A frozen soil direct shear creep test device and method based on hydro-thermal coupling

Abstract

This invention discloses a hydrothermal coupled direct shear creep testing device and method for frozen soil. The hydrothermal coupled direct shear creep testing device for frozen soil includes: a test cylinder with a top cover; a liquid-isolating chamber located inside the test cylinder; a shear box located inside the liquid-isolating chamber, with its bottom connected to the bottom of the test cylinder, and a sample placed inside the shear box; a cooling plate located inside the shear box, positioned at both ends of the sample; a water replenishment plate located inside the shear box and connected to the cooling plate; a pressure load assembly that passes through the top cover and the liquid-isolating chamber sequentially and connects to the top of the shear box; a tensile load assembly connected to the outer wall of the shear box; and a variable speed motor connected to the tensile load assembly. The hydrothermal coupled direct shear creep testing device for frozen soil of this invention is easy to operate and can perform multiple tests, including direct shear creep of frozen soil under hydrothermal coupling.

Description

Technical Field

[0001] This invention belongs to the field of frozen soil mechanics, specifically relating to a hydrothermal coupled frozen soil direct shear creep test device and method. Background Technology

[0002] In recent years, with the intensification of global warming and human engineering activities, the temperature and groundwater conditions of permafrost are constantly changing. Affected by the combined influence of boundary conditions such as ground temperature, atmospheric temperature, rainfall, and groundwater, permafrost materials are constantly in a complex environment of hydrothermal coupling. As an important foundation material for buildings and structures in cold regions, permafrost's creep characteristics are exceptionally sensitive to temperature, moisture, and load. A thorough understanding of the creep characteristics of permafrost under hydrothermal coupling is of great significance for evaluating the stability of buildings and structures in cold regions.

[0003] After the construction of buildings and structures in cold regions is completed, the moisture field, temperature field, and stress field of the original permafrost foundation undergo certain changes, altering the mechanical properties of the permafrost. The overall deformation of the permafrost foundation exhibits significant creep over time. When the deformation exceeds the allowable range of the building or structure, the foundation becomes unstable or even fails. Therefore, studying the hydrothermal coupled creep characteristics of permafrost is of great significance for maintaining the stability of engineering foundations in cold regions.

[0004] Current research on the direct shear creep characteristics of frozen soil is mainly conducted in a constant low-temperature environment, without considering the water migration phenomenon caused by changes in the internal temperature of the frozen soil. Although the experimental results obtained in this way can guide engineering practice to a certain extent, they cannot objectively and truly reflect the influence of the thermo-mechanical coupling evolution law caused by changes in the temperature field and moisture field on its deformation characteristics. Therefore, the research on the deformation mechanism of frozen soil engineering under the action of hydro-thermal coupling has not been able to achieve new breakthroughs and progress.

[0005] To gain a comprehensive and in-depth understanding of the mechanical behavior and deformation characteristics of frozen soil under hydrothermal coupling, it is essential to first establish a reasonable experimental platform and experimental apparatus, and to develop a complete set of experimental methods. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a hydrothermal coupled direct shear creep testing device and method for frozen soil.

[0007] The hydrothermal coupled frozen soil direct shear creep testing device of this invention includes: a test cylinder with a test cylinder top cover; a liquid-separating chamber disposed inside the test cylinder; a shear box disposed inside the liquid-separating chamber, with its bottom connected to the bottom of the test cylinder, and a sample placed inside the shear box; a cooling plate disposed inside the shear box, with the cooling plate located at both ends of the sample; a water replenishment plate disposed inside the shear box and connected to the cooling plate; a pressure load assembly that passes through the test cylinder top cover and the liquid-separating chamber in sequence and is connected to the top of the shear box; a tensile load assembly that is connected to the outer wall of the shear box; and a variable speed motor connected to the tensile load assembly.

[0008] The hydrothermal coupled frozen soil direct shear creep test device of the present invention is easy to operate and can perform multiple tests such as direct shear test, uniaxial compression test and uniaxial creep test of frozen soil under hydrothermal coupling.

