Testing device and method for influence of uneven freezing construction on tunnel bearing performance

Abstract

A kind of testing device of the influence of uneven freezing construction on tunnel bearing performance, including device box, tunnel, side freezing system, corner freezing system and internal freezing system, the corner freezing system is located at four right angles in device box, the side freezing system is located at four side edges in device box, the tunnel is located inside device box, the device box is filled with soil between tunnel outside, the internal freezing system is located inside subway tunnel, the internal freezing system is filled with soil between subway tunnel inside, and soil area is provided with earth pressure cell, displacement meter and moisture content probe head.A kind of testing method of the influence of uneven freezing construction on tunnel bearing performance is provided.The present application can quickly test the adverse effects of regional uneven frost heaving on tunnel internal force and deformation.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering technology and relates to a testing device and method for the impact of uneven freezing construction on the bearing capacity of tunnels, which is applicable to the testing of the effects of uneven freezing on tunnel properties. Background Technology

[0002] Freezing methods utilize artificial refrigeration to transform natural soil and rock into frozen soil, increasing their strength and stability, and are widely used in underground engineering. However, artificial freezing causes a rapid drop in ground temperature, generating enormous frost heave forces that can lead to damage to surrounding underground structures. Existing freezing simulation devices employ a long-term energy exchange method between a low-temperature medium and the soil to achieve frost heave, but this method struggles to precisely control the size of the frozen area. Therefore, existing methods still have the following shortcomings:

[0003] 1) Conventional freezing devices use freezing tubes, which typically require more than 48 days of freezing time to achieve the desired freezing effect, making it impossible to quickly test the impact of frost heave on the tunnel.

[0004] 2) Freezing methods that use low-temperature media for heat exchange produce frozen areas that are uniformly distributed along the axial direction of the freezing tube, making it impossible to test for uneven axial freezing expansion.

[0005] 3) Existing frost heave devices can only test tunnel changes caused by frost heave on the outside of the tunnel, and cannot simulate frost heave inside the tunnel. Summary of the Invention

[0006] To overcome the shortcomings of existing frost heave testing methods, such as the inability to quickly measure frost heave, the inability to measure axially uneven frost heave, and the inability to simulate frost heave within tunnels, this invention provides a testing device and method for the impact of uneven freezing construction on the load-bearing capacity of tunnels. This device can quickly test the adverse effects of regional uneven frost heave on the internal forces and deformations of tunnels. This device can not only achieve uneven frost heave testing at any position along the tunnel axis, but is also simple, convenient, low-cost, and quick.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] A testing device for the impact of uneven freezing construction on the bearing capacity of tunnels includes a device box, a tunnel, an edge freezing system, a corner freezing system, and an internal freezing system. The corner freezing systems are located at the four right angles inside the device box, the edge freezing systems are located on the four sides inside the device box, the tunnel is located inside the device box, and the space between the device box and the outside of the tunnel is filled with soil. The internal freezing system is located inside the tunnel, and the space between the internal freezing system and the inside of the tunnel is filled with soil. A soil pressure gauge, a displacement gauge, and a moisture content probe are installed in the soil area.

[0009] Furthermore, the device box includes a box body, a box body cover, and a connection port. The device box is formed by splicing the box body cover and the box body, and the connection port is located on the front and rear panels of the device box.

[0010] Furthermore, the corner freezing system includes a corner fixing frame, a corner control rod, a corner barometer, a corner strip airbag, and a telescopic rotating rod. The corner control rod is installed in a reserved track in the corner fixing frame. One end of the corner strip airbag is fixed to the corner fixing frame, and the other end is fixed to the end of the corner control rod. A corner barometer is installed between the corner fixing frame and the corner strip airbag. The telescopic rotating rod is an independent component that can be inserted into the corner control rod during use.

[0011] Furthermore, the edge freezing system includes an edge connecting pipe, an edge telescopic rod, an edge control shaft, an edge control panel, an edge barometer, an edge strip-shaped airbag, an edge rotary joint, an edge rotary cover, and an edge self-locking button. The edge telescopic rod is embedded in a pre-drilled hole in the edge control shaft. The edge self-locking button is fixed to the end of the edge control shaft. Multiple edge self-locking buttons are combined to form the edge control panel. The edge connecting pipe is connected via the edge rotary joint using a sleeve method. The edge control panel is fixed to the front end of the edge connecting pipe, the edge rotary cover is fixed to the rear end of the edge connecting pipe, the edge control shaft is fixed inside the edge connecting pipe, and the two ends of the edge strip-shaped airbag are fixed to both sides of the edge rotary joint. An edge barometer is installed between the edge strip-shaped airbag and the edge rotary joint.

[0012] Furthermore, the tunnel includes a main tunnel segment and a tunnel segment capping block, which are spliced ​​together to form the tunnel.

[0013] Furthermore, the internal freezing system includes a fixed circular tube, an internal airbag, a telescopic mechanical plate, a fixed circular tube connector, an air vent, a fixing buckle, and an internal pressure gauge. The small hole pre-drilled on the telescopic mechanical plate is the air vent. One end of the telescopic mechanical plate is connected to the fixed circular tube via the fixing buckle, and the other end is connected to the internal airbag. The two ends of the internal airbag are fixed to the ends of two adjacent telescopic mechanical plates. An internal pressure gauge is installed between the internal airbag and the fixed circular tube. The fixed circular tube connector is installed at both ends of the fixed circular tube and can be embedded into the connection port of the device box.

