A subway tunnel vertical connection and horizontal freezing test device and method

Abstract

The invention provides a subway tunnel vertical joint and horizontal freezing test device and method, belonging to the field of subway tunnel freezing construction test device, including a test model box, a loading system, a refrigeration cycle system and a monitoring system; a shield machine is arranged in the test model box; the top of the test model box is open; the loading system is located at the top of the test model box; the refrigeration cycle system includes a low-temperature cold bath machine, brine, a connecting pipe, a liquid distributor, a liquid collector and a freezing pipe; the low-temperature cold bath machine is connected with a plurality of freezing pipes through the connecting pipe, the liquid distributor and the liquid collector to form a circulation loop for the circulation of brine, and flow meters are provided on the two connecting pipes, the low-temperature cold bath machine cools the refluxed brine and flows out, and the circulation of brine freezes the soil; the freezing pipe includes a horizontal freezing pipe and a vertical freezing pipe, the horizontal freezing pipe is horizontally arranged along the axial direction of the shield machine, and the vertical freezing pipe is vertically arranged perpendicular to the axial direction of the shield machine. The problem that the vertical joint horizontal freezing for shield opening and maintenance cannot be simulated at present is solved.

Description

Technical Field

[0001] The invention relates to the field of subway tunnel freezing construction test devices, in particular to a subway tunnel vertical connection and horizontal freezing test device and method. Background Art

[0002] With the development of large-scale urban rail transit construction, shield technology has become an indispensable key technology in the field of underground engineering construction. Subway tunnel construction faces complex and diverse geological environments. For example, in special working conditions such as water-rich sand and gravel formations, mechanical failures such as cutterhead wear occur frequently, often causing the shield machine to shut down and urgently need to be opened for maintenance.

[0003] In recent years, the freezing method has been widely used in the field of urban underground rail transit construction due to its significant advantages such as high strength, strong water-stopping ability and low environmental impact. After freezing the ground, it is safer for maintenance personnel to open the warehouse for maintenance. Compared with field tests, model tests are less expensive and easier to change influencing factors such as the spacing of freezing pipes, soil moisture content, and cooling rate. In addition, model tests are also more advantageous in arranging sensors, which can easily obtain temperature and displacement data during the freezing process.

[0004] However, in the existing test device, the arrangement of the freezing pipes is single, and it is impossible to study the test methods of vertical connection and horizontal freezing. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a subway tunnel vertical combination and horizontal freezing test device and method to solve the problem that the current technology cannot simulate the vertical combination and horizontal freezing for shield opening and maintenance.

[0006] To achieve the above-mentioned and other related purposes, the present invention provides a subway tunnel vertical connection and horizontal freezing test device, including a test model box, a loading system, a refrigeration cycle system and a monitoring system;

[0007] A shield machine is arranged in the test model box;

[0008] The top of the test model box is open and is used to fill soil;

[0009] The loading system is located at the top of the test model box and is used to apply pressure to the filled soil;

[0010] The refrigeration cycle system includes a low-temperature cold bath, brine, connecting pipes, a liquid separator, a liquid collector and a freezing pipe;

[0011] The low temperature cold bath machine is connected to the plurality of freezing pipes through a connecting pipe, a liquid distributor and a liquid collector to form a circulation loop for the circulation of brine. Flow meters are provided on the two connecting pipes. The low temperature cold bath machine cools the refluxed brine and then flows out. The circulation of the brine freezes the soil.

[0012] The freezing pipes include horizontal freezing pipes and vertical freezing pipes. The horizontal freezing pipes are horizontally arranged along the axial direction of the shield machine, and the vertical freezing pipes are vertically arranged perpendicular to the axial direction of the shield machine.

