Rapid testing device and method for tunnel frost heaving damage characteristics

Abstract

A kind of quick test device of tunnel frost heaving damage characteristics, including device box, external freezing system, internal freezing system, tunnel segment and position adjusting system, the external freezing system is located in device box and is tangent with four faces of device box, the tunnel segment is located in external freezing system, the soil body between external freezing system and tunnel segment is filled, the position adjusting system is located in the front and rear ends of device box, the internal freezing system is located in tunnel segment, the internal freezing system is connected with the position adjusting system, the soil body between tunnel segment and internal freezing system is filled, and soil pressure gauge, displacement meter and moisture content probe head are arranged in soil body area.A kind of quick test method of tunnel frost heaving damage characteristics is provided.The present application can quickly test the adverse effects of point-like uneven frost heaving on internal force and deformation of tunnel, and is simple, convenient, low in cost and short in time.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tunnel engineering, and relates to a rapid testing device and method for tunnel frost heaving damage characteristics, which is suitable for testing the force properties of a tunnel affected by soil frost heaving. BACKGROUND

[0002] The existing freezing method construction is a construction method for developing underground engineering in a frozen area after artificially freezing soil to a certain strength. In the implementation process, frost heaving force is generated due to soil frost heaving, which has an adverse effect on the tunnel near the frozen area. Common engineering accidents include lining cracking, lining water seepage, and lining structure damage. The soil is usually frozen by using salt water to absorb heat. This method generates a frozen area along the axial direction of the freezing pipe, and it is difficult to simulate local frost heaving. Therefore, the existing frost heaving method has the following disadvantages:

[0003] 1) The salt water heat absorption speed is slow, and it usually takes months to achieve the target freezing effect, so the period for testing the influence of frost heaving on the internal force and deformation of the tunnel is long.

[0004] 2) The conventional freezing device adopts a freezing pipe mode, and the frozen area is distributed along the axial direction of the freezing pipe, so it is impossible to realize point frost heaving testing.

[0005] 3) The existing frost heaving device is basically fixed after freezing, and it is impossible to realize the testing of frost heaving effect at any position. SUMMARY

[0006] In order to overcome the disadvantages of the existing frost heaving testing method, which cannot realize rapid frost heaving, point frost heaving, and frost heaving testing at any position of the tunnel, the application provides a rapid testing device and method for tunnel frost heaving damage characteristics, which can quickly test the adverse effect of point uneven frost heaving on the internal force and deformation of the tunnel. The device can realize frost heaving testing at any position inside and outside the tunnel segment, and it is simple, convenient, low in cost, and short in time.

[0007] The application adopts the following technical scheme to solve the technical problem:

[0008] A rapid testing device for tunnel frost heaving damage characteristics, comprising a device box, an external freezing system, an internal freezing system, a tunnel segment, and a position adjusting system. The external freezing system is located in the device box and tangent to the four faces of the device box. The tunnel segment is located in the external freezing system. Soil is filled between the external freezing system and the tunnel segment. The position adjusting system is located at the front and rear ends of the device box. The internal freezing system is located in the tunnel segment. The internal freezing system is connected with the position adjusting system. Soil is filled between the tunnel segment and the internal freezing system. The soil area is provided with a soil pressure gauge, a displacement gauge, and a water content probe.

[0009] Further, the device box comprises a retaining plate and a fixing plate, the retaining plate is composed of multiple transparent organic glass plates and can be embedded into the front and rear ends of the fixing plate.

[0010] Further, the position adjusting system comprises sliding supports, position telescopic rods and a circular pipe fixing support, one end of the position telescopic rod is connected with the sliding support and the other end is connected with the circular pipe fixing support.

[0011] Further, the external freezing system comprises a sliding rail track, an external spherical air bag, an air bag sliding device, an external air hole and an external air pressure gauge, the external air pressure gauge is embedded into the external spherical air bag, the external spherical air bag is fixed in the air bag sliding device, the air bag sliding device is located in the gap in the sliding rail track, the external air hole is a small hole reserved in the air bag sliding device, and the outer surface of the sliding rail track is tangent to the inner surface of the device box.

[0012] Further, the internal freezing system comprises a fixed circular pipe, a fixed circular pipe connector, a combined telescopic rod, an internal high-pressure air pipe, a rotating ball hinge, an internal air bag and an internal air pressure gauge, one end of the combined telescopic rod is connected with the fixed circular pipe through the rotating ball hinge, and the other end is fixed with the internal air bag, the internal air pressure gauge is arranged between the internal air bag and the fixed circular pipe, and the fixed circular pipe connector is installed at the front and rear ends of the fixed circular pipe and placed on the circular pipe fixing support.

