A device and method for freezing local parts of overlapping tunnel ends in stages

Abstract

The present invention provides a device for partial vertical freezing of the ends of upper and lower overlapping tunnels and a freezing method thereof. The partial freezer is mainly composed of a water inlet pipe, a water return pipe, a freezing pipe, and a prefabricated vacuum sleeve. A perforated partition is provided in the freezing pipe, which divides the entire freezing pipe into a freezing zone and a non-freezing zone. The outer vacuum sleeve can reduce the cooling loss in the non-freezing zone. The partial freezer can be designed to have freezing and non-freezing zones according to different overlapping tunnel projects, and the positions of the perforated partition and the vacuum sleeve can be flexibly adjusted. By freezing in different zones, the cooling loss in the non-freezing section can be reduced, and the secondary pulling up of the freezing pipe can be avoided. Because the brine temperature is lower and the brine flow rate is greater than that of the prior art, rapid freezing can be achieved, meeting the engineering needs of partial vertical rapid freezing of the ends of upper and lower overlapping tunnels, and ensuring the safety and reliability of the ends when the shield machine of the upper and lower overlapping tunnels is started or received.

Description

Technical Field

[0001] The present invention relates to the technical field of civil engineering, and in particular to a device for sequential vertical local freezing at the ends of upper and lower overlapping tunnels and a freezing method thereof. Background Art

[0002] Due to limited urban space, more and more subway tunnels need to be laid out in overlapping patterns, which will inevitably lead to a large number of projects with overlapping tunnels. In the end starting or receiving projects of overlapping tunnels, the choice of end reinforcement scheme and the quality of reinforcement directly affect the progress and safety of the starting or receiving. If not handled properly, engineering accidents such as sand and water gushing may easily occur during the portal excavation and shield starting or receiving process.

[0003] Therefore, based on the structural characteristics of overlapping tunnels, the present invention uses a phased vertical local freezing method to reinforce the portal ends. Local freezers are used to freeze the soil within the portal reinforcement range, while preventing heat exchange between the freezers and the soil outside the reinforcement range. During the launch or reception of shield machines in the upper and lower overlapping tunnels, the start and stop of each freezing zone are adjusted in a timely manner to achieve the effect of phased vertical local freezing, allowing the shield machine to launch or receive safely and quickly in the upper and lower overlapping tunnels, ensuring a safe construction process. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a device and a freezing method for the end of overlapping tunnels. The device uses a step-by-step vertical local freezing method to reinforce the end, and by timely adjusting the start and stop of each freezing zone, the safety of the shield starting or receiving process of the overlapping tunnels is guaranteed.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A device for vertical partial freezing in stages at the ends of upper and lower overlapping tunnels, comprising a partial freezer and a four-way control valve. The device is characterized in that the partial freezer and the four-way control valve are connected by an extension pipe, a plurality of freezing areas and non-freezing areas are provided in the partial freezer, the freezing areas and non-freezing areas are arranged at intervals, and a drill bit is installed at the end of the partial freezer.

[0007] Preferably, the local freezer includes a low-temperature resistant steel pipe, and the interior of the low-temperature resistant steel pipe is respectively provided with an upper freezing zone water inlet pipe, an upper freezing zone return pipe, a lower freezing zone water inlet pipe and a lower freezing zone return pipe, the inner wall of the low-temperature resistant steel pipe is sequentially connected with an upper perforated partition, a middle perforated partition and a lower perforated partition from top to bottom, the area above the upper perforated partition and the area between the middle perforated partition and the lower perforated partition are non-freezing areas, the area below the lower perforated partition is the lower freezing area of ​​the freezer, the area between the upper perforated partition and the middle perforated partition is the upper freezing area of ​​the freezer, the upper freezing area water inlet pipe and the upper freezing area return pipe pass through the upper perforated partition and are connected with the upper freezing area of ​​the freezer to form a loop, the lower freezing area water inlet pipe and the lower freezing area return pipe pass through the upper perforated partition, the middle perforated partition and the lower perforated partition in sequence and are connected with the lower freezing area of ​​the freezer to form a loop, and an insulation structure is provided outside the non-freezing area.