[0013] Optionally, the loading system includes an electric hydraulic pump, a loading rod, a loading bracket, a bottom plate and a top plate;

[0014] The loading bracket is fixedly connected to the base plate via a plurality of vertical poles distributed at intervals. The loading rod is retractable. One end of the loading rod is fixedly connected to the top plate, and the other end is fixedly connected to the loading bracket. The electric hydraulic pump is connected to the loading rod to provide power for the extension and retraction of the loading rod. The bottom end of the test model box is connected to the base plate.

[0015] Optionally, the monitoring system includes a temperature sensor, an array displacement sensor, a data acquisition instrument and a data analysis system;

[0016] The temperature sensor is used to detect the temperature change of the soil in the test model box, and the array displacement sensor is used to detect the frost heave and thaw settlement of the soil during the freezing process. The temperature sensor and the array displacement sensor are both data-connected to the data acquisition instrument, and the data acquisition instrument is data-connected to the data analysis system. The data acquisition instrument transmits the data collected by the temperature sensor and the array displacement sensor to the data analysis system, and the data analysis system is used to analyze the data.

[0017] Optionally, a first hole is opened on the side of the test model box, and the first hole is used to install a shield machine. After the shield machine passes through the first hole of the test model box, it is placed on a support frame, and the support frame fixes the shield machine.

[0018] Optionally, a steel plate is provided on one side of the shield machine facing the soil in the test model box, and the steel plate is connected to the shield machine through angle steel. The steel plate is used to simulate a soil bin panel, and the space in front of the soil bin panel is a soil bin filled with layered compacted soil. The steel plate is provided with a plurality of second holes for the horizontal freezing pipes to pass through.

[0019] Optionally, the top plate starts with a plurality of third holes, wherein the third holes are for the vertical freezing pipes to pass through, and the number of the third holes corresponds to the number of the vertical freezing pipes.

[0020] Optionally, the horizontal freezing pipe and the vertical freezing pipe have the same structure, and the freezing pipe includes a liquid supply pipe, a liquid return pipe, a partition and a freezing pipe body;

[0021] The freezing tube body is a seamless steel tube, which is sleeved outside the liquid supply tube and the liquid return tube. One end of the freezing tube body is connected to the outside atmosphere, and the other end is closed. The liquid supply tube and the liquid return tube are fixedly connected to the inside of the freezing tube body through the partition. The partition, the liquid supply tube, the liquid return tube and the freezing tube body form a sealed cavity for brine circulation. One end of the liquid supply tube is connected to one end of the liquid return tube, and the other ends of several of the liquid supply tubes are connected to the liquid outlet end of the low-temperature cooling bath machine through a liquid separator, and the other ends of several of the liquid return tubes are connected to the liquid inlet end of the low-temperature cooling bath machine through a liquid collector.

[0022] Optionally, the length of the horizontal freezing pipe is greater than the thickness of the soil bin.

[0023] Optionally, the vertical freezing pipes are provided with four groups, namely the first group, the second group, the third group and the fourth group, the first group and the second group are located in front of the shield machine cutter head, the third group and the fourth group are located behind the shield machine cutter head, and the lengths of the vertical freezing pipes of the first group and the second group are both Ls+D;

[0024] Among them, Ls is the buried depth of the shield axis, and D is the diameter of the shield machine;

[0025] The horizontal arrangement range of the vertical freezing pipes of the first group, the second group, the third group and the fourth group is greater than D;

[0026] In the third and fourth groups, the length of the vertical freezing pipe in contact with the shield machine is the distance from the soil surface to the shield machine casing. In the third and fourth groups, the length of the vertical freezing pipe located on both sides of the shield machine is Ls+D.