[0014] A test method for the impact of uneven freezing construction on the bearing capacity of tunnels includes the following steps:

[0015] Step 1: Determine the similarity ratio of the testing device based on the relationship between the tunnel pipe diameter, tunnel burial depth, soil layer thickness, and device box size;

[0016] Step 2: Determine the soil layers required for testing based on the geological survey report and tunnel depth, and determine the thickness and distribution of the soil layers;

[0017] Step 3: Install a testing device to test the impact of uneven freezing construction on the bearing capacity of the tunnel. The testing device includes a device box, a tunnel, an edge freezing system, a corner freezing system, and an internal freezing system. The corner freezing system is located at the four right angles inside the device box, the edge freezing system is located on the four sides inside the device box, the tunnel is located inside the device box, strain gauges are installed on the inner and outer sides of the tunnel, and soil is filled between the device box and the outer side of the tunnel. The internal freezing system is located inside the tunnel, and soil is filled between the internal freezing system and the inner side of the tunnel. Soil pressure gauges, displacement gauges, and moisture content detectors are installed in the soil area.

[0018] Step 4: Adjust the size of the airbags in the corresponding area according to the location and size of the frost heave volume, so that the expansion position and volume of the airbags are the same as the location and size determined by the project requirements; calculate the corresponding frost heave force according to the size of the frost heave volume, soil parameters and other indicators, and convert it into air pressure.

[0019] Step 5: Start the test and collect data: Record the initial data of each sensor before the test begins. After each barometer reading reaches the determined pressure value and remains constant, record the data of each monitoring point at set time intervals. Stop the test when the data of the monitoring points stabilizes.

[0020] Step 6: Test the frost heave at any location outside the tunnel. Repeat steps 3 to 5 to test the frost heave at any location outside the tunnel.

[0021] Step 7: Test the frost heave at different locations inside the tunnel. Repeat steps 3 to 5 to test the frost heave at any location inside the tunnel.

[0022] Step 8: Simultaneous frost heave test at different locations inside and outside the tunnel. Repeat steps 3 to 5 to achieve simultaneous frost heave test at different locations inside and outside the tunnel.

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

[0024] Furthermore, in step 5, the set time period is half an hour.

[0025] In step 3, the process of installing the testing device for the impact of uneven freezing construction on the tunnel's bearing capacity is as follows:

[0026] 3.1. Based on the tunnel's inner diameter, burial depth, and the location of freezing points in the internal environment, determine the size and quantity of each component in the internal freezing system. The fixed circular pipe is located at the center of the device box. Considering the size of the freezing area, internal airbags and telescopic mechanical plates are arranged on the fixed circular pipe. The telescopic mechanical plates have the same axial length as the fixed circular pipe.

[0027] 3.2 Based on the tunnel's outer diameter, burial depth, and the location of freezing points in the external environment, determine the dimensions and quantity of each component in the edge freezing system and corner freezing system. Arrange the edge freezing system and corner freezing system in the device box. The edge strip airbags can form a semicircle with a maximum radius of 100mm, and the corner strip airbags can form a quarter circle with a maximum radius of 300mm.

[0028] 3.3 Assemble the corner freezing system and install it inside the device box. First, install the corner control rods at equal intervals on the corner fixing frame. Then, fix one end of the corner strip airbag to the corner fixing frame and the other end to the end of the corner control rod. Next, place the corner barometer between the corner strip airbag and the corner fixing frame to form a corner freezing system. After assembling the corner freezing system in the above order, install it at the four corners of the device box.

[0029] 3.4 Assemble the edge freezing system and install it inside the device box. First, fix the edge telescopic rods at equal intervals on the edge control shaft and install the edge self-locking button to form the edge control panel. Then, connect the edge connecting pipe through the edge swivel joint and install the edge swivel cap at the tail end. Next, fix the edge control shaft with the edge telescopic rods inside the connected edge connecting pipe. Then, fix the edge strip airbag to the connected edge connecting pipe and place an external barometer between the external strip airbag and the connecting pipe to form an external freezing system. Assemble the edge freezing system in the above order and install it on the four sides of the device box according to the set interval.

[0030] 3.5 Fill the soil below the tunnel and install sensors. Fill the soil layer into the device box to the set depth and install the corresponding sensors. The installation of sensors is carried out simultaneously with the soil filling. The soil pressure gauge, displacement gauge and moisture content probe are arranged inside the soil between the device box and the tunnel. In the radial direction, the three types of sensors are arranged around the center point of the device box at intervals of 10° central angle. In the axial direction, the sensors are arranged at equal intervals.

[0031] 3.6 Adhere strain gauges and install them in the tunnel inside the device box. Adhere the strain gauges symmetrically to the inner and outer walls of the tunnel. Arrange the strain gauges radially at a central angle of 30° and axially at equal intervals of 150mm. Then place the main body of the tunnel on top of the filled soil layer.

[0032] 3.7 Fill the soil below the internal freezing system and bury the sensors. Continue filling the soil to the preset depth and bury the corresponding sensors. The burying of the sensors is carried out simultaneously with the soil filling. The sensor arrangement inside the tunnel is as follows: In the radial direction, the earth pressure gauge, displacement gauge and moisture content probe are arranged alternately around the center point of the device box at intervals of 15° central angle. In the axial direction, the sensors are arranged at equal intervals.