[0008] Preferably, the thermal insulation structure includes an upper non-freezing zone vacuum casing and a lower non-freezing zone vacuum casing which are sleeved on the low-temperature resistant steel pipe, the upper end of the upper non-freezing zone vacuum casing and the lower end of the lower non-freezing zone vacuum casing are threadedly connected through freezer threads and vacuum pipe threads, and the ends of the upper non-freezing zone vacuum casing and the lower non-freezing zone vacuum casing are sealed and connected to the low-temperature resistant steel pipe through incisions and full welding through sealing steel rings, and a vacuum insulation zone is formed between the upper non-freezing zone vacuum casing, the lower non-freezing zone vacuum casing and the low-temperature resistant steel pipe.

[0009] Preferably, the upper perforated partition plate, the middle perforated partition plate and the lower perforated partition plate are all connected with insulation gaskets on the side away from the non-freezing area.

[0010] Preferably, sealing gaskets are connected to the connections between the upper freezing zone water inlet pipe, the upper freezing zone return pipe, the lower freezing zone water inlet pipe and the lower freezing zone return pipe and the upper perforated partition plate, the middle perforated partition plate and the lower perforated partition plate.

[0011] Preferably, the thermal insulation gasket is made of aerogel felt, and the sealing gasket is made of low-temperature resistant rubber material.

[0012] Preferably, the upper freezing zone water inlet pipe, upper freezing zone return pipe, lower freezing zone water inlet pipe, lower freezing zone return pipe and low-temperature resistant steel pipe are all made of Fe-Mn-Al series austenitic low-temperature steel pipe.

[0013] Preferably, the control circuits of the refrigeration systems of the lower freezing zone and the upper freezing zone of the freezer are independent of each other.

[0014] Preferably, the outer diameter of the upper non-freezing zone vacuum sleeve and the lower non-freezing zone vacuum sleeve is 200 mm, the outer wall thickness is 5 mm, the inner diameter is 170 mm, and the vacuum cavity thickness of the vacuum insulation zone is 10 mm.

[0015] A method for sequential vertical partial freezing of the ends of upper and lower overlapping tunnels, the method comprising the following steps:

[0016] The freezing method involves the following structures: the downline tunnel portal, the downline tunnel portal freezing zone, the upline tunnel portal, the upline tunnel portal freezing zone, the shield machine and the support frame; the brine is a calcium chloride solution with a mass concentration of 29.9% and a freezing point of -55°C; the low-temperature brine temperature of the upper freezing zone inlet pipe, the upper freezing zone return pipe, the lower freezing zone inlet pipe and the lower freezing zone return pipe is between -36°C and -40°C; the single-hole brine flow rate is 10m 3 / h, the brine flow rate in the annular space of the freezing pipe is 0.4-0.5m / s;

[0017] The thickness of the freezing curtain in the freezing zone of the offline tunnel portal and the upstream tunnel portal is 1.6m, the average soil temperature is -15°C, and the active freezing time is 21 days. After the offline tunnel portal has been actively frozen for 10 days, the four-way control valves are controlled to actively freeze the upstream tunnel portal. After the active freezing time of the offline tunnel portal freezing zone reaches 21 days and the freezing curtain development and the average soil temperature meet the design requirements, the shield machine for the offline tunnel portal can be started or received within 12 days. After the shield machine for the offline tunnel portal is started or received, it will be started or received.

[0018] After the active freezing time of the freezing zone of the portal of the upline tunnel has reached 21 days and the freezing curtain development and the average soil temperature have reached the design requirements, the shield machine of the portal of the downline tunnel can be started or received. During the process of starting or receiving the shield machine of the portal of the downline tunnel, the freezing zone under the freezer remains in a maintenance frozen state until the start or reception of the shield machine of the portal of the downline tunnel is completed;

[0019] During the process of starting or receiving the shield machine of the online tunnel portal, the freezing area on the freezer remains in a maintenance freezing state until the shield machine of the online tunnel portal starts or receives the end, and then stops freezing.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The freezing and non-freezing areas of the local freezer can be flexibly adjusted according to the needs of the project to meet the needs of freezing reinforcement of shield ends of different overlapping tunnels;

[0022] (2) Using partial vertical freezing to locally reinforce the soil within the upper and lower tunnel portals, a high-strength and well-sealed reinforcement body can be formed to ensure safe and reliable tunnel opening during the shield starting or receiving process.