[0027] A method for testing a vertical combined horizontal freezing test device in a subway tunnel comprises the following steps:

[0028] S1: The test soil is configured to the moisture content required for the test, and then the soil is gradually filled into the test model box in layers, and the filling and compaction are performed every 10 cm. After the soil is left to stand and consolidate, soil is taken from different areas of the test box for physical experiments to ensure that the physical parameters of the test soil are consistent with those on site;

[0029] S2: While the soil is backfilled and compacted, temperature sensors, array displacement sensors and freezing pipes are placed at preset positions; the positions of the freezing pipes are continuously measured, and any deviations must be corrected in time to ensure that the freezing pipes are buried according to the designed positions;

[0030] S3: Turn on the electric hydraulic pump to pressurize the soil. At the beginning of the test, the loading frequency is set to be small. As the test progresses, the loading frequency is gradually increased until the applied load makes the soil meet the gravity similarity ratio requirements;

[0031] S4: Check whether each sensor is working properly, then operate the refrigeration cycle system, adjust the brine flow rate, and use a low-temperature cold bath to cool the brine and then pump it out;

[0032] S5: collecting the frozen wall development situation during the freezing process through the temperature sensor, and analyzing the surface frost heave and thaw settlement value caused by the vertical combined horizontal freezing through the array displacement sensor;

[0033] S6: When the temperature at each measuring point no longer changes, turn off the refrigeration system and the test soil enters a natural melting state. After that, continue to monitor the soil temperature and surface displacement until the soil thaws.

[0034] As described above, the present invention has the following beneficial effects:

[0035] This application aims to solve the problem in the above-mentioned prior art that it is impossible to simulate the vertical combined horizontal freezing for shield opening and maintenance. This application, through the loading system, refrigeration cycle system and monitoring system, has the ability to monitor the changes in the temperature field and displacement field of the soil layer during the freezing process, and can then reveal the development characteristics of the frozen wall of the vertical combined horizontal freezing method and the changing laws of the surface frost heave and thaw settlement, thereby providing a safety assessment for the operation of reinforcing the shield opening using the freezing method. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the main viewing direction of the present invention.

[0037] Figure 2 It is a side view schematic diagram of the present invention.

[0038] Figure 3 It is a schematic diagram of the structure of the shield machine of the present invention.

[0039] Figure 4 It is a top view of the vertical freezing pipe arrangement in the present invention.

[0040] Figure 5 It is a schematic diagram of the structure of the freezing pipe of the present invention.

[0041] Figure 6 It is a bottom view of the liquid dispenser of the present invention.

[0042] Figure 7 It is a top view of the liquid dispenser of the present invention.

[0043] Component number description

[0044] Among them: test model box 1, shield machine 2, electric hydraulic pump 3, loading rod 4, loading bracket 5, bottom plate 6, top plate 7, low-temperature cooling bath 8, flow meter 9, liquid distributor 10, second interface 101, pipeline 102, first interface 103, liquid collector 11, connecting pipe 12, vertical freezing pipe 13, liquid supply pipe 131, liquid return pipe 132, partition 133, horizontal freezing pipe 14, data acquisition instrument 15, data analysis system 16, support frame 17, array displacement sensor 18, temperature sensor 19, soil bin panel 20, angle steel 21. DETAILED DESCRIPTION

[0045] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0046] See also Figures 1 to 7 . It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0047] The following embodiments are only for illustration purposes and can be combined with each other, and are not limited to the contents presented in the following single embodiments.

[0048] See also Figure 1-Figure 7 The present invention provides a subway tunnel vertical connection and horizontal freezing test device, including a test model box 1, a loading system, a refrigeration cycle system and a monitoring system;

[0049] In this embodiment, the size of the test model box 1 is 3.7m×1.6m×2.25m (length×width×height). The model box is made of five steel plates, namely four side panels at the front, rear, left and right, and a base plate, which are tightly spliced ​​by bolts. Water stop strips are affixed to the joints to prevent the evaporation of moisture in the soil during the test; at the same time, in order to reduce the influence of the external temperature on the inside of the test model box as much as possible, thereby causing errors in the test results, the inner wall and bottom of the test model box 1 are equipped with geotextiles to reduce the loss of cold; at the same time, the outer wall of the test model box 1 is affixed with an insulation layer, which is made of rubber-plastic insulation material with a thickness of 30mm and a thermal conductivity of no more than 0.04wm / k, and the insulation layer needs to fit the model box tightly without any gaps.

