Pressure freezing triaxial test device and method for rock and soil medium

Abstract

The invention relates to a pressure freezing triaxial test device and method for a rock-soil medium, and belongs to the technical field of rock-soil pressure freezing experiments. The device comprises a pressure bearing mechanism, a triaxial loading control mechanism, a confining pressure loading mechanism, a freezing mechanism and a stress and deformation monitoring mechanism, and can realize accurate control of confining pressure, axial load, pore water pressure and temperature of a sample; through the CT imaging unit, the change of the rock and soil medium in freezing and triaxial loading processes can be monitored in real time. The method comprises the steps of sample placement, CT imaging, confining pressure control, pore water pressure adjustment, axial load application and stress deformation monitoring so as to analyze the mechanical property of the rock and soil medium. According to the invention, the change condition of the rock-soil medium in freezing and triaxial loading processes can be obtained in real time, and a test means is provided for the research of the mechanical properties of underground frozen rock-soil.

Description

Technical Field

[0001] The invention relates to the technical field of rock and soil pressurized freezing experiments, and in particular to a pressurized freezing triaxial test device and method for rock and soil media. Background Art

[0002] With the rapid development of underground space development and frozen soil engineering, the study of the mechanical behavior of geotechnical media under different stress states and temperature conditions has become increasingly important. Especially in cold regions or under artificial freezing conditions, the physical and mechanical properties of geotechnical materials will change significantly, which poses new challenges to the design and construction of tunnel excavation, foundation pit support and other projects.

[0003] At present, traditional triaxial test devices can simulate the deformation and failure process of specimens under three-dimensional stress states, but these devices usually do not consider the influence of temperature factors, especially the lack of research on the properties of geotechnical materials under freezing conditions. In addition, existing testing methods often make it difficult to simultaneously monitor multiple parameters, such as pore water pressure, radial deformation, axial deformation and other key indicators, which limits researchers' comprehensive understanding of the comprehensive mechanical properties of geotechnical media.

[0004] More importantly, current experimental methods lack an effective method to visually observe the changes in the internal structure of rock and soil, especially during the freezing process, the evolution of the rock and soil microstructure and its impact on the macroscopic mechanical properties are still unclear. Therefore, how to obtain the real-time changes of rock and soil samples during freezing and loading through advanced imaging technology has become one of the urgent problems to be solved in this field. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a pressurized freezing triaxial test device and method for rock and soil media. By setting a freezing mechanism that cooperates with a confining pressure loading mechanism, the experimenter can simulate and understand the mechanical behavior of rock and soil media in a complex environment, so as to study the evolution of rock and soil microstructure and its effect on macroscopic mechanics, and provide support for practical engineering applications.

[0006] To achieve the above-mentioned purpose, the present invention provides a pressurized freezing triaxial test device for rock and soil media, a pressurized freezing triaxial test device for rock and soil media, comprising:

[0007] A pressure-bearing mechanism, used to provide a stable pressure-bearing environment, the pressure-bearing mechanism comprising at least one component capable of forming a closed space, the closed space being used to accommodate a rock and soil sample to be tested;

[0008] A triaxial loading control mechanism is used to apply a controllable axial load to the geotechnical specimen;

[0009] A confining pressure loading mechanism, connected to the closed space, for controlling the confining pressure of the rock and soil sample during triaxial loading;

[0010] A freezing mechanism, located outside the enclosed space and connected to a cold source through a circulating cooling system, to achieve freezing of the rock and soil sample;

[0011] The stress and deformation monitoring mechanism is used to monitor the stress and deformation of the rock and soil samples in real time during the test.

[0012] Further, the pressure-bearing mechanism comprises a lower base, a PEEK pressure-bearing cylinder is arranged on the lower base, an upper flange is arranged at the upper end of the PEEK pressure-bearing cylinder, and a cavity for placing a sample is formed between the inner wall of the PEEK pressure-bearing cylinder, the upper flange and the lower base; a plurality of connecting columns are arranged on the upper surface of the upper flange, and a plurality of advancing screw covers are installed at the upper ends of the connecting columns;

[0013] The three-axis loading control mechanism includes a motor and a planetary reducer, the output end of the motor is connected to the planetary reducer, the output end of the planetary reducer is connected to a propulsion screw, the lower end of the planetary reducer is fixed to the top of the propulsion screw cover, the center of the propulsion screw passes through the propulsion screw cover, the lower end of the propulsion screw is sleeved with a propulsion cylinder, and the lower end of the propulsion cylinder is connected to an axial pressure head.