[0033] 3.8 Assemble the internal freezing system and install it in the device box. First, connect the bottom of the telescopic mechanical plate to the fixed round tube through the fixing buckle. Then, fix the internal airbags at both ends of each telescopic mechanical plate. Next, install the internal pressure gauge in each airbag. Then, connect the fixed round tube connector to the fixed round tube and install it on the connection port.

[0034] 3.9 Continue filling the soil and burying the sensors. After filling the soil to the specified depth, install the tunnel capping block, then fill the device box with soil and install the box cover. The burying of the sensors is carried out simultaneously with the soil filling.

[0035] 3.10 Determine the frost heave force parameters. Considering that the frost heave occurring inside and outside the tunnel is all linear frost heave, it is assumed that the tunnel and the frozen soil are in elastic deformation, according to... Calculate the initial frost heave force and determine the corrected frost heave force based on the actual engineering conditions, whereby... Porosity The coefficient of volume expansion when water turns into ice. This represents the elastic modulus of the soil after freezing. Poisson's ratio for the lining and the frozen soil, respectively. This is the ratio of the elastic modulus of the frozen soil to the elastic modulus of the lining. This is a coefficient related to lining dimensions, frozen area size, etc.

[0036] In step 4, the internal freezing system adjustment process is as follows: based on the actual engineering situation, determine the location and distribution of frost heave inside the tunnel, and then adjust the telescopic mechanical plate at the corresponding position of the internal freezing system to change the position and size of the internal airbags so that the frost heave area inside the tunnel is consistent with the actual engineering.

[0037] The adjustment process of the edge and corner freezing system is as follows: Based on the actual situation of the project, determine the location and distribution of frost heave outside the tunnel, then use the edge control panel to adjust the edge rotary joint to change the size of the airbags at the corresponding positions of the edge strip airbags, and then use the telescopic swivel to rotate the corner control rod to change the size of the airbags at the corresponding positions of the corner strip airbags, so that the frost heave area outside the tunnel is consistent with the actual project.

[0038] In step 6, based on the frost heave at any location outside the tunnel, step 4 is repeated to calculate the frost heave force at any location outside the tunnel; by adjusting the edge rotary joints at different locations in a certain edge freezing system or the corner control rods at different locations in a certain corner freezing system, the location of frost heave and the size of the frost heave area can be changed axially; repeating step 5 can realize the test of frost heave at any location outside the tunnel.

[0039] In step 7, based on the frost heave at any location inside the tunnel, step 4 is repeated to calculate the frost heave force at any location inside the tunnel; adjusting the length of a telescopic mechanical plate in the internal freezing system can change the size of the frost heave area axially; repeating step 5 can realize the test of frost heave occurring at any location inside the tunnel.

[0040] This invention provides a testing device for the impact of uneven freezing construction on the load-bearing capacity of tunnels, capable of efficiently testing uneven frost heave occurring inside and outside the tunnel. It has the following advantages: 1) It can quickly achieve the frost heave effect, using air pressure to simulate frost heave force and rapidly simulating the frost heave force and volume changes caused by frost heave through inflation; 2) It can control the size of the axial uneven freezing area, using telescopic mechanical plates and internal airbags to control the strip-shaped freezing area inside the tunnel; and controlling the strip-shaped freezing area outside the tunnel by controlling the axis and the strip-shaped airbags; 3) By inflating airbags at different locations to simulate frost heave, it can simultaneously test the frost heave effect inside and outside the tunnel; 4) By controlling air pressure changes, it can simulate the impact of different degrees of frost heave on the tunnel, with simple and convenient simulation, low cost, and short time. Attached Figure Description

[0041] Figure 1 This is a front view of a testing device for the impact of uneven freezing construction on the load-bearing capacity of tunnels.

[0042] Figure 2 This is an AA cross-sectional view of the test device for the impact of uneven freezing construction on the load-bearing capacity of tunnels.

[0043] Figure 3 This is a detailed drawing of the telescopic mechanical plate.

[0044] Figure 4 This is a cross-sectional view of the edge freezing system.

[0045] Figure 5 This is a cross-sectional view of the edge freezing system.

[0046] Figure 6 These are detailed diagrams of the edge control panel and the edge rotary joint, where (a) is the edge control panel, (b) is in the active state, and (c) is in the locked state.

[0047] Figure 7 This is a detailed diagram of the edge control axis, where (a) is the active state and (b) is the locked state.

[0048] Figure 8 This is a cross-sectional view of the corner freezing system.

[0049] Figure 9 This is a cross-sectional view of the corner freezing system.

[0050] The attached diagram is labeled as follows: 1-1. Box body; 1-2. Box body top cover; 2-1. Segment body; 2-2. Segment top block; 3-1. Side connecting pipe; 3-2. Side telescopic rod; 3-3. Side control shaft; 3-4. Side control panel; 3-5. Side barometer; 3-6. Side strip-shaped airbag; 3-7. Side rotary joint; 3-8. Side rotating cover; 3-9. Side self-locking button; 4-1. 4-2. Corner fixing bracket; 4-3. Corner control rod; 4-4. Corner barometer; 4-5. Corner strip airbag; 4-6. Telescopic rotating rod; 5-1. Fixed round tube; 5-2. Internal airbag; 5-3. Telescopic mechanical plate; 5-4. Fixed round tube connector; 5-5. Air outlet; 5-6. Fixing buckle; 5-7. Internal barometer; 6. Soil pressure gauge; 7. Displacement gauge; 8. Moisture content probe; 9. Strain gauge. Detailed Implementation

[0051] The present invention will now be further described with reference to the accompanying drawings.