[0013] A rapid test method for tunnel frost heaving damage characteristics, comprising the following steps:

[0014] Step 1, determining the similarity ratio of the test device according to the mutual relationship among the tunnel pipe diameter, the tunnel burial depth, the soil layer thickness and the device box size;

[0015] Step 2, determining the soil layer required for the test according to the geological exploration report and the tunnel burial depth, and determining the soil layer thickness and distribution;

[0016] Step 3, installing the rapid test device for tunnel frost heaving damage characteristics, the implementation device comprises a device box, an external freezing system, an internal freezing system, a tunnel pipe segment and a position adjusting system, the external freezing system is located in the device box and tangent to the four faces of the device box, the tunnel pipe segment is located in the external freezing system, soil is filled between the external freezing system and the tunnel pipe segment, the position adjusting system is located at the front and rear ends of the device box, the internal freezing system is located in the tunnel pipe segment, the internal freezing system is connected with the position adjusting system, soil is filled between the tunnel pipe segment and the internal freezing system, and the soil area is provided with a soil pressure gauge, a displacement gauge and a water content probe;

[0017] Step 4, determine the location of frost heaving, adjust the air bag position to the frost heaving area, so that the frost heaving position is the same as the position determined by the engineering requirements; calculate the corresponding frost heaving force according to the size of the frost heaving volume, soil parameters and other indicators, and convert it into air pressure;

[0018] Step 5, start the test and collect data: record the initial data of each sensor before the test starts, when the readings of each air gauge reach the test pressure, record the data of each monitoring point at a set time interval, and stop the test when the data of the monitoring point reaches stability;

[0019] Step 6, test of frost heaving at any position outside the segment, repeat steps 3 to 5 to realize the test of frost heaving at any position outside the segment of the tunnel;

[0020] Step 7, test of frost heaving at different positions inside the segment, repeat steps 3 to 5 to realize the test of frost heaving at any position inside the segment of the tunnel;

[0021] Step 8, test of frost heaving at different positions inside and outside the segment, repeat steps 3 to 5 to realize the test of frost heaving at different positions inside and outside the segment of the tunnel;

[0022] Step 9, end the test, release the pressure, clean the soil, and remove the device.

[0023] Further, in step 5, the set time is half an hour.

[0024] In step 3, the process of installing the rapid test device for tunnel frost heaving damage characteristics is as follows:

[0025] 3.1 According to the inner diameter, buried depth and position of the freezing point in the internal environment of the tunnel, determine the size and number of each component in the internal freezing system; considering the size of the freezing area, arrange the internal air bag and combined telescopic rod along the fixed circular pipe in the axial direction, and each set of internal air bag and combined telescopic rod is distributed with internal air bag and combined telescopic rod in the radial direction;

[0026] 3.2 According to the outer diameter, buried depth and position of the freezing point in the external environment of the tunnel, determine the size and number of each component in the external freezing system, arrange sliding rail tracks in the device box, and each sliding rail track has an external spherical air bag and an air bag sliding device;

[0027] 3.3 Place the device box and install the position adjusting system, assemble the fixed plate of the device box, then place the device box on the test platform and adjust the level, install a sliding support on each of the four edges in front and back of the device box, fix one end of the position telescopic rod to the sliding support, and connect the other end to the circular pipe fixed support;

[0028] 3.4 Assemble the external freezing system and install it in the device box. First, place the external barometer in the external spherical airbag, then install the external spherical airbag in the airbag sliding device, and then install the airbag sliding device in the sliding rail track to form an external freezing system. Assemble the external freezing system in the above order and fix it in the device box through the sliding rail track;

[0029] 3.5 Fill the soil under the tunnel and bury the sensors. Install the retaining boards in front and back of the device box, then fill the soil in the device box to the specified height and bury the corresponding sensors. The burial of the sensors is synchronized with the filling of the soil. The moisture content probe, displacement meter, and soil pressure gauge are arranged inside the soil between the external freezing system and the tunnel segment. In the radial direction, the three types of sensors are arranged around the center of the external freezing system at intervals of 10° central angle. In the axial direction, the sensors are arranged at equal intervals.

[0030] 3.6 Paste the strain gauges and install the tunnel in the device box. Symmetrically paste the strain gauges on the inner and outer walls of the tunnel segment at a radial interval of 30° central angle and an axial interval of 150 mm, and then place the tunnel segment above the soil layer.

[0031] 3.7 Assemble the internal freezing system and adjust its position in the device box. First, connect the bottom of the combined telescopic rod to the fixed circular pipe through the rotating ball hinge, then fix the internal airbag using the four corners of the adjacent combined telescopic rod, then install the internal barometer in each airbag, and then connect the fixed circular pipe connector to the fixed circular pipe and install the circular pipe fixing bracket. Adjust the length of the telescopic rod so that the center of the assembled internal freezing system is above the bottom of the device box.