[0050] A shield machine 2 is arranged in the test model box 1; the shield machine 2 is made of stainless steel and is scaled according to the actual model of the shield machine;

[0051] The top of the test model box 1 is open and is used to fill soil;

[0052] The loading system is located at the top of the test model box 1 and is used to apply pressure to the filled soil. In the soil mechanics model test, in order to simulate the behavior of the prototype soil under gravity, it is necessary to ensure that the gravity effect of the model soil is similar to that of the prototype soil. In this embodiment, the method of applying the load through the loading system satisfies the soil gravity similarity ratio.

[0053] The refrigeration cycle system includes a low temperature cold bath machine 8, brine, a connecting pipe 12, a liquid separator 10, a liquid collector 11 and a freezing pipe;

[0054] The low-temperature cold bath machine 8 is connected to multiple freezing pipes through a connecting pipe 12, a liquid distributor 10 and a liquid collector 11 to form a circulation loop for the circulation of brine. Flow meters 9 are provided on the two connecting pipes 12. The low-temperature cold bath machine 8 cools the refluxed brine and then flows out. The circulation of brine freezes the soil. The function of the flow meter 9 is to adjust the brine pumping speed.

[0055] The freezing pipes include horizontal freezing pipes 14 and vertical freezing pipes 13. The horizontal freezing pipes 14 are arranged horizontally along the axis of the shield machine 2, and the vertical freezing pipes 13 are arranged vertically perpendicular to the axis of the shield machine 2. The present application aims to solve the problem existing in the above-mentioned prior art that it is impossible to simulate the vertical combined horizontal freezing used for shield opening and maintenance. The present application, through the loading system, the refrigeration cycle system and the monitoring system, has the ability to monitor the changes in the temperature field and displacement field of the soil layer during the freezing process, and can then reveal the development characteristics of the frozen wall of the vertical combined horizontal freezing method and the changing laws of the surface frost heave and thaw settlement, thereby providing a safety assessment for the operation of reinforcing the shield opening by the freezing method.

[0056] In this embodiment, Figure 1, the loading system includes an electric hydraulic pump 3, a loading rod 4, a loading bracket 5, a bottom plate 6 and a top plate 7;

[0057] The loading bracket 5 is fixedly connected to the bottom plate 6 through a plurality of vertical poles distributed at intervals. The loading rod 4 is retractable. One end of the loading rod 4 is fixedly connected to the top plate 7, and the other end is fixedly connected to the loading bracket 5. The electric hydraulic pump 3 is connected to the loading rod 4 to provide power for the loading rod 4 to be extended and retracted. The bottom end of the test model box 1 is connected to the bottom plate 6. In this embodiment, the electric hydraulic pump 3 works to drive the loading rod 4 to extend and retract downward. The loading rod 4 drives the top plate 7 to apply pressure to the soil. The main function of the top plate 7 is to disperse the pressure of the pressure rod 4 so that the force on the surface of the soil is uniform. In this embodiment, the top plate 7 begins to have several third holes, and the third holes are for the vertical freezing pipes 13 to pass through. The number of the third holes corresponds to the number of the vertical freezing pipes 13. In this embodiment, the third holes are designed to facilitate the vertical freezing pipes 13 to pass through the top plate 7 and be inserted into the soil.

[0058] In this embodiment, the monitoring system includes a temperature sensor 19, an array displacement sensor 18, a data acquisition device 15 and a data analysis system 16;

[0059] The temperature sensor 19 is used to detect the temperature change of the soil in the test model box 1, and the array displacement sensor 18 is used to detect the frost heave and thaw settlement of the soil during the freezing process. The temperature sensor 19 and the array displacement sensor 18 are both connected to the data acquisition instrument 15, and the data acquisition instrument 15 is connected to the data analysis system 16. The data acquisition instrument 15 transmits the data collected by the temperature sensor 19 and the array displacement sensor 18 to the data analysis system 16, and the data analysis system 16 is used to analyze the data. In this embodiment, the temperature sensor 19 can be a Pt100 temperature sensor. The Pt100 temperature sensor can accurately measure the temperature within a wide temperature range (-200°C to +850°C) and is suitable for monitoring the temperature change of the soil. And it can be converted into a temperature value by the data acquisition instrument. The array displacement sensor 18 can use the RT-1010 array displacement meter. The RT-1010 array displacement meter is a sensor capable of three-dimensional deformation monitoring. The frost heave and thaw settlement of the soil during the freezing process can be detected by the RT-1010 array displacement meter. In this embodiment, if Figure 2 , the array displacement sensor 18 is arranged in the shallower soil layer, and is arranged along the direction of the tunnel face and the tunnel axis. The temperature sensor 19 needs to be arranged at three depths, Ls-D, Ls, and Ls+D, respectively (where Ls is the buried depth of the shield axis, and D is the diameter of the shield machine 2). The arrangement positions are the front and side of the freezing pipe arrangement area, the tunnel face, and the soil bin. The data is measured by the array displacement sensor 18 and the temperature sensor 19, and then collected by the data acquisition device 15. Finally, the temperature change curve of each measuring point over time and the displacement change curve over time are obtained in the data analysis system.

[0060] In this embodiment, Figure 2 A first hole is provided on the side of the test model box 1, and the first hole is used to load the shield machine 2. After the shield machine 2 passes through the first hole of the test model box 1, it is placed on the support frame 17, and the support frame 17 fixes the shield machine 2. In this embodiment, the support frame 17 is in an I-shape, and supports and fixes the shield machine 2.

[0061] In this embodiment, Figure 2 and Figure 3 A steel plate is provided on one side of the shield machine 2 facing the soil in the test model box 1. The steel plate is connected to the shield machine 2 through an angle steel 21. The steel plate is used to simulate a soil bin panel 20. The space in front of the soil bin panel 20 is a soil bin filled with layered compacted soil. The steel plate is provided with a plurality of second holes for the horizontal freezing pipes 14 to pass through.

[0062] In this embodiment, the horizontal freezing pipe 14 and the vertical freezing pipe 13 have the same structure. Taking the vertical freezing pipe 13 as an example, Figure 5 The freezing pipe includes a liquid supply pipe 131, a liquid return pipe 132, a partition 133 and a freezing pipe body;

[0063] The freezing tube body is a seamless steel tube in the shape of a cylindrical shell. The freezing tube body is sleeved outside the liquid supply tube 131 and the liquid return tube 132. One end of the freezing tube body is connected to the outside atmosphere, and the other end is closed. The liquid supply tube 131 and the liquid return tube 132 are fixedly connected to the inside of the freezing tube body through a partition 133. The partition 133, the liquid supply tube 131, the liquid return tube 132 and the freezing tube body form a sealed cavity for brine circulation. One end of the liquid supply tube 131 is connected to one end of the liquid return tube 132, and the other ends of several liquid supply tubes 131 are connected to the liquid outlet end of the low-temperature cooling bath machine 8 through the liquid distributor 10, and the other ends of several liquid return tubes 132 are connected to the liquid inlet end of the low-temperature cooling bath machine 8 through the liquid collector 11. In this embodiment, the liquid distributor 10 and the liquid collector 11 have the same structure, such as Figure 6 and Figure 7The liquid distributor 10 includes a pipeline 102, a first interface 103 and a second interface 101, wherein the second interface 101 is provided with a plurality of liquid supply pipes 131, and the first interface 103 is one, and the first interface 103 is connected to the liquid outlet of the low temperature cold bath machine 8 through a connecting pipe 12, and the first interface 103 is communicated with a plurality of second interfaces 101 through a pipeline 102. The liquid collector 11 connects a plurality of liquid return pipes 132 to the liquid inlet of the low temperature cold bath machine 8 in the same manner. In this embodiment, the partition 133 separates the freezing tube body into two areas. During the freezing process, the lower part of the partition 133 is filled with low temperature brine. Thanks to the water-stopping effect of the partition 133, there is only air above the partition 133 except for the liquid supply pipe 131 and the liquid return pipe 132. This design can make full use of the cold capacity to freeze the soil around the shield machine, and avoid freezing the soil in the upper non-reinforced area, thereby wasting energy. In this embodiment, low-temperature brine flows into the freezing tube body from the liquid supply pipe 131 and flows out from the liquid return pipe 132, causing the freezing tube body to cool down, thereby gradually forming a freezing circle next to the freezing tube body. As the range of the freezing circle gradually increases, a complete freezing curtain is eventually formed.

