Freezing soil dynamic pressure melting test device and method

Abstract

The invention relates to the technical field of pressure-melt testing, and particularly discloses a frozen soil dynamic pressure-melt testing device and method.The frozen soil dynamic pressure-melt testing device comprises a triaxial tester body used for containing a sample body and simulating the stress environment of the sample body; the test assembly is arranged on the sample main body, the test assembly comprises two connecting strips, and a plurality of connecting units are arranged between the two connecting strips; according to the frozen soil dynamic pressure melting test device and method, the connecting strip, the connecting unit, the test electrode and the thermistor are integrated together, and the test electrode and the thermistor are next to the sample main body, so that the layered resistivity change and the temperature change of the sample main body can be simultaneously and accurately tested. And the thermistor and the test electrode have the same height, so that the characteristic change of the sample main body at the same height can be measured, and the test diversity is improved.

Description

Technical Field

[0001] The invention relates to the technical field of compression-thawing testing, and in particular to a frozen soil dynamic compression-thawing testing device and method. Background Art

[0002] The distribution area of ​​frozen soil areas in my country accounts for about 75.9% of my country's land area. The soil filling materials used to build transportation infrastructure in this area have been subjected to the combined effects of vehicle dynamic loads and seasonal freeze-thaw for a long time. The deformation characteristics have changed significantly during operation and service, resulting in a large number of engineering diseases, which require huge resources to be rectified every year. The volume of transportation infrastructure such as roads and railways built in frozen soil areas has increased significantly, making the design of geotechnical structures in this area and the effective treatment of diseases more important. Studies have shown that the compression-thaw characteristics of frozen soil under dynamic action are the root cause of excessive deformation diseases in geotechnical structures in this area. A systematic study of the compression-thaw characteristics of frozen soil is of great significance for revealing the above-mentioned disease mechanism.

[0003] In the related technology, for example, a Chinese patent document with publication number CN113238026A discloses a soil freezing and thawing testing instrument. In the freeze-thaw test, the patent document realizes the experimental study of the multi-dimensional freeze-thaw characteristics of soil under plane strain state by loading pressure on the left and right, top and bottom of the sample, controlling the temperature, and monitoring the moisture, temperature and stress changes as well as the deformation of the sample.

[0004] The current test equipment for testing the compression-thaw characteristics of frozen soil measures the unfrozen water content test and the temperature field test separately when testing the unfrozen water content or temperature field inside the frozen soil. The test positions are not synchronized, which limits the results of the compression-thaw characteristics test of the frozen soil.

[0005] Therefore, the present invention proposes a frozen soil dynamic compression and thawing test device and method, which are used to reveal the disease occurrence mechanism of the above-mentioned transportation infrastructure under the combined action of freeze-thaw and dynamic load. Summary of the invention

[0006] The present invention provides a frozen soil dynamic compression-thawing test device and method, aiming to solve the problem in the related art that the unfrozen water content test and the temperature field test are measured separately, there is no close contact with the frozen soil, and the test positions are not consistent, resulting in inaccurate results of the frozen soil compression-thawing characteristics test.

[0007] A frozen soil dynamic compression melting test device of the present invention comprises: a triaxial test instrument body, the triaxial test instrument body is used to place a sample body and simulate the stress environment of the sample body; a test assembly is arranged on the sample body, the test assembly comprises two connecting strips, a plurality of connecting units are arranged between the two connecting strips, wherein a plurality of thermistors are arranged from top to bottom on one of the connecting units located at the edge, a plurality of test electrodes are arranged from top to bottom on the other plurality of connecting units, and the interval between two adjacent thermistors is the same as the interval between two adjacent test electrodes, and the characteristics of the sample body are detected simultaneously by the test electrodes and thermistors. By integrating the connecting strips, the connecting units, the test electrodes and thermistors together, and placing the test electrodes and thermistors close to the sample body, the unfrozen water content and temperature change of the sample body at the same height can be tested.

[0008] Furthermore, it also includes a triaxial membrane, the test component is installed on the triaxial membrane, the test component is installed on the sample body through the triaxial membrane, and the test component and the sample body are closely attached under the action of the test confining pressure.

[0009] Furthermore, it also includes a pressure chamber assembly, the pressure chamber assembly includes a protective cover, the sample body is located inside the protective cover, and a cooling copper tube is installed inside the protective cover. The cooling copper tube is connected to an external thermostatic device to adjust the temperature inside the protective cover to ensure the test temperature of the sample body.

[0010] Furthermore, the protective cover is also provided with a water inlet and an exhaust valve for injecting ethylene glycol solution into the protective cover.

[0011] Furthermore, it also includes an insulation tube, which is arranged outside the protective cover to form a sealed space between the protective cover and the insulation tube.

[0012] Furthermore, the heat insulating cylinder is provided with an air inlet and an air outlet for filling an inert gas into the sealed space formed between the protective cover and the heat insulating cylinder. By filling the inert gas, the heat insulating effect of the heat insulating cylinder can be improved, ensuring that the temperature of the test does not change too much.

[0013] Furthermore, the pressure chamber assembly also includes a top plate and a locking piece, the protective cover is mounted on the top plate, and the pressure chamber assembly is mounted to the triaxial testing instrument body through the locking piece.

[0014] Furthermore, a mounting hole is provided on the main body of the triaxial tester, a connecting piece is provided at the bottom of the top plate, and the lower end of the locking piece passes through the through hole and the connecting piece and is threadedly connected to the inner surface of the mounting hole. With this structure, the pressure chamber assembly can be easily installed and removed by twisting the connecting piece.

[0015] The second aspect of the present invention also provides a dynamic compression melting test method for frozen soil, comprising: fitting a test component on a triaxial membrane, and wrapping the triaxial membrane on the outer surface of a sample body, wherein a test electrode and a thermistor in the test component are tightly fitted to the sample body; starting a triaxial test instrument body, the triaxial test instrument body is used to simulate the stress condition of the sample body, and record data collected by the test electrodes and the thermistor.

[0016] By adopting the above technical solution, the beneficial effects of the present invention are as follows: by integrating the connecting strip, the connecting unit, the test electrode and the thermistor together, and placing the test electrode and the thermistor close to the sample body, the unfrozen water content and temperature change of the sample body can be tested simultaneously and accurately. The thermistor and the test electrode have the same height, and the characteristic changes of the sample body at the same height can be measured, thereby improving the diversity of the test and realizing the joint synchronous test of the mechanical parameters and the pressure melting characteristic parameters of the soil unit sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the overall structure of an embodiment of the present invention; Figure 2 is a schematic diagram of the internal structure of the protective cover according to an embodiment of the present invention; Figure 3 is a schematic diagram of a top view of the sample stage according to an embodiment of the present invention; Figure 4 is a schematic diagram of the interior of a heat-insulating cylinder according to an embodiment of the present invention; Figure 5 is a schematic diagram of a top view of the structure of a sample body according to an embodiment of the present invention; Figure 6 is a schematic diagram of the installation of a test assembly according to an embodiment of the present invention; Figure 7 It is a schematic diagram of the structure of the test component of an embodiment of the present invention.

[0018] Reference numerals: 11. Main body of triaxial testing machine; 111. Mounting hole; 12. Sample table; 13. Sample body; 20. Pressure chamber assembly; 21. Top plate; 211. Connector; 22. Protective cover; 23. Locking piece; 24. Cooling copper tube; 25. Exhaust valve; 26. Water inlet; 31. heat insulation tube; 311. sealing ring; 312. air inlet; 313. air outlet; 51. test assembly; 511. connection bar; 512. connection unit; 513. test electrode; 514. thermistor; 52. triaxial film; 60. Constant temperature device; 61. Transmission pipe; 70. Processor. DETAILED DESCRIPTION Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0019] In one embodiment, the current test device for testing the compression-thawing characteristics of frozen soil tests the frozen soil in a static environment when testing the unfrozen water content or temperature field inside the frozen soil. However, the soil fillings of some transportation facilities, such as railways, highways, airports and other transportation infrastructure, are subjected to the dynamic loads of upper vehicles for a long time. Therefore, the test method in a static environment is used to test the frozen soil under dynamic loads. It is impossible to truly simulate the actual storage environment and state of the soil fillings, which will cause great limitations in the test results.

[0020] In one embodiment, the test of the unfrozen water content or temperature field of frozen soil is an important means to study the engineering properties of frozen soil, the freeze-thaw process, and the effect of ice water changes on soil mechanical properties. Unfrozen water refers to the water in the soil that is below the freezing point but not frozen, while the temperature field reveals the temperature distribution in different areas of the soil. These tests help understand the water dynamics, heat transfer processes, and soil structural changes in frozen soil.

[0021] In one embodiment, a triaxial tester is a device used to study the mechanical properties and deformation characteristics of soil in soil mechanics tests. The triaxial test simulates the stress state of the soil in three axial directions and measures the response of the soil under different stress conditions, thereby helping engineers understand the strength, deformation, compressibility and other properties of the soil under different working conditions. In this embodiment, an improvement is made on the basis of the triaxial tester, so that it can simultaneously and accurately test the unfrozen water content and temperature changes of the sample body 13 at different heights. At the same time, by applying a dynamic load to the sample body 13 through the triaxial tester, the dynamic compression melting characteristics of the frozen soil can be tested.

[0022] like Figures 1 to 7 As shown, the dynamic compression-thawing test device for frozen soil of the present invention comprises a triaxial test instrument body 11. Through the triaxial test instrument body 11, the behavior of frozen soil under different stress states can be simulated, and the compression-thawing characteristics of frozen soil under dynamic state can be studied. A pressure chamber assembly 20 is arranged on the triaxial test instrument body 11 for simulating the environment of frozen soil under natural environment. A test assembly 51 is arranged inside the pressure chamber assembly 20. The test assembly 51 is used to synchronously test the unfrozen water content and temperature field inside the frozen soil, so as to obtain the compression-thawing characteristics of the frozen soil.

[0023] In one embodiment, a sample table 12 is provided in the main body 11 of the triaxial tester, and the sample table 12 is used to place a sample body 13, which is also a frozen soil body. In general, the sample body 13 is cylindrical in shape, because the cylindrical sample body 13 has the advantage of standardization in various mechanical experiments, and the cylindrical sample body 13 has a uniform geometric shape and symmetry, which is convenient for applying uniform stress during the experiment, thereby ensuring the accuracy and comparability of the test results. In addition, a mounting hole 111 is also provided on the main body 11 of the triaxial tester, and the mounting hole 111 is used to install the pressure chamber assembly 20, and is convenient for the subsequent disassembly and installation of the pressure chamber assembly 20. It should be noted that in this embodiment, the number of the mounting holes 111 is six, and in other embodiments, the number of the mounting holes 111 can be three, four or five, etc., which can be adjusted according to the specific implementation situation.

[0024] In one embodiment, the pressure chamber assembly 20 includes a top plate 21 and a locking member 23. The top plate 21 is circular in shape. A protective cover 22 is fixedly connected to the bottom of the top plate 21. The protective cover 22 is circular in shape. In other embodiments, the protective cover 22 may be square or other polygonal in shape. The protective cover 22 is made of a transparent material, which is convenient for the staff to observe the internal test process of the pressure chamber assembly 20. In addition, a connecting member 211 is also installed at the bottom of the top plate 21. The connecting member 211 is a hollow round rod. The number of the connecting members 211 is the same as the number of the mounting holes 111. A through hole is opened at the top of the top plate 21. The through hole is connected to the hollow inner cavity of the connecting member 211, so that the lower end of the locking member 23 passes through the through hole and the hollow inner cavity of the connecting member 211 and is threadedly connected to the inner surface of the mounting hole 111, thereby realizing the installation of the pressure chamber assembly 20 on the triaxial tester body 11, and the pressure chamber assembly 20 is conveniently removed from the triaxial tester body 11 by twisting the locking member 23.

[0025] In one embodiment, a cooling copper tube 24 and a temperature sensor are installed inside the protective cover 22, and the cooling copper tube 24 is connected to an external thermostat 60. Specifically, the thermostat 60 is connected to the cooling copper tube 24 through a transmission tube 61. Through the structure of the thermostat 60 and the cooling copper tube 24, the interior of the protective cover 22 can be cooled, and the temperature inside the protective cover 22 can be obtained through the temperature sensor and the test temperature can be effectively regulated to ensure that the test temperature does not deviate or lag from the set temperature.

[0026] A water inlet 26 is also installed on the pressure chamber assembly 20, through which ethylene glycol solution can be injected into the interior of the protective cover 22, and an exhaust valve 25 is installed on the top plate 21, and the exhaust valve 25 is connected to the interior of the protective cover 22. With the above structure, the exhaust valve 25 is opened, and the ethylene glycol solution is injected into the interior of the protective cover 22 through the water inlet 26 until the ethylene glycol solution is discharged from the exhaust valve 25. The ethylene glycol solution can exhaust gas during injection, ensuring that the test is not affected by bubbles, which helps to improve the accuracy of the experiment. At this time, the water inlet 26 and the exhaust valve 25 are closed, and the excess ethylene glycol solution on the top plate 21 is cleaned. In this embodiment, ethylene glycol solution is used as the confining pressure medium. With its low freezing point, good thermal conductivity, adaptability to high-pressure environment and high stability, it can ensure uniform transmission of confining pressure during the experiment, avoid bubble interference, and provide stable hydraulic conditions. It should be noted that, at the beginning of the test, the constant temperature device 60 controls the cooling copper tube 24 to cool down by controlling the negative temperature of the ethylene glycol solution circulating in the input transmission tube 61, and the cooling copper tube 24 is located in the ethylene glycol solution, thereby cooling down the ethylene glycol solution, thereby cooling and freezing the sample body 13. After freezing, the sample body 13 is subjected to a dynamic pressure melting characteristic test.

[0027] In one embodiment, an insulating tube 31 is further provided on the outside of the pressure chamber assembly 20. The insulating tube 31 is in the shape of a circular ring and is made of a transparent material, which is convenient for observing the internal test conditions. The insulating tube 31 is sleeved on the outside of the pressure chamber assembly 20, and sealing rings 311 are embedded at both upper and lower ends of the inner surface of the insulating tube 31 for sealing between the insulating tube 31 and the pressure chamber assembly 20, and an air inlet 312 and an air outlet 313 are provided on the insulating tube 31. By means of the above structure, inert gas is filled into the interior of the insulating tube 31 through the air inlet 312. The inert gas has a better thermal insulation effect and keeps the interior of the protective cover 22 warm.

[0028] In one embodiment, the test assembly 51 includes a connecting strip 511, and the connecting strip 511 is fixed on the triaxial film 52. The test assembly 51 is wrapped on the sample body 13 through the triaxial film 52 to test the sample body 13. There are two connecting strips 511, and a plurality of connecting units 512 are arranged between the two connecting strips 511. In this embodiment, the number of the connecting units 512 is four. In other embodiments, the number of the connecting units 512 can be five or six, etc., which can be adjusted according to specific actual conditions. Among the plurality of connecting units 512, a plurality of thermistors 514 are arranged on the connecting units 512 at the edge. The plurality of thermistors 514 are arranged equidistantly on the connecting units 512 from top to bottom. In this embodiment, the number of the plurality of thermistors 514 is four. In other embodiments, the number of the plurality of thermistors 514 can also be five or six, etc., which can be adjusted according to specific implementation conditions. A plurality of test electrodes 513 are arranged on the remaining plurality of connection units 512, and the arrangement of the plurality of test electrodes 513 is the same as that of the plurality of thermistors 514, and the number of the plurality of test electrodes 513 is the same as that of the plurality of thermistors 514. It should be noted that the four test electrodes 513 located at the same layer (or at the same height) are integrated into one channel, wherein the integration method can adopt PCB technology to measure the resistivity of this layer on the sample body 13.

[0029] In this embodiment, the connection strip 511, the connection unit 512, the test electrode 513 and the thermistor 514 are integrated together, and the test electrode 513 and the thermistor 514 are placed close to the sample body 13, so that the unfrozen water content and temperature change of the sample body 13 can be tested simultaneously and accurately. Specifically, through the multiple test electrodes 513 arranged up and down, the unfrozen water content change data of the sample body 13 at different heights can be measured by the resistivity change of the test electrodes 513, wherein the change of the unfrozen water content is characterized by the change of the resistivity; through the multiple thermistors 514 arranged up and down, the temperature change data of the sample body 13 at different heights can be measured by the thermistor 514. And the thermistor 514 is at the same height as the test electrode 513, so the characteristic change of the sample body 13 at the same height can be measured, thereby improving the diversity of the test.

[0030] In one embodiment, a temperature-sensitive color sticker may be attached to the outer surface of the triaxial film 52 and located in the observation slot of the cooling copper tube 24 to facilitate staff or cameras to observe the deformation morphology and temperature field changes of the sample in real time.

[0031] In addition, through the characteristics of the triaxial tester body 11, an adjustable dynamic load can be applied to the sample body 13 to simulate the test environment of the sample body 13 in various states, thereby realizing the research and testing of the dynamic compression-thawing characteristics of frozen soil.

[0032] The present invention also provides a frozen soil dynamic compression melting test method, comprising: fitting a test assembly 51 on a triaxial membrane 52, and wrapping the triaxial membrane 52 on the outer surface of a sample body 13, wherein the test electrode 513 and the thermistor 514 in the test assembly 51 are tightly fitted with the sample body 13. The sample body 13 is placed on a sample table 12, and the insulation tube 31 and the pressure chamber assembly 20 are installed on the triaxial tester body 11. The air inlet 312 and the air outlet 313 on the insulation tube 31 are opened, and an inert gas is filled through the air inlet 312, and the air inlet 312 and the air outlet 313 are closed after being filled. The exhaust valve 25 on the protective cover 22 is opened, and ethylene glycol solution is injected into the interior of the protective cover 22 through the water inlet 26 until the ethylene glycol solution is discharged from the exhaust valve 25, and the water inlet 26 and the exhaust valve 25 are closed. The constant temperature device 60 is started, and the constant temperature device 60 adjusts the internal temperature of the protective cover 22 to the test temperature through the cooling copper tube 24. The triaxial tester body 11 is started, and the triaxial tester body 11 is used to simulate the stress condition of the sample body 13 , and record the data collected by the test electrode 513 and the thermistor 514 through the processor 70 .

[0033] In one embodiment, the processor 70 is one of the core components in the computer system, responsible for executing program instructions, processing data and coordinating the work of various components inside the computer. The processor 70 is usually composed of millions or even billions of transistors, which are used for logical calculations and data transmission.

[0034] According to the above steps, the unfrozen water content and temperature field inside the sample body 13 are synchronously tested by the test electrode 513 and the thermistor 514; while realizing the dynamic loading mechanical property test of the soil during freezing and melting, the deformation morphology and temperature field changes of the sample body 13 can be observed in real time through the observation seam and the thermochromic sticker.

[0035] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0036] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0037] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A frozen soil dynamic compression melting test device, characterized in that: include: A triaxial testing machine body (11), wherein the triaxial testing machine body (11) is used to place a sample body (13) and simulate a stress environment of the sample body (13); A test component (51) is arranged on the sample body (13), the test component (51) comprising two connecting strips (511), a plurality of connecting units (512) being arranged between the two connecting strips (511), wherein a plurality of thermistors (514) are arranged from top to bottom on one of the connecting units (512) located at the edge, and a plurality of test electrodes (513) are arranged from top to bottom on the other plurality of connecting units (512), and the interval between two adjacent thermistors (514) is the same as the interval between two adjacent test electrodes (513), and the pressure melting characteristics of the sample body (13) are detected simultaneously through the test electrodes (513) and the thermistors.

2. The frozen soil dynamic compression thawing test device according to claim 1 is characterized in that: It also comprises a triaxial membrane (52), the test assembly (51) being mounted on the triaxial membrane (52), the test assembly (51) being mounted on the specimen body (13) via the triaxial membrane (52), and the test assembly (51) and the specimen body (13) being in close contact with each other under the action of the test confining pressure.

3. The frozen soil dynamic compression thawing test device according to claim 1 is characterized in that: The invention also comprises a pressure chamber assembly (20), wherein the pressure chamber assembly (20) comprises a protective cover (22), the sample body (13) is located inside the protective cover (22), and a cooling copper tube (24) is installed inside the protective cover (22) for adjusting the temperature around the sample body (13) inside the protective cover (22).

4. The frozen soil dynamic compression thawing test device according to claim 3 is characterized in that: The protective cover (22) is also provided with a water inlet (26) and an exhaust valve (25) for injecting ethylene glycol solution into the protective cover (22).

5. The frozen soil dynamic compression and thawing test device according to claim 1 is characterized in that: It also includes a heat-insulating cylinder (31), which is arranged outside the protective cover (22) so that a sealed space is formed between the protective cover (22) and the heat-insulating cylinder (31).

6. The frozen soil dynamic compression thawing test device according to claim 5 is characterized in that: An air inlet (312) and an air outlet (313) are provided on the heat-insulating cylinder (31) for filling an inert gas into a sealed space formed between the protective cover (22) and the heat-insulating cylinder (31).

7. The frozen soil dynamic compression thawing test device according to claim 3 is characterized in that: The pressure chamber assembly (20) further comprises a top plate (21) and a locking member (23); the protective cover (22) is mounted on the top plate (21); and the pressure chamber assembly (20) is mounted to the triaxial testing machine body (11) via the locking member (23).

8. The frozen soil dynamic compression thawing test device according to claim 7 is characterized in that: A mounting hole (111) is also provided on the main body (11) of the triaxial testing instrument. A connecting piece (211) is also installed on the bottom of the top plate (21). The lower end of the locking piece (23) passes through the through hole and the connecting piece (211) and is threadedly connected to the inner surface of the mounting hole (111).

9. A method for dynamic compression thawing of frozen soil, characterized in that: The frozen soil dynamic compression melting test device as claimed in claim 1 comprises: The test component (51) is bonded to the triaxial film (52), and the triaxial film (52) is wrapped around the outer surface of the sample body (13), wherein the test electrode (513) and the thermistor (514) in the test component (51) are tightly bonded to the sample body (13); The triaxial tester main body (11) is started, and the triaxial tester main body (11) is used to simulate the stress condition of the sample main body (13) and record the data collected by the test electrode (513) and the thermistor (514).

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