[0032] 3.8 Continue to fill the soil and bury the sensors. Continue to fill the soil to the top of the device box. During the filling process, install the corresponding retaining boards as the filling height increases. The burial of the sensors is synchronized with the filling of the soil. The sensor arrangement inside the tunnel segment is as follows: in the radial direction, around the center of the internal freezing system, at intervals of 15° central angle, and in each angle, the sensors are arranged, and their positions are adjusted according to the changes in the internal freezing system; in the axial direction, the sensors are arranged at equal intervals.

[0033] 3.9 Determine the frost heaving force parameters. Considering that the frost heaving inside and outside the tunnel is local point frost heaving, and considering the elastic deformation properties of the soil after freezing, calculate the initial frost heaving force according to and determine the corrected frost heaving force according to the actual engineering situation, where k r is the compressive strength of the soil, k L is the compressive stiffness of the lining, α is the volume expansion rate of water-ice phase transition, and a1 is the edge length of the regular tetrahedron of frost heaving space.

[0034] In step 4, the internal freezing system adjustment process is: according to the actual situation of the project, the position and distribution of the tunnel internal frost heave are determined, then the combined telescopic rod in the corresponding position of the internal freezing system is adjusted, the position and size of the internal air bag are changed, so that the tunnel internal frost heave area is consistent with the actual project;

[0035] The external freezing system adjustment process is: according to the actual situation of the project, the position and distribution of the tunnel external frost heave are determined, then the air bag sliding device in the corresponding position of the external freezing system is adjusted, the position and size of the external spherical air bag are changed, so that the frost heave area is consistent with the actual project.

[0036] In step 6, according to the frost heave situation at any position outside the tunnel, the frost heave force at any position outside the tunnel is calculated repeatedly in step 4; by adjusting the position of the air bag sliding device in a certain set of external freezing systems, the position of the frost heave can be changed in the radial direction; by adjusting the air bag sliding device in different sets of external freezing systems, the position of the frost heave can be changed in the axial direction; by repeating step 4, the test of frost heave at any position outside the tunnel can be realized;

[0037] In step 7, according to the frost heave situation at any position of the tunnel, the frost heave force at any position inside the tunnel is calculated repeatedly in step 4; by adjusting the length of the combined telescopic rod in a certain set of internal freezing systems, the position of the frost heave and the size of the frost heave area can be changed in the radial direction; by adjusting the combined telescopic rod in different sets of internal freezing systems, the position of the frost heave can be changed in the axial direction; by repeating step 4, the test of frost heave at any position inside the tunnel can be realized.

[0038] The beneficial effects of the present application mainly include: it can be quickly used for testing the effect of uneven frost heave at any position on the internal force and deformation of the tunnel, and has the following advantages: 1) it can quickly simulate the actual frost heave effect, and the pressure air bag device corresponding to the frost heave force is used to realize the change of the stress of the soil body and the tunnel; 2) it can realize point frost heave and the size of the frost heave is controllable, the size of the point frost heave inside the tunnel can be controlled through the combined telescopic rod and the internal air bag device, and the size of the point frost heave outside the tunnel can be controlled through the air bag sliding rail and the external spherical air bag; 3) it can realize frost heave at any position, and the frost heave can occur at any position inside and outside the tunnel through the air bag sliding device and the position adjustment system; 4) the effect of frost heave on the internal force and deformation of the tunnel can be quickly tested through the air bag pressure, and the test is simple, convenient, low in cost and short in time. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a front view of the rapid test device for tunnel frost heave damage characteristics.

[0040] Figure 2 It is an A-A sectional view of the rapid test device for tunnel frost heave damage characteristics.

[0041] Figure 3 is a schematic diagram of the external freezing system.

[0042] Figure 4 is a schematic diagram of the internal freezing system.

[0043] Figure 5 is a schematic diagram of the fixed circular pipe connector.

[0044] Figure 6 is a B-B sectional view of Figure 4

[0045] Figure 7 is a sectional view of the combined telescopic rod.

[0046] Figure 8 is a top view of the combined telescopic rod.

[0047] Figure 9 is a schematic diagram of the device box.

[0048] The reference signs are: 1. device box, 1-1. soil retaining plate; 1-2. fixed plate; 2. external freezing system, 2-1. sliding rail track; 2-2. external spherical air bag; 2-3. air bag sliding device; 2-4. external air hole; 2-5. external air pressure gauge; 3. internal freezing system, 3-1. fixed circular pipe; 3-2. fixed circular pipe connector; 3-3. combined telescopic rod; 3-4. internal high-pressure air pipe; 3-5. rotating spherical hinge; 3-6. internal air bag; 3-7. internal air pressure gauge; 4. tunnel segment; 5. position adjusting system, 5-1. sliding support; 5-2. position telescopic rod; 5-3. circular pipe fixing support; 6. water content probe; 7. strain gauge; 8. displacement meter; 9. soil pressure gauge. DETAILED DESCRIPTION

[0049] The present application is further described below with reference to the accompanying drawings.