[0014] Furthermore, the confining pressure loading mechanism includes a confining pressure loading chamber and a confining pressure controller. The confining pressure loading chamber is located in the center of the cavity body and is connected to the confining pressure controller to control the confining pressure of the sample during the triaxial loading process.

[0015] Furthermore, the freezing mechanism comprises a sample freezing circulation pipeline groove arranged on the inner wall of the PEEK pressure-bearing cylinder, the sample freezing circulation pipeline groove is located outside the confining pressure loading chamber, and is connected to a freezing cold station through a cold medium circulation pipeline to achieve freezing of the sample.

[0016] Furthermore, it also includes a stress and deformation monitoring mechanism, which includes an LVDT sensor and a load sensor. The LVDT sensor is arranged on the propulsion screw cover and is configured to detect the downward displacement of the axial pressure head. The load sensor is arranged below the propulsion screw cover, and the propulsion cylinder passes through the center of the load sensor. The load sensor is used to obtain the axial force applied to the sample during loading.

[0017] Furthermore, it also includes a pore water pressure loading mechanism, which includes a pore water pressure controller, and the pore water pressure controller is connected to the confining pressure loading chamber to control the size of the pore water pressure in the sample.

[0018] Furthermore, the center of the axial pressure head passes through the upper flange, and a side seal is used to achieve blocking of the axial loading and radial confining pressure loading cavity space.

[0019] Furthermore, a fixing frame is provided on one of the connecting columns, and the propulsion cylinder slides through the fixing frame.

[0020] Furthermore, it also includes a CT imaging unit arranged outside the confining pressure loading mechanism, and the CT imaging unit is configured to obtain in real time the changes of the rock and soil medium during the freezing and triaxial loading process.

[0021] Furthermore, a method for conducting a test using the pressurized freezing triaxial test device for rock and soil media according to claim 9 comprises the following steps:

[0022] S1. Taking out a sample from the rock medium and placing it in the confining pressure loading cavity in the PEEK pressure-bearing cylinder for testing;

[0023] S2. Turn on the CT imaging unit to obtain the changes of the sample in the process in real time to carry out three-dimensional reconstruction;

[0024] S3, controlling the confining pressure of the sample during the triaxial loading process by the confining pressure controller, and applying a predetermined confining pressure to the sample;

[0025] S4. According to the preset requirements of the experiment, the pore water pressure inside the sample is adjusted by the pore water pressure loading mechanism, the temperature of the sample is adjusted or frozen by the freezing mechanism, and the pore water pressure in the sample is controlled by the pore water pressure controller to simulate freezing under different pore water pressure conditions;

[0026] S5. Apply a downward axial load to the sample through a three-axis loading control mechanism, wherein the motor drives the planetary reducer, and the planetary reducer drives the propulsion cylinder and the axial pressure head to move through the propulsion screw;

[0027] S6. The stress and deformation monitoring mechanism is used to monitor in real time the pore water pressure, radial deformation, axial deformation and axial pressure of the sample during the loading process.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention can accurately control the confining pressure, axial load, and pore water pressure of the sample through the confining pressure loading mechanism, the pore water pressure loading mechanism and the freezing mechanism. At the same time, the freezing mechanism can simulate different temperature conditions, thereby simulating the complex conditions of the underground environment, providing a reliable experimental platform for studying the mechanical behavior of rock and soil media in actual engineering.

[0030] (2) The present invention utilizes a CT imaging unit to monitor in real time the changes in the internal structure of the sample during freezing and triaxial loading, realizes three-dimensional reconstruction, and intuitively observes the evolution of the internal structure of the rock and soil. This comprehensive control and monitoring method enables researchers to comprehensively study the mechanical behavior of rock and soil media under different stress states and temperature conditions while simulating actual engineering conditions.