[0023] (3) The use of phased vertical partial freezing technology can significantly reduce the amount of freezing and pipe pulling, reduce energy consumption and construction costs, shorten the construction period, and reduce the amount of frozen soil generated, thereby reducing the disturbance to the tunnel and surrounding environment caused by frost heave and thaw settlement of the soil.

[0024] (4) This local freezer uses a larger pipe diameter than conventional freezers, a lower brine temperature and a larger brine flow rate to improve heat exchange efficiency, shorten the active freezing time, achieve rapid freezing, and shorten the construction period. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more specifically and intuitively illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0026] Figure 1 It is a top view of a double freezing zone freezer and its 1-1 and 2-2 cross-sectional views;

[0027] Figure 2 Here are some pictures of several types of perforated partitions;

[0028] Figure 3 This is a diagram of a four-way valve control device;

[0029] Figure 4 This is a detailed view of the prefabricated vacuum jacket and freezing pipe;

[0030] Figure 5 It is a schematic diagram of the shield position and freezing zone when the shield starts or receives in the lower tunnel of the upper and lower overlapping tunnels;

[0031] Figure 6 It is a schematic diagram of the shield position and freezing zone when the shield is started or received in the upper and lower overlapping tunnels.

[0032] In the figure: local freezer 1, upper freezing zone water inlet pipe 101, upper freezing zone return pipe 102, lower freezing zone water inlet pipe 103, lower freezing zone return pipe 104, upper perforated baffle 105, middle perforated baffle 106, lower perforated baffle 107, freezer lower freezing zone 108, freezer upper freezing zone 109, low-temperature resistant steel pipe 1010, insulation gasket 2, sealing gasket 3, freezer thread 4, upper non-freezing zone vacuum casing 5, vacuum insulation zone 501, sealing steel ring 502, vacuum pipe thread 6, full weld of incision 7, four-way control valve 8, lower non-freezing zone vacuum casing 9, lower line tunnel portal 10, lower line tunnel portal freezing zone 11, upper line tunnel portal 12, upper line tunnel portal freezing zone 13, shield machine 14, support frame 15. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0034] Reference Figure 1-6A device for vertical partial freezing at the ends of overlapping tunnels, comprising a partial freezer 1 and a four-way control valve 8, characterized in that the partial freezer 1 and the four-way control valve 8 are connected by an extension pipe, a plurality of freezing areas and non-freezing areas are provided in the partial freezer 1, the freezing areas and non-freezing areas are arranged at intervals, and a drill bit is installed at the end of the partial freezer 1.

[0035] In this embodiment, the local freezer 1 includes a low-temperature resistant steel pipe 1010, and the interior of the low-temperature resistant steel pipe 1010 is respectively provided with an upper freezing zone water inlet pipe 101, an upper freezing zone return pipe 102, a lower freezing zone water inlet pipe 103 and a lower freezing zone return pipe 104. The inner wall of the low-temperature resistant steel pipe 1010 is connected with an upper perforated partition 105, a middle perforated partition 106 and a lower perforated partition 107 from top to bottom. The area above the upper perforated partition 105 and the area between the middle perforated partition 106 and the lower perforated partition 107 are non-freezing areas, and the area above the lower perforated partition 107 is non-freezing area. The lower area is the lower freezing zone 108 of the freezer, and the area between the upper perforated partition 105 and the middle perforated partition 106 is the upper freezing zone 109 of the freezer. The upper freezing zone water inlet pipe 101 and the upper freezing zone return pipe 102 pass through the upper perforated partition 105 and are connected with the upper freezing zone 109 of the freezer to form a loop. The lower freezing zone water inlet pipe 103 and the lower freezing zone return pipe 104 pass through the upper perforated partition 105, the middle perforated partition 106 and the lower perforated partition 107 in turn and are connected with the lower freezing zone 108 of the freezer to form a loop. An insulation structure is provided outside the non-freezing area.