[0050] Referring to Figures 1-9 , a rapid testing device for tunnel frost heaving damage characteristics comprises a device box 1, an external freezing system 2, an internal freezing system 3, a tunnel segment 4 and a position adjusting system 5, the external freezing system 2 is located in the device box 1 and is tangent to the four faces of the device box 1, the tunnel segment 4 is located in the external freezing system 2, soil is filled between the external freezing system 2 and the tunnel segment 4, the position adjusting system 5 is located at the front and rear ends of the device box 1, the internal freezing system 3 is located in the tunnel segment 4, the internal freezing system 3 is connected with the position adjusting system 2, soil is filled between the tunnel segment 4 and the internal freezing system 3, and the soil area is provided with a soil pressure gauge 6, a displacement meter 8 and a water content probe 9.

[0051] ​Further, the device box 1 comprises a retaining board 1-1 and a fixed board 1-2, the retaining board is composed of multiple transparent organic glass, and can be embedded into the front and rear ends of the fixed board.

[0052] Further, the position adjusting system 5 comprises a sliding support 5-1, a position telescopic rod 5-2 and a circular tube fixing support 5-3, the sliding support is located on the four edges of the front and rear of the device box, one end of the position telescopic rod is connected with the sliding support, and the other end is connected with the circular tube fixing support.

[0053] Further, the external freezing system 2 comprises a sliding rail track 2-1, an external spherical air bag 2-2, an air bag sliding device 2-3, an external air hole 2-4 and an external air pressure gauge 2-5, the external air pressure gauge is embedded into the external spherical air bag, the external spherical air bag is fixed in the air bag sliding device, the air bag sliding device is located in the gap in the sliding rail track, the external air hole is a small hole reserved in the air bag sliding device, and the outer surface of the sliding rail track is tangent to the inner surface of the device box.

[0054] Further, the internal freezing system 3 comprises a fixed circular tube 3-1, a fixed circular tube connecting piece 3-2, a combined telescopic rod 3-3, an internal high-pressure air pipe 3-4, a rotating ball hinge 3-5, an internal air bag 3-6 and an internal air pressure gauge 3-7, one end of the combined telescopic rod is connected with the fixed circular tube through the rotating ball hinge, and the other end is fixed with the internal air bag, the internal air pressure gauge is arranged between the internal air bag and the fixed circular tube, and the fixed circular tube connecting piece is installed at the front and rear ends of the fixed circular tube and placed on the circular tube fixing support.

[0055] A rapid test method for tunnel frost heaving damage characteristics, comprising the following steps:

[0056] Step 1, determining the similarity ratio of the test device according to the mutual relationship of the tunnel pipe diameter, the tunnel buried depth, the soil layer thickness and the device box size;

[0057] Step 2, determining the required soil layer for testing according to the geological exploration report and the tunnel buried depth, and determining the soil layer thickness and distribution;

[0058] Step 3, installing the rapid test device for tunnel frost heaving damage characteristics, the device comprises a device box 1, an external freezing system 2, an internal freezing system 3, a tunnel pipe piece 4 and a position adjusting system 5, the external freezing system 2 is located in the device box 1 and tangent to the four faces of the device box 1, the tunnel pipe piece 4 is located in the external freezing system 2, soil is filled between the external freezing system 2 and the tunnel pipe piece 4, the position adjusting system 5 is located at the front and rear ends of the device box 1, the internal freezing system 3 is located in the tunnel pipe piece 4, the internal freezing system 3 is connected with the position adjusting system 2, soil is filled between the tunnel pipe piece 4 and the internal freezing system 3, and the soil area is provided with a soil pressure gauge 6, a displacement gauge 8 and a water content probe 9.

[0059] Step 4, determine the location of the frost heaving, adjust the air bag position to the frost heaving area, make the frost heaving position same as the position determined by engineering requirements; calculate the corresponding frost heaving force according to the size of the frost heaving volume, soil parameters and other indicators, and convert it into air pressure;

[0060] Step 5, start the test and collect data: record the initial data of each sensor before the test starts, when the readings of each air gauge reach the test pressure, record the data of each monitoring point at a set time interval, and stop the test when the data of the monitoring point reaches stability;

[0061] Step 6, test the frost heaving at any position outside the pipe, repeat steps 3 to 5 to achieve the test of the frost heaving at any position outside the tunnel pipe.

[0062] Step 7, test the frost heaving at different positions inside the pipe, repeat steps 3 to 5 to achieve the test of the frost heaving at any position inside the tunnel pipe.

[0063] Step 8, test the frost heaving at different positions inside and outside the pipe, repeat steps 3 to 5 to achieve the test of the frost heaving at different positions inside and outside the tunnel pipe

[0064] Step 9, end the test, release the pressure, remove the soil, and remove the device.

