Vertical and Horizontal Freezing Construction Method for Connecting Passage between Overlapping Tunnels in Water-rich Strata

Abstract

The invention discloses a vertical and horizontal freezing construction method for a connection passage between upper and lower overlapping tunnels in a water-rich stratum, belonging to the field of civil engineering. Vertical freezing pipes are arranged downward from the ground, and a row of bottom-sealing freezing pipes is arranged obliquely below the connection passage to be excavated in the lower line; around the portals of the connection passages to be excavated in the upper and lower lines, horizontal freezing pipes, upward-inclined freezing pipes for the upper-line connection passage, downward-inclined freezing pipes for the upper-line connection passage, and upward-inclined freezing pipes for the lower-line connection passage are respectively drilled; then the vertical freezing pipes and the bottom-sealing freezing pipes are actively frozen. After the vertical and bottom freezing curtains are formed, the shaft is excavated, and at the same time, the freezing pipes near the upper-line and lower-line connection passages are actively frozen. The construction method of the invention forms a freezing curtain that fits the complex structure of the connection passage between the upper and lower overlapping tunnels by flexibly arranging the vertical and horizontal freezing pipes, prevents sand gushing and water inrush, and ensures the safety and reliability of the connection passage construction. It has the advantages of reducing construction costs and shortening the construction period.

Description

Technical Field

[0001] The present invention belongs to the field of civil engineering, and particularly relates to a vertical and horizontal freezing construction method for a connecting passage between upper and lower overlapping tunnels in a water-rich stratum. Background Art

[0002] A connecting passage, also known as an "escape passage", connects two different tunnel lines. When an accident occurs in one tunnel, people can escape through the connecting passage to another relatively safe tunnel for the rescue work to be carried out.

[0003] In recent years, more and more tunnels are constructed by shield tunneling in an up-and-down crossing manner. Especially when constructing a connecting passage between upper and lower overlapping tunnels in a water-rich stratum, due to the more complex structural shape compared with the construction of a general connecting passage, the construction and technical difficulties are higher, and there are many engineering problems caused by groundwater during the process, which are likely to cause personal and economic losses. When the ground site is limited and cannot support the construction of large-scale equipment and supporting pile foundations such as deep mixing piles, the freezing method is adopted. The freezing method can play a good water-stop effect when applied to the construction of the connecting passage, and at the same time take into account the effect of soil reinforcement; the vertical and horizontal freezing construction method can provide a safe and reliable construction environment during the construction of the upper and lower connecting passages. However, due to the complex structure of the connecting passage between overlapping tunnels, especially the quality of the freezing curtain at the junction of the vertical freezing system and the horizontal freezing system (i.e., the portal junction of the upper and lower connecting passages and the shaft structure) needs to be ensured. Therefore, a vertical and horizontal freezing construction method for a connecting passage between upper and lower overlapping tunnels in a water-rich stratum is needed. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a vertical and horizontal freezing construction method for a connecting passage between upper and lower overlapping tunnels in a water-rich stratum. By flexibly arranging vertical and horizontal freezing pipes, a freezing curtain that fits the complex structure of the connecting passage between upper and lower overlapping tunnels is formed to prevent sand gushing and water inrush, and ensure the safety and reliability of the connecting passage construction.

[0005] The technical solution adopted by the present invention is as follows: A vertical and horizontal freezing construction method for a connecting passage between upper and lower overlapping tunnels in a water-rich stratum, comprising the following steps:

[0006] S1: When the tunnel is being excavated, steel pipe segments for the portal of the connecting passage are reserved in both the upper and lower connecting passages to be excavated.