[0052] Reference Figures 1-9 A testing device for the impact of uneven freezing construction on the bearing capacity of a tunnel includes a device box, a tunnel, an edge freezing system, a corner freezing system, and an internal freezing system. The corner freezing systems are located at the four right angles inside the device box, the edge freezing systems are located on the four sides inside the device box, the tunnel is located inside the device box, and the space between the device box and the outside of the tunnel is filled with soil. The internal freezing system is located inside the tunnel, and the space between the internal freezing system and the inside of the tunnel is filled with soil. The soil area is equipped with an earth pressure gauge 6, a displacement gauge 7, and a moisture content detector 8.

[0053] Furthermore, the device box includes a box body 1-1, a box body cover 1-2, and a connection port. The device box is formed by splicing the box body cover and the box body, and the connection port is located on the front and rear panels of the device box.

[0054] Furthermore, the corner freezing system includes a corner fixing frame 4-1, a corner control rod 4-2, a corner barometer 4-3, a corner strip airbag 4-4, and a telescopic rotating rod 4-5. The corner control rod is installed in the reserved track of the corner fixing frame. One end of the corner strip airbag is fixed to the corner fixing frame, and the other end is fixed to the end of the corner control rod. A corner barometer is set between the corner fixing frame and the corner strip airbag. The telescopic rotating rod is an independent component that can be inserted into the corner control rod during use.

[0055] Furthermore, the edge freezing system includes an edge connecting pipe 3-1, an edge telescopic rod 3-2, an edge control shaft 3-3, an edge control panel 3-4, an edge barometer 3-5, an edge strip-shaped airbag 3-6, an edge rotary joint 3-7, an edge rotating cover 3-8, and an edge self-locking button 3-9. The edge telescopic rod is embedded in a pre-drilled hole in the edge control shaft. The edge self-locking button is fixed to the end of the edge control shaft. Multiple edge self-locking buttons are combined to form the edge control panel. The edge connecting pipe is connected via the edge rotary joint using a sleeve method. The edge control panel is fixed to the front end of the edge connecting pipe, the edge rotating cover is fixed to the rear end of the edge connecting pipe, the edge control shaft is fixed inside the edge connecting pipe, and the two ends of the edge strip-shaped airbag are fixed to both sides of the edge rotary joint. An edge barometer is installed between the edge strip-shaped airbag and the edge rotary joint.

[0056] Furthermore, the tunnel includes a main segment 2-1 and a segment capping block 2-2, which are spliced ​​together to form the tunnel.

[0057] Furthermore, the internal freezing system includes a fixed circular tube 5-1, an internal airbag 5-2, a telescopic mechanical plate 5-3, a fixed circular tube connector 5-4, an air outlet 5-5, a fixing buckle 5-6, and an internal pressure gauge 5-7. The small holes pre-drilled on the telescopic mechanical plate are air outlets. One end of the telescopic mechanical plate is connected to the fixed circular tube via a fixing buckle, and the other end is connected to the internal airbag. The two ends of the internal airbag are fixed to the ends of two adjacent telescopic mechanical plates. An internal pressure gauge is installed between the internal airbag and the fixed circular tube. The fixed circular tube connector is installed at both ends of the fixed circular tube and can be embedded into the connection port of the device box. A test method for the impact of uneven freezing construction on the load-bearing capacity of a tunnel includes the following steps:

[0058] Step 1: Determine the similarity ratio of the testing device based on the relationship between the tunnel pipe diameter, tunnel burial depth, soil layer thickness, and device box size;

[0059] Step 2: Determine the soil layers required for testing based on the geological survey report and tunnel depth, and determine the thickness and distribution of the soil layers;

[0060] Step 3: Install a testing device to test the impact of uneven freezing construction on the bearing capacity of the tunnel. The testing device includes a device box, a tunnel, an edge freezing system, a corner freezing system, and an internal freezing system. The corner freezing system is located at the four right angles inside the device box, the edge freezing system is located on the four sides inside the device box, the tunnel is located inside the device box, and the space between the device box and the outside of the tunnel is filled with soil. The internal freezing system is located inside the tunnel, and the space between the internal freezing system and the inside of the tunnel is filled with soil. The soil area is equipped with an earth pressure gauge 6, a displacement gauge 7, and a moisture content detector 8.

[0061] Step 4: Adjust the size of the airbags in the corresponding area according to the location and size of the frost heave volume, so that the expansion position and volume of the airbags are the same as the location and size determined by the project requirements; calculate the corresponding frost heave force according to the size of the frost heave volume, soil parameters and other indicators, and convert it into air pressure.

[0062] Step 5: Start the test and collect data: Record the initial data of each sensor before the test begins. After each barometer reading reaches the determined pressure value and remains constant, record the data of each monitoring point every half hour. Stop the test when the data of the monitoring point reaches stability.

