CN112098231A - A large-scale triaxial mechanical test device and test method for coarse-grained soil simulating freeze-thaw cycles - Google Patents

Abstract

A large triaxial mechanical test device and a test method for simulating freeze-thaw cycle coarse-grained soil relate to a triaxial mechanical test device and a test method. The invention solves the problem that the existing test device can not test the mechanical property parameters of the coarse aggregate sample after consolidation and drainage under the conditions of freeze-thaw cycle and loading. The cylinder body is arranged on a bottom plate, and a surrounding pressure system is connected with the bottom plate; the lower pressure plate is arranged on the bottom plate in a sealing mode, the lower water permeable plate is arranged at the upper end of the lower pressure plate, the sample is arranged at the upper end of the lower water permeable plate, the upper pressure plate is arranged at the upper end of the sample, the circulating pipe is sleeved on the sample through a barrel cover arranged on the barrel body, the freeze-thaw circulating system is connected with the circulating pipe, the guide sleeve is arranged at the upper end of the barrel cover, and the lower portion of the bearing rod penetrates through the guide sleeve and the barrel cover to be connected with the upper pressure plate. The method comprises a saturation and consolidation process, a freeze-thaw cycle-loading process and a triaxial compression process in sequence. The invention is used for large triaxial mechanical test of simulation freeze-thaw cycle coarse-grained soil.

Description

A large-scale triaxial mechanical test device and test method for coarse-grained soil simulating freeze-thaw cycles

technical field

The invention relates to a triaxial mechanical test device and a test method, in particular to a large-scale triaxial mechanical test device and a test method for simulating a freeze-thaw cycle of coarse-grained soil, belonging to the technical field of geotechnical mechanics and test testing.

Background technique

Earth-rock dams have been widely used in the construction of hydropower projects in my country. In recent years, 300m-level extra-high earth-rock dams have been built, especially high earth-rock dam projects in cold regions. Due to the changeable climate in cold regions, the large temperature difference between day and night, the freezing and thawing environment and complex stress conditions, the construction and operation of dams are affected. During the process, the deformation and stability of the dam body and the strength of the dam-building coarse-grained materials have a great influence, which endangers the safe operation of the dam. Therefore, it is of guiding significance for the design, construction and stability evaluation of high earth-rockfill dams in cold regions to carry out research on the deterioration law of strength and deformation characteristics of coarse-grained materials for dam construction during freeze-thaw cycles.

The research on the mechanical properties of coarse-grained materials for dam construction at home and abroad is mainly completed by means of large-scale triaxial tests and large-scale direct shear tests. Strength, deformation and rheological properties and establishment of constitutive models. There is no domestic test standard for the deterioration of the mechanical properties of coarse-grained materials under freeze-thaw cycles and complex stress, and there is no domestic report on the equipment and methods for large-scale triaxial tests of coarse-grained materials under freezing and thawing drainage conditions. The relevant equipment and methods for the deformation and strength deterioration test of coarse aggregates under different constant stress levels are also blank. Therefore, the existing large-scale triaxial mechanical test device for coarse-grained soil has the problem that it cannot test the mechanical properties of the coarse-grained sample after consolidation and drainage under freeze-thaw cycles and loading conditions.

SUMMARY OF THE INVENTION

The present invention solves the problem that the existing large-scale triaxial mechanical test device for coarse-grained soil cannot test the mechanical performance parameters of the coarse-grained material sample after consolidation and drainage under freeze-thaw cycles and loading conditions. Furthermore, a large-scale triaxial mechanical test device and a test method for coarse-grained soil simulating a freeze-thaw cycle are provided.

The technical scheme of the present invention is a large-scale triaxial mechanical test device for simulating freeze-thaw cycles of coarse-grained soil, which includes a control system, a data acquisition system, a surrounding pressure system, a freeze-thaw cycle system and an axial pressure system, and also includes a test system. Sample mold system, sample mold system includes bottom plate, cylinder body connection seat, lower pressure plate, lower water permeable plate, cylinder body, circulation pipe, half insulation barrel, upper water permeable plate, upper pressure plate, barrel cover, guide sleeve, half insulation The barrel cover, the supporting rod, the nut and the indenter, the cylinder body is installed on the bottom plate through the cylinder body connecting seat, the surrounding pressure system is connected with the bottom plate and exerts confining pressure on the sample; the lower pressure plate is sealed and installed in the middle of the upper end face of the bottom plate to control The system is connected with the data acquisition system, and the data acquisition system is connected with multiple sensor interfaces on the lower pressure plate. The pressure plate is installed on the upper end of the upper permeable plate, and the upper pressure plate is provided with an exhaust valve. The circulation pipe is sleeved on the sample through the barrel cover installed on the cylinder body. The freeze-thaw circulation system is connected to the upper part of the circulation pipe. The upper end of the barrel cover and the lower part of the support rod pass through the guide sleeve and the barrel cover in turn and are connected to the upper pressure plate. The upper part of the support rod is sequentially installed with a pressure head and a nut from top to bottom. Externally, the half-insulated barrel cover is installed on the upper end of the half-insulated barrel, the sample mold system is installed in the frame, and the axial pressure system is connected with the indenter of the sample mold system and axially pressurizes the sample.

The present invention also provides a test method using a large-scale triaxial mechanical test device for simulating a freeze-thaw cycle of coarse-grained soil, which comprises the following steps:

Step 1: The process of saturation and consolidation;

Step 11: According to the predetermined consolidation stress state of the sample, a vertical downward prestress is applied to the sample by the axial compression system;

Steps 1 and 2: The surrounding pressure system applies pre-confining pressure to the sample, the water discharged from the consolidation of the sample is discharged to the outside world through the lower permeable plate and the drainage port on the bottom plate, and the drainage volume of the sample is monitored by the data acquisition system;

So far, by applying different confining pressures to the sample to collect the drainage data of the consolidation of the sample;

Step 2: Freeze-thaw cycle - loading process;

According to the predetermined freeze-thaw cycle mode, the freeze-thaw cycle system continuously transports the circulating liquid of the set temperature to the circulation tube to raise/lower the temperature of the sample. During the heating/cooling process, a temperature sensor is set inside the bottom plate to monitor the inside of the sample in real time. temperature, to form the sample at the target temperature, the sample is subjected to constant axial load and confining pressure during the freeze-thaw cycle;

Step 3: Triaxial Compression Process:

Keeping the temperature of the sample in step 2 unchanged, according to the preset stress path, the set axial pressure and surrounding pressure are applied to the sample at a certain shear rate, during which the deformation and surrounding pressure of the sample are monitored by the data acquisition system. Changes in load, confining pressure, pore pressure and temperature.

Compared with the prior art, the present invention has the following improvement effects:

1. The large-scale triaxial test method for coarse-grained materials of the present invention realizes the consolidation and drainage, freeze-thaw cycle under constant load and shear integration test process of the formed sample through preset confining pressure and axial pressure in the triaxial pressure chamber , to realize the automatic collection of axial pressure, confining pressure, deformation, temperature, and drainage of the sample during the freeze-thaw loading process, with efficient testing and accurate and reliable data.

2. The present invention cooperates with the existing servo-controlled hydraulic source, low-temperature cold source and testing instrument, or cooperates with the existing three-axis servo mechanical testing machine (system), and can simulate the freezing and thawing cycle formation conditions to carry out the three-axis mechanics of coarse granular material samples. The test can real-time test the parameters of the mechanical properties of the coarse-grained samples after consolidation and drainage under freeze-thaw cycles and loading conditions.

Description of drawings

Fig. 1 is the structural representation of the test mold of the present invention;

Fig. 2 is the schematic diagram of equipment connection in the test process of the present invention;

Fig. 3 is the schematic diagram of the backplane interface of the present invention;

Figure 4 is a consolidated drainage-time curve;

Fig. 5 is the temperature-time change curve during the freeze-thaw cycle of the sample;

Figure 6 is a stress-strain curve.

In the picture: 1. Bottom plate, 2. Cylinder connecting plate, 3. Lower pressing plate, 4. Lower permeable plate, 5. Sample, 6. Cylinder body, 7. Circulation pipe, 8. Half insulation barrel, 9. Upper Permeable plate, 10. Upper pressure plate, 11. Bucket cover, 12. Guide sleeve, 13. Half-insulated bucket cover, 14. Upright rod, 15. Nut, 16. Indenter, 17. First sealing ring, 18. The second sealing ring, 19. the third sealing ring, 20. the fourth sealing ring, 21. the fifth sealing ring.

Detailed ways

Embodiment 1: This embodiment is described with reference to FIG. 1 to FIG. 3. A large-scale triaxial mechanical test device for coarse-grained soil simulating a freeze-thaw cycle in this embodiment includes a control system A, a data acquisition system B, and an ambient pressure system. C. Freeze-thaw cycle system D and axial pressure system E, it also includes a sample mold system F, and the sample mold system F includes a bottom plate 1, a cylinder body connecting seat 2, a lower pressure plate 3, a lower water permeable plate 4, and a cylinder body. 6. Circulation pipe 7, half insulation barrel 8, upper permeable plate 9, upper pressure plate 10, barrel cover 11, guide sleeve 12, half insulation barrel cover 13, support rod 14, nut 15 and pressure head 16, cylinder body 6. Installed on the bottom plate 1 through the cylinder connecting seat 2, and the surrounding pressure system C is connected to the bottom plate 1 and exerts confining pressure on the sample 5; B is connected, the data acquisition system B is connected to a plurality of sensor interfaces on the lower pressure plate 3, the lower permeable plate 4 is installed on the upper end of the lower pressure plate 3, the sample 5 is installed on the upper end of the lower water permeable plate 4, and the upper water permeable plate 9 is installed on the sample 5 The upper end of the upper pressure plate 10 is installed on the upper end of the upper water permeable plate 9, the upper pressure plate 10 is provided with an exhaust valve, the circulation pipe 7 is set on the sample 5 through the barrel cover 11 installed on the cylinder body 6, and the freeze-thaw circulation system D is connected to the upper part of the circulation pipe 7, the guide sleeve 12 is installed on the upper end of the barrel cover 11, the lower part of the support rod 14 passes through the guide sleeve 12 and the barrel cover 11 in sequence and is connected to the upper pressure plate 10, and the upper part of the support rod 14 is connected to the upper pressure plate 10 by The pressure head 16 and the nut 15 are installed in sequence from top to bottom, the half insulation barrel 8 is sleeved on the outside of the cylinder 6, the half insulation barrel cover 13 is installed on the upper end of the half insulation barrel 8, and the sample mold system is installed on the frame. Inside, the axial compression system E presses the sample 5 axially by connecting with the indenter 16 of the sample mold system.

Embodiment 2: This embodiment will be described with reference to FIG. 1 . The cylindrical body connecting seat 2 of this embodiment is sealed and installed on the bottom plate 1 through a fifth sealing ring 21 . This arrangement is convenient to ensure the airtightness of the test mold. Other components and connection relationships are the same as in the first embodiment.

Embodiment 3: This embodiment will be described with reference to FIG. 1 and FIG. 3 . The lower pressure plate 3 of this embodiment is provided with a temperature sensor interface 3-1, a hole pressure sensor interface 3-2, a water supply and drainage interface 3-3, and a confining pressure interface. Liquid inlet port 3-4, confining pressure gauge port 3-5, temperature sensor port 3-1, port pressure sensor port 3-2 and confining pressure gauge port 3-5 are respectively installed with temperature sensor and port pressure sensor and confining pressure gauge. This arrangement facilitates the measurement of relevant data parameters in the test process, and is installed on the lower pressure plate to ensure the safe and accurate use of the sensor, and the structure is compact. Other compositions and connection relationships are the same as in the first or second embodiment.

Embodiment 4: The present embodiment will be described with reference to FIG. 1 . The support rod 14 and the guide sleeve 12 of the present embodiment are connected in a sealed manner. This arrangement is convenient to ensure the airtightness of the test mold. Other compositions and connection relationships are the same as in the first, second or third embodiment.

Embodiment 5: This embodiment will be described with reference to FIG. 1 . The circulation pipe 7 in this embodiment is a spiral disk type circulation pipe. This setting is convenient for simulating the actual working conditions of coarse-grained soil in an actual freeze-thaw cycle. Other compositions and connection relationships are the same as in the first, second, third or fourth embodiment.

Embodiment 6: This embodiment will be described in conjunction with FIG. 1 and FIG. 3 . The sample mold system of this embodiment is a cylindrical mold system, and a mounting hole is provided in the middle of the half-insulation barrel cover 13 , which is coaxial with the mounting hole. A plurality of circulation tubes pass through the holes. This arrangement facilitates disassembly and assembly and production. Other compositions and connection relationships are the same as in the first, second, third, fourth or fifth embodiment.

In the large-scale triaxial mechanical sample device for simulating the freeze-thaw cycle of coarse-grained soil of the present invention, the joint surfaces between the bottom plate and the cylinder cover and the cylinder body are provided with sealing rings; There are sealing rings, and five sealing rings are used for sealing to ensure the airtightness of the test mold;

The test mold of the present invention is covered with a half thermal insulation barrel and a half thermal insulation barrel cover;

The test mold of the present invention is a hollow structure, and is provided with a lower pressure plate, a lower permeable plate, a sample, a circulation pipe, an upper permeable plate, and an upper pressure plate, and the order of placement in the experiment is the lower pressure plate, the lower permeable plate, the sample, the upper pressure plate, and the upper pressure plate. The permeable plate, the upper pressure plate, the upper pressure plate is provided with an exhaust valve, which is used to exhaust the air when the confining pressure liquid is injected; , Confining pressure gauge interface;

The temperature sensor interface and pore pressure sensor interface of the present invention are used for the temperature sensor and pore pressure sensor installed near the central axis of the bottom plate and drawn from the bottom plate to measure the internal temperature and pore pressure of the sample; the supplement/drain port is used for Saturate the sample and consolidate the drainage during the test; the confining pressure liquid inlet is used to inject the confining pressure liquid into the gap between the sample and the mold, and the antifreeze is added into the mold through the confining pressure liquid inlet, and the upper The exhaust valve above the pressure plate is opened, and when antifreeze flows out, immediately close the exhaust valve. The sample is located between the lower permeable plate and the upper permeable plate, and is wrapped on the outside of the sample by a latex film, and the upper and lower ends are sealed at the outer edge of the lower permeable plate and the outer edge of the upper permeable plate by sealing rings;

The ambient pressure system of the present invention can fill the test mold with confining pressure liquid through a computer-controlled pressure pump, and can apply different confining pressures to the sample according to different test requirements.

The axial pressurizing system of the present invention is composed of a servo hydraulic source, a reaction force frame and a hydraulic cylinder, which is used to axially load the sample, and the servo hydraulic source is controlled by the computer of the control system, which is convenient and accurate;

The freeze-thaw circulation system of the present invention is composed of a circulation pipe inside the test mold and an external freeze-thaw cycle machine connected to form a frozen sample. The circulation pipe is a spiral serpentine pipe, and the inlet and outlet are located above the barrel cover. , the freeze-thaw cycle machine is connected with the inlet and outlet of the circulation pipe.

The control system of the present invention includes a computer, which can control the surrounding pressure system, the axial pressure system, and the freeze-thaw cycle system and monitor their operating states; the data acquisition system is connected with the computer, and can monitor the temperature inside the sample during the test process. , pore water pressure, consolidation drainage, sample volume strain and other data are collected in real time;

Embodiment 7: The present embodiment will be described with reference to FIG. 1 to FIG. 3 , and the test method of the large-scale triaxial mechanical test device for simulating the freeze-thaw cycle of coarse-grained soil of the present embodiment includes the following steps:

Step 1: The process of saturation and consolidation;

Step 11: According to the predetermined sample consolidation stress state, the axial compression system E applies a vertical downward prestress to the sample 5;

Step 1 and 2: The surrounding pressure system C applies a pre-confining pressure to the sample 5, the water discharged from the consolidation of the sample 5 is discharged to the outside world through the drainage port on the lower permeable plate 4 and the bottom plate 3, and the drainage volume of the sample 5 passes through the data acquisition system B. monitor;

So far, by applying different confining pressures to the sample 5 to collect the consolidated drainage data of the sample 5;

Step 2: Freeze-thaw cycle - loading process;

According to the predetermined freeze-thaw cycle mode, the freeze-thaw cycle system D continuously transports the circulating liquid of the set temperature to the circulation pipe 7 to raise/lower the temperature of the sample 5. During the heating/cooling process, a temperature sensor is set inside the bottom plate 1 for real-time Monitor the internal temperature of the sample to form a sample of the target temperature, and the sample is subjected to constant axial load and confining pressure during the freeze-thaw cycle;

Step 3: Triaxial Compression Process:

Maintain the temperature of the sample 5 in step 2 unchanged, according to the preset stress path, apply the set axial pressure and ambient pressure to the sample 5 at a certain shear rate, during which the sample is monitored by the data acquisition system B 5. Changes in deformation, load, confining pressure, pore pressure and temperature. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth or sixth embodiment.

The large-scale triaxial mechanical test method for simulating freeze-thaw cycles of coarse-grained soils in this embodiment includes a saturation and consolidation process, a freeze-thaw cycle-loading process, and a triaxial compression process;

The saturation and consolidation process: according to the predetermined consolidation stress state of the specimen, the axial compression system applies pre-stress to the specimen; the surrounding pressure system applies pre-confining pressure, and the water discharged from the consolidation of the specimen passes through the lower permeable plate. And the drainage port is discharged to the outside world, and the drainage volume of the sample can be monitored by the data acquisition system;

The freeze-thaw cycle-loading process: according to the predetermined freeze-thaw cycle mode, the freeze-thaw cycle system continuously transports the circulating liquid of the set temperature to the circulation tube to raise/lower the temperature of the sample, and the temperature inside the bottom plate is set during the heating/cooling process. The sensor is used to monitor the internal temperature of the sample in real time to form a sample with a target temperature, and the sample is subjected to constant axial load and confining pressure during the freeze-thaw cycle.

The triaxial compression process: maintaining the temperature of the sample unchanged, applying the set axial pressure and surrounding pressure to the sample at a certain shear rate according to the preset stress path, during which the sample is monitored by the data acquisition system The deformation, load, confining pressure, pore pressure and temperature change.

The surrounding pressure system, axial pressure system, and freeze-thaw cycle system are all controlled by the control system, with high precision, and the axial pressure system can be loaded according to constant strain-stress control, which improves the accuracy of the test. , which greatly facilitates the conduct of the experiment.

Embodiment 8: This embodiment will be described with reference to FIG. 1 to FIG. 3 . The sample mold system of this embodiment is a cylindrical mold system, and a mounting hole is provided in the middle of the half-insulation barrel cover 13 , which is coaxial with the mounting hole. A plurality of circulation tubes pass through the holes. This arrangement facilitates connection with the plug-in sliding platform and can be firmly installed on the experimental platform. Other compositions and connection relationships are the same as in the first, second, third, fourth, fifth, sixth or seventh embodiment.

Example:

Taking the triaxial test as an example, the steps are as follows:

1) Test device assembly of the present invention:

First, place the third sealing ring 19 , the fourth sealing ring 20 and the fifth sealing ring 21 in the corresponding grooves of the base plate 1 , assemble the lower pressing plate 3 on the base plate 1 , and connect them with bolts. Place the lower permeable plate 4 on the lower pressure plate 3, and place the sample 6 on the lower permeable plate 4; place the upper permeable plate 9 on the upper end of the sample 5, and then place the upper pressure plate 10. For the convenience of description, this part is defined as part I.

Next, seal the guide sleeve 12 and the barrel cover 11 and connect them with bolts, pass the support rod 14 through the guide sleeve 12, tighten the nut 15, and then fasten the barrel 6 and the barrel cover 11 with bolts. Fasten the circulation pipe 7 through the bucket cover 11 . For the convenience of description, this part is defined as part II.

Then, fit part II onto part I and fasten it with bolts. Then the whole is hoisted into the loading frame of the testing machine. The two-half thermal insulation barrels are assembled around the cylinder body 6, and the half thermal insulation barrels cover 13 are covered.

Finally, the indenter 16 is mounted on the pressure sensor of the test machine loading frame. The positions of the confining pressure gauge, the confining pressure liquid inlet, the water replenishing port, the pore pressure measuring port, and the temperature sensor are shown in Figure 3. The circulation pipe 7 has two connection ports, one in and one out, a freeze-thaw cycle machine; the confining pressure liquid is injected into the test mold through the confining pressure liquid inlet, and the exhaust valve above the barrel lid is opened. outflow, close the exhaust valve immediately.

2) Consolidation stage

First, according to the predetermined consolidation stress state of the sample, the axial pressure system applies pre-stress to the sample; the surrounding pressure system can fill the test mold with confining pressure liquid through the computer-controlled pressure pump to apply the pre-confining pressure, And open the exhaust valve above the barrel cover, and close the exhaust valve immediately when antifreeze flows out. Different confining pressures can be applied to the samples according to different test requirements, and the water seeping out from the consolidation of the samples is discharged to the outside world through the lower permeable plate and the drain. At this time, the sensor string is connected to the data acquisition system and starts to collect data. The variation curve of the consolidated drainage volume of the sample with time is shown in Figure 4 below.

3) Freeze-thaw cycle stage in loading state

After the consolidation is completed according to the preset consolidation time, the confining pressure applied to the sample is maintained, and a predetermined axial pressure is applied at the same time to enter the freeze-thaw cycle stage under the loading state. According to the predetermined freeze-thaw cycle mode, the freeze-thaw cycle system continuously transports the circulating liquid of the set temperature to the circulation tube to raise/lower the temperature of the sample. During the heating/cooling process, a temperature sensor is set inside the bottom plate to monitor the inside of the sample in real time. temperature to form a sample at the target temperature. The temperature-dependent curve of the sample during the freeze-thaw cycle is shown in Figure 5 below.

4) Triaxial compression test stage

Keeping the temperature of the sample unchanged, according to the preset stress path, the axial pressure and confining pressure that change according to the set rule are applied to the sample, during which the deformation of the sample is detected by the control system.

After that, the triaxial compression test was carried out according to the preset mode until the specimen failed. During the test, the internal temperature and strain value of the sample were measured by the sensor; the data acquisition system was used to collect the axial displacement, axial pressure, confining pressure and other related data. The stress-strain curve of the coarse aggregate in the triaxial compression test is shown in Fig. 6 below.

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (8)

1. A large-scale triaxial mechanical test device for simulating freeze-thaw cycle coarse-grained soil, which includes a control system (A), a data acquisition system (B), an ambient pressure system (C), a freeze-thaw cycle system (D) and an axial The pressurizing system (E) is characterized in that: it also includes a sample mold system (F), and the sample mold system (F) includes a bottom plate (1), a cylinder body connecting seat (2), a lower pressing plate (3), a lower Water permeable plate (4), cylinder body (6), circulation pipe (7), half insulation barrel (8), upper permeable plate (9), upper pressure plate (10), barrel cover (11), guide sleeve (12) , the half-insulated barrel cover (13), the support rod (14), the nut (15) and the pressure head (16), The cylinder body (6) is installed on the bottom plate (1) through the cylinder body connecting seat (2), and the surrounding pressure system (C) is connected with the bottom plate (1) and exerts confining pressure on the sample (5); the lower pressure plate (3) is sealed Installed in the middle of the upper end face of the bottom plate (1), the control system (A) is connected with the data acquisition system (B), the data acquisition system (B) is connected with a plurality of sensor interfaces on the lower pressure plate (3), and the lower water permeable plate (4) ) is installed on the upper end of the lower pressure plate (3), the sample (5) is installed on the upper end of the lower water permeable plate (4), the upper water permeable plate (9) is installed on the upper end of the sample (5), and the upper pressure plate (10) is installed on the upper water permeable plate The upper end of the plate (9), the upper pressure plate (10) is provided with an exhaust valve, and the circulation pipe (7) is sleeved on the sample (5) through the barrel cover (11) installed on the cylinder (6), freeze-thawed The circulation system (D) is connected to the upper part of the circulation pipe (7), the guide sleeve (12) is installed on the upper end of the barrel cover (11), and the lower part of the support rod (14) passes through the guide sleeve (12) and the barrel cover (11) in turn. 11) and then connected to the upper pressure plate (10), the upper part of the support rod (14) is sequentially installed with a pressure head (16) and a nut (15) from top to bottom, and the half insulation barrel (8) is sleeved on the cylinder body (6) ), the half-insulated barrel cover (13) is mounted on the upper end of the half-insulated barrel (8), the sample mold system is installed in the frame, and the axial pressure system (E) is pressed against the sample mold system. The head (16) is attached and axially pressurizes the specimen (5). 2. A large-scale triaxial mechanical test device for simulating a freeze-thaw cycle of coarse-grained soil according to claim 1, characterized in that: the cylinder connecting seat (2) is sealed and installed on the bottom plate (1) through the fifth sealing ring (21). )superior. 3. A large-scale triaxial mechanical test device for simulating a freeze-thaw cycle coarse-grained soil according to claim 2, characterized in that: the lower pressure plate (3) is provided with a temperature sensor interface, a hole pressure sensor interface, a water supply interface, A temperature sensor, a pore pressure sensor and a confining pressure gauge are respectively installed in the confining liquid inlet hole, the confining pressure gauge interface, the temperature sensor interface, the pore pressure sensor interface and the confining pressure gauge interface. 4. A large-scale triaxial mechanical test device for simulating a freeze-thaw cycle of coarse-grained soil according to claim 3, characterized in that the support rod (14) and the guide sleeve (12) are hermetically connected. 5 . The large-scale triaxial mechanical test device for simulating freeze-thaw cycles of coarse-grained soil according to claim 4 , wherein the circulation pipe ( 7 ) is a spiral disk type circulation pipe. 6 . 6. A kind of large-scale triaxial mechanical testing device for simulating freeze-thaw cycle coarse-grained soil according to claim 5, characterized in that: the sample mold system is a cylindrical mold system, and the middle part of the half-insulation barrel cover (13) is provided with There are installation holes, and a plurality of circulation pipe passing holes are opened coaxially with the installation holes. 7. A test method using the large-scale triaxial mechanical test device for simulating freeze-thaw cycle coarse-grained soil according to any one of claims 1 to 6, characterized in that: it comprises the following steps: Step 1: The process of saturation and consolidation; Step 11: According to the predetermined sample consolidation stress state, the axial compression system (E) applies a vertical downward prestress to the sample (5); Step 1 and 2: The surrounding pressure system (C) applies a pre-confining pressure to the sample (5), and the water discharged from the consolidation of the sample (5) is discharged to the outside world through the water outlet on the lower permeable plate (4) and the bottom plate (3). The displacement of the sample (5) is monitored by the data acquisition system (B); So far, the consolidated drainage data of the sample (5) is collected by applying different confining pressures to the sample (5); Step 2: Freeze-thaw cycle - loading process; According to the predetermined freeze-thaw cycle mode, the freeze-thaw cycle system (D) continuously transports the circulating liquid at the set temperature to the circulation pipe (7) to raise/lower the temperature of the sample (5). During the raising/lowering process, the bottom plate (1) A temperature sensor is set inside to monitor the internal temperature of the sample in real time to form a sample with the target temperature, and the sample is subjected to constant axial load and confining pressure during the freeze-thaw cycle; Step 3: Triaxial Compression Process: Maintain the temperature of the sample (5) in step 2 unchanged, and according to the preset stress path, apply the set axial pressure and ambient pressure to the sample (5) at a certain shear rate, during which the data acquisition system is passed. (B) Monitor the deformation, load, confining pressure, pore pressure and temperature changes of the sample (5). 8. a kind of test method of using simulated freeze-thaw cycle coarse-grained soil large-scale triaxial mechanical test device according to claim 7, is characterized in that: in step one or two, in the surrounding pressure system (C) to the sample (5 ) When the pre-confining pressure is applied, the surrounding pressure system (C) controls the pressure pump to fill the confining pressure liquid into the sample mold system through the computer control system (A), applies the pre-confining pressure, and puts the Open the exhaust valve, and close the exhaust valve immediately when antifreeze flows out.

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