[0007] S2: Vertically at certain intervals within the design elevation range, multiple vertical freezing pipes are arranged downward from the ground around the shaft to be excavated. The drilling depth of each vertical freezing pipe is below the design elevation of the bottom slab of the lower connecting passage. Around the portal of the upper connecting passage to be excavated, multiple horizontal freezing pipes of the upper connecting passage are arranged horizontally at certain intervals, surrounding the upper connecting passage to be excavated, arranging a row of upward-inclined freezing pipes of the upper connecting passage obliquely upward and a row of downward-inclined freezing pipes of the upper connecting passage obliquely downward, and all approaching the vertical freezing pipes on the side of the upper connecting passage to be excavated. Around the portal of the lower connecting passage, multiple horizontal freezing pipes of the lower connecting passage are arranged horizontally at certain intervals around the lower connecting passage to be excavated, arranging a row of upward-inclined freezing pipes of the lower connecting passage obliquely upward, and all approaching the vertical freezing pipes on the side of the lower connecting passage to be excavated. A row of bottom-sealing freezing pipes is arranged obliquely below the lower connecting passage to be excavated, and all approaching the lower ends of multiple vertical freezing pipes.

[0008] S3: Each vertical freezing pipe and bottom-sealing freezing pipe are actively frozen to form a vertical and bottom freezing curtain. Then, the shaft is excavated and the initial support is constructed. While the shaft is being excavated, each horizontal freezing pipe of the upper connecting passage, horizontal freezing pipe of the lower connecting passage, upward-inclined freezing pipe of the upper connecting passage, downward-inclined freezing pipe of the upper connecting passage, and upward-inclined freezing pipe of the lower connecting passage are actively frozen.

[0009] S4: After the shaft is excavated to the elevation of the lower connecting passage to be excavated, the secondary lining structure of the shaft is constructed and grouting pipes are embedded.

[0010] S5: After the freezing walls of the upper and lower connecting passages to be excavated meet the design requirements, the reserved steel pipe segments of the connecting passage portal are demolished, and the upper and lower connecting passages are mined and the initial support is constructed.

[0011] S6: The upper and lower connecting passages are excavated to the vertical freezing curtain to prepare for demolishing the portal.

[0012] S7: First, stop freezing the two rows of vertical freezing pipes on the side of the portal close to the upper and lower connecting passages, and cut off these two rows of vertical freezing pipes. After the portal of the lower connecting passage is demolished, a working platform is erected in the shaft to demolish the portal of the upper connecting passage. After the portal is demolished, the secondary lining construction of the upper and lower connecting passages is carried out. After the construction is completed, stop freezing the horizontal freezing pipes of the upper connecting passage, horizontal freezing pipes of the lower connecting passage, upward-inclined freezing pipes of the upper connecting passage, downward-inclined freezing pipes of the upper connecting passage, and upward-inclined freezing pipes of the lower connecting passage.

[0013] S8: Stop the freezing of all freezing pipes, pull out each vertical freezing pipe, and seal each bottom freezing pipe, each horizontal freezing pipe for the upper connection passage, each horizontal freezing pipe for the lower connection passage, each upwardly inclined freezing pipe for the upper connection passage, each downwardly inclined freezing pipe for the upper connection passage, each upwardly inclined freezing pipe for the lower connection passage, and the vertical freezing holes.

[0014] S9: Grouting for thaw settlement.

[0015] Furthermore, multiple said vertical freezing pipes surround the shaft to be excavated to form a multi-ring freezing pipe surrounding structure, and the pipe spacing of the outer ring vertical freezing pipes is smaller than that of the inner ring vertical freezing pipes; multiple said horizontal freezing pipes for the upper connection passage surround the upper connection passage to be excavated to form a multi-ring freezing pipe surrounding structure, and the pipe spacing of the outer ring horizontal freezing pipes for the upper connection passage is smaller than that of the inner ring horizontal freezing pipes for the upper connection passage; multiple said horizontal freezing pipes for the lower connection passage surround the lower connection passage to be excavated to form a multi-ring freezing pipe surrounding structure, and the pipe spacing of the outer ring horizontal freezing pipes for the lower connection passage is smaller than that of the inner ring horizontal freezing pipes for the lower connection passage.

[0016] Furthermore, the distance between the end of each said horizontal freezing pipe for the upper connection passage, the end of the horizontal freezing pipe for the lower connection passage and the innermost vertical freezing pipe is 0.5 m, the distance between the lower end of each vertical freezing pipe and the bottom freezing pipe is 0.5 m, and the end of each bottom freezing pipe extends 0.5 m beyond the outermost side of the vertical freezing pipe.