[0065] Further, in step 5, the set time is half an hour.

[0066] A city subway tunnel shield tunnel diameter is 6.2m, buried depth is 17m, and the line interval connecting channel excavation needs to be constructed by freezing method. In order to quickly test the adverse effects of point-like uneven frost heaving on the internal force and deformation of the tunnel, the rapid test device and method for tunnel frost heaving damage characteristics provided by the application are used.

[0067] In this embodiment, according to the field geological exploration report, the soil layers through which the connecting channel passes are miscellaneous fill, clay, silt-silty clay and sandy silt from top to bottom, with thicknesses of 3m, 3m, 6m and 8m respectively. The size of the device box is 2m x 2.7m x 2m (length x width x height). The front and back of the device box are made of transparent organic glass, and the other sides are made of stainless steel material.

[0068] The embodiment of the application is:

[0069] (1) According to the actual situation of the project and the present situation of the test site, the similarity ratio of the test device is determined to be 10:1 according to the tunnel pipe diameter and the thickness of the soil layer.

[0070] (2) Determine the size of the device box. According to the similarity ratio in step (1), the size of the device box 1 is determined to be 2m x 2.7m x 2m (length x width x height). According to the actual situation of the project, it is determined that the soil retaining plate 1-1 in the device box 1 is composed of 5 transparent organic glass plates with a height of 400mm, and the other surfaces are made of stainless steel.

[0071] (3) According to the inner diameter, buried depth and position of the freezing point in the internal environment of the tunnel, the size and number of each component in the internal freezing system 3 are determined. According to the actual situation of the project, the diameter of the fixed circular pipe 3-1 is determined to be 240mm, and the center of the circular pipe is located 835mm from the bottom of the device box. Considering the size of the freezing area, 10 sets of internal air bags 3-6 and 11 sets of combined telescopic rods 3-3 are arranged along the axis of the fixed circular pipe 3-1, and each set of internal air bag 3-6 and combined telescopic rod 3-3 is distributed with 8 internal air bags 3-6 and combined telescopic rods 3-3 in the radial direction, a total of 80 internal air bags 3-6 and 88 combined telescopic rods 3-3, and the minimum length of the combined telescopic rod 3-3 is 94mm and the maximum length is 250mm.

[0072] (4) According to the outer diameter, buried depth and position of the freezing point in the external environment of the tunnel, the size and number of each component in the external freezing system 2 are determined. According to the actual situation of the project, 10 slide rail tracks 2-1 are arranged in the device box 1, the diameter of the slide rail track 2-1 is 2m, the width of each track is 250mm, and each slide rail track 2-1 has an external spherical air bag 2-2 and an air bag sliding device 2-3.

[0073] (5) Determine the thickness and distribution of the soil layer. According to the geological exploration report, the soil layer required for testing is determined. In this example, the soil layer from top to bottom is plain fill, silt soil, silty clay, and sand, and the thickness of each layer is 3m, 3m, 6m, and 8m respectively. According to the similarity ratio in step (1), the thickness of the soil layer in the device box is determined to be 0.3m, 0.3m, 0.6m, and 0.8m respectively.

[0074] (6) Place the device box and install the position adjusting system. Assemble the fixed plate 1-2 of the device box 1, then place the device box 1 on the test platform and adjust the level, install one sliding support 5-1 on each of the four edges of the front and rear of the device box 1, a total of 8. Fix one end of the position telescopic rod 5-2 to the sliding support 5-1, and connect the other end to the circular pipe fixing bracket 5-3.

[0075] (7) Assemble the external freezing system and install it in the device box. First, place the external air gauges 2-5 in the external spherical air bag 2-2, then install the external spherical air bag 2-2 in the air bag sliding device 2-3, and then install the air bag sliding device 2-3 in the sliding rail track 2-1 to form an external freezing system 2. Assemble 10 sets of external freezing systems 2 in the above order, and fix the 10 sets of external freezing systems 2 in the device box 1 through the sliding rail track 2-1.

[0076] (8) Fill the soil under the tunnel and bury the sensors. Install two soil retaining plates 1-1 at the front and back of the device box 1, respectively, and then fill the soil in the device box 1 to a height of 300 mm and bury the corresponding sensors. The burial of the sensors is synchronized with the filling of the soil. The moisture content probe 6, the displacement meter 8, and the soil pressure gauge 9 are arranged inside the soil between the external freezing system 2 and the tunnel segment 4. In the radial direction, the three types of sensors are arranged around the center of the external freezing system 2 at intervals of 10° central angle, with radii of 790 mm and 860 mm, respectively. In the axial direction, the spacing between each sensor is 150 mm.

[0077] (9) Paste the strain gauges and install the tunnel in the device box. Symmetrically paste the strain gauges 7 on the inner and outer walls of the tunnel segment 4, with the strain gauges 7 arranged radially at intervals of 30° central angle and axially at intervals of 150 mm, and then place the tunnel segment 4 above the soil filled in step (8).

[0078] (10) Assemble the internal freezing system and adjust its position inside the device box. First, connect the bottom of the combined telescopic rod 3-3 to the fixed circular pipe 3-1 through the rotating ball hinge 3-5, then use the four corners of the adjacent combined telescopic rod 3-3 to fix the internal air bag 3-6, then install the internal air gauges 3-7 in each air bag, and then connect the fixed circular pipe connector 3-2 to the fixed circular pipe 3-1 and install it on the circular pipe fixing support 5-3 in step (6). Adjust the length of the position telescopic rod 5-2 so that the center of the assembled internal freezing system 3 is located 835 mm above the bottom of the device box 1.

[0079] (11) Continue to fill the soil and bury the sensors. Continue to fill the soil to the top of the device box 1, and during the filling process, install the corresponding soil retaining plate 1-1 as the filling height increases. The burial of the sensors is synchronized with the filling of the soil. The sensor arrangement on the outside of the tunnel segment 4 is the same as in step (8), and the sensor arrangement on the inside of the tunnel segment 4 is as follows: in the radial direction, around the center of the internal freezing system 3, at intervals of 15° central angle, 4 sensors are arranged at each angle, and their positions are adjusted as the internal freezing system 3 changes; in the axial direction, the spacing between each sensor is 150 mm.

[0080] (12) Determine the frost heave force parameter. Considering that the frost heaving of the tunnel inside and outside is local point frost heaving, considering the elastic deformation property of the soil after freezing, according to Calculate the initial frost heaving force, and determine the corrected frost heaving force according to the actual engineering situation, wherein k r is the compressive strength of the soil, k L is the compressive stiffness of the lining, and a is the volume expansion rate of the water-ice phase change, and a1 is the edge length of the frost heaving space tetrahedron.

[0081] (13) Internal freezing system adjustment. According to the actual engineering situation, the internal frost heaving position and distribution of the tunnel are determined, and then the combined expansion rod 3-3 at the corresponding position in the internal freezing system 3 is adjusted, the position and size of the internal air bag 3-6 are changed, so that the internal frost heaving area of the tunnel is consistent with the actual engineering.

[0082] (14) External freezing system adjustment. According to the actual engineering situation, the external frost heaving position and distribution of the tunnel are determined, and then the air bag sliding device 2-3 at the corresponding position in the external freezing system 2 is adjusted, the position and size of the external spherical air bag 2-2 are changed, so that the frost heaving area is consistent with the actual engineering.

[0083] (15) Start the frost heaving test and collect data. First, record the initial data of each sensor before the test starts, then inflate and pressurize the internal air bag 3-6 at the corresponding position in the internal freezing system 3 in step (13), so that the reading of the internal air pressure gauge 3-7 reaches the value determined in step (12), inflate and pressurize the external spherical air bag 2-2 at the corresponding position in the external freezing system 2 in step (14), until the reading of the external air pressure gauge 2-5 reaches the value determined in step (12). Record the data of each monitoring point every half hour, and stop the test when the data of the monitoring point reaches stability.

[0084] (16) Test of frost heaving at any position outside the tunnel. According to the frost heaving situation at any position outside the tunnel, repeat step (12) to calculate the frost heaving force at any position outside the tunnel; repeat step (14) to adjust the position of the air bag sliding device 2-3 in a certain set of external freezing systems 2, so that the position of frost heaving changes in the radial direction; adjust the air bag sliding device 2-3 in different sets of external freezing systems 2, so that the position of frost heaving changes in the axial direction; repeat step (15) to realize the test of frost heaving at any position outside the tunnel.

[0085] (17) Test of frost heaving at any position inside the tunnel. According to the frost heaving at any position inside the tunnel, repeat step (10) to adjust the position of the internal freezing system 3; repeat step (12) to calculate the frost heaving force at any position inside the tunnel; repeat step (13) to adjust the length of the combined telescopic rod 3-3 in the internal freezing system 3, so as to change the position and the size of the frost heaving area in the radial direction; adjust the combined telescopic rod 3-3 in different internal freezing systems 3, so as to change the position of the frost heaving in the axial direction; repeat step (15) to realize the test of frost heaving at any position inside the tunnel.

[0086] (18) Test of uneven frost heaving inside and outside the tunnel. Repeat step (16)

[0087] and (17) to realize the test of uneven frost heaving inside and outside the tunnel.

[0088] (19) End the experiment. Turn off the test instrument, first deflate and depressurize the external spherical air bag 2-2 and the internal air bag 3-6, then shrink the combined telescopic rod 3-3 to the minimum, and then clean the soil in the device box 1 layer by layer, and sequentially remove the internal freezing system 3, the tunnel segment 4, and the external freezing system 2, to complete the experiment.

[0089] The content described in the embodiments of the present specification is only a list of implementation forms of the inventive concept, and is only for the purpose of description. The protection scope of the present application should not be regarded as being limited to the specific forms described in the present embodiments, and the protection scope of the present application also extends to equivalent technical means that can be thought of by those skilled in the art according to the inventive concept.

Claims

1. A method for rapid testing of tunnel frost heave failure characteristics, characterized in that, The method comprises the following steps: Step 1, determining the similarity ratio of the testing device according to the mutual relationship of the tunnel pipe diameter, the tunnel depth, the soil layer thickness and the device box size; Step 2, determining the soil layer required for testing according to the geological exploration report and the tunnel depth, and determining the soil layer thickness and distribution; Step 3, installing the rapid testing device for tunnel frost heaving damage characteristics, which comprises a device box, an external freezing system, an internal freezing system, a tunnel segment and a position adjusting system, the external freezing system is located in the device box and tangent to the four faces of the device box, the tunnel segment is located in the external freezing system, the soil body is filled between the external freezing system and the tunnel segment, the position adjusting system is located at the front and rear ends of the device box, the internal freezing system is located in the tunnel segment, the internal freezing system is connected with the position adjusting system, the soil body is filled between the tunnel segment and the internal freezing system, and the soil body area is provided with a soil pressure gauge, a displacement gauge and a water content probe; Step 4, determining the position of frost heaving, adjusting the position of the air bag to the frost heaving area, so that the frost heaving position is the same as the position determined by the engineering requirement, and calculating the corresponding frost heaving force according to the size of the frost heaving volume, the soil body parameters and other indexes, and converting the frost heaving force into air pressure; Step 5, starting the test and collecting data: recording the initial data of each sensor before the test starts, recording the data of each monitoring point at a set time interval after the reading of each air pressure gauge reaches the test pressure, and stopping the test when the data of the monitoring point reaches stability; Step 6, testing the frost heaving at any position outside the segment, repeating steps 3 to 5 to realize the testing of the frost heaving at any position outside the tunnel segment; Step 7, testing the frost heaving at different positions inside the segment, repeating steps 3 to 5 to realize the testing of the frost heaving at any position inside the tunnel segment; Step 8, testing the frost heaving at different positions inside and outside the segment at the same time, repeating steps 3 to 5 to realize the testing of the frost heaving at different positions inside and outside the tunnel segment at the same time Step 9, ending the test, deflating and decompressing, removing the soil body and disassembling the device.

2. The method of rapid testing of tunnel frost heave damage properties of claim 1, wherein, The device box comprises a soil retaining plate and a fixing plate, the soil retaining plate is composed of multiple transparent organic glass plates and can be embedded into the front and rear ends of the fixing plate.

3. A method of rapid testing of tunnel freeze-thaw damage properties according to claim 1 or 2, characterized in that, The position adjusting system comprises a sliding support, a position telescopic rod and a circular pipe fixing support, one end of the position telescopic rod is connected with the sliding support, and the other end is connected with the circular pipe fixing support.

4. The method of rapid testing of tunnel freeze-thaw damage properties according to claim 1 or 2, characterized in that, The external freezing system comprises a sliding rail track, an external spherical air bag, an air bag sliding device, an external air hole and an external air pressure gauge, the external air pressure gauge is installed in the external spherical air bag, the external spherical air bag is fixed in the air bag sliding device, the air bag sliding device is located in the gap in the sliding rail track, the external air hole is a small hole reserved in the air bag sliding device, and the outer surface of the sliding rail track is tangent to the inner surface of the device box.

5. The method of rapid testing of tunnel freeze-thaw damage properties according to claim 1 or 2, wherein, The internal freezing system comprises a fixed circular pipe, a fixed circular pipe connector, a combined telescopic rod, an internal high-pressure air pipe, a rotating ball hinge, an internal air bag and an internal air gauge, one end of the combined telescopic rod is connected with the fixed circular pipe through the rotating ball hinge, and one end of the combined telescopic rod is fixed with the internal air bag, the internal air gauge is arranged between the internal air bag and the fixed circular pipe, and the fixed circular pipe connector is installed at the front and rear ends of the fixed circular pipe and is placed on the circular pipe fixing support.

6. The method of claim 1, wherein, In step 5, the time is set to half an hour.

7. The method of claim 1 or 6, wherein, In step 3, the process of installing the rapid test device for tunnel frost heaving damage characteristics is as follows: 3.1 According to the internal diameter, buried depth and position of the freezing point in the internal environment of the tunnel, the sizes and quantities of the components in the internal freezing system are determined; considering the size of the freezing area, the internal air bags and the combined telescopic rods are arranged axially along the fixed circular pipe, and each set of internal air bags and combined telescopic rods is distributed with internal air bags and combined telescopic rods in the radial direction; 3.2 According to the external diameter, buried depth and position of the freezing point in the external environment of the tunnel, the sizes and quantities of the components in the external freezing system are determined, and slide rail tracks are arranged in the device box, and each slide rail track has an external spherical air bag and an air bag sliding device; 3.3 Place the device box and install the position adjusting system, assemble the fixing plate of the device box, then place the device box on the test platform and adjust the level, install a sliding support on each of the four edges in front and behind the device box, fix one end of the position telescopic rod to the sliding support, and connect the other end to the circular pipe fixing support; 3.4 Assemble the external freezing system and install it in the device box, first place the external air gauge in the external spherical air bag, then install the external spherical air bag in the air bag sliding device, then install the air bag sliding device in the slide rail track to form a set of external freezing system, and then fix the external freezing system in the device box through the slide rail track; 3.5 Fill the soil under the tunnel and bury the sensors, install the soil retaining plates in front and behind the device box, then fill the soil layer in the device box to the set height and bury the corresponding sensors, the sensor burying and soil filling are carried out synchronously, the moisture content probe, displacement meter and soil pressure gauge are arranged in the soil inside the external freezing system and the tunnel segment; in the radial direction, the three types of sensors are arranged around the center of the external freezing system according to equal central angles, and in the axial direction, the sensors are arranged at equal intervals; 3.6 Paste the strain gauges and install the tunnel in the device box, symmetrically paste the strain gauges on the inner and outer walls of the tunnel segment, the strain gauges are arranged radially according to equal central angles and axially according to equal intervals, and then place the tunnel segment above the soil layer; 3.7 Assemble the internal freezing system and adjust the position in the device box, first connect the bottom of the combined telescopic rod to the fixed circular pipe through the rotating ball hinge, then fix the internal air bag by using the four corners of the adjacent combined telescopic rod, then install the internal air gauge in each air bag, then connect the fixed circular pipe connector with the fixed circular pipe and install the circular pipe fixing support; adjust the length of the position telescopic rod so that the center of the combined internal freezing system is above the bottom of the device box. 3.8 Continue to fill the soil and bury the sensor, continue to fill the soil to the top of the device box, during the filling process, as the filling height increases, install the corresponding retaining plate, the burial of the sensor is synchronized with the soil filling; the sensor arrangement mode inside the tunnel segment is as follows: in the radial direction, around the center of the internal freezing system, staggered arrangement according to the equal central angle interval, each angle is arranged with the sensor, and the position is adjusted with the change of the internal freezing system; in the axial direction, the sensors are arranged at equal intervals; 3.9 Determine the frost heave force parameter, considering that the frost heaving inside and outside the tunnel is local point frost heaving, considering the elastic deformation properties of the soil after freezing, according to Calculate the initial frost heave force, and determine the corrected frost heave force according to the actual engineering situation, wherein The compressive strength of the soil is The compressive stiffness of the lining is The volume expansion rate of water-ice phase change is The space of frost heaving regular tetrahedron edge length is 8. The method of claim 1 or 6, wherein, In step 4, the internal freezing system adjustment process is: according to the actual situation of the project, the internal frost heaving position and distribution of the tunnel are determined, then the combined telescopic rod in the corresponding position of the internal freezing system is adjusted, the position and size of the internal air bag are changed, so that the internal frost heaving area of the tunnel is consistent with the actual project; The external freezing system adjustment process is: according to the actual situation of the project, the external frost heaving position and distribution of the tunnel are determined, then the air bag sliding device in the corresponding position of the external freezing system is adjusted, the position and size of the external spherical air bag are changed, so that the frost heaving area is consistent with the actual project.

9. The method of claim 1 or 6, wherein, In step 6, according to the frost heaving condition of any position outside the tunnel, the frost heaving force of any position outside the tunnel is calculated repeatedly in step 4; by adjusting the position of the air bag sliding device in a set of external freezing systems, the position of frost heaving can be changed in the radial direction; by adjusting the air bag sliding device in different sets of external freezing systems, the position of frost heaving can be changed in the axial direction; repeating step 4 can realize the test of frost heaving at any position outside the tunnel; In step 7, according to the frost heaving condition of any position of the tunnel, the frost heaving force of any position inside the tunnel is calculated repeatedly in step 4; by adjusting the length of the combined telescopic rod in a set of internal freezing systems, the position of frost heaving and the size of the frost heaving area can be changed in the radial direction; by adjusting the combined telescopic rod in different sets of internal freezing systems, the position of frost heaving can be changed in the axial direction; repeating step 4 can realize the test of frost heaving at any position inside the tunnel.

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