[0063] Step 6: Test the frost heave at any location outside the tunnel. Repeat steps 3 to 5 to test the frost heave at any location outside the tunnel.

[0064] Step 7: Test the frost heave at different locations inside the tunnel. Repeat steps 3 to 5 to test the frost heave at any location inside the tunnel.

[0065] Step 8: Simultaneous frost heave test at different locations inside and outside the tunnel. Repeat steps 3 to 5 to achieve simultaneous frost heave test at different locations inside and outside the tunnel.

[0066] Step 9: End the test, release the air and pressure, remove the soil, and dismantle the device.

[0067] A subway tunnel in a certain city has a shield tunnel diameter of 6.2m and a burial depth of 20m. The excavation of the connecting passage between lines requires the freezing method. In order to quickly test the adverse effects of uneven regional frost heave on the internal forces and deformation of the tunnel, the testing device and method for the impact of uneven freezing construction on the tunnel bearing capacity provided by this invention are adopted.

[0068] In this embodiment, according to the on-site geological survey report, the soil layers traversed by the tunnel boring machine, from top to bottom, are miscellaneous fill, clay, silty clay, and sandy silt, with thicknesses of 2m, 5m, 8m, and 9m respectively. The dimensions of the model box are 1.2m × 1.6m × 1.2m (length × width × height). The box body is made of stainless steel.

[0069] The implementation process of this embodiment is as follows:

[0070] Based on the actual conditions of the project and the current status of the test site, the similarity ratio of the test device was determined to be 20:1, determined by the tunnel diameter and soil thickness.

[0071] Determine the dimensions of the device box. Based on the similarity ratio in step (1), the dimensions of the device box are determined to be 1.2m × 1.6m × 1.2m (length × width × height), and the device box is made of stainless steel.

[0072] Based on the tunnel's inner diameter, burial depth, and the location of freezing points in the internal environment, the dimensions and quantity of each component in the internal freezing system are determined. According to the actual conditions of this project, the diameter of the fixed circular pipe 5-1 is determined to be 144mm. The fixed circular pipe 5-1 is located at the exact center of the device box. Considering the size of the freezing area, eight internal airbags 5-2 and eight telescopic mechanical plates 5-3 are arranged on the fixed circular pipe 5-1. The telescopic mechanical plates 5-3 have the same axial length as the fixed circular pipe 5-1. The length of the telescopic mechanical plate 5-3 when fully retracted is 56mm, and its maximum length when extended is 150mm.

[0073] Based on the tunnel's outer diameter, burial depth, and the location of freezing points in the external environment, the dimensions and quantity of each component in the edge and corner freezing systems are determined. Considering the actual conditions of this project, 12 sets of edge freezing systems and 4 sets of corner freezing systems are arranged in the equipment box. The edge strip airbags 3-6 can form a semi-cylinder with a maximum radius of 100mm, and the corner strip airbags 4-6 can form a quarter-cylinder with a maximum radius of 300mm.

[0074] Determine the soil layer thickness and distribution. Based on the geological survey report, determine the soil layers required for the test. In this embodiment, the soil layers from top to bottom are miscellaneous fill, clay, silty clay, and sandy silt, with thicknesses of 2m, 5m, 8m, and 9m respectively. Based on the similarity ratio in step (1), the soil layer thicknesses in the device box are determined to be 0.1m, 0.25m, 0.4m, and 0.45m respectively.

[0075] Assemble the corner freezing system and install it inside the device box. First, install 11 corner control levers 4-2 at equal intervals on the corner mounting bracket 4-1. Then, fix one end of the corner strip airbag 4-4 ​​to the corner mounting bracket 4-1 and the other end to the end of the corner control lever 4-2. Next, place the corner barometer 4-3 between the corner strip airbag 4-4 ​​and the corner mounting bracket 4-1 to form a corner freezing system. After assembling four corner freezing systems in the above order, install them at the four corners of the device box.

[0076] Assemble the edge freezing system and install it inside the device box. First, fix 11 edge telescopic rods 3-2 at equal intervals on the edge control shaft 3-3 and install 11 edge self-locking buttons 3-9 to form the edge control panel 3-4. Then, connect 10 sections of edge connecting pipe 3-1 through the edge swivel joint 3-7 and install the edge swivel cap 3-8 at the tail end. Next, fix the edge control shaft 3-3 with the edge telescopic rods 3-2 inside the connected edge connecting pipe 3-1. Then, fix the edge strip airbag 3-6 to the connected edge connecting pipe 3-1 and place an external pressure gauge 3-5 between the external strip airbag 3-6 and the connecting pipe 3-1 to form an external freezing system 3. Assemble 12 sets of edge freezing systems in the above order and install them sequentially on the four sides of the device box at 200mm intervals.

[0077] The soil beneath the tunnel was filled and sensors were installed. Soil was filled into the device housing to a depth of 180mm, and the corresponding sensors were installed. The sensor installation was carried out simultaneously with the soil filling. Earth pressure gauges 6, displacement gauges 7, and moisture content detectors 8 were arranged inside the soil between the device housing and the tunnel. Radially, the three types of sensors were arranged around the center point of the device housing, staggered at 10° central angle intervals, with radii of 465mm and 520mm respectively; axially, the spacing between the sensors was 150mm.