[0036] In this embodiment, the insulation structure includes an upper non-freezing zone vacuum sleeve 5 and a lower non-freezing zone vacuum sleeve 9 which are sleeved on the low-temperature resistant steel pipe 1010. The upper end of the upper non-freezing zone vacuum sleeve 5 and the lower end of the lower non-freezing zone vacuum sleeve 9 are threadedly connected through the freezer thread 4 and the vacuum pipe thread 6, and the ends of the upper non-freezing zone vacuum sleeve 5 and the lower non-freezing zone vacuum sleeve 9 are sealedly connected to the low-temperature resistant steel pipe 1010 through a sealing steel ring 502 by a full incision weld 7, and a vacuum insulation zone 501 is formed between the upper non-freezing zone vacuum sleeve 5 and the lower non-freezing zone vacuum sleeve 9 and the low-temperature resistant steel pipe 1010.

[0037] In this embodiment, the upper perforated partition 105, the middle perforated partition 106 and the lower perforated partition 107 are connected to the side away from the non-freezing area with an insulating gasket 2, which is set on the side of the perforated partition in contact with the low-temperature brine to reduce heat loss from the perforated partition.

[0038] In this embodiment, the connections between the upper freezing zone water inlet pipe 101, the upper freezing zone return pipe 102, the lower freezing zone water inlet pipe 103 and the lower freezing zone return pipe 104 and the upper perforated partition 105, the middle perforated partition 106 and the lower perforated partition 107 are all connected with sealing gaskets 3, which are arranged at the openings of each perforated partition to improve the sealing of the brine cavity. The insulating gasket 2 is aerogel felt, and the sealing gasket 3 is made of low-temperature resistant rubber material.

[0039] In this embodiment, the upper freezing zone water inlet pipe 101, the upper freezing zone return pipe 102, the lower freezing zone water inlet pipe 103, the lower freezing zone return pipe 104 and the low-temperature resistant steel pipe 1010 are all made of Fe-Mn-Al austenitic low-temperature steel pipe.

[0040] In this embodiment, the control circuits of the refrigeration systems of the lower freezing zone 108 and the upper freezing zone 109 of the freezer are independent of each other, and the four-way control valve 8 at the top of the freezer can be manually controlled to control the active freezing or freezing stop of the freezing zone 11 of the lower tunnel portal and the freezing zone 13 of the upper tunnel portal.

[0041] In this embodiment, the upper non-freezing zone vacuum sleeve 5 and the lower non-freezing zone vacuum sleeve 9 have an outer diameter of 200 mm, an outer wall thickness of 5 mm, an inner diameter of 170 mm, and a vacuum cavity thickness of the vacuum insulation zone 501 of 10 mm.

[0042] A method for sequential vertical partial freezing of the ends of upper and lower overlapping tunnels, the method comprising the following steps:

[0043] The freezing method involves the following structures: a downline tunnel portal 10, a downline tunnel portal freezing zone 11, an upline tunnel portal 12, an upline tunnel portal freezing zone 13, a shield machine 14 and a support frame 15; the brine is a calcium chloride solution with a mass concentration of 29.9% and a freezing point of -55°C; the temperature of the low-temperature brine of the upper freezing zone inlet pipe 101, the upper freezing zone return pipe 102, the lower freezing zone inlet pipe 103 and the lower freezing zone return pipe 104 is between -36°C and -40°C; the single-hole brine flow rate is 10m 3 / h, the brine flow rate in the annular space of the freezing pipe is 0.4-0.5m / s;

[0044] The thickness of the freezing curtain of the offline tunnel portal freezing zone 11 and the online tunnel portal 12 is 1.6m, the average soil temperature is -15°C, and the active freezing time is 21 days; after the offline tunnel portal 10 has been actively frozen for 10 days, the four-way control valve 8 is controlled to actively freeze the online tunnel portal 12. After the active freezing time of the offline tunnel portal freezing zone 11 reaches 21 days and the development of the freezing curtain and the average soil temperature meet the design requirements, the shield machine for the offline tunnel portal 10 is started or received within 12 days, and the start or reception of the offline tunnel portal 10 is completed after the start or reception of the offline tunnel portal 10 is completed;

[0045] After the active freezing time of the freezing zone 13 of the upper tunnel portal has reached 21 days and the freezing curtain development and the average soil temperature have reached the design requirements, the shield machine of the lower tunnel portal 10 is started or received; during the process of starting or receiving the shield machine of the lower tunnel portal 10, the freezing zone 108 below the freezer remains in a maintenance frozen state until the start or reception of the shield machine of the lower tunnel portal 10 is completed;

[0046] During the start or reception of the shield machine of the online tunnel portal 12, the freezing area 109 on the freezer remains in a maintenance freezing state until the start or reception of the shield machine of the online tunnel is completed, and then the freezing is stopped.