[0009] Optionally, the top cover of the test tube is also provided with a coolant injection port, and a sealing plug is provided at the coolant injection port.

[0010] Optionally, the shear box includes an upper shear box and a lower shear box, the lower shear box is disposed at the bottom of the test tube, the sample is disposed between the upper shear box and the lower shear box, and a gap is provided between the upper shear box and the lower shear box.

[0011] Optionally, the cooling tray includes an upper cooling tray and a lower cooling tray, the upper cooling tray is located at the top of the upper shear box, the lower cooling tray is located at the bottom of the lower shear box, the water replenishment tray is located above the lower cooling tray, and the sample is located between the upper cooling tray and the water replenishment tray.

[0012] Optionally, the tension load assembly includes a hook located on the outer side of the upper shear box.

[0013] Optionally, the tension load assembly further includes a first pulley and an LVDT displacement sensor. The LVDT displacement sensor and the first pulley are respectively located on the outer sides of the lower shear box, and the first pulley and the hook are located on the same side of the shear box. The LVDT displacement sensor is in contact with the outer wall of the upper shear box.

[0014] Optionally, the tension load assembly further includes a tension sensor and a steel strand, with both ends of the steel strand connected to the hook outside the upper shear box and the tension sensor, respectively, and the tension sensor connected to the variable speed motor through the steel strand.

[0015] Optionally, the device further includes multiple thermocouples, one end of which passes through the upper shear box and the lower shear box respectively and is connected to the sample, and the other end of which passes through the bottom of the test tube.

[0016] Optionally, the pressure load assembly includes a pressure sensor and a vertical force transmission rod. The pressure sensor is connected to the vertical force transmission rod, and the vertical force transmission rod passes through the top cover of the test cylinder and the liquid-separating chamber in sequence before contacting the top of the upper shear box.

[0017] The method of using the hydrothermal coupled frozen soil direct shear creep test device according to an embodiment of the present invention includes the following steps:

[0018] S1. Sample installation: The sample is installed in the shear box of the hydrothermal coupled frozen soil direct shear creep test device.

[0019] S2. Freezing of the sample: Inject coolant into the test cylinder, evacuate the inside of the liquid separator, adjust the temperature of the coolant in the test cylinder and circulate the refrigerant in the cooling pan to freeze the sample. When the thermocouple inside the sample reaches -20°C, keep it constant for 24 hours to complete the freezing of the sample.

[0020] S3. Hydrothermal Coupling Creep: After the sample is frozen, the circulation of refrigerant in the cooling pan is stopped, and the temperature of the coolant in the test cylinder is adjusted to control the ambient temperature. When the internal temperature of the sample reaches the constant temperature of the test, a load is applied to the top of the sample through the pressure loading component, and water is replenished to the bottom of the sample through the water replenishment pan. The temperature of the refrigerant in the cooling pan is set to induce a hydrothermal coupling phenomenon inside the sample. The thermocouples inside the sample are observed. When the sample reaches the temperature gradient set for the test, the variable speed motor is started, and the constant load required for the creep test is adjusted through the tensile sensor. Then, the temperature data and deformation data of the sample are collected in real time.

[0021] The hydrothermal coupled frozen soil direct shear creep test device of the present invention is easy to operate and can perform multiple tests such as direct shear test, uniaxial compression test and uniaxial creep test of frozen soil under hydrothermal coupling. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the hydrothermal coupling frozen soil direct shear creep test device according to an embodiment of the present invention.