[0078] Attach the strain gauges and install the tunnel inside the device box. Attach the strain gauges 9 symmetrically to the inner and outer walls of the tunnel. Arrange the strain gauges 9 radially at a central angle of 30° and axially at equal intervals of 150mm. Then place the tunnel body 2-1 above the soil layer filled in step (8).

[0079] Fill the soil below the internal freezing system and bury the sensors. Continue filling the soil to 470mm and bury the corresponding sensors. The burying of the sensors is carried out simultaneously with the soil filling. The sensor arrangement on the outside of the tunnel is the same as in step (8), and the sensor arrangement on the inside of the tunnel is as follows: In the radial direction, the earth pressure gauge 6, displacement gauge 7 and moisture content probe 8 are arranged around the center point of the device box at intervals of 15° central angle, with radii of 210mm and 295mm respectively; in the axial direction, the spacing between each sensor is 150mm.

[0080] Assemble the internal freezing system and install it inside the device box. First, connect the bottom of the telescopic mechanical plate 5-3 to the fixed round tube 5-1 using the fixing buckle 6-6. Then, fix the internal airbags 5-2 at both ends of each telescopic mechanical plate 5-3. Next, install the internal pressure gauges 5-7 inside each airbag. Then, connect the fixed round tube connector 5-4 to the fixed round tube 5-1 and install it on the connection port.

[0081] Continue filling the soil and burying the sensors. After filling the soil to 980mm, install the segment capping block 2-2, then fill the device box with soil and install the box cover 1-2. The burying of the sensors is carried out simultaneously with the soil filling. The sensor arrangement on the outside of the tunnel is the same as in step (8), and the sensor arrangement on the inside of the tunnel is the same as in step (10).

[0082] Determine the frost heave force parameters. Considering that the frost heave occurring inside and outside the tunnel is all linear regional frost heave, assume that the tunnel and the frozen soil are in elastic deformation, and follow... Calculate the initial frost heave force and determine the corrected frost heave force based on the actual engineering conditions, whereby... Porosity The coefficient of volume expansion when water turns into ice. This represents the elastic modulus of the soil after freezing. Poisson's ratio for the lining and the frozen soil, respectively. This is the ratio of the elastic modulus of the frozen soil to the elastic modulus of the lining. This is a coefficient related to lining dimensions, frozen area size, etc.

[0083] Internal freezing system adjustment. Based on the actual engineering conditions, determine the location and distribution of frost heave inside the tunnel, and then adjust the telescopic mechanical plate 5-3 at the corresponding position of the internal freezing system to change the position and size of the internal airbag 5-2, so that the frost heave area inside the tunnel is consistent with the actual engineering.

[0084] Adjustment of the edge and corner freezing system. Based on the actual engineering conditions, determine the location and distribution of frost heave outside the tunnel. Then, use the edge control panel 3-4 to adjust the edge rotary joint 3-7 to change the size of the airbags at the corresponding positions of the edge strip airbags 3-6. Next, use the telescopic rod 4-5 to rotate the corner control rod 4-2 to change the size of the airbags at the corresponding positions of the corner strip airbags 4-4, so that the frost heave area outside the tunnel is consistent with the actual engineering conditions.

[0085] The freeze-thaw test was started and data was collected. First, the initial data of each sensor was recorded before the test began. Then, the internal airbags 5-2 at the corresponding positions in the internal freezing system in step (14) were inflated and pressurized until the reading of the internal barometer 5-7 reached the value determined in step (13). The edge strip airbags 3-6 at the corresponding positions in the edge freezing system in step (15) were inflated and pressurized until the reading of the edge barometer 3-5 reached the value determined in step (13). The corner strip airbags 4-4 at the corresponding positions in the corner freezing system in step (15) were inflated and pressurized until the reading of the corner barometer 4-3 reached the value determined in step (13). Data at each monitoring point was recorded every half hour. The test was stopped when the data at the monitoring points stabilized.

[0086] Test for frost heave at any location outside the tunnel. Based on the frost heave at any location outside the tunnel, repeat step (13) to calculate the frost heave force at any location outside the tunnel; repeat step (15) to adjust the edge rotary joint 3-7 at different locations in a certain edge freezing system or the corner control rod 4-2 at different locations in a certain corner freezing system, so that the location of frost heave and the size of the frost heave area can be changed axially; repeat step (16) to realize the test for frost heave at any location outside the tunnel.

[0087] Test for frost heave at any location inside the tunnel. Based on the frost heave situation at any location inside the tunnel, repeat step (13) to calculate the frost heave force at any location inside the tunnel; repeat step (15) to adjust the length of a telescopic mechanical plate 5-3 in the internal freezing system so that the size of the frost heave area can change in the axial direction; repeat step (16) to realize the test for frost heave at any location inside the tunnel.

[0088] Tests for uneven frost heave occurring simultaneously inside and outside the tunnel. Repeating steps (18) and (19) can achieve tests for uneven frost heave occurring simultaneously inside and outside the tunnel.

[0089] End the experiment. Turn off the experimental apparatus. First, deflate and depressurize the edge strip airbags 3-6, corner strip airbags 4-4, and internal airbags 5-2. Then, retract the telescopic mechanical plate 5-3 to its minimum. After removing the top cover 1-2 of the box, clean the soil in the device box layer by layer. Then, remove the segment capping block 2-2, the internal freezing system, the segment body 2-1, the corner freezing system, and the edge freezing system in sequence to complete the experiment.