[0047] The length of the upper non-freezing zone vacuum casing 5 and the extension pipe is determined by the buried depth of the upper tunnel, and the position of the thread on the low-temperature resistant steel pipe 1010 is determined; the upper and lower clearances of the overlapping tunnel portals are used to determine whether the lower non-freezing zone vacuum casing 9 is required. The lower part is the manufacturing process of the double freezing zone local freezer, which means that the lower non-freezing zone vacuum casing 9 is required;

[0048] Assemble the pipelines: Weld the upper freezing zone water inlet pipe 101, upper freezing zone return pipe 102, lower freezing zone water inlet pipe 103, and lower freezing zone return pipe 104 to the upper perforated baffle 105, middle perforated baffle 106, and lower perforated baffle 107. During installation, ensure that the distance between the end of the water inlet pipe and the perforated baffle is 20 mm, and install the insulation gasket 2 and the sealing gasket 3 at the perforated area.

[0049] After completing the S2 welding work, the entirety of the pipe is covered with a low-temperature resistant steel pipe 1010, and the upper ends of the upper freezing zone water inlet pipe 101, the upper freezing zone return pipe 102, the lower freezing zone water inlet pipe 103, and the lower freezing zone return pipe 104 extend out of the low-temperature resistant steel pipe 1010 and are connected to the four-way control valve 8;

[0050] Insert the upper non-freezing area vacuum sleeve 5 from above the assembled low-temperature resistant steel pipe 1010, tighten it through the reserved threads on the sleeve and the freezer, then weld the upper non-freezing area vacuum sleeve 5 and the low-temperature resistant steel pipe 1010 into one, and when installing the lower non-freezing area vacuum sleeve 9, insert it from the bottom of the low-temperature resistant steel pipe 1010. The subsequent steps are the same as those for installing the upper non-freezing area vacuum sleeve 5; after the local freezer 1 is assembled, pressure testing and liquid testing operations should be carried out.

[0051] The soil layers of a subway access tunnel, from top to bottom, consist of miscellaneous fill, silty clay, silty clay, fully weathered diorite, strongly weathered diorite (gravel), strongly weathered diorite, moderately weathered diorite (relatively crushed), and moderately weathered diorite. Phreatic water occurs in shallow soil layers. Fine-grained soils are present in the fully weathered diorite and strongly weathered diorite (gravel) layers, which are prone to soil flow and piping under certain hydrodynamic conditions. The water-richness of the soil layers varies significantly. Silty clay, silty clay, and gravelly silty clay layers are locally distributed in the upper part, exhibiting certain confined water properties. The lower tunnel portal has a floor elevation of -28.2m and a roof elevation of -21.5m. The upper tunnel portal has a floor elevation of -14.5m and a roof elevation of -7.8m. The clearance between the upper and lower portals is 7m, and the clearance between the tunnels is 7.6m.

[0052] 1. Based on the buried depth of the upper and lower overlapping tunnel portals, the length of the upper non-freezing zone vacuum casing 5 was determined to be 4.8m, and the length of the lower non-freezing zone vacuum casing 9 was determined to be 1m. It is expected that the refrigeration capacity will be saved by about 40%.

[0053] 2. Construction of vertical freezing pipes: After tightening the inner pipe clamps of the joints between the freezing steel pipes, use manual arc welding to ensure welding strength. Drill holes and bury local freezers according to different design positions. Monitor the deflection in real time during drilling. If the deflection is greater than 150mm, stop drilling immediately and correct the deviation. After drilling, check the length of the freezing pipe. Grouting is carried out in time after each drilling is completed to ensure a stable combination of steel pipes, slurry and soil. Pressurize the vertical freezing pipe for leak testing, and maintain the pressure at 0.8MPa. If it is stable for more than 15 minutes, it is considered that the freezing pipe is leak-free. Debug the refrigeration system, brine circulation system, and detection system, and pay attention to dynamic parameters such as pressure and temperature. Freon F-22 is used as the refrigerant, and the cooling brine is calcium chloride solution.