[0023] Figure label:

[0024] Test cylinder 1; Test cylinder top cover 101; Coolant 102; Sealing plug 103; Latex gasket 104; Temperature sensor 105; Refrigerant inlet channel 106; Refrigerant outlet channel 107; Test cylinder base 108;

[0025] Liquid separator 2; fixing screw 201; vacuum channel 202;

[0026] Clipping box 3; Upper clipping box 301; Lower clipping box 302;

[0027] Refrigeration plate 4; Upper refrigeration plate 401; Upper refrigeration plate temperature control liquid inlet conduit 4011; Upper refrigeration plate temperature control liquid outlet conduit 4012; Lower refrigeration plate 402; Lower refrigeration plate temperature control liquid inlet conduit 4021; Lower refrigeration plate temperature control liquid outlet conduit 4022;

[0028] 5. Water replenishment tray; 501 Mascherano bottle; 6. Thermocouple;

[0029] Pressure load assembly 7; pressure sensor 701; vertical force transmission rod 702; specimen 8;

[0030] Tension load assembly 9; hook 901; first pulley 902; second pulley 903; steel strand 904; tension sensor 905; LVDT displacement sensor 906;

[0031] Variable speed motor 10; bracket base 11; test bracket 1101; bracket nut 1102. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] like Figure 1 As shown, the hydrothermal coupled frozen soil direct shear creep test device of this invention includes a test cylinder 1, a liquid-separating chamber 2, a shear box 3, a cooling plate 4, a water replenishment plate 5, a pressure load assembly 7, a tensile load assembly 9, and a variable speed motor 10. A test cylinder top cover 101 is provided on the top of the test cylinder 1, and the test cylinder top cover 101 and the test cylinder 1 are detachably connected. The liquid-separating chamber 2 is located inside the test cylinder 1 and is attached to the bottom of the test cylinder 1. The liquid-separating chamber 2 is hollow and its opening faces downward and is connected to the bottom of the test cylinder 1. The shear box 3 is located inside the liquid-separating chamber 2, and the bottom of the shear box 3 is connected to the bottom of the test cylinder 1. A sample 8 is placed inside the shear box 3. When the test cylinder 1 is filled with coolant 102, the liquid-separating chamber 2 separates the shear box 3 from the coolant 102 in the test cylinder 1.

[0034] The cooling plate 4 is located inside the shear box 3 and at both ends of the sample 8, facilitating cooling of both ends of the sample 8. The water replenishment plate 5 is located inside the shear box 3 and connected to the cooling plate 4. The water replenishment plate 5 is positioned between the sample 8 and the cooling plate 4, allowing water to be replenished to the sample 8 at the bottom. The pressure load assembly 7 passes through the top cover of the test cylinder 1 and the liquid-separating chamber 2 in sequence and connects to the top of the shear box 3. The pressure load assembly 7 is used to apply pressure to the top of the shear box 3. The tensile load assembly 9 is connected to the outer wall of the shear box 3. The tensile load assembly 9 is used to apply tensile force to the shear box 3, thereby indirectly applying tensile force to the sample 8 for shearing tests. The variable speed motor 10 is connected to the tensile load assembly 9 and is used to provide tensile force to the tensile load assembly 9.

[0035] The following is for reference. Figure 1 This document briefly describes the operation of a hydrothermal coupled direct shear creep testing apparatus for frozen soil. First, coolant 102 is injected into the test chamber 1, and a vacuum is created inside the liquid-separating chamber 2. Then, the temperature of the coolant 102 and the temperature of the cooling plate 4 are adjusted to freeze the sample 8. Once the internal temperature of the sample 8 reaches -20°C, it is kept constant for 24 hours, completing the freezing process. Next, the circulation of refrigerant in the cooling plate 4 is stopped, and the temperature of the coolant 102 in the test chamber 1 is adjusted to control the ambient temperature. After the internal temperature of the sample 8 reaches the constant temperature for the test, a load is applied to the top of the sample 8 through the pressure loading assembly 7, and water is replenished to the bottom of the sample 8 through the water replenishment plate 5. The temperature of the refrigerant in the cooling plate 4 is then adjusted to induce a hydrothermal coupling phenomenon inside the sample 8. When the sample 8 reaches the temperature gradient set for the test, the variable speed motor 10 is started, and the constant load required for the creep test is adjusted through the tensile load assembly 9. Then, the temperature and deformation data of the sample 8 are collected in real time.