[0090] 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 impact of uneven freezing construction on the bearing capacity of tunnels, characterized in that, The test device, which uses air pressure to simulate frost heave, includes a device box, a tunnel, an edge freezing system, a corner freezing system, and an internal freezing system. The corner freezing systems are located at the four right angles inside the device box, the edge freezing systems are located on the four sides inside the device box, the tunnel is located inside the device box, and the space between the device box and the outside of the tunnel is filled with soil. The internal freezing system is located inside the tunnel, and the space between the internal freezing system and the inside of the tunnel is filled with soil. The soil area is equipped with an earth pressure gauge, a displacement gauge, and a moisture content detector. The corner freezing system includes a corner fixing frame, a corner control rod, a corner barometer, a corner strip airbag, and a telescopic rotating rod. The corner control rod is installed in a reserved track in the corner fixing frame. One end of the corner strip airbag is fixed to the corner fixing frame, and the other end is fixed to the end of the corner control rod. A corner barometer is installed between the corner fixing frame and the corner strip airbag. The telescopic rotating rod is an independent component that is inserted into the corner control rod during use. The edge freezing system includes an edge connecting pipe, an edge telescopic rod, an edge control shaft, an edge control panel, an edge barometer, an edge strip airbag, an edge rotary joint, an edge rotary cover, and an edge self-locking button. The edge telescopic rod is embedded in a pre-drilled hole in the edge control shaft. The edge self-locking button is fixed to the end of the edge control shaft. Multiple edge self-locking buttons are combined to form the edge control panel. The edge connecting pipe is connected via an edge rotary joint using a sleeve. The edge control panel is fixed to the front end of the edge connecting pipe. The edge rotary cover is fixed to the rear end of the edge connecting pipe. The edge control shaft is fixed inside the edge connecting pipe. The two ends of the edge strip airbag are fixed to both sides of the edge rotary joint. An edge barometer is installed between the edge strip airbag and the edge rotary joint. The internal freezing system includes a fixed circular tube, an internal airbag, a telescopic mechanical plate, a fixed circular tube connector, an air vent, a fixing buckle, and an internal pressure gauge. The small hole pre-drilled on the telescopic mechanical plate is the air vent. One end of the telescopic mechanical plate is connected to the fixed circular tube via the fixing buckle, and the other end is connected to the internal airbag. The two ends of the internal airbag are fixed to the ends of two adjacent telescopic mechanical plates. An internal pressure gauge is installed between the internal airbag and the fixed circular tube. The fixed circular tube connector is installed at both ends of the fixed circular tube and is embedded in the connection port of the device box.

2. The testing device for the impact of uneven freezing construction on the bearing capacity of tunnels as described in claim 1, characterized in that, The device box includes a box body, a box body cover, and a connection port. The device box is formed by splicing the box body cover and the box body together, and the connection port is located on the front and rear panels of the device box.

3. The testing device for the impact of uneven freezing construction on the bearing capacity of tunnels as described in claim 1 or 2, characterized in that, The tunnel comprises a main tunnel segment and a roof segment block, which are joined together to form the tunnel.

4. A method for implementing the testing device for the impact of uneven freezing construction on the bearing capacity of tunnels as described in claim 1, characterized in that, The method includes the following steps: Step 1: Determine the similarity ratio of the testing device based on the relationship between the tunnel pipe diameter, tunnel burial depth, soil layer thickness, and device box size; Step 2: Determine the soil layers required for testing based on the geological survey report and tunnel depth, and determine the thickness and distribution of the soil layers; Step 3: Install a testing device to test the impact of uneven freezing construction on the bearing capacity of the tunnel. The testing device includes a device box, a tunnel, an edge freezing system, a corner freezing system, and an internal freezing system. The corner freezing system is located at the four right angles inside the device box, the edge freezing system is located on the four sides inside the device box, the tunnel is located inside the device box, strain gauges are installed on the inner and outer sides of the tunnel, and soil is filled between the device box and the outer side of the tunnel. The internal freezing system is located inside the tunnel, and soil is filled between the internal freezing system and the inner side of the tunnel. Soil pressure gauges, displacement gauges, and moisture content detectors are installed in the soil area. Step 4: Adjust the size of the airbags in the corresponding area according to the location and size of the frost heave volume, so that the expansion position and volume of the airbags are the same as the location and size determined by the engineering requirements; calculate the corresponding frost heave force according to the size of the frost heave volume and soil parameters, and convert it into air pressure. Step 5: Start the test and collect data: Record the initial data of each sensor before the test begins. After each barometer reading reaches the determined pressure value and remains constant, record the data of each monitoring point at set time intervals. Stop the test when the data of the monitoring points stabilizes. Step 6: Test the frost heave at any location outside the tunnel. Repeat steps 4 and 5 to test the frost heave at any location outside the tunnel. Step 7: Test the frost heave at different locations inside the tunnel. Repeat steps 4 and 5 to test the frost heave at any location inside the tunnel. Step 8: Simultaneous frost heave test at different locations inside and outside the tunnel. Repeat steps 4 to 5 to achieve simultaneous frost heave test at different locations inside and outside the tunnel. Step 9: End the test, release the air and pressure, remove the soil, and dismantle the device.