[0064] In this embodiment, Figure 2 , the length of the horizontal freezing pipe 14 is greater than the thickness of the soil bin. In this embodiment, horizontal freezing pipes 14 are evenly distributed in the soil bin and along the arc of the shield shell at the bottom of the shield machine. The purpose of setting the horizontal freezing pipes 14 is to form a frozen wall with sufficient strength at the bottom of the shield machine. The length of the horizontal freezing pipe 14 is greater than the thickness of the soil bin. According to the actual test situation, the length of the horizontal freezing pipe 14 can be slightly greater than the thickness of the soil bin.

[0065] In this embodiment, Figure 4 There are four groups of vertical freezing pipes 13, which are distributed in a plum blossom shape. From bottom to top, they are the first group, the second group, the third group and the fourth group. The first group and the second group are located in front of the cutterhead of the shield machine 2, and the third group and the fourth group are located behind the cutterhead of the shield machine 2. The lengths of the vertical freezing pipes 13 of the first group and the second group are both Ls+D;

[0066] Wherein, Ls is the buried depth of the shield axis, and D is the diameter of the shield machine 2;

[0067] The horizontal arrangement range of the vertical freezing pipes 13 of the first, second, third and fourth groups is greater than D; the horizontal range of the arrangement area of ​​the vertical freezing pipes 13 must exceed the diameter D of the shield machine, so that the formed freezing wall can wrap around the end of the shield machine;

[0068] In the third and fourth groups, the length of the vertical freezing pipe 13 in contact with the shield machine 2 is the distance from the soil surface to the casing of the shield machine 2. In the third and fourth groups, the length of the vertical freezing pipe 13 located on both sides of the shield machine 2 is Ls+D, that is, Figure 4In the viewing angle, the length of the vertical freezing pipes 13 on the left and right sides of the shield machine 2 is Ls+D.

[0069] A subway tunnel vertical combined horizontal freezing test device method, using the above-mentioned subway tunnel vertical combined horizontal freezing test device, includes the following steps:

[0070] S1: The test soil is configured to have the moisture content required for the test, and then the soil is gradually filled into the test model box 1 in layers, and the filling and compaction are performed every 10 cm. After the soil is left to stand and consolidate, soil is taken from different areas of the test box for physical experiments to ensure that the physical parameters of the test soil are consistent with those on site;

[0071] S2: While the soil is backfilled and compacted, the temperature sensor 19, the array displacement sensor 18 and the freezing pipe are arranged at the preset position; the position of the freezing pipe is continuously measured, and any deviation needs to be corrected in time to ensure that the freezing pipe is buried according to the designed position;

[0072] S3: Turn on the electric hydraulic pump 3 to pressurize the soil. At the beginning of the test, the loading frequency is set to be small. As the test progresses, the loading frequency is gradually increased until the applied load makes the soil meet the gravity similarity ratio requirement.