[0036] The hydrothermal coupled frozen soil direct shear creep test device of the present invention is easy to operate and can perform multiple tests such as direct shear creep test, direct shear test, uniaxial compression test and uniaxial creep test of frozen soil under hydrothermal coupling.

[0037] like Figure 1 As shown, the hydrothermal coupled frozen soil direct shear creep test device of this invention includes a test cylinder 1, a liquid-separating chamber 2, a shear box 3, a cooling plate 4, a water replenishment plate 5, a pressure load assembly 7, a tensile load assembly 9, and a variable speed motor 10. A test cylinder top cover 101 is provided on the top of the test cylinder 1. A latex gasket 104 is provided at the contact surface between the test cylinder top cover 101 and the test cylinder 1 to increase the sealing effect between the test cylinder 1 and the test cylinder top cover 101. The test cylinder top cover 101 is provided with a refrigerant inlet / outlet circulation channel, a temperature sensor 105, and a coolant injection port. A sealing plug 103 is provided at the coolant injection port, through which coolant 102 is injected into the test cylinder 1. The temperature sensor 105 is used to measure the temperature of the coolant 102 inside the test cylinder 1.

[0038] The refrigerant inlet and outlet circulation channels include a refrigerant inlet channel 106 and a refrigerant outlet channel 107, and temperature control is achieved by circulating the internal coolant.

[0039] A test cylinder base 108 is located below the test cylinder 1, and the test cylinder base 108 is mounted on a support base 11. Test supports 1101 are located on both sides of the support base 11. The upper part of the test supports 1101 has external threads. The test supports 1101 are connected to the test cylinder top cover 101 via support nuts 1102. Specifically, the test cylinder top cover 101 has four through holes at its four corners. There are four test supports 1101, which can pass through the four through holes one-to-one, and the test supports 1101 mate with the through holes. After passing through the through holes, the test supports 1101 are connected to the support nuts 1102. Tightening the support nuts 1102 seals the test cylinder top cover 101 to the test cylinder 1. Alternatively, two through holes can be provided for the test supports 1101 and the test cylinder top cover 101. The two test supports 1101 are located at the middle positions at both ends of the support base 11, and the positions of the through holes in the test cylinder top cover 101 correspond to the positions of the test supports 1101.

[0040] The liquid separator 2 is located inside the test cylinder 1 and is fixed to the bottom of the test cylinder 1 by fixing screws 201. A latex pad 4 is provided on the contact surface between the liquid separator 2 and the test cylinder 1. After the coolant 102 enters the test cylinder 1, it fills the space between the liquid separator 2 and the inner wall of the test cylinder 1, thus separating the coolant 102 from its internal components such as the shear box 3. The liquid separator 2 contains the shear box 3, the cooling plate 4, the water replenishment plate 5, the thermocouple 6, the hook 901, the first pulley 902, and the LVDT displacement sensor 8.

[0041] The shear box 3 includes an upper shear box 301 and a lower shear box 302, which have the same diameter. The lower shear box 302 is located at the bottom of the test cylinder 1, and the sample 8 is located between the upper shear box 301 and the lower shear box 302. A gap is provided between the upper shear box 301 and the lower shear box 302. The outer wall of the upper shear box 301 is connected to the tensile load assembly 9. This arrangement allows the sample to be sheared along the gap between the upper shear box 301 and the lower shear box 302 when the tensile load assembly 9 applies a tensile force to the upper shear box 301.

[0042] The hydrothermal coupling frozen soil direct shear creep test device of this invention further includes thermocouples 6. There are multiple thermocouples 6. One end of the multiple thermocouples 6 passes through the upper shear box 301 and the lower shear box 302 respectively and is connected to the sample 8. The other end of the multiple thermocouples 6 passes through the bottom of the test cylinder 1.