[0054] 3. Active freezing of vertical freezing pipes: The designed active freezing time is 35 days, with a single freezing hole flow rate greater than 10m³ / h. The brine temperature must drop below -30°C after 7 days of active freezing and below -36°C after 21 days. The brine temperature must drop below -36°C when the shield machine is launched or terminated. The designed freeze curtain closing time is 21 days. The designed frozen wall thickness is 1.6m, with an average temperature of -15°C.

[0055] 4. The order of launching or receiving and the freezing time arrangement: The active freezing time of the portals of the offline and online tunnels is 21 days; after the portals of the offline tunnel have been actively frozen for 10 days, the four-way valves are controlled to actively freeze the portals of the online tunnel. After the active freezing time of the freezing zone of the portals of the offline tunnel reaches 21 days and the development of the freezing curtain and the average temperature of the soil have reached the design requirements, the shield of the offline tunnel is launched or received (launching or receiving is completed within 12 days). After the launch or reception of the shield of the offline tunnel is completed, the active freezing time of the freezing zone of the portals of the online tunnel has also reached 21 days and the development of the freezing curtain and the average temperature of the soil have reached the design requirements, the shield of the offline tunnel is launched or received; during the launch or reception of the shield of the offline tunnel, the lower freezing zone of the freezer remains in a maintenance-frozen state until the launch or reception of the shield of the offline tunnel is completed; similarly, during the launch or reception of the shield of the online tunnel, the upper freezing zone of the freezer remains in a maintenance-frozen state until the launch or reception of the shield of the online tunnel is completed, and the freezing is stopped.

[0056] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A device for performing vertical partial freezing at the ends of upper and lower overlapping tunnels, comprising a partial freezer (1) and a four-way control valve (8), characterized in that: The local freezer (1) and the four-way control valve (8) are connected via an extension pipe. A plurality of freezing areas and non-freezing areas are provided in the local freezer (1). The freezing areas and non-freezing areas are arranged at intervals. A drill bit is installed at the end of the local freezer (1). The local freezer (1) comprises a low-temperature resistant steel pipe (1010), wherein an upper freezing zone water inlet pipe (101), an upper freezing zone return pipe (102), a lower freezing zone water inlet pipe (103) and a lower freezing zone return pipe (104) are respectively provided inside the low-temperature resistant steel pipe (1010), and an upper perforated partition (105), a middle perforated partition (106) and a lower perforated partition (107) are sequentially connected to the inner wall of the low-temperature resistant steel pipe (1010) from top to bottom. The area above the upper perforated partition (105) and the area between the middle perforated partition (106) and the lower perforated partition (107) are non-freezing areas, and the area below the lower perforated partition (107) is non-freezing areas. The area is the lower freezing area (108) of the freezer, the area between the upper perforated partition (105) and the middle perforated partition (106) is the upper freezing area (109) of the freezer, the upper freezing area water inlet pipe (101) and the upper freezing area return pipe (102) pass through the upper perforated partition (105) and are connected to the upper freezing area (109) of the freezer to form a loop, the lower freezing area water inlet pipe (103) and the lower freezing area return pipe (104) pass through the upper perforated partition (105), the middle perforated partition (106) and the lower perforated partition (107) in sequence and are connected to the lower freezing area (108) of the freezer to form a loop, and a heat insulation structure is provided outside the non-freezing area; The thermal insulation structure comprises an upper non-freezing zone vacuum sleeve (5) and a lower non-freezing zone vacuum sleeve (9) sleeved on a low-temperature resistant steel pipe (1010); the upper end of the upper non-freezing zone vacuum sleeve (5) and the lower end of the lower non-freezing zone vacuum sleeve (9) are both threadedly connected via a freezer thread (4) and a vacuum pipe thread (6); and the ends of the upper non-freezing zone vacuum sleeve (5) and the lower non-freezing zone vacuum sleeve (9) are both sealedly connected to the low-temperature resistant steel pipe (1010) via a sealing steel ring (502) through a full incision weld (7); and a vacuum thermal insulation zone (501) is formed between the upper non-freezing zone vacuum sleeve (5), the lower non-freezing zone vacuum sleeve (9) and the low-temperature resistant steel pipe (1010).