[0073] S4: Check whether each sensor is working properly, then operate the refrigeration cycle system, adjust the brine flow rate, and pump out the brine after the low-temperature cold bath machine 8 cools the brine;

[0074] S5: collecting the frozen wall development situation during the freezing process through the temperature sensor 19, and analyzing the surface frost heave and thaw settlement value caused by the vertical combined horizontal freezing through the array displacement sensor 18;

[0075] S6: When the temperature at each measuring point no longer changes, turn off the refrigeration system and the test soil enters a natural melting state. After that, continue to monitor the soil temperature and surface displacement until the soil thaws.

[0076] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A subway tunnel vertical joint and horizontal freezing test device, used to simulate the vertical joint and horizontal freezing of shield opening and maintenance, characterized in that: It includes a test model box (1), a loading system, a refrigeration cycle system and a monitoring system; A shield machine (2) is arranged in the test model box (1); The top of the test model box (1) is open and is used to fill soil; The loading system is located at the top of the test model box (1) and is used to apply pressure to the filled soil; The refrigeration cycle system comprises a low-temperature cold bath (8), brine, a connecting pipe (12), a liquid separator (10), a liquid collector (11) and a freezing pipe; The low-temperature cold bath (8) is connected to the plurality of freezing pipes via a connecting pipe (12), a liquid distributor (10) and a liquid collector (11) to form a circulation loop for the circulation of brine. A flow meter (9) is provided on each of the two connecting pipes (12). The low-temperature cold bath (8) cools the refluxed brine and then flows out. The circulation of the brine freezes the soil. The freezing pipe comprises a horizontal freezing pipe (14) and a vertical freezing pipe (13); the horizontal freezing pipe (14) is horizontally arranged along the axial direction of the shield machine (2); and the vertical freezing pipe (13) is vertically arranged perpendicular to the axial direction of the shield machine (2); The loading system comprises an electric hydraulic pump (3), a loading rod (4), a loading bracket (5), a bottom plate (6) and a top plate (7); The loading bracket (5) is fixedly connected to the bottom plate (6) via a plurality of vertical rods distributed at intervals; the loading rod (4) is retractable; one end of the loading rod (4) is fixedly connected to the top plate (7) and the other end is fixedly connected to the loading bracket (5); the electric hydraulic pump (3) is connected to the loading rod (4) to provide power for the retraction and extension of the loading rod (4); and the bottom end of the test model box (1) is connected to the bottom plate (6); A steel plate is provided on one side of the shield machine (2) facing the soil in the test model box (1); the steel plate is connected to the shield machine (2) via an angle steel (21); the steel plate is used to simulate a soil bin panel (20); the space in front of the soil bin panel (20) is a soil bin, and the soil bin is filled with layered compacted soil; the steel plate is provided with a plurality of second holes, and the second holes are for the horizontal freezing pipes (14) to pass through; The top plate (7) is provided with a plurality of third holes, the third holes being used for the vertical freezing pipes (13) to pass through, and the number of the third holes corresponds to the number of the vertical freezing pipes (13).

2. A subway tunnel vertical connection and horizontal freezing test device according to claim 1, characterized in that: The monitoring system comprises a temperature sensor (19), an array displacement sensor (18), a data acquisition device (15) and a data analysis system (16); The temperature sensor (19) is used to detect the temperature change of the soil in the test model box (1); the array displacement sensor (18) is used to detect the frost heave and thaw settlement of the soil during the freezing process; the temperature sensor (19) and the array displacement sensor (18) are both data-connected to the data acquisition instrument (15); the data acquisition instrument (15) is data-connected to the data analysis system (16); the data acquisition instrument (15) transmits the data collected by the temperature sensor (19) and the array displacement sensor (18) to the data analysis system (16); and the data analysis system (16) is used to analyze the data.

3. A subway tunnel vertical connection and horizontal freezing test device according to claim 1, characterized in that: A first hole is provided on the side of the test model box (1), and the first hole is used to load the shield machine (2). After the shield machine (2) passes through the first hole of the test model box (1), it is placed on a support frame (17), and the support frame (17) fixes the shield machine (2).