[0043] Both the upper shear box 301 and the lower shear box 302 have channels for thermocouples 6 to enter and exit on one side. One end of each thermocouple 6 enters the upper shear box 301 and the lower shear box 302 through the channels and connects to the sample 8. Specifically, each of the upper shear box 301 and the lower shear box 302 has two channels for thermocouples 6 to enter and exit, and these channels are located on the left side of the upper shear box 301 and the lower shear box 302.

[0044] The bottom of the test cylinder 1 is also provided with a thermocouple channel for the thermocouple 6 to enter and exit. An O-ring is provided in the thermocouple channel to seal the gap between the thermocouple channel and the thermocouple 6, so as to ensure that the liquid separator can be evacuated.

[0045] The cooling tray 4 includes an upper cooling tray 401 and a lower cooling tray 402. The upper cooling tray 401 and the lower cooling tray 402 have the same diameter. The upper cooling tray 401 is located at the top inside the upper shear box 301, and the lower cooling tray 402 is located at the bottom inside the lower shear box 301. The water replenishment tray 5 is located above the lower cooling tray 402, and the sample 8 is located between the upper cooling tray 401 and the water replenishment tray 5.

[0046] The upper cooling plate 401 is provided with an upper cooling plate temperature control liquid inlet conduit 4011 and an upper cooling plate temperature control liquid outlet conduit 4012. The upper cooling plate temperature control liquid inlet conduit 4011 and the upper cooling plate temperature control liquid outlet conduit 4012 are located on the top two sides of the upper cooling plate 401, respectively. The upper cooling plate temperature control liquid inlet conduit 4011 and the upper cooling plate temperature control liquid outlet conduit 4012 pass through the upper shear box 301 and the bottom of the test cylinder 1 in sequence, and then connect to the external cold bath box to form a circulation channel, so that the upper part of the sample 8 can be temperature controlled.

[0047] The lower cooling plate 402 is provided with a lower cooling plate temperature control liquid inlet conduit 4021 and a lower cooling plate temperature control liquid outlet conduit 4022. The lower cooling plate temperature control liquid inlet conduit 4021 and the lower cooling plate temperature control liquid outlet conduit 4022 are located on both sides of the bottom of the lower cooling plate 402, respectively. The lower cooling plate temperature control liquid inlet conduit 4021 and the lower cooling plate temperature control liquid outlet conduit 4022 pass through the lower shear box 302 and the bottom of the test cylinder 1 in sequence, and then connect to the external cold bath box to form a circulation channel, so that the lower part of the sample 8 can be temperature controlled.

[0048] The bottom of the test cylinder 1 is provided with channels for the upper refrigeration plate temperature control liquid inlet conduit 4011, the upper refrigeration plate temperature control liquid outlet conduit 4012, the lower refrigeration plate temperature control liquid inlet conduit 4021, and the lower refrigeration plate temperature control liquid outlet conduit 4022 to pass through, and each of these channels is provided with an O-ring seal to further ensure that the liquid separation chamber 2 can be evacuated.

[0049] The temperature control of the upper cooling plate 401 and lower cooling plate 402 inside the shear box 3 is achieved by circulating the refrigerant connected to the external cold bath box. The temperature control of the coolant inside the test cylinder 1 is also achieved by circulating the internal coolant. In other words, the external test cylinder 1 and the upper cooling plate 401 and lower cooling plate 402 are all used to control the temperature, achieving the effect of dual-layer temperature control inside and outside.

[0050] A water replenishment tray 5 is positioned between the lower cooling tray 402 and the sample 8. The water replenishment tray 5 is connected to a Marvin flask 501 via a water replenishment tray conduit. The Marvin flask 501 is mounted on the support base 11. A valve is installed on the water replenishment tray conduit, and a channel for the water replenishment tray conduit to pass through is also provided at the bottom of the test cylinder 1. The water replenishment tray conduit exits through this channel, which also contains an O-ring seal to further ensure that the liquid-separating chamber 2 can be evacuated. Opening the valve on the water replenishment tray conduit allows water to be added to the water replenishment tray 5 through the Marvin flask 501, thereby replenishing water to the bottom of the sample 8. Replenishing water to the bottom of the sample is to prevent moisture migration within the sample under temperature gradient conditions. Using a Marvin flask for sample replenishment ensures that it is not affected by external pressure.