5. The method as described in claim 4, characterized in that, In step 3, the main process of testing the impact of uneven freezing construction on the tunnel's bearing capacity is as follows: 3.

1. Based on the tunnel's inner diameter, burial depth, and the location of freezing points in the internal environment, determine the size and quantity of each component in the internal freezing system. Considering the size of the freezing area, determine the number of internal airbags and telescopic mechanical plates to be arranged on the fixed circular pipe, and ensure that the telescopic mechanical plates have the same axial length as the fixed circular pipe. 3.2 Based on the tunnel's outer diameter, burial depth, and the location of freezing points in the external environment, determine the dimensions and quantity of each component in the edge freezing system and the corner freezing system. The edge strip airbags form semi-cylinders of the corresponding dimensions, and the corner strip airbags form quarter-cylinders. 3.3 Assemble the corner freezing system and install it inside the device box. First, install the corner control rods at equal intervals on the corner fixing frame. Then, fix one end of the corner strip airbag to the corner fixing frame and the other end to the end of the corner control rod. Next, place the corner barometer between the corner strip airbag and the corner fixing frame to form a corner freezing system. After assembling the corner freezing system in the above order, install it at the four corners of the device box. 3.4 Assemble the edge freezing system and install it inside the device box. First, fix the edge telescopic rods at equal intervals on the edge control shaft and install the edge self-locking button to form the edge control panel. Then, connect the edge connecting pipe through the edge swivel joint and install the edge swivel cap at the tail end. Next, fix the edge control shaft with the edge telescopic rods inside the connected edge connecting pipe. Then, fix the edge strip airbag to the connected edge connecting pipe and place an external barometer between the external strip airbag and the connecting pipe to form an external freezing system. Assemble the edge freezing system in the above order and install it on the four sides of the device box according to the set interval. 3.5 Fill the soil below the tunnel and bury the sensors. Fill the soil layer into the device box to the set depth and bury the corresponding sensors. In the radial direction, the three types of sensors are arranged around the center point of the device box in an alternating pattern at intervals of 10° central angles. In the axial direction, the sensors are arranged at equal intervals. 3.6 Adhere strain gauges and install them in the tunnel inside the device box. Adhere the strain gauges symmetrically to the inner and outer walls of the tunnel. Arrange the strain gauges radially at equal central angles and axially at equal intervals. Then place the main body of the tunnel on top of the filled soil layer. 3.7 Fill the soil below the internal freezing system and bury the sensors. In the radial direction, the earth pressure gauge, displacement gauge and moisture content probe are arranged alternately around the center point of the device box at intervals of 15° central angle. In the axial direction, the sensors are arranged at equal intervals. 3.8 Assemble the internal freezing system and install it in the device box. First, connect the bottom of the telescopic mechanical plate to the fixed round tube through the fixing buckle. Then, fix the internal airbags at both ends of each telescopic mechanical plate. Next, install the internal pressure gauge in each airbag. Then, connect the fixed round tube connector to the fixed round tube and install it on the connection port. 3.9 After continuing to fill the soil to the specified depth, install the segment capping block, then fill the device box with soil and install the box cover. The sensor installation is carried out simultaneously with the soil filling. 3.10 Determine the frost heave force parameters. Considering that the frost heave occurring inside and outside the tunnel is all in strip-shaped areas, according to... Calculate the initial frost heave force, where Porosity The coefficient of volume expansion when water turns into ice. This represents the elastic modulus of the soil after freezing. Poisson's ratio for the lining and the frozen soil, respectively. This is the ratio of the elastic modulus of the frozen soil to the elastic modulus of the lining. The coefficients are related to the lining size and the size of the frozen area, and the corrected frost heave force is determined based on the actual engineering conditions.

6. The method as described in claim 4 or 5, characterized in that, In step 4, the internal freezing system adjustment process is as follows: based on the actual engineering situation, determine the location and distribution of frost heave inside the tunnel, and then adjust the telescopic mechanical plate at the corresponding position of the internal freezing system to change the position and size of the internal airbags so that the frost heave area inside the tunnel is consistent with the actual engineering. The adjustment process of the edge and corner freezing system is as follows: Based on the actual situation of the project, determine the location and distribution of frost heave outside the tunnel, then use the edge control panel to adjust the edge rotary joint to change the size of the airbags at the corresponding positions of the edge strip airbags, and then use the telescopic swivel to rotate the corner control rod to change the size of the airbags at the corresponding positions of the corner strip airbags, so that the frost heave area outside the tunnel is consistent with the actual project.

7. The method as described in claim 4 or 5, characterized in that, In step 6, based on the frost heave at any location outside the tunnel, step 4 is repeated to calculate the frost heave force at any location outside the tunnel; the edge rotary joints at different locations in a certain edge freezing system or the corner control rods at different locations in a certain corner freezing system are adjusted to change the location of frost heave and the size of the frost heave area in the axial direction; step 5 is repeated to test the frost heave at any location outside the tunnel. In step 7, based on the frost heave at any location inside the tunnel, step 4 is repeated to calculate the frost heave force at any location inside the tunnel; the length of a telescopic mechanical plate in the internal freezing system is adjusted so that the size of the frost heave area changes axially; step 5 is repeated to test the frost heave at any location inside the tunnel.

Images