step 4, carrying out thermal physical property parameter testing under the stage of axial compression by adopting the method in the step 3, thereby obtaining thermal physical property parameter testing under different axial compressions;
and 6, adjusting the set pressure value of the confining pressure applied to the rock-soil sample in the step 2, and repeating the steps 3 to 5 to obtain the thermophysical property parameter tests under different confining pressures.
7. The method for testing the thermophysical parameters of the geotechnical material under the complex stress state according to claim 6, wherein: in step 3A, a double-needle thermal probe is adopted to test the initial thermal conductivity k0-1The method specifically comprises the following steps:
step 3A1, heating a rock soil sample: actively heating the rock soil sample by adopting a heating probe, wherein the total heating time is thIn seconds;
step 3a2, recording the temperature change start time: in the heating process of the step 3A1, the heating probe also monitors the temperature of the rock-soil sample in real time and records the start time t of the temperature change of the rock-soil sample1And an end time t2The units are seconds; wherein, 0 < t1＜t2＜th，t1Corresponding rock-soil sample temperature is theta1，t2Corresponding rock-soil sample temperature is theta2；
Step 3A3, calculating the temperature change delta theta of the sample, wherein the specific calculation formula is as follows: Δ θ ═ θ1-θ2；
Step 3A4, calculating initial thermal conductivity k0-1The specific calculation formula is as follows:
wherein Q is the heat energy input into the rock soil sample by the heating probe with unit length.
8. The method for testing the thermophysical parameters of the geotechnical material under the complex stress state according to claim 7, wherein: in step 3A, a double-needle thermal probe is adopted to test the initial volumetric specific heat capacity c0-1The method comprises the following steps:
step 3A5, calculating thermal diffusivity D: according to the difference of the current test time t of the temperature probe, selecting the following formula (2) to calculate and obtain the thermal diffusivity D; wherein, the unit of the current test time t is second, and the formula (2) is:
where Δ T is the temperature change measured by the temperature probe, r is the distance between the heating probe and the temperature probe, and Ei is the exponential integral;
step 3A6, calculating initial volume specific heat capacity c0-1The specific calculation formula is as follows:
wherein rho is the density of the rock-soil sample.
9. The method for testing the thermophysical parameters of the geotechnical material under the complex stress state according to claim 6, wherein: in step 3B, the initial thermal conductivity k is tested by adopting a hard sample heating assembly0-2The method comprises the following steps:
step 3B1, heating the rock-soil sample: heating the rock soil sample by adopting a heating plate; the heat generated by heating is gradually transferred from the bottom of the rock-soil sample to the top of the rock-soil sample and the cooling plate; wherein, in a set time T, the input heat energy of the heating plate is equal to the heat flux q passing through the rock-soil sample under a steady state condition;
step 3B2, calculating the temperature gradient: in the heating process of the step 3B1, the bottom heat flow sensor and the top heat flow sensor respectively monitor the temperatures of the bottom and the top of the rock-soil sample in real time; wherein, in a set time T, when the rock-soil sample is in a steady state condition, the temperature monitored by the bottom heat flow sensor is set to be K1The temperature monitored by the top heat flow sensor is K2And the temperature gradient delta K of the upper and lower surfaces of the rock-soil sample is equal to K1-K2；
Step 3B3, calculating initial thermal conductivity k0-2The specific calculation formula is as follows:
wherein L is the height of the rock soil sample;
and 3B4, stopping heating the heating plate, and gradually cooling the rock-soil sample to the initial temperature.
10. The method for testing the thermophysical parameters of the geotechnical material under the complex stress state according to claim 6, wherein the method comprises the following steps: step 4, while loading the axial pressure, monitoring the axial deformation of the rock-soil sample in real time by using a displacement sensor, and when the hourly deformation of the rock-soil sample is less than 0.01mm after each level of load is applied, determining that the axial deformation of the rock-soil sample is stable; when the axial deformation of the rock-soil sample is stable, the test of the thermal physical property parameters under the axial pressure can be carried out.
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