[0051] The pressure load assembly 7 includes a pressure sensor 701 and a vertical force transmission rod 702. The pressure sensor 701 is connected to the vertical force transmission rod 702, which passes through the test cylinder top cover 101 and the liquid-separating chamber 2 in sequence before contacting the top of the upper shear box 301. Both the test cylinder top cover 101 and the liquid-separating chamber 2 have through holes at their tops for the vertical force transmission rod 702 to pass through. The vertical force transmission rod 702 is inserted into the liquid-separating chamber 2 through these through holes and contacts the top of the upper shear box 301. O-rings are also installed in the through holes at the tops of the test cylinder top cover 101 and the liquid-separating chamber 2 to provide a seal, further ensuring that the liquid-separating chamber 2 can be evacuated.

[0052] The pressure sensor 701 is located above the top cover 101 of the test tube and is used to detect the pressure applied to the upper shear box 301 by the vertical force transmission rod 702.

[0053] The tension load assembly 9 includes a hook 901, a first pulley 902, a second pulley 903, an LVDT displacement sensor 906, a tension sensor 905, and a steel strand 904. The hook 901 is located on the outer side of the upper shear box 301 and is used to fix one end of the steel strand 904.

[0054] The LVDT displacement sensor 906 and the first pulley 902 are respectively located on the outer sides of the lower shear box 302. Both outer sides of the lower shear box 302 are provided with L-shaped steel plates, and the positions of the two L-shaped steel plates are corresponding. The first pulley 902 is provided on one of the L-shaped steel plates, and the LVDT displacement sensor 906 is provided on the other L-shaped steel plate. The first pulley 902 and the hook 901 are located on the same side of the shear box 302. That is to say, the position of the first pulley 902 on the lower shear box 302 corresponds to the position of the hook 901 on the upper shear box 301. After the steel strand 904 is fixed on the hook 901, it can pass around the first pulley 902. Preferably, the LVDT displacement sensor 906 is on the left side of the lower shear box 302, the first pulley 902 is located on the right side of the lower shear box 302, and the hook 901 is located on the right side of the upper shear box 301.

[0055] The LVDT displacement sensor 906 is fixed on the corresponding L-shaped steel sheet and, after the range is set, it comes into contact with the outer wall of the upper shear box 301. That is to say, one end of the LVDT displacement sensor 906 is in contact with the upper shear box 301.

[0056] The support base 11 is also equipped with a second pulley 903. The steel strand 904 passes around the first pulley 902 and then exits through the channel at the bottom of the test cylinder 1, passes around the second pulley 902, and then connects to the tension sensor 905. The bottom of the test cylinder 1 is provided with a channel for the steel strand 904 to pass through. An O-ring is provided in the channel to seal it and further ensure that the liquid-sealing chamber 2 can be evacuated.

[0057] The two ends of the steel strand 904 are connected to hooks 901 and tension sensors 905, respectively. The tension sensors 905 are connected to the variable speed motor 10 through the steel strand 904. In other words, the steel strand 904 is connected to the tension sensor 905 and then to the variable speed motor 10. Applying a horizontal shear load to the specimen 8 through the steel strand 904 and the variable speed motor 10 has the advantages of simple operation and precise and stable load application, which can minimize the disturbance to the specimen during the test.

[0058] By changing the model of the variable speed motor, direct shear creep tests of frozen soil under different scale loads can be carried out. Direct shear tests of frozen soil under different shear rates under hydrothermal coupling can also be carried out, which is convenient for studying the load effect of frozen soil creep and the loading rate effect of direct shear under hydrothermal coupling.

[0059] For example, replacing the motor with a more powerful one can enable tests under greater shear forces.

[0060] The following is for reference. Figure 1 A detailed description of the method of using the hydrothermal coupled frozen soil direct shear creep testing device according to an embodiment of the present invention includes the following steps:

[0061] S1. Sample Installation: After fixing the lower shear box 302 at the bottom of the test cylinder 1, install the lower cooling plate 402, water replenishment plate 5, sample 8, upper cooling plate 401, upper shear box 301, and thermocouple 6 in sequence. Pass the conduits connected to the upper cooling plate 401, lower cooling plate 402, and water replenishment plate 5, as well as the thermocouple 6, through the bottom channel of the test cylinder 1. Fix the LVDT displacement sensor 906, set the range, and then make the LVDT displacement sensor 906 contact the upper shear box 301. After connecting the steel strand 904 to the hook 901 on the right side of the upper shear box 301, it passes around... The first pulley 902, fixed on the right side of the lower shear box 302, passes through the bottom channel of the test cylinder 1, then goes around the second pulley 903 on the bracket base 11, and then connects to the tension sensor 905 and the speed motor 10. The liquid separator 2 is fixed to the bottom of the test cylinder 1 with the fixing screw 201. The vertical force transmission rod 702, which connects to the pressure sensor 701, is inserted from the through hole at the top of the test cylinder cover 101 and the top of the liquid separator 2, so that the vertical force transmission rod 702 contacts the top of the upper shear box 301. The test cylinder cover 101 is fixed to the test cylinder 1 by the bracket nut 1102.

[0062] S2. Freezing of the sample: Coolant 102 is injected into the coolant injection port of the top cover 101 of the test cylinder and the sealing plug 103 is tightened. The inside of the liquid-separating chamber 2 is evacuated through the vacuum channel 202. The temperature of the coolant 102 in the test cylinder 1 is adjusted and the refrigerant in the upper cooling plate 401 and the lower cooling plate 402 is circulated to freeze the sample 8. When the thermocouple 6 inside the sample 8 shows -20℃, it is kept constant for 24 hours. The freezing of the sample 8 is then complete.

[0063] S3. Hydrothermal Coupling Creep: After the specimen 8 is frozen, the circulation of refrigerant in the cooling pan 4 is stopped, and the temperature of the coolant 102 in the test cylinder 1 is adjusted to control the ambient temperature. When the internal temperature of the specimen 8 reaches the constant temperature of the test, a load is applied to the top of the specimen 8 through the vertical force transmission rod 702, and the valve between the water replenishment pan 5 and the Martens bottle 501 is opened to replenish water to the bottom of the specimen 8. The refrigerant temperature in the upper cooling pan 401 and the lower cooling pan 402 is adjusted to generate a hydrothermal coupling phenomenon inside the specimen 8. The thermocouple inside the specimen 8 is observed. When the specimen 8 reaches the temperature gradient set for the test, the variable speed motor 10 is started, and the constant load required for the creep test is adjusted through the tensile sensor 905. Then, the temperature data and deformation data of the specimen 8 are collected in real time.

[0064] The hydrothermal coupled frozen soil direct shear creep testing apparatus of the present invention can rapidly freeze the sample in a vacuum environment by adjusting the temperature of the coolant inside the test cylinder 1 and the refrigerant temperature of the upper cooling plate 401 and the lower cooling plate 402. By changing the dimensions of the shear box, the upper cooling plate, the lower cooling plate, and the water replenishment plate, the hydrothermal coupling characteristics of frozen soil samples of different sizes can be studied, facilitating the study of the scale effect of frozen soil mechanical properties under hydrothermal coupling. With appropriate modifications to the shear box, the apparatus can perform uniaxial compression and uniaxial creep tests of frozen soil under hydrothermal coupling.

[0065] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0067] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0069] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A device for frozen soil direct shear creep test with hydro-thermal coupling, characterized in that, include: The test tube has a top cover; the top cover is also provided with a coolant inlet, and a sealing plug is provided at the coolant inlet. A liquid separator is disposed inside the test cylinder; A shear box is disposed inside the liquid separator, and the bottom of the shear box is connected to the bottom of the test tube. A sample is placed inside the shear box. When the test tube is filled with coolant, the liquid separator separates the shear box from the coolant in the test tube, and the temperature of the coolant in the test tube is adjusted to control the ambient temperature. The shearing box includes an upper shearing box and a lower shearing box. The lower shearing box is located at the bottom of the test tube. The sample is located between the upper shearing box and the lower shearing box, and a gap is provided between the upper shearing box and the lower shearing box. A cooling plate is disposed inside the shear box and at both ends of the sample; A water replenishment tray is disposed inside the shear box and is connected to the refrigeration tray; The cooling tray includes an upper cooling tray and a lower cooling tray. The upper cooling tray is located at the top of the upper shear box, the lower cooling tray is located at the bottom of the lower shear box, the water replenishment tray is located above the lower cooling tray, and the sample is located between the upper cooling tray and the water replenishment tray. A pressure loading assembly, which passes sequentially through the top cover of the test cylinder and the liquid-separating chamber, and is then connected to the top of the shear box; A tensile load assembly, wherein the tensile load assembly is connected to the outer wall of the shear box; A variable speed motor, which is connected to the tension load assembly.

2. The hydrothermal coupled frozen soil direct shear creep test device according to claim 1, characterized in that, The tensile load assembly includes a hook located on the outer side of the upper shear box.

3. The hydrothermal coupled frozen soil direct shear creep test device according to claim 2, characterized in that, The tension load assembly further includes a first pulley and an LVDT displacement sensor. The LVDT displacement sensor and the first pulley are respectively located on the outer sides of the lower shear box, and the first pulley and the hook are located on the same side of the shear box. The LVDT displacement sensor is in contact with the outer wall of the upper shear box.

4. The hydrothermal coupled frozen soil direct shear creep test device according to claim 3, characterized in that, The tension load assembly further includes a tension sensor and a steel strand. The two ends of the steel strand are respectively connected to the hook outside the upper shear box and the tension sensor. The tension sensor is connected to the variable speed motor through the steel strand.

5. The hydrothermal coupled frozen soil direct shear creep test device according to claim 4, characterized in that, It further includes thermocouples, of which there are multiple thermocouples. One end of each thermocouple passes through the upper shear box and the lower shear box and is connected to the sample. The other end of each thermocouple passes through the bottom of the test tube.

6. The hydrothermal coupled frozen soil direct shear creep test device according to claim 5, characterized in that, The pressure load assembly includes a pressure sensor and a vertical force transmission rod. The pressure sensor is connected to the vertical force transmission rod, which passes through the top cover of the test cylinder and the liquid-separating chamber in sequence before contacting the top of the upper shear box.

7. A method of using the hydrothermal coupled frozen soil direct shear creep test device according to any one of claims 6, characterized in that, Includes the following steps: S1. Sample installation: The sample is installed in the shear box of the hydrothermal coupled frozen soil direct shear creep test device. S2. Freezing of the sample: Inject coolant into the test cylinder, evacuate the inside of the liquid separator, adjust the temperature of the coolant in the test cylinder and circulate the refrigerant in the cooling plate to freeze the sample. When the thermocouple inside the sample shows -20°C, keep it constant for 24 hours to complete the freezing of the sample. S3. Hydrothermal Coupling Creep: After the sample is frozen, the circulation of refrigerant in the cooling pan is stopped, and the temperature of the coolant in the test cylinder is adjusted to control the ambient temperature. When the internal temperature of the sample reaches the constant temperature of the test, a load is applied to the top of the sample through the pressure loading component, and water is replenished to the bottom of the sample through the water replenishment pan. The temperature of the refrigerant in the cooling pan is set to induce a hydrothermal coupling phenomenon inside the sample. The thermocouples inside the sample are observed. When the sample reaches the temperature gradient set for the test, the variable speed motor is started, and the constant load required for the creep test is adjusted through the tensile sensor. Then, the temperature data and deformation data of the sample are collected in real time.

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