[0031] (3) The present invention integrates a variety of monitoring means, including LVDT sensors and load sensors, through stress and deformation monitoring mechanisms, which can monitor in real time the changes in multiple parameters of the sample during the loading process, including pore water pressure, radial deformation, axial deformation and axial pressure. The comprehensive analysis of these data helps to fully understand the comprehensive mechanical properties of rock and soil media, and provides important support for engineering designs such as tunnel excavation and foundation pit support in cold areas or under artificial freezing conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of a pressurized freezing triaxial test device for rock and soil media provided in an embodiment of the present invention; Explanation of reference numerals: 1. confining pressure controller; 2. pore water pressure controller; 3. high-pressure hose; 4. freezing cold station; 5. cold medium circulation pipeline; 6. motor; 7. planetary reducer; 8. LVDT sensor; 9. load sensor; 10. axial pressure head; 11. PEEK pressure cylinder; 12. upper flange; 13. lower base; 14. confining pressure loading chamber; 15. specimen freezing circulation pipeline groove; 16. specimen; 17. thrust screw; 18. thrust cylinder; 19. thrust screw cover; 20. connecting column; 21. fixing bracket. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0034] In the description of the present invention, it should be understood that the terms "center", "axial", "lateral", "upper", "lower", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0035] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0036] like Figure 1 As shown, an embodiment of the present invention provides a pressurized freezing triaxial test device for rock and soil media, comprising:

[0037] A pressure-bearing mechanism, used to provide a stable pressure-bearing environment, the pressure-bearing mechanism comprising at least one component capable of forming a closed space, the closed space being used to accommodate a rock and soil sample to be tested;

[0038] A triaxial loading control mechanism is used to apply a controllable axial load to the geotechnical specimen;

[0039] A confining pressure loading mechanism, connected to the closed space, for controlling the confining pressure of the rock and soil sample during triaxial loading;

[0040] A freezing mechanism, located outside the enclosed space and connected to a cold source through a circulating cooling system, to achieve freezing of the rock and soil sample;

[0041] The stress and deformation monitoring mechanism is used to monitor the stress and deformation of the rock and soil samples in real time during the test.

[0042] Specifically, the pressure-bearing mechanism includes a lower base 13, on which a PEEK pressure-bearing cylinder 11 is arranged, and an upper flange 12 is provided at the upper end of the PEEK pressure-bearing cylinder 11. A cavity for placing a sample 16 is formed between the inner wall of the PEEK pressure-bearing cylinder 11 and the upper flange 12 and the lower base 13; the PEEK pressure-bearing cylinder 11 is made of PEEK engineering plastic that is transparent to X-rays to facilitate detection of the sample 16.

[0043] A plurality of connecting columns 20 are arranged on the upper surface of the upper flange 12, and a propulsion screw cover 19 is installed on the upper end of the plurality of connecting columns 20;

[0044] Furthermore, the three-axis loading control mechanism includes a motor 6 and a planetary reducer 7, the output end of the motor 6 is connected to the planetary reducer 7, the output end of the planetary reducer 7 is connected to a propulsion screw 17, the lower end of the planetary reducer 7 is fixed to the top of the propulsion screw cover 19, the center of the propulsion screw 17 passes through the propulsion screw cover 19, the lower end of the propulsion screw 17 is sleeved with a propulsion cylinder 18, and the lower end of the propulsion cylinder 18 is connected to an axial pressure head 10;

[0045] Specifically, the confining pressure loading mechanism includes a confining pressure loading chamber 14 and a confining pressure controller 1. The confining pressure loading chamber 14 is located in the center of the cavity and is connected to the confining pressure controller 1 to control the confining pressure of the sample 16 during the triaxial loading process.

[0046] Specifically, the freezing mechanism includes a sample freezing circulation pipeline groove 15 arranged on the inner wall of the PEEK pressure-bearing cylinder 11 . The sample freezing circulation pipeline groove 15 is located outside the confining pressure loading chamber 14 and is connected to the freezing cold station 4 through the cold medium circulation pipeline 5 to achieve freezing of the sample 16 .

[0047] Furthermore, the pressurized frozen triaxial testing device for rock and soil media also includes a stress and deformation monitoring mechanism, which includes an LVDT sensor 8 and a load sensor 9. The LVDT sensor 8 is arranged on the thrust screw cover 19 and is configured to detect the downward displacement of the axial pressure head 10. The load sensor 9 is arranged below the thrust screw cover 19, and a thrust cylinder 18 passes through the center of the thrust screw cover. The load sensor 9 is used to obtain the axial force applied to the sample 16 during the loading process.

[0048] Optionally, the stress and deformation monitoring mechanism further includes a monitoring device for monitoring radial deformation.

[0049] Furthermore, the pressurized freezing triaxial testing device for rock and soil media also includes a pore water pressure loading mechanism, which includes a pore water pressure controller 2, which is connected to the confining pressure loading chamber 14 to control the size of the pore water pressure in the sample 16.

[0050] Preferably, the pore water pressure controller 2 is connected to the confining pressure loading chamber 14 via a high-pressure hose 3 .

[0051] Specifically, the center of the axial pressure head 10 passes through the upper flange 12 and adopts side sealing to achieve the blocking of the axial loading and radial confining pressure loading cavity space.

[0052] Specifically, a fixing frame 21 is disposed on one of the connecting columns 20 , and the propulsion tube 18 slides through the fixing frame 21 .

[0053] Furthermore, the pressurized freezing triaxial testing device for rock and soil media also includes a CT imaging unit arranged outside the confining pressure loading mechanism, and the CT imaging unit is configured to obtain in real time the changes of the rock and soil media during freezing and triaxial loading.

[0054] As an embodiment, a method for conducting a test using a pressurized frozen triaxial test apparatus for geotechnical media includes the following steps:

[0055] S1. Take out a sample 16 from the rock medium and place it in the confining pressure loading chamber 14 in the PEEK pressure tube 11 for testing;

[0056] S2, turning on the CT imaging unit to obtain the changes of the sample 16 in the process in real time to carry out three-dimensional reconstruction;

[0057] S3, controlling the confining pressure of the sample 16 during the triaxial loading process by the confining pressure controller 1, and applying a predetermined confining pressure to the sample 16;

[0058] S4. According to the preset requirements of the experiment, the pore water pressure inside the sample 16 is adjusted by the pore water pressure loading mechanism, the temperature of the sample 16 is adjusted or frozen by the freezing mechanism, and the magnitude of the pore water pressure in the sample 16 is controlled by the pore water pressure controller 2 to simulate freezing under different pore water pressure conditions;

[0059] S5, applying a downward axial load to the sample 16 through the three-axis loading control mechanism, wherein the motor 6 drives the planetary reducer 7, and the planetary reducer 7 drives the propulsion cylinder 18 and the axial pressure head 10 to move through the propulsion screw 17;

[0060] S6. The pore water pressure, radial deformation, axial deformation and axial pressure of the sample 16 during the loading process are monitored in real time by a stress and deformation monitoring mechanism.

[0061] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A pressurized freezing triaxial test device for rock and soil media, characterized in that: include: A pressure-bearing mechanism, used to provide a stable pressure-bearing environment, the pressure-bearing mechanism comprising at least one component capable of forming a closed space, the closed space being used to accommodate a rock and soil sample to be tested; A triaxial loading control mechanism is used to apply a controllable axial load to the geotechnical specimen; A confining pressure loading mechanism, connected to the closed space, for controlling the confining pressure of the rock and soil sample during triaxial loading; A freezing mechanism, located outside the enclosed space and connected to a cold source through a circulating cooling system, so as to achieve freezing of the rock and soil sample; The stress and deformation monitoring mechanism is used to monitor the stress and deformation of the rock and soil samples in real time during the test.

2. The pressurized freezing triaxial test device for rock and soil media according to claim 1 is characterized in that: The pressure-bearing mechanism comprises a lower base (13), a PEEK pressure-bearing cylinder (11) is arranged on the lower base (13), an upper flange (12) is arranged at the upper end of the PEEK pressure-bearing cylinder (11), and a cavity for placing a sample (16) is formed between the inner wall of the PEEK pressure-bearing cylinder (11), the upper flange (12) and the lower base (13); a plurality of connecting columns (20) are arranged on the upper surface of the upper flange (12), and a propulsion screw cover (19) is installed at the upper end of the plurality of connecting columns (20); The three-axis loading control mechanism comprises a motor (6) and a planetary reducer (7), the output end of the motor (6) is connected to the planetary reducer (7), the output end of the planetary reducer (7) is connected to a propulsion screw (17), the lower end of the planetary reducer (7) is fixed to the top of the propulsion screw cover (19), the center of the propulsion screw (17) passes through the propulsion screw cover (19), the lower end of the propulsion screw (17) is sleeved with a propulsion cylinder (18), and the lower end of the propulsion cylinder (18) is connected to an axial pressure head (10).

3. The pressurized freezing triaxial test device for rock and soil media according to claim 2 is characterized in that: The confining pressure loading mechanism comprises a confining pressure loading chamber (14) and a confining pressure controller (1); the confining pressure loading chamber (14) is located at the center of the cavity body and is connected to the confining pressure controller (1) to control the confining pressure of the sample (16) during the triaxial loading process.

4. The pressurized freezing triaxial test device for rock and soil media according to claim 3 is characterized in that: The freezing mechanism comprises a sample freezing circulation pipeline groove (15) arranged on the inner wall of the PEEK pressure-bearing cylinder (11); the sample freezing circulation pipeline groove (15) is located outside the confining pressure loading chamber (14) and is connected to a freezing cold station (4) via a cold medium circulation pipeline (5) to achieve freezing of the sample (16).

5. The pressurized freezing triaxial test device for rock and soil media according to claim 4 is characterized in that: The invention also comprises a stress and deformation monitoring mechanism, wherein the stress and deformation monitoring mechanism comprises an LVDT sensor (8) and a load sensor (9), wherein the LVDT sensor (8) is arranged on a propulsion screw cover (19) and is configured to detect the downward displacement of the axial pressure head (10), and the load sensor (9) is arranged below the propulsion screw cover (19) and has the propulsion cylinder (18) passing through its center, and the load sensor (9) is used to obtain the axial force applied to the sample (16) during the loading process.

6. The pressurized freezing triaxial test device for rock and soil media according to claim 5, characterized in that: It also includes a pore water pressure loading mechanism, which includes a pore water pressure controller (2). The pore water pressure controller (2) is connected to the confining pressure loading chamber (14) to control the magnitude of the pore water pressure in the sample (16).

7. The pressurized freezing triaxial test device for rock and soil media according to claim 2 is characterized in that: The center of the axial pressure head (10) passes through the upper flange (12), and a side seal is used to block the axial loading and radial confining pressure loading cavity space.

8. The pressurized freezing triaxial test device for rock and soil media according to claim 2 is characterized in that: A fixing frame (21) is provided on one of the connecting columns (20), and the propulsion cylinder (18) slides through the fixing frame (21).

9. The pressurized freezing triaxial test device for rock and soil media according to claim 6, characterized in that: It also includes a CT imaging unit arranged outside the confining pressure loading mechanism, and the CT imaging unit is configured to obtain in real time the changes of the rock and soil medium during freezing and triaxial loading.

10. A method for conducting a test using the pressurized freezing triaxial test device for rock and soil media according to claim 9, characterized in that: The following steps are involved: S1. taking out a sample (16) from a rock medium and placing it in the confining pressure loading chamber (14) in the PEEK pressure-bearing cylinder (11) for testing; S2, turning on the CT imaging unit to obtain the changes of the sample (16) in the process in real time to carry out three-dimensional reconstruction; S3, controlling the confining pressure of the sample (16) during the triaxial loading process by means of the confining pressure controller (1), and applying a predetermined confining pressure to the sample (16); S4. According to the preset requirements of the experiment, the pore water pressure inside the sample (16) is adjusted by the pore water pressure loading mechanism, the temperature of the sample (16) is adjusted or frozen by the freezing mechanism, and the magnitude of the pore water pressure in the sample (16) is controlled by the pore water pressure controller (2) to simulate freezing under different pore water pressure conditions; S5. Apply a downward axial load to the sample (16) through a three-axis loading control mechanism, wherein the motor (6) drives the planetary reducer (7), and the planetary reducer (7) drives the propulsion cylinder (18) and the axial pressure head (10) to move through the propulsion screw (17); S6. The stress and deformation monitoring mechanism is used to monitor in real time the pore water pressure, radial deformation, axial deformation and axial pressure of the sample (16) during the loading process.

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