[0017] Furthermore, the upward inclination angle of each said upwardly inclined freezing pipe for the upper connection passage is 15°, the downward inclination angle of the downwardly inclined freezing pipe for the upper connection passage is 15°, the upward inclination angle of the upwardly inclined freezing pipe for the lower connection passage is 15°, and the downward inclination angle of the bottom freezing pipe is 12°.

[0018] The beneficial effects and advantages of the present invention: The method of the present invention ensures that the frozen soil strength at the weak part of the frozen curtain meets the design requirements, and avoids sand gushing and water gushing at the weak part; first, vertical freezing and the construction of vertical structures are carried out, horizontal freezing is carried out simultaneously, and then the undercutting of the connection passage and the construction of breaking the portal are carried out, which can reduce the frost heaving influence between each structure and reduce the frost heaving and thaw settlement of the overall structure; the method of the present invention can form a frozen curtain with high strength and good sealing performance, which can effectively ensure the safety and reliability of the excavation construction, shorten the construction period, and reduce the construction cost; at the same time, the environmental pollution caused by the formation and melting process of the frozen wall is small, and the low-carbon steel pipes used for freezing can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the layout of the connection passage between the upper and lower overlapping tunnels and the vertical and horizontal freezing pipes of the present invention;

[0020] Figure 2 is Figure 1 the top view of;

[0021] Figure 3 is Figure 1 the sectional view taken along line A-A of;

[0022] Figure 4 is Figure 1 the sectional view taken along line B-B of;

[0023] Figure 5 is the schematic diagram of the secondary lining of the connecting passage and the layout of grouting pipes;

[0024] Figure 6 is the schematic diagram of the secondary lining of the shaft and the layout of grouting pipes;

[0025] Wherein, 1 is the portal steel segment, 2 is the vertical freezing curtain, 3 is the vertical freezing pipe, 4 is the upper connecting passage, 5 is the lower connecting passage, 6 is the shaft, 7 is the bottom freezing pipe, 8 is the horizontal freezing pipe of the upper connecting passage, 9 is the horizontal freezing pipe of the lower connecting passage, 10 is the upward freezing pipe of the upper connecting passage, 11 is the downward freezing pipe of the upper connecting passage, 12 is the upward freezing pipe of the lower connecting passage, 13 is the designed freezing curtain, 15 is the driven tunnel, 16 is the grouting reinforcement area at the crown of the connecting passage, 17 is the grouting reinforcement area on the side wall of the connecting passage, 18 is the grouting reinforcement area under the side wall of the connecting passage, 19 is the grouting reinforcement area at the bottom slab of the connecting passage, 20 is the grouting pipe of the connecting passage, 21 is the secondary lining of the connecting passage, 22 is the grouting pipe of the shaft, 23 is the grouting reinforcement area of the shaft, 24 is the secondary lining of the shaft. Specific Embodiments

[0026] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0027] Embodiment 1

[0028] A connecting passage of a subway in Nanjing. The soil layers from top to bottom are: miscellaneous fill, silty clay, silty clay, completely weathered diorite, strongly weathered diorite (in gravel form), strongly weathered diorite, moderately weathered diorite (relatively fractured), and moderately weathered diorite. Phreatic water is stored in the shallow soil layers. The completely weathered diorite and strongly weathered diorite (in gravel form) soil layers contain fine-grained soil, which is prone to soil flow or piping under certain hydrodynamic actions. The water-rich degree of the soil layers varies greatly. In the upper part, there are locally distributed silty clay, silty clay, and gravel-containing silty clay layers, which have certain confined water properties. The buried depths of the roof slabs of the upper and lower connecting passages are 18.2m and 30.2m respectively. The designed net width of the upper connecting passage is 2.4m, and the designed net height is 4.13m. The designed net width of the lower connecting passage is 2.4m, and the designed net height is 4.46m. The depth of the connecting passage foundation pit is about 36.9m, and the plane size of the foundation pit is 7.4m×7.4m. The upper and lower connecting passages are connected by a vertical structure. The soil body is frozen and reinforced vertically and horizontally. A shaft structure is constructed downward from the ