Device and method for testing performance of subway tunnel under circumferential uneven freeze-thaw condition

Abstract

A testing device for the performance of subway tunnels under circumferential uneven freeze-thaw conditions is disclosed. A cold source is surrounded by a cold source pipe, and a heat source is surrounded by a heat source pipe. Water thermometers are installed within both the cold and heat sources. The cold and heat source pipes are fixed to a circumferential position adjustment system on the pipe wall, arranged in a ring. Thermal insulation material is located in the gap between the cold and heat source pipes. A thermal conductivity material thickness adjustment system is located inside the cold and heat source pipes. The subway tunnel segment is located at the annular center of the entire testing device, and the segment thickness adjustment system is located inside the segment. Front and rear panels are located at the front and rear ends of the device, respectively. The cavity formed by the front and rear panels and the circumferential position adjustment system is filled with soil. A soil pressure cell, displacement gauge, and moisture content probe are installed within the soil area. A testing method for the performance of subway tunnels under circumferential uneven freeze-thaw conditions is also provided. This invention enables simultaneous testing of circumferential uneven freeze-thaw settlement in subway tunnels, and is simple, easy to operate, inexpensive, and has a short cycle time.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering technology and relates to a testing device and method for the performance of subway tunnels under circumferential non-uniform freeze-thaw conditions, which is applicable to the testing of subway tunnel performance. Background Technology

[0002] Shield tunneling is a fully mechanized construction method in the cut-and-cover method, commonly used in subway tunnel excavation. Tunnel segments are the main assembly components in shield tunneling and the permanent lining structure of the tunnel, directly impacting the overall quality and safety of the tunnel. With the increasing prevalence of subways, the application of shield tunneling is becoming more widespread. However, the freeze-thaw effect caused by soil temperature changes can adversely affect tunnel segments, potentially leading to engineering accidents such as segment misalignment and excessive convergence deformation. Existing testing equipment cannot account for the simultaneous effects of soil freeze-thaw and thaw settlement on tunnel segments. Furthermore, the freeze-thaw and thaw settlement zones around the frozen section are uniform, and the method cannot consider variations in segment thickness. Therefore, existing methods have the following shortcomings: 1) They can only be tested according to the sequence of freeze-thaw followed by thaw settlement, failing to consider the simultaneous effects of soil freeze-thaw and thaw settlement on the segments; 2) They are only applicable to segments of uniform thickness, unable to test the effects of variations in segment thickness; 3) They can only consider uniform freeze-thaw or thaw settlement effects, while in actual engineering projects, circumferentially non-uniform freeze-thaw and thaw settlement zones often occur. Summary of the Invention

[0003] To overcome the shortcomings of existing freeze-thaw testing methods, such as the inability to simultaneously measure the freeze-thaw effect of soil on subway tunnels and the inability to test the impact of circumferentially uneven freeze-thaw effects on shield tunnel performance, this invention provides a testing device and method for subway tunnel performance under circumferentially uneven freeze-thaw conditions. This method can simultaneously test the circumferentially uneven freeze-thaw settlement of subway tunnels, and is simple, easy to operate, inexpensive, and has a short cycle time.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] A testing device for the performance of a subway tunnel under circumferentially uneven freeze-thaw conditions includes a pipe wall circumferential position adjustment system, thermal insulation material, a thermally conductive material thickness adjustment system, tunnel segments, a segment thickness adjustment system, a heat source, a heat source pipe, a cold source, a cold source pipe, and front and rear panels. The cold source is surrounded by the cold source pipe, and the heat source is surrounded by the heat source pipe. A water thermometer is installed in the cold and heat sources. The cold and heat source pipes are fixed on the pipe wall circumferential position adjustment system and are arranged in a ring. The thermal insulation material is located in the gap at the junction of the cold and heat source pipes. The thermally conductive material thickness adjustment system is located inside the cold and heat source pipes. The tunnel segments are located at the annular center of the entire testing device. The segment thickness adjustment system is located inside the tunnel segments. The front and rear panels are located at the front and rear ends of the entire testing device, respectively. The cavity formed by the front and rear panels and the pipe wall circumferential position adjustment system is filled with soil. An earth pressure cell, a displacement gauge, and a moisture content probe are installed in the soil area.

[0006] Furthermore, the pipe wall circumferential position adjustment system includes a pipe wall circumferential slide rail, a pipe wall circumferential fixing knob, and a pipe wall. The pipe wall is located on two inner and outer pipe wall circumferential slide rails, and the pipe wall circumferential fixing knob is located at the position of each pipe wall adjacent to the pipe wall circumferential slide rail.

[0007] Furthermore, the thermally conductive material thickness adjustment system includes thermally conductive material, a thermally conductive material clamp, and a thermally conductive material clamp telescopic adjustment knob. The thermally conductive material clamp is located within the thermal insulation material. The thermally conductive material clamp telescopic adjustment knob is installed in a pre-drilled hole on the clamp, and the thermally conductive material of the corresponding size is fixed to the inside of the heat source pipe by the clamp. In this solution, the central angle and thickness of the thermally conductive material fixed to the inside of the heat source pipe are set according to engineering requirements, and the thermally conductive material is fixed by the thermally conductive material clamp telescopic adjustment knob.

[0008] Furthermore, the tunnel segment includes an inner segment and an outer segment, and the segment thickness adjustment system is located inside the tunnel segment.

[0009] The segment thickness adjustment system includes a telescopic plate, a fixed end plate, a hinged joint connecting plate, and a hinged joint. The fixed end plate is located between the inner segment and the outer segment. The telescopic plate is connected to the two fixed end plates, and the hinged joint is used to fix the two hinged joint connecting plates to the fixed end plates as a whole.

[0010] Furthermore, the front and rear panels include a cold source interface, a heat source interface, and a soil baffle. The cold source interface and the heat source interface are distributed in a ring on the front and rear panels, and their specific positions coincide with the positions of the cold source pipe and the heat source pipe. The soil baffle is located on the front and rear panels and coincides with the position of the soil.

[0011] The tunnel segments are divided into several regions along the ring direction and distinguished by tunnel segment zone numbers.

[0012] The locations of the hot and cold sources are arranged in several zones along the ring direction, and are distinguished by hot and cold source zone numbers.

[0013] A method for testing the performance of subway tunnels under circumferential non-uniform freeze-thaw conditions includes the following steps:

[0014] Step 1: Determine the material, inner diameter, and zoning of the tunnel segments based on the project characteristics and testing requirements;

[0015] Step 2: Install a testing device for the performance of subway tunnels under circumferential uneven freeze-thaw conditions. The testing device includes a pipe wall circumferential position adjustment system, thermal insulation material, thermal conductive material thickness adjustment system, tunnel segments, segment thickness adjustment system, heat source, heat source pipe, cold source, cold source pipe, and front and rear panels. The cold source is surrounded by the cold source pipe, and the heat source is surrounded by the heat source pipe. A water thermometer is installed in the cold source and the heat source. The cold source pipe and the heat source pipe are fixed on the pipe wall circumferential position adjustment system and are arranged in a ring. The thermal insulation material is located in the gap at the junction of the cold source pipe and the heat source pipe. The thermal conductive material thickness adjustment system is located inside the cold source pipe and the heat source pipe. The tunnel segment is located at the ring center of the entire testing device. The segment thickness adjustment system is located inside the tunnel segment. The front and rear panels are located at the front and rear ends of the entire testing device, respectively. The cavity formed by the front and rear panels and the pipe wall circumferential position adjustment system is filled with soil. An earth pressure cell, a displacement gauge, and a moisture content probe are installed in the soil area.

[0016] Step 3: Determine the temperature parameters of the cold source and heat source, turn on the external cold source and heat source switches, connect the cold source pipe and heat source pipe to the external cold source and heat source respectively, and reach the corresponding test temperature; set the cold source temperature and heat source temperature according to the test requirements; supply cold source to the installed cold source pipe through the cold source interface reserved on the front panel; supply heat source to the installed heat source pipe through the heat source interface reserved on the device box; the cold and heat sources flow back to the external cold and heat source system from the cold and heat source interfaces reserved on the rear panel and then flow into the cold and heat source pipes, forming an internal and external circulation of cold and heat sources;

[0017] Step 4: Start the experiment and collect data: Record the initial data of each sensor before the experiment begins. Once the temperature of the cold source and the heat source reaches the test temperature and remains constant, record the corresponding test data every half hour. Stop the experiment when the data at the test points stabilizes.

[0018] Step 5: Cyclic testing of different cold and heat source temperatures. Repeat steps 3 to 4. By changing the temperature of the external cold and heat source, the frost heave and thaw settlement of soil at different cold and heat source temperatures can be tested simultaneously.

[0019] Furthermore, in step 2, the positions of the cold source pipe and the heat source pipe on the circumferential position adjustment system of the pipe wall are determined according to engineering requirements; the thickness of the thermally conductive material is determined according to engineering requirements; the thickness of the tunnel segment is determined according to engineering requirements; and the testing method further includes the following steps:

[0020] Step 6: Cyclic test at different cold and heat source locations. Repeat steps 2 to 4. By changing the location of the cold and heat source interfaces, freeze-thaw tests can be performed at different cold and heat source locations and different cold and heat source temperatures in the circumferential direction.

[0021] Step 7: Cyclic test of different thermal conductive material thicknesses. Repeat steps 2 to 4. By changing the position of the cold source and heat source interface, the thickness of the thermal conductive material can be adjusted by adjusting the thermal conductive material thickness adjustment system. This can achieve test of uneven freeze-thaw expansion and thaw settlement, circumferential cold source and heat source positions and different cold and heat source temperatures.

[0022] Step 8: Cyclic test of different tunnel segment thicknesses. Repeat steps 2 to 4. By changing the position of the cold source and heat source interface, adjusting the thickness of the heat-conducting material through the heat-conducting material thickness adjustment system, and adjusting the length of the telescopic plate, it is possible to achieve working condition testing for circumferential uneven freeze-thaw expansion and thaw settlement, different cold source and heat source positions, different tunnel segment thicknesses, and different cold and heat source temperatures.

[0023] Step 9: End the test, remove the soil, and dismantle the device.

[0024] The beneficial effects of this invention are mainly reflected in: (1) it can test the simultaneous effects of soil frost heave and thaw settlement on tunnel segments; (2) it can test the influence of circumferential uneven frost heave and thaw settlement on tunnel segments; (3) it can test the influence of segment performance on thickness variation; (4) it is easy to operate, low in cost, and short in cycle. Attached Figure Description

[0025] Figure 1 This is a front view of a testing device for the performance of a subway tunnel under circumferential uneven freeze-thaw conditions.

[0026] Figure 2 yes Figure 1 AA section view.

[0027] Figure 3 This is a structural diagram of a thermally conductive material thickness adjustment system.

[0028] Figure 4 This is a structural diagram of the segment thickness adjustment system.

[0029] Figure 5 This is a structural diagram of the front and rear panels of the testing device.

[0030] Figure 6 This is a structural diagram of the pipe wall circumferential position adjustment system.

[0031] Figure 7 This is a structural diagram of a tunnel segment.

[0032] The components include: 1. Pipe wall circumferential position adjustment system; 1-1. Pipe wall circumferential slide rail; 1-2. Pipe wall circumferential fixing knob; 1-3. Pipe wall; 2. Thermal insulation material; 3. Thermal conductive material thickness adjustment system; 3-1. Thermal conductive material; 3-2. Thermal conductive material clamp; 3-3. Thermal conductive material clamp telescopic adjustment knob; 4. Tunnel segment; 4-1. Inner segment; 4-2. Outer segment; 5. Segment thickness adjustment system; 5-1. Telescopic plate; 5-2. 5-3. Fixed end plate; 5-4. Hinge joint connecting plate; 5-5. Hinge joint; 6. Earth pressure cell; 7. Strain gauge; 8. Water thermometer; 9. Moisture content probe; 10. Displacement gauge; 11. Heat source; 12. Heat source pipe; 13. Cold source; 14. Cold source pipe; 15. Front and rear panels; 15-1. Cold source interface; 15-2. Heat source interface; 15-3. Soil baffle; 16. Tunnel segment zoning number; 17. Cold and heat source zoning number; 18. Soil. Detailed Implementation

[0033] The present invention will now be further described with reference to the accompanying drawings.

[0034] Reference Figures 1 to 7 A testing device for the performance of a subway tunnel under circumferentially uneven freeze-thaw conditions includes a pipe wall circumferential position adjustment system 1, thermal insulation material 2, thermally conductive material thickness adjustment system 3, tunnel segments 4, segment thickness adjustment system 5, a heat source 11, a heat source pipe 12, a cold source 13, a cold source pipe 14, and front and rear panels 15. The cold source 13 is surrounded by the cold source pipe 14, and the heat source 11 is surrounded by the heat source pipe 12. A water thermometer 8 is installed in the cold source 13 and the heat source 11. The cold source pipe 14 and the heat source pipe 12 are fixed on the pipe wall circumferential position adjustment system 1 and are arranged in a ring shape. Distribution: The thermal insulation material 2 is located in the gap at the junction of the cold source pipe 14 and the heat source pipe 12. The thermal conductive material thickness adjustment system 3 is located inside the cold source pipe 14 and the heat source pipe 12. The tunnel segment 4 is located at the annular center of the entire test device. The segment thickness adjustment system 5 is located inside the tunnel segment 4. The front and rear panels 15 are located at the front and rear ends of the entire test device, respectively. The cavity formed by the front and rear panels 15 and the pipe wall circumferential position adjustment system 1 is filled with soil 18. The soil area is equipped with an earth pressure cell 6, a displacement gauge 10, and a moisture content probe 9.

[0035] Furthermore, the pipe wall circumferential position adjustment system 1 includes a pipe wall circumferential slide rail 1-1, a pipe wall circumferential fixing knob 1-2, and a pipe wall 1-3. The pipe wall is located on two inner and outer pipe wall circumferential slide rails, and the pipe wall circumferential fixing knob is located at the position of each pipe wall adjacent to the pipe wall circumferential slide rail.

[0036] Furthermore, the thermally conductive material thickness adjustment system 3 includes a thermally conductive material 3-1, a thermally conductive material clamp 3-2, and a thermally conductive material clamp telescopic adjustment knob 3-3. The thermally conductive material clamp is located within the insulation material. The thermally conductive material clamp telescopic adjustment knob is installed in a pre-drilled hole on the clamp, and the thermally conductive material of the corresponding size is fixed to the inside of the heat source pipe by the clamp. In this solution, the central angle and thickness of the thermally conductive material fixed to the inside of the heat source pipe are set according to engineering needs, and the thermally conductive material is fixed by the thermally conductive material clamp telescopic adjustment knob.

[0037] Furthermore, the tunnel segment 4 includes an inner segment 4-1 and an outer segment 4-2, and the segment thickness adjustment system is located inside the tunnel segment.

[0038] The segment thickness adjustment system 5 includes a telescopic plate 5-1, a fixed end plate 5-2, a hinge joint connecting plate 5-3, and a hinge joint 5-4. The fixed end plate is located between the inner segment and the outer segment. The telescopic plate is connected to the two fixed end plates, and the hinge joint is used to fix the two hinge joint connecting plates to the fixed end plates into a whole.

[0039] Furthermore, the front and rear panels 15 include a cold source interface 15-1, a heat source interface 15-2, and a soil baffle 15-1. The cold source interface and the heat source interface are distributed in a ring on the front and rear panels, and their specific positions coincide with the positions of the cold source pipe and the heat source pipe. The soil baffle is located on the front and rear panels and coincides with the position of the soil.

[0040] Tunnel segment 4 is divided into several areas in the circumferential direction and distinguished by tunnel segment area numbers.

[0041] The locations of the hot and cold sources are arranged in several zones along the ring direction, and are distinguished by hot and cold source zone numbers.

[0042] A method for testing the performance of subway tunnels under circumferential non-uniform freeze-thaw conditions includes the following steps:

[0043] Step 1: Determine the material, inner diameter, and zoning of the tunnel segments based on the project characteristics and testing requirements;

[0044] Step 2: Install a testing device for the performance of subway tunnels under circumferential uneven freeze-thaw conditions. The testing device includes a pipe wall circumferential position adjustment system 1, thermal insulation material 2, a thermally conductive material thickness adjustment system 3, tunnel segments 4, segment thickness adjustment system 5, a heat source 11, a heat source pipe 12, a cold source 13, a cold source pipe 14, and front and rear panels 15. The cold source 13 is surrounded by the cold source pipe 14, and the heat source 11 is surrounded by the heat source pipe 12. A water thermometer 8 is installed in both the cold source 13 and the heat source 11. The cold source pipe 14 and the heat source pipe 12 are fixed to the pipe wall circumferential position adjustment system 1. The components are arranged in a circular pattern. The thermal insulation material 2 is located in the gap between the cold source pipe 14 and the heat source pipe 12. The thermal conductive material thickness adjustment system 3 is located inside the cold source pipe 14 and the heat source pipe 12. The tunnel segment 4 is located at the center of the entire test device. The segment thickness adjustment system 5 is located inside the tunnel segment 4. The front and rear panels 15 are located at the front and rear ends of the entire test device, respectively. The cavity formed by the front and rear panels 15 and the pipe wall circumferential position adjustment system 1 is filled with soil 18. The soil area is equipped with an earth pressure cell 6, a displacement gauge 10, and a moisture content probe 9.

[0045] Step 3: Determine the temperature parameters of the cold source and heat source, turn on the external cold source and heat source switches, connect the cold source pipe and heat source pipe to the external cold source and heat source respectively, and reach the corresponding test temperature; set the cold source temperature and heat source temperature according to the test requirements; supply cold source to the installed cold source pipe through the cold source interface reserved on the front panel; supply heat source to the installed heat source pipe through the heat source interface reserved on the device box; the cold and heat sources flow back to the external cold and heat source system from the cold and heat source interfaces reserved on the rear panel and then flow into the cold and heat source pipes, forming an internal and external circulation of cold and heat sources;

[0046] Step 4: Start the experiment and collect data: Record the initial data of each sensor before the experiment begins. Once the temperature of the cold source and the heat source reaches the test temperature and remains constant, record the corresponding test data every half hour. Stop the experiment when the data at the test points stabilizes.

[0047] Step 5: Cyclic testing of different cold and heat source temperatures. Repeat steps 3 to 4. By changing the temperature of the external cold and heat source, the frost heave and thaw settlement of soil at different cold and heat source temperatures can be tested simultaneously.

[0048] Furthermore, in step 2, the positions of the cold source pipe and the heat source pipe on the circumferential position adjustment system of the pipe wall are determined according to engineering requirements; the thickness of the thermally conductive material is determined according to engineering requirements; the thickness of the tunnel segment is determined according to engineering requirements; and the testing method further includes the following steps:

[0049] Step 6: Cyclic test at different cold and heat source locations. Repeat steps 2 to 4. By changing the location of the cold and heat source interfaces, freeze-thaw tests can be performed at different cold and heat source locations and different cold and heat source temperatures in the circumferential direction.

[0050] Step 7: Cyclic test of different thermal conductive material thicknesses. Repeat steps 2 to 4. By changing the position of the cold source and heat source interface, the thickness of the thermal conductive material can be adjusted by adjusting the thermal conductive material thickness adjustment system. This can achieve test of uneven freeze-thaw expansion and thaw settlement, circumferential cold source and heat source positions and different cold and heat source temperatures.

[0051] Step 8: Cyclic test of different tunnel segment thicknesses. Repeat steps 2 to 4. By changing the position of the cold source and heat source interface, adjusting the thickness of the heat-conducting material through the heat-conducting material thickness adjustment system, and adjusting the length of the telescopic plate, it is possible to achieve working condition testing for circumferential uneven freeze-thaw expansion and thaw settlement, different cold source and heat source positions, different tunnel segment thicknesses, and different cold and heat source temperatures.

[0052] Step 9: End the test, remove the soil, and dismantle the device.

[0053] A shield tunnel for Metro Line 5 in a certain city has a diameter of 6.2m and a burial depth of 18m. The excavation of the connecting passage between lines requires the freezing method. In order to test the simultaneous effects of frost heave and thaw settlement, and to consider the influence of tunnel segment thickness variations and circumferential uneven frost heave and thaw settlement, the circumferential uneven frost heave testing device and operation method for tunnel segments and soil provided in this invention are used to test the influence of soil frost heave and thaw settlement on tunnel segments of different circumferential thicknesses.

[0054] In this embodiment, the testing device is a cylinder with a length of 5m, an inner diameter of 6.2m, and an outer diameter of 12m. The cold source and the heat source are connected to the cold source pipe and the heat source pipe of the device from the front, forming a circulation system for the cold source and the heat source, respectively.

[0055] The implementation process of this invention is as follows:

[0056] 1) Determine the material, inner diameter, and area of ​​tunnel segment 4. Based on the project characteristics and testing requirements, C80 reinforced concrete tunnel segments were used in this test. The inner diameter of the tunnel segments is 6.2m, and the entire tunnel segment is divided into 24 areas in the circumferential direction.

[0057] 2) Assemble the segment thickness adjustment system. First, install a fixed end plate between the inner segment 4-1 and the outer segment 4-2. Then, connect the two fixed end plates 5-2 with a telescopic plate 5-1. Finally, fix the two hinged joint connecting plates 5-3 into a whole with a hinged joint 5-4. The corresponding thickness of the segments in each area can be achieved by changing the length of the telescopic plate 5-1 in the segment thickness adjustment system 5.

[0058] 3) Determine the corresponding thickness and center angle of the pipe segment according to the project requirements. Use the pipe segment thickness adjustment system to make each area of ​​the pipe segment in step 1 reach the predetermined thickness requirements. Determine the arc length of the pipe segment in each area according to the pipe segment diameter and center angle in step 1. The specific dimensions of the thickness and center angle of each area of ​​the pipe segment are shown in Table 1.

[0059]

[0060] Table 1

[0061] 4) Assemble the pipe segments and attach the strain gauges 7. Based on the arc length and location of each pipe segment determined in step 3, adjacent pipe segments are assembled with bolts, and three sets of strain gauges 7 are installed at equal intervals on the inner side of each pipe segment.

[0062] 5) Assemble cold source pipe 14. Based on the project characteristics and testing requirements, there are a total of 6 cold source pipes, numbered from Cold-I to Cold-VI. First, loosen the circumferential fixing knobs on both sides of pipe walls 1-3.

[0063] 1-2, Based on the width of each pipe from Cold-I to Cold-VI, make the pipe wall 1-3 follow the circumferential slide rail on the pipe wall.

[0064] Move 1-1 to the corresponding position, then tighten the circumferential fixing knob 1-2 to fix the position of the cold source pipe. To test the effect of uneven frost heave, the cold source pipe is made of steel, with a fan-shaped cross-section. The large fan radius is 0.6m, and the small fan radius is 0.5m. The thickness of the thermal conductive material 3-1 on the inner side of each cold source pipe 14 is determined according to the project requirements. The thermal conductive material 3-1 uses solid thermal conductive silicone with a thermal conductivity of 5W / mk. The central angle of the cold source pipe and the thickness of the thermal conductive material are detailed in Table 2.

[0065]

[0066] Table 2

[0067] 6) Assemble heat source pipe 12. Based on the project characteristics and testing requirements, there are a total of 6 heat source pipes, numbered from Heat-I to Heat-VI. First, loosen the circumferential fixing knobs on both sides of pipe walls 1-3.

[0068] 1-2, Based on the width of each pipe from heat-I to heat-VI, make the pipe wall 1-3 follow the circumferential slide rail on the pipe wall.

[0069] Move 1-1 to the corresponding position, then tighten the circumferential fixing knob 1-2 to fix the position of the heat source pipe. To test the effect of uneven melting and settling, a steel pipe is used for the heat source pipe, with a fan-shaped cross-section. The large fan radius is 0.6m, and the small fan radius is 0.5m. The thickness of the thermally conductive material 3-1 on the inner side of each heat source pipe 12 is determined according to engineering requirements. The thermally conductive material 3-1 uses solid thermally conductive silicone with a thermal conductivity of 8W / mK.

[0070] The central angle of the heat source pipe and the thickness of the heat-conducting material are detailed in Table 3.

[0071]

[0072] Table 3

[0073] 7) The simultaneous action of the changing tunnel segments 4 and the soil 18 arranges the cold source pipes assembled in step 5 and the heat source pipes assembled in step 6 in a ring shape according to their serial numbers from smallest to largest, forming a layout where the right half of the ring is the cold source area and the left half of the ring is the heat source area. A thermally conductive insulating material with excellent thermal conductivity, using thermally conductive silicone grease, with a thickness of 40mm, is filled between adjacent cold source pipes in the cold source area and adjacent heat source pipes in the heat source area. Thermally conductive insulating material with significantly different thermal conductivity, using PEF, is filled into the gaps at the boundaries between the cold source area and the heat source area.

[0074] 8) Assemble the thermal conductive material thickness adjustment system 3 and install the thermal conductive material 3-1. Place the thermal conductive material clamp 3-2 among all the insulation materials 2, and install the thermal conductive material clamp telescopic adjustment knob 3-3 in the pre-drilled holes on the clamp. Open the telescopic knob and adjust the telescopic amount of the thermal conductive material clamp to achieve the thickness of the thermal conductive material 3-1 for the cold and hot source pipes in Tables 2 and 3. Then fix the thermal conductive material 3-1 of the corresponding thickness to the inside of the cold and hot source pipes.

[0075] 9) Connect external cold and heat sources. Connect the external cold source to the cold source pipe 14 through the cold source interface 15-1, and connect the external heat source to the heat source pipe 12 through the heat source interface 15-2.

[0076] 10) Install sensors in the soil layer. Based on the thickness of the soil layer and the required locations for testing, install the corresponding sensors in the soil layer. Sensor installation is synchronized with soil layer filling. When the soil layer reaches the bottom elevation of the tunnel segment, install the tunnel segment ring. The soil layer baffle 15-3 consists of 5 plates. When the internal soil layer reaches the top of the corresponding baffle, install the next baffle until the internal soil layer is completely filled. The specific locations of the sensors are as follows: eight groups of moisture content probes 9 are arranged circumferentially at equal intervals, 3.5m from the center of the tunnel segment ring. Earth pressure cells 6 and displacement gauges 10 are arranged circumferentially. Three groups of earth pressure cells 6 and displacement gauges 10 are arranged equidistantly on the inner sides of each cold and heat source pipe, 3.8m and 4.8m from the center of the tunnel segment ring, respectively.

[0077] 11) Determine the temperature parameters of the cold and heat sources. Turn on the external cold and heat source switches, and connect cold source pipe 14 and heat source pipe 12 to the external cold and heat sources respectively, reaching the corresponding test temperatures. According to the test requirements, the temperature of cold source 13 is -35℃, and the temperature of heat source 11 is...

[0078] 25℃. Connect the installed cold source pipes through the pre-installed cold source interface 15-1 on the front panel 15.

[0079] 14. A cold source is supplied, using liquid nitrogen at -35℃ according to testing requirements. A heat source is supplied to the installed heat source pipe 12 via the pre-installed heat source interface 15-2 on the front panel, using pure water at 25℃ according to testing requirements. The cold and heat sources flow back from the pre-installed cold and heat source interfaces on the rear panel to the external cold and heat source system before flowing back into the cold and heat source pipes, forming an internal and external circulation of the cold and heat sources.

[0080] 12) Begin the experiment and collect data. Record the initial data from each sensor before the experiment begins.

[0081] Once the temperatures of the cold and heat sources in step 11) reach the test temperature and remain constant, record the corresponding test data every half hour. Stop the test when the data at the test points stabilizes.

[0082] 13) Cyclic testing of different cold and heat source temperatures: Repeat steps 10) to 11). By changing the temperature of the external cold and heat source, the soil frost heave and thaw settlement at different cold and heat source temperatures can be tested simultaneously.

[0083] 14) Cyclic testing at different cold and heat source locations: Repeat steps 9) to 11). By changing the location of the cold and heat source interfaces, freeze-thaw tests can be performed at different cold and heat source locations and different cold and heat source temperatures in a circumferential manner.

[0084] 15) Cyclic test with different thermal conductive material thicknesses: Repeat steps 7) to 11). By adjusting the thermal conductive material thickness adjustment system 3, the thickness of the thermal conductive material can be changed, which can realize the test of uneven freeze-thaw expansion and thaw settlement, different cold and heat source positions in the circumferential direction and different cold and heat source temperatures.

[0085] 16) Cyclic testing of different tunnel segment thicknesses, repeating steps 2) to 11). By adjusting the length of the telescopic plate 5-1, circumferential uneven frost heave and thaw settlement, and different cold sources can be controlled.

[0086] Tests were conducted under various conditions, including heat source location, tunnel segment thickness, and different hot and cold source temperatures. 17) The test was terminated, the soil was removed, and the equipment was dismantled. The testing equipment was shut down, and the soil was cleared. 18.

[0087] Remove the hot and cold source pipes and complete the test.

[0088] The embodiments described in this specification are merely examples of implementations of the inventive concept and are for illustrative purposes only. The scope of protection of this invention should not be considered limited to the specific forms described in these embodiments; rather, it extends to equivalent technical means conceived by those skilled in the art based on the inventive concept.

Claims

1. A testing device for the performance of subway tunnels under circumferential non-uniform freeze-thaw conditions, characterized in that, The device includes a pipe wall circumferential position adjustment system, thermal insulation material, a thermally conductive material thickness adjustment system, a subway tunnel segment, a segment thickness adjustment system, a heat source, a heat source pipe, a cold source, a cold source pipe, and front and rear panels. The cold source is surrounded by a cold source pipe, and the heat source is surrounded by a heat source pipe. A water thermometer is installed in the cold and heat sources. The cold and heat source pipes are fixed on the pipe wall circumferential position adjustment system and are arranged in a ring. The thermal insulation material is located in the gap at the junction of the cold and heat source pipes. The thermally conductive material thickness adjustment system is located inside the cold and heat source pipes. The subway tunnel segment is located at the annular center of the entire testing device. The segment thickness adjustment system is located inside the subway tunnel segment. The front and rear panels are located at the front and rear ends of the entire testing device, respectively. The cavity formed by the front and rear panels and the pipe wall circumferential position adjustment system is filled with soil. A soil pressure cell, a displacement gauge, and a moisture content probe are installed in the soil area. The pipe wall circumferential position adjustment system includes a pipe wall circumferential slide rail, a pipe wall circumferential fixing knob, and a pipe wall. The pipe wall is located on two inner and outer pipe wall circumferential slide rails, and the pipe wall circumferential fixing knob is located at the position of each pipe wall adjacent to the pipe wall circumferential slide rail. The thermal conductive material thickness adjustment system includes thermal conductive material, thermal conductive material clamp, and thermal conductive material clamp telescopic adjustment knob. The thermal conductive material clamp is located in the thermal insulation material. The thermal conductive material clamp telescopic adjustment knob is installed in the pre-drilled hole on the clamp to fix the thermal conductive material of the corresponding size inside the hot and cold source pipe through the clamp. The subway tunnel segment includes an inner tunnel segment and an outer tunnel segment, and the tunnel segment thickness adjustment system is located inside the subway tunnel segment; The segment thickness adjustment system includes a telescopic plate, a fixed end plate, a hinged joint connecting plate, and a hinged joint. The fixed end plate is located between the inner segment and the outer segment. The telescopic plate is connected to the two fixed end plates, and the hinged joint is used to fix the two hinged joint connecting plates to the fixed end plates as a whole.

2. The testing device for the performance of subway tunnels under circumferential non-uniform freeze-thaw conditions as described in claim 1, characterized in that, The front and rear panels include a cold source interface, a heat source interface, and a soil baffle. The cold source interface and the heat source interface are distributed in a ring on the front and rear panels, and their specific positions coincide with the positions of the cold source pipe and the heat source pipe. The soil baffle is located on the front and rear panels and coincides with the position of the soil.

3. The testing device for the performance of subway tunnels under circumferential non-uniform freeze-thaw conditions as described in claim 1, characterized in that, The subway tunnel segments are divided into several areas in the ring direction and distinguished by subway tunnel segment zone numbers.

4. The testing device for the performance of subway tunnels under circumferential non-uniform freeze-thaw conditions as described in claim 1, characterized in that, The locations of the hot and cold sources are arranged in several zones along the ring direction, and are distinguished by hot and cold source zone numbers.

5. A method for testing the performance of a subway tunnel under circumferential non-uniform freeze-thaw conditions as described in claim 1, characterized in that, The method includes the following steps: Step 1: Determine the material, inner diameter, and zones of the subway tunnel segments based on the project characteristics and testing requirements; Step 2: Install a testing device for the performance of subway tunnels under circumferential uneven freeze-thaw conditions. The testing device includes a pipe wall circumferential position adjustment system, thermal insulation material, thermal conductive material thickness adjustment system, subway tunnel segments, tunnel segment thickness adjustment system, heat source, heat source pipe, cold source, cold source pipe, and front and rear panels. The cold source is surrounded by the cold source pipe, and the heat source is surrounded by the heat source pipe. A water thermometer is installed in the cold source and the heat source. The cold source pipe and the heat source pipe are fixed on the pipe wall circumferential position adjustment system and are arranged in a ring. The thermal insulation material is located in the gap at the junction of the cold source pipe and the heat source pipe. The thermal conductive material thickness adjustment system is located inside the cold source pipe and the heat source pipe. The subway tunnel segment is located at the ring center of the entire testing device. The tunnel segment thickness adjustment system is located inside the subway tunnel segment. The front and rear panels are located at the front and rear ends of the entire testing device, respectively. The cavity formed by the front and rear panels and the pipe wall circumferential position adjustment system is filled with soil. An earth pressure cell, a displacement gauge, and a moisture content probe are installed in the soil area. Step 3: Determine the temperature parameters of the cold source and heat source, turn on the external cold source and heat source switches, connect the cold source pipe and heat source pipe to the external cold source and heat source respectively, and reach the corresponding test temperature; set the cold source temperature and heat source temperature according to the test requirements; supply cold source to the installed cold source pipe through the cold source interface reserved on the front panel; supply heat source to the installed heat source pipe through the heat source interface reserved on the device box; the cold and heat sources flow back to the external cold and heat source system from the cold and heat source interfaces reserved on the rear panel and then flow into the cold and heat source pipes, forming an internal and external circulation of cold and heat sources; Step 4: Start the experiment and collect data: Record the initial data of each sensor before the experiment begins. Once the temperature of the cold source and the heat source reaches the test temperature and remains constant, record the corresponding test data every half hour. Stop the experiment when the data at the test points stabilizes. Step 5: Cyclic testing of different cold and heat source temperatures. Repeat steps 3 to 4. By changing the temperature of the external cold and heat sources, the frost heave and thaw settlement of soil at different cold and heat source temperatures can be tested simultaneously.

6. The method as described in claim 5, characterized in that, In step 2, the positions of the cold source pipe and the heat source pipe on the circumferential position adjustment system of the pipe wall are determined according to engineering requirements; the thickness of the thermally conductive material is determined according to engineering requirements; the thickness of the subway tunnel segment is determined according to engineering requirements. The testing method also includes the following steps: Step 6: Cyclic test at different cold and heat source locations. Repeat steps 2 to 4. By changing the location of the cold and heat source interfaces, freeze-thaw tests can be performed at different cold and heat source locations and different cold and heat source temperatures in the circumferential direction. Step 7: Cyclic test of different thermal conductive material thicknesses. Repeat steps 2 to 4. By changing the position of the cold source and heat source interface, the thickness of the thermal conductive material can be adjusted by adjusting the thermal conductive material thickness adjustment system. This can achieve test of uneven freeze-thaw expansion and thaw settlement, circumferential cold source and heat source positions and different cold and heat source temperatures. Step 8: Cyclic test of different subway tunnel segment thicknesses. Repeat steps 2 to 4. By changing the position of the cold source and heat source interface, adjusting the thickness of the heat-conducting material through the heat-conducting material thickness adjustment system, and adjusting the length of the telescopic plate, it is possible to achieve working condition testing for circumferential uneven freeze-thaw expansion and thaw settlement, different cold source and heat source positions, different subway tunnel segment thicknesses, and different cold and heat source temperatures. Step 9: End the test, remove the soil, and dismantle the device.

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