4. A subway tunnel vertical connection and horizontal freezing test device according to claim 1, characterized in that: The horizontal freezing pipe (14) and the vertical freezing pipe (13) have the same structure, and the freezing pipe comprises a liquid supply pipe (131), a liquid return pipe (132), a partition (133) and a freezing pipe body; The freezing tube body is a seamless steel tube. The freezing tube body is sleeved outside the liquid supply tube (131) and the liquid return tube (132). One end of the freezing tube body is connected to the outside atmosphere, and the other end is closed. The liquid supply tube (131) and the liquid return tube (132) are fixedly connected to the inside of the freezing tube body through the partition (133). The partition (133), the liquid supply tube (131), the liquid return tube (132) and the freezing tube body form a sealed cavity for salt water to flow. One end of the liquid supply tube (131) is connected to one end of the liquid return tube (132). The other ends of a plurality of the liquid supply tubes (131) are connected to the liquid outlet end of the low-temperature cooling bath (8) through a liquid distributor (10). The other ends of a plurality of the liquid return tubes (132) are connected to the liquid inlet end of the low-temperature cooling bath (8) through a liquid collector (11).

5. The subway tunnel vertical connection and horizontal freezing test device according to claim 1 is characterized in that: The length of the horizontal freezing pipe (14) is greater than the thickness of the soil bin.

6. A subway tunnel vertical connection and horizontal freezing test device according to claim 1, characterized in that: The vertical freezing pipes (13) are provided with four groups, namely a first group, a second group, a third group and a fourth group. The first group and the second group are located in front of the cutterhead of the shield machine (2), and the third group and the fourth group are located behind the cutterhead of the shield machine (2). The lengths of the vertical freezing pipes (13) of the first group and the second group are both Ls+D. Wherein, Ls is the buried depth of the shield axis, and D is the diameter of the shield machine (2); The horizontal arrangement range of the vertical freezing pipes (13) of the first group, the second group, the third group and the fourth group is greater than D; In the third and fourth groups, the length of the vertical freezing pipe (13) in contact with the shield machine (2) is the distance from the soil layer surface to the casing of the shield machine (2); in the third and fourth groups, the length of the vertical freezing pipe (13) located on both sides of the shield machine (2) is Ls+D.

7. A method for testing a vertical combined horizontal freezing test device for a subway tunnel, using a vertical combined horizontal freezing test device for a subway tunnel as described in any one of claims 1 to 6, characterized in that: The steps include: S1: The test soil is configured to have the required moisture content for the test, and then the soil is gradually filled into the test model box (1) in layers, and the filling and compaction are performed every 10 cm. After the soil is left to stand and consolidate, soil is taken from different areas of the test box for physical experiments to ensure that the physical parameters of the test soil are consistent with those on site; S2: while the soil is backfilled and compacted, a temperature sensor (19), an array displacement sensor (18) and a freezing pipe are arranged at a preset position; the position of the freezing pipe is continuously measured, and any deviation is corrected in time to ensure that the freezing pipe is buried in accordance with the designed position; S3: turning on the electric hydraulic pump (3) to pressurize the soil. At the beginning of the test, the loading frequency is set to be relatively low. As the test progresses, the loading frequency is gradually increased until the applied load makes the soil meet the gravity similarity ratio requirement. S4: Check whether each sensor is working properly, then operate the refrigeration cycle system, adjust the brine flow rate, and use a low-temperature cold bath machine (8) to cool the brine and then pump it out; S5: collecting the frozen wall development situation during the freezing process through the temperature sensor (19), and analyzing the surface frost heave and thaw settlement value caused by the vertical combined horizontal freezing through the array displacement sensor (18); S6: When the temperature at each measuring point no longer changes, turn off the refrigeration system and the test soil enters a natural melting state. After that, continue to monitor the soil temperature and surface displacement until the soil thaws.

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