2. A device for partial vertical freezing at the ends of overlapping tunnels according to claim 1, characterized in that: The upper perforated partition plate (105), the middle perforated partition plate (106) and the lower perforated partition plate (107) are all connected with a heat insulating gasket (2) on one side away from the non-freezing area.

3. The device for partial vertical freezing at the ends of overlapping tunnels according to claim 2, characterized in that: Sealing gaskets (3) are connected at the connections between the upper freezing zone water inlet pipe (101), the upper freezing zone return pipe (102), the lower freezing zone water inlet pipe (103) and the lower freezing zone return pipe (104) and the upper perforated partition plate (105), the middle perforated partition plate (106) and the lower perforated partition plate (107).

4. The device for partial vertical freezing of the ends of upper and lower overlapping tunnels according to claim 3 is characterized in that: The thermal insulation gasket (2) is aerogel felt, and the sealing gasket (3) is made of a low-temperature-resistant rubber material.

5. The device for partial vertical freezing at the ends of upper and lower overlapping tunnels according to claim 4, characterized in that: The upper freezing zone water inlet pipe (101), the upper freezing zone water return pipe (102), the lower freezing zone water inlet pipe (103), the lower freezing zone water return pipe (104) and the low-temperature resistant steel pipe (1010) are all made of Fe-Mn-Al series austenitic low-temperature steel pipes.

6. The device for partial vertical freezing at the ends of upper and lower overlapping tunnels according to claim 5, characterized in that: The control circuits of the refrigeration systems of the freezer lower freezing zone (108) and the freezer upper freezing zone (109) are independent of each other.

7. The device for partial vertical freezing at the ends of upper and lower overlapping tunnels according to claim 6, characterized in that: The upper non-freezing zone vacuum sleeve (5) and the lower non-freezing zone vacuum sleeve (9) have an outer diameter of 200 mm, an outer wall thickness of 5 mm, an inner diameter of 170 mm, and a vacuum cavity thickness of the vacuum insulation zone (501) of 10 mm.

8. A freezing method for a vertical local freezing device at the end of an upper and lower overlapping tunnel according to claim 7, characterized in that: The method comprises the following steps: The freezing method involves the following structure: a lower line tunnel portal (10), a lower line tunnel portal freezing zone (11), an upper line tunnel portal (12), an upper line tunnel portal freezing zone (13), a shield machine (14) and a support frame (15); the brine is a calcium chloride solution with a mass concentration of 29.9% and a freezing point of -55°C; the low-temperature brine temperature of the upper freezing zone water inlet pipe (101), the upper freezing zone return pipe (102), the lower freezing zone water inlet pipe (103) and the lower freezing zone return pipe (104) is between -36°C and -40°C; the single-hole brine flow rate is 10m 3 / h, the brine flow rate in the annular space of the freezing pipe is 0.4-0.5m / s; The thickness of the freezing curtain of the offline tunnel portal freezing zone (11) and the online tunnel portal (12) is 1.6m, the average soil temperature is -15°C, and the active freezing time is 21 days; after the offline tunnel portal (10) is actively frozen for 10 days, the four-way control valve (8) is controlled to actively freeze the online tunnel portal (12), and after the active freezing time of the offline tunnel portal freezing zone (11) reaches 21 days and the freezing curtain development and the average soil temperature meet the design requirements, the shield machine of the offline tunnel portal (10) is started or received within 12 days, and the shield machine of the offline tunnel portal (10) is started or received; After the active freezing time of the freezing zone (13) of the upper tunnel portal is 21 days and the freezing curtain development and the average soil temperature have reached the design requirements, the shield machine of the lower tunnel portal (10) is started or received; during the process of starting or receiving the shield machine of the lower tunnel portal (10), the freezing zone (108) under the freezer is kept in a maintenance freezing state until the start or reception of the shield machine of the lower tunnel portal (10) is completed; During the shield starting or receiving process of the tunnel portal (12) on the line, the freezing area (109) on the freezer keeps the maintenance freezing state until the shield starting or receiving of the tunnel portal on the line is completed, and then stops freezing.

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