A frozen soil high-pressure freezing test device for complex stress paths

Abstract

The utility model discloses a kind of frozen soil high-pressure freezing test devices for complex stress path, it is related to geotechnical engineering test technical field, device is through integrated pressure chamber, force assembly, temperature control system, pressure regulating system and data acquisition system, constitute a closed controllable test environment, can continuously execute isotropic consolidation, pressurized freezing and systematic multi-stress path shearing to hollow cylindrical sample. First, pressurized freezing sample under target average principal stress p, simulate deep stratum environment;Subsequently, under the condition that p remains unchanged, system changes intermediate principal stress coefficient b and principal stress direction angle α, carries out multi-path directional shearing test, to reveal the strength and deformation law of frozen soil in three-dimensional stress space completely, and calibrates three-dimensional strength criterion. The utility model realizes the coupling simulation of high-pressure freezing history and complex stress path, provides key technology and data support for the design and stability analysis of deep artificial freezing engineering.

Description

Technical Field

[0001] This utility model relates to the field of geotechnical engineering testing technology, and more specifically to a high-pressure freezing test device for frozen soil oriented towards complex stress paths, particularly a frozen soil mechanics test device that can couple and simulate the "high-pressure freezing" conditions of deep strata with "complex three-dimensional stress paths". Background Technology

[0002] Artificial ground freezing is increasingly being used in the construction of deep, water-rich strata. Deep frozen soil walls are situated in a high-stress environment and are subjected to complex three-dimensional stress paths caused by excavation and accompanied by rotation of the principal stress axes. Therefore, accurately understanding their mechanical behavior under complex stress conditions is crucial for engineering safety and design optimization.

[0003] Currently, conventional frozen soil mechanics testing equipment suffers from the following two significant technical bottlenecks:

[0004] First, existing equipment struggles to simulate real high-pressure freezing environments. Most permafrost testing equipment freezes under conditions of no confining pressure or normal pressure, failing to replicate the high ground stress state during the formation of permafrost in deep strata. This results in significant differences between the ice-cemented structure and initial stress state inside the sample and actual engineering conditions, affecting the reliability of the test results.

[0005] Secondly, traditional equipment has limited stress path control capabilities. Although hollow cylinder apparatuses can theoretically achieve complex stress paths, their temperature control systems lack precision and are not designed in conjunction with the loading system, making it impossible to achieve the "pressure freezing" process under high confining pressure. For example, existing temperature control devices (such as patent CN105183029A) mainly address the problem of static temperature field uniformity and lack the function of linkage with the loading system under high pressure. While conventional dynamic triaxial apparatuses can achieve freezing under solid pressure, their stress state is limited to axisymmetric conditions (i.e., intermediate principal stress coefficient b = 0), and they cannot independently control the principal stress coefficient b and principal stress direction angle α, thus failing to simulate a true three-dimensional stress path.

[0006] Therefore, there is an urgent need in this field for an experimental device that can integrate the two key technical aspects of "high-pressure freezing environment simulation" and "complex three-dimensional stress path loading" to achieve a realistic simulation of the entire process of deep permafrost from formation to failure. Utility Model Content

[0007] In view of this, the present invention provides a high-pressure freezing test device for frozen soil with complex stress paths, which aims to solve the above-mentioned technical problems.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A high-pressure freezing test apparatus for frozen soil with complex stress paths includes: a pressure chamber base and a pressure chamber shell sealed on the pressure chamber base; and further includes:

[0010] The sample assembly includes a cylindrical sample, an annular lower end, an annular upper end, a lower pressure head, and an upper pressure head; the annular lower end and the annular upper end are respectively pressed against the two ends of the cylindrical sample; the lower pressure head is sealed and engaged with the annular lower end, and the upper pressure head is sealed and engaged with the annular upper end, so that a sealed inner cavity is formed on the inner side of the cylindrical sample and a sealed outer cavity is formed on the outer side of the cylindrical sample.

[0011] The force-applying component has its working end passing through the top wall of the pressure chamber shell from top to bottom and connected to the upper pressure head. The force-applying component can apply axial pressure and torque to the cylindrical sample through its working end.

[0012] A temperature control system is used to regulate the temperature of the sealed inner cavity and the sealed outer cavity;

[0013] A pressure regulating system for regulating the pressure of the sealed inner cavity and the sealed outer cavity;

[0014] The data acquisition system collects data from the test process using temperature and pressure sensors.

[0015] Through the above technical solution, this utility model organically integrates the pressure chamber, force application components, temperature control system, pressure regulation system, and data acquisition system through an integrated structural design, constructing a closed and controllable high-pressure freezing test environment. Its core advantage lies in its ability to continuously complete sample consolidation, pressure freezing, and shear testing under complex stress paths within a single system. This achieves high-precision simulation of the entire process of deep permafrost formation and stress, solving the key technical challenge of traditional equipment's inability to couple the high-stress freezing history with the actual three-dimensional stress path.

[0016] Preferably, in the above-mentioned high-pressure freezing test device for frozen soil oriented to complex stress paths, an inner membrane layer that adheres to the inner wall of the cylindrical specimen is sealed between the inner edges of the lower annular end and the upper annular end, and an outer membrane layer that adheres to the outer wall of the cylindrical specimen is sealed between the outer edges of the lower annular end and the upper annular end.

[0017] Preferably, in the above-mentioned high-pressure freezing test device for frozen soil oriented to complex stress paths, a lower sealing ring is provided between the lower annular end and the lower pressure head, and an upper sealing ring is provided between the upper annular end and the upper pressure head.

[0018] Preferably, in the above-mentioned high-pressure freezing test device for frozen soil oriented towards complex stress paths, the force application component includes a reaction gantry frame arranged across the outer shell of the pressure chamber. A fixed cylinder of an axial force application cylinder is rotatably connected to the top crossbeam of the reaction gantry frame. An axial force application rod is connected to the telescopic cylinder of the axial force application cylinder via a coupling. The axial force application rod passes through the top wall of the outer shell of the pressure chamber and is connected to the upper pressure head. A dynamic seal is provided between the axial force application rod and the top wall of the outer shell of the pressure chamber. A fixed cylinder of a torque force application cylinder is fixedly connected to one side of the reaction gantry frame. A connecting seat is fixedly sleeved on the outer side of the axial force application cylinder. The telescopic cylinder of the torque force application cylinder is hinged to one side of the connecting seat, so that the telescopic movement of the torque force application cylinder can drive the axial force application cylinder to rotate.

[0019] Preferably, in the above-mentioned high-pressure freezing test device for frozen soil oriented to complex stress paths, the temperature control system includes an inner cavity temperature control subsystem and an outer cavity temperature control subsystem; the inner cavity temperature control subsystem and the outer cavity temperature control subsystem are respectively used to regulate the temperature of the sealed inner cavity and the sealed outer cavity.

[0020] Preferably, in the above-mentioned high-pressure freezing test device for frozen soil with complex stress paths, the internal cavity temperature control subsystem includes an internal cavity heating and cooling section, an inverted U-shaped temperature control tube, and an internal cavity temperature control circulation pipeline; the internal cavity heating and cooling section is located outside the outer shell of the pressure chamber, the inverted U-shaped temperature control tube is fixed to the top surface of the lower pressure head and located in the sealed inner cavity, and the internal cavity temperature control circulation pipeline is connected between the two openings of the inverted U-shaped temperature control tube and the internal cavity heating and cooling section.

[0021] Preferably, in the above-mentioned high-pressure freezing test device for frozen soil with complex stress paths, the external cavity temperature control subsystem includes an external cavity heating and cooling unit, a double helix circulation pipeline, and an external cavity temperature control circulation pipeline; the external cavity heating and cooling unit is located outside the outer shell of the pressure chamber, the double helix circulation pipeline is fixed to the inner wall of the outer shell of the pressure chamber, and the external cavity temperature control circulation pipeline is connected between the inlet and outlet of the double helix circulation pipeline and the external cavity heating and cooling unit.

[0022] Preferably, in the above-mentioned high-pressure freezing test device for frozen soil with complex stress paths, the pressure regulation system includes an outer cavity pressure-volume servo-controlled booster and an inner cavity pressure-volume servo-controlled booster. The outer cavity pressure-volume servo-controlled booster is connected to the sealed outer cavity, and the inner cavity pressure-volume servo-controlled booster is connected to the sealed inner cavity. Pressure is increased by injecting hydraulic oil.

[0023] Preferably, the above-mentioned high-pressure freezing test device for frozen soil with complex stress paths further includes a counter-pressure-volume servo-controlled booster, which is connected to the top and bottom of the cylindrical specimen through drainage pipes.

[0024] This utility model also provides a test method for a high-pressure freezing test device for frozen soil with complex stress paths, including the following steps:

[0025] Pressure freezing step: Inside the pressure chamber shell, the cylindrical specimen is frozen to the target temperature T while maintaining a non-zero target average principal stress p.

[0026] Systematic multi-stress path test procedure: Under the condition of keeping the target average principal stress p constant, for the cylindrical specimen that has been frozen under pressure, one or two variables of the intermediate principal stress coefficient b and principal stress direction angle α are systematically changed by independently controlling the axial force, torque, inner confining pressure and outer confining pressure, and a directional shear test is performed for each stress path combination.

[0027] Three-dimensional mechanical property characterization steps: Based on the test results under different stress paths, construct constitutive relations or strength criteria to characterize the mechanical response of high-pressure frozen soil in a three-dimensional stress space containing variables b and α.

[0028] Through the above technical solution, this utility model takes "pressure freezing - system variable path shearing - three-dimensional mechanical characterization" as the core process, and for the first time introduces the history of high-pressure freezing into the study of complex stress paths. Under the condition of keeping the average principal stress constant, it can systematically control the principal stress coefficient b and the principal stress direction angle α, comprehensively reveal the mechanical behavior of frozen soil in three-dimensional stress space, and provide a reliable data basis for calibrating three-dimensional strength criteria and constitutive models applicable to deep freezing engineering.

[0029] As can be seen from the above technical solution, compared with the prior art, this utility model discloses a high-pressure freezing test device for frozen soil with complex stress paths, which has the following beneficial effects:

[0030] 1. It pioneered a complete "environmental simulation-mechanical testing" chain: by introducing the key factor of "high-pressure freezing history" into the study of complex stress paths, it has achieved a complete reproduction of the life cycle of deep permafrost in the laboratory.

[0031] 2. It provides unprecedented research capabilities: It can independently and systematically control b and α, and for the first time realizes a comprehensive and systematic mapping of the mechanical properties of high-pressure frozen soil in three-dimensional stress space.

[0032] 3. Output results directly serve engineering practice: The three-dimensional strength criteria and constitutive models obtained through this method can be directly used for the three-dimensional stability analysis and optimization design of projects such as deep frozen walls, significantly improving the accuracy and economy of the design. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0034] Figure 1 The attached figure is a schematic diagram of the high-pressure freezing test device for frozen soil with complex stress paths provided by this utility model.

[0035] Figure 2 The attached figure is a structural schematic diagram of the force-applying component provided by this utility model;

[0036] Figure 3 The attached figure is a schematic diagram of the longitudinal section projection distribution of the temperature sensor provided by this utility model along the sample height direction;

[0037] Figure 4 The attached figure is a schematic diagram showing the distribution of the temperature sensor provided by this utility model along the radial cross section of the sample;

[0038] Figure 5 The attached figure shows the cooling curves of the device provided by this utility model at different target temperatures;

[0039] Figure 6 The attached figure shows the variation of peak generalized shear strength under different b-values ​​provided by this utility model;

[0040] Figure 7 The attached figure is a comparison of the prediction and experimental data of the extended SMP criterion provided by this utility model on the π plane.

[0041] in:

[0042] 1-Pressure chamber base; 2-Pressure chamber shell; 3-Cylindrical sample; 4-Annular lower end; 5-Annular upper end; 6-Lower pressure head; 7-Upper pressure head; 8-Sealed inner cavity; 9-Sealed outer cavity; 10-Data acquisition system; 11-Temperature sensor; 12-Pressure sensor; 13-Inner membrane layer; 14-Outer membrane layer; 15-Lower sealing ring; 16-Upper sealing ring; 17-Reaction gantry frame; 18-Axial force cylinder; 19-Coupling; 2 0-Axial force-applying rod; 21-Torque force-applying cylinder; 22-Connecting seat; 23-Inner cavity heating and cooling unit; 24-Inverted U-shaped temperature control tube; 25-Inner cavity temperature control circulation pipeline; 26-Outer cavity heating and cooling unit; 27-Double spiral circulation pipeline; 28-Outer cavity temperature control circulation pipeline; 29-Outer cavity pressure-volume servo control booster; 30-Inner cavity pressure-volume servo control booster; 31-Back pressure-volume servo control booster; 32-Drainage pipeline. Detailed Implementation

[0043] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0044] See appendix Figure 1 This utility model discloses a high-pressure freezing test device for frozen soil with complex stress paths, comprising: a pressure chamber base 1 and a pressure chamber outer shell 2 sealed and fastened to the pressure chamber base 1; and further comprising:

[0045] The sample assembly includes a cylindrical sample 3, an annular lower end 4, an annular upper end 5, a lower pressure head 6, and an upper pressure head 7. The annular lower end 4 and the annular upper end 5 are respectively pressed against the two ends of the cylindrical sample 3. The lower pressure head 6 is sealed and engaged with the annular lower end 4, and the upper pressure head 7 is sealed and engaged with the annular upper end 5, so that a sealed inner cavity 8 is formed on the inner side of the cylindrical sample 3, and a sealed outer cavity 9 is formed on the outer side of the cylindrical sample 3.

[0046] The force application component has its working end passing through the top wall of the pressure chamber shell 2 from top to bottom and connected to the upper pressure head 7. The force application component can apply axial pressure and torque to the cylindrical sample 3 through its working end.

[0047] The temperature control system is used to regulate the temperature of the sealed inner cavity 8 and the sealed outer cavity 9;

[0048] The pressure regulation system is used to regulate the pressure in the sealed inner cavity 8 and the sealed outer cavity 9;

[0049] The data acquisition system 10 collects test process data through temperature sensor 11 and pressure sensor 12.

[0050] Temperature sensor 11 Figure 1 As shown, the pressure sensor 12 is represented by a triangle. Figure 1 The diagram is represented by black squares, and the specific distribution is as follows: Figure 1 As shown.

[0051] Temperature sensor 11 is arranged in the sealed outer cavity 9 corresponding to the top, middle and bottom of the cylindrical sample 3, and is also arranged in the middle of the sealed inner cavity 8, and is also arranged in the top, middle and bottom of the cylindrical sample 3.

[0052] Pressure sensors 12 are arranged at the working end of the force application component, at the bottom of the cylindrical sample 3, and on each pipeline.

[0053] To further optimize the above technical solution, an inner membrane layer 13 that adheres to the inner wall of the cylindrical sample 3 is sealed between the inner edges of the annular lower end 4 and the annular upper end 5, and an outer membrane layer 14 that adheres to the outer wall of the cylindrical sample 3 is sealed between the outer edges of the annular lower end 4 and the annular upper end 5.

[0054] To further optimize the above technical solution, a lower sealing ring 15 is provided between the lower annular end head 4 and the lower pressure head 6, and an upper sealing ring 16 is provided between the upper annular end head 5 and the upper pressure head 7.

[0055] See appendix Figure 2 The force-applying component includes a reaction gantry 17 arranged across the outer shell 2 of the pressure chamber. The fixed cylinder of the axial force-applying cylinder 18 is rotatably connected to the top crossbeam of the reaction gantry 17. The telescopic cylinder of the axial force-applying cylinder 18 is connected to an axial force-applying rod 20 through a coupling 19. The axial force-applying rod 20 passes through the top wall of the pressure chamber outer shell 2 and is connected to the upper pressure head 7. A dynamic seal is provided between the axial force-applying rod 20 and the top wall of the pressure chamber outer shell 2. The fixed cylinder of the torque force-applying cylinder 21 is fixedly connected to one side of the reaction gantry 17. A connecting seat 22 is fixedly sleeved on the outer side of the axial force-applying cylinder 18. The telescopic cylinder of the torque force-applying cylinder 21 is hinged to one side of the connecting seat 22, so that the telescopic movement of the torque force-applying cylinder 21 can drive the axial force-applying cylinder 18 to rotate.

[0056] To further optimize the above technical solution, the temperature control system includes an inner cavity temperature control subsystem and an outer cavity temperature control subsystem; the inner cavity temperature control subsystem and the outer cavity temperature control subsystem are used to regulate the temperature of the sealed inner cavity 8 and the sealed outer cavity 9, respectively.

[0057] To further optimize the above technical solution, the internal cavity temperature control subsystem includes an internal cavity heating and cooling section 23, an inverted U-shaped temperature control tube 24, and an internal cavity temperature control circulation pipeline 25. The internal cavity heating and cooling section 23 is located outside the pressure chamber shell 2. The inverted U-shaped temperature control tube 24 is fixed on the top surface of the lower pressure head 6 and located in the sealed internal cavity 8. The internal cavity temperature control circulation pipeline 25 is connected between the two openings of the inverted U-shaped temperature control tube 24 and the internal cavity heating and cooling section 23.

[0058] To further optimize the above technical solution, the external cavity temperature control subsystem includes an external cavity heating and cooling unit 26, a double helix circulation pipe 27, and an external cavity temperature control circulation pipe 28. The external cavity heating and cooling unit 26 is located outside the pressure chamber shell 2, the double helix circulation pipe 27 is fixed to the inner wall of the pressure chamber shell 2, and the external cavity temperature control circulation pipe 28 is connected between the inlet and outlet of the double helix circulation pipe 27 and the external cavity heating and cooling unit 26.

[0059] Both the inner cavity heating and cooling section 23 and the outer cavity heating and cooling section 26 are conventional cooling and heating structures, which can be achieved through structures such as compressors or heating wires, and will not be described in detail here.

[0060] To further optimize the above technical solution, the pressure regulation system includes an external cavity pressure-volume servo control booster 29 and an internal cavity pressure-volume servo control booster 30. The external cavity pressure-volume servo control booster 29 is connected to the sealed external cavity 9, and the internal cavity pressure-volume servo control booster 30 is connected to the sealed internal cavity 8. Pressure is increased by injecting hydraulic oil. The sealed internal cavity 8 and the sealed external cavity 9 are also filled with hydraulic oil.

[0061] To further optimize the above technical solution, a back pressure-volume servo control booster 31 is also included. The back pressure-volume servo control booster 31 is connected to the top and bottom of the cylindrical sample 3 through a drainage pipe 32.

[0062] The external cavity pressure-volume servo control booster 29, the internal cavity pressure-volume servo control booster 30, and the reverse pressure-volume servo control booster 31 are all hydraulic cylinder-type pressurization structures, which will not be described in detail here.

[0063] Pressure sensor 12 is arranged on the connecting pipes of axial force rod 20, external cavity pressure-volume servo control booster 29 and internal cavity pressure-volume servo control booster 30, and drain pipe 32.

[0064] The test method for the high-pressure freezing test device for frozen soil with complex stress paths provided in this embodiment includes the following steps:

[0065] Pressure freezing procedure: Inside the pressure chamber shell 2, under the condition of maintaining a non-zero target average principal stress p, the cylindrical specimen 3 is frozen to the target temperature T.

[0066] Systematic multi-stress path test procedure: Under the condition of keeping the target average principal stress p constant, for the cylindrical specimen 3 that has been frozen under pressure, one or two variables of the intermediate principal stress coefficient b and principal stress direction angle α are systematically changed by independently controlling the axial force, torque, inner confining pressure and outer confining pressure, and a directional shear test is performed for each stress path combination.

[0067] Three-dimensional mechanical property characterization steps: Based on the test results under different stress paths, construct constitutive relations or strength criteria to characterize the mechanical response of high-pressure frozen soil in a three-dimensional stress space containing variables b and α.

[0068] To further optimize the above technical solution, the systematic multi-stress path testing procedure specifically includes at least one of the following research modes:

[0069] Fixed α variable b mode: Keep the principal stress direction angle α at a fixed value, and systematically vary the intermediate principal stress coefficient b between 0 and 1 to conduct a set of shear tests;

[0070] Fixed b variable α mode: Keep the intermediate principal stress coefficient b at a fixed value, and systematically vary the principal stress direction angle α between 0° and 90° to conduct a set of shear tests.

[0071] To further optimize the above technical solution, the constructed three-dimensional strength criterion is an extended spatially active plane criterion, which introduces a temperature-dependent cementation stress f. T (T) is used to characterize the contribution of ice cementation to strength, and the peak strength data obtained by the systematic multi-stress path test procedure are used to calibrate the parameters of the criterion.

[0072] To further optimize the above technical solution, the temperature control system is configured to perform a pressure freezing step while maintaining the target average principal stress p in the device, and to maintain the uniformity error of the sample temperature field ≤ ±0.1℃ throughout the test.

[0073] To further optimize the above technical solution, the data acquisition system 10 includes a programmable stress path generation module, which allows users to define the b-value, α-value, and generalized shear stress q. s The functional relationship is determined and automatically solved by the system to control W and M. T P i P o This is to achieve the custom stress path.

[0074] To further optimize the above technical solution, the pressure regulation system is configured to maintain the target average principal stress p within ±2% of its set value during the pressurization and freezing step and the systematic multi-stress path test step.

[0075] Example 1:

[0076] The influence of the intermediate principal stress coefficient b on the strength of high-pressure frozen saturated medium sand under the conditions of mean principal stress p = 4 MPa and temperature T = -10℃ was systematically studied, and the extended SMP criterion was calibrated.

[0077] Sample preparation and installation: Prepare and saturate cylindrical specimens 3 according to standard methods.

[0078] Saturation and consolidation: The cylindrical specimen 3 was subjected to back pressure saturation (B value > 0.97) inside the outer shell 2 of the pressure chamber. Then, a confining pressure of p = 4 MPa was applied for drainage consolidation.

[0079] Pressure freezing: Maintain p = 4 MPa, start the temperature control system, cool the sample to -10 ± 0.1℃ and keep the temperature constant.

[0080] Systematic multi-stress path test: Using software settings, while keeping p = 4 MPa and α = 30° constant, b = 0, 0.25, 0.5, 0.75, and 1 were sequentially set, and deviatoric stress was applied at a constant rate to induce shear failure. The peak strength q at each b value was recorded. f .

[0081] Three-dimensional mechanical property characterization: The experimental data points (b, q) are used to characterize the mechanical properties. f By fitting the data, we obtain the intensity attenuation formula: q f =-2.41b 2 +0.38b+10.31. Using this complete set of intensity data, the temperature dependence parameter in the extended SMP criterion was calibrated, and the results show that the criterion has high prediction accuracy (error <3%).

[0082] This embodiment demonstrates the powerful ability of the present invention's method to reveal the three-dimensional strength law of high-pressure frozen soil, as well as the reliability and accuracy of the device in implementing the method.

[0083] Example 2:

[0084] like Figure 3 and Figure 4 As shown, a cross-sectional view along the height of the sample reveals the distribution of the eight internal temperature sensors 11, with two located at the top and bottom, and six distributed at different heights and radially within the sample. A cross-sectional view of the middle section of the sample shows the circumferential and radial distribution of the temperature sensors.

[0085] The cooling curves of the device at different target temperatures are shown in the figure below. Figure 5 (Example: -5℃ cooling curve) As shown, multiple curves represent the temperature changes over time at different locations of the sample (outer top, outer middle, outer bottom, inner middle, upper end, lower end), and they all converge to the target temperature line, indicating excellent uniformity and stability.

[0086] Figure 6 The graph shows the variation of peak generalized shear strength under different b values.

[0087] Figure 7 A graph showing the comparison between predictions and experimental data for the extended SMP criterion in the π plane is presented.

[0088] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0089] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-pressure freezing test apparatus for frozen soil under complex stress paths, comprising: A pressure chamber base (1) and a pressure chamber outer shell (2) with a sealing buckle disposed on the pressure chamber base (1); characterized in that it further includes: The sample assembly includes a cylindrical sample (3), an annular lower end (4), an annular upper end (5), a lower pressure head (6), and an upper pressure head (7); the annular lower end (4) and the annular upper end (5) are respectively pressed against the two ends of the cylindrical sample (3); the lower pressure head (6) is sealed and engaged with the annular lower end (4), and the upper pressure head (7) is sealed and engaged with the annular upper end (5), so that a sealed inner cavity (8) is formed on the inner side of the cylindrical sample (3), and a sealed outer cavity (9) is formed on the outer side of the cylindrical sample (3); The force-applying component has its working end passing through the top wall of the pressure chamber shell (2) from top to bottom and connected to the upper pressure head (7). The force-applying component can apply axial pressure and torque to the cylindrical sample (3) through its working end. A temperature control system for adjusting the temperature of the sealed inner cavity (8) and the sealed outer cavity (9); A pressure regulating system for regulating the pressure of the sealed inner cavity (8) and the sealed outer cavity (9); The data acquisition system (10) acquires test process data through a temperature sensor (11) and a pressure sensor (12).

2. The high-pressure freezing test device for frozen soil with complex stress paths according to claim 1, characterized in that, An inner membrane layer (13) that adheres to the inner wall of the cylindrical sample (3) is sealed between the inner edges of the lower annular end (4) and the upper annular end (5), and an outer membrane layer (14) that adheres to the outer wall of the cylindrical sample (3) is sealed between the outer edges of the lower annular end (4) and the upper annular end (5).

3. The high-pressure freezing test device for frozen soil with complex stress paths according to claim 1, characterized in that, A lower sealing ring (15) is provided between the lower annular end (4) and the lower pressure head (6), and an upper sealing ring (16) is provided between the upper annular end (5) and the upper pressure head (7).

4. The high-pressure freezing test device for frozen soil with complex stress paths according to claim 1, characterized in that, The force-applying assembly includes a reaction gantry (17) arranged across the pressure chamber shell (2). A fixed cylinder of an axial force-applying cylinder (18) is rotatably connected to the top crossbeam of the reaction gantry (17). An axial force-applying rod (20) is connected to the telescopic cylinder of the axial force-applying cylinder (18) via a coupling (19). The axial force-applying rod (20) passes through the top wall of the pressure chamber shell (2) and is connected to the upper pressure head (7). A dynamic seal is provided between the pressure chamber shell (2) and the top wall. The fixed cylinder of the torque-applying cylinder (21) is fixedly connected to one side of the reaction force gantry (17). A connecting seat (22) is fixedly sleeved on the outer side of the axial force-applying cylinder (18). The telescopic cylinder of the torque-applying cylinder (21) is hinged to one side of the connecting seat (22), so that the telescopic action of the torque-applying cylinder (21) can drive the axial force-applying cylinder (18) to rotate.

5. The high-pressure freezing test device for frozen soil with complex stress paths according to claim 1, characterized in that, The temperature control system includes an inner cavity temperature control subsystem and an outer cavity temperature control subsystem; the inner cavity temperature control subsystem and the outer cavity temperature control subsystem are respectively used to regulate the temperature of the sealed inner cavity (8) and the sealed outer cavity (9).

6. The high-pressure freezing test device for frozen soil with complex stress paths according to claim 5, characterized in that, The internal cavity temperature control subsystem includes an internal cavity heating and cooling unit (23), an inverted U-shaped temperature control tube (24), and an internal cavity temperature control circulation pipeline (25). The internal cavity heating and cooling unit (23) is located outside the outer shell (2) of the pressure chamber. The inverted U-shaped temperature control tube (24) is fixed to the top surface of the lower pressure head (6) and located in the sealed internal cavity (8). The internal cavity temperature control circulation pipeline (25) is connected between the two openings of the inverted U-shaped temperature control tube (24) and the internal cavity heating and cooling unit (23).

7. The high-pressure freezing test device for frozen soil with complex stress paths according to claim 5, characterized in that, The external cavity temperature control subsystem includes an external cavity heating and cooling unit (26), a double helix circulation pipeline (27), and an external cavity temperature control circulation pipeline (28). The external cavity heating and cooling unit (26) is located outside the pressure chamber shell (2). The double helix circulation pipeline (27) is fixed to the inner wall of the pressure chamber shell (2). The external cavity temperature control circulation pipeline (28) is connected between the inlet and outlet of the double helix circulation pipeline (27) and the external cavity heating and cooling unit (26).

8. The high-pressure freezing test device for frozen soil with complex stress paths according to claim 1, characterized in that, The pressure regulation system includes an external cavity pressure-volume servo control booster (29) and an internal cavity pressure-volume servo control booster (30). The external cavity pressure-volume servo control booster (29) is connected to the sealed external cavity (9), and the internal cavity pressure-volume servo control booster (30) is connected to the sealed internal cavity (8). Pressure is increased by injecting hydraulic oil.

9. The high-pressure freezing test device for frozen soil with complex stress paths according to claim 1, characterized in that, It also includes a back pressure-volume servo control booster (31), which is connected to the top and bottom of the cylindrical sample (3) through a drain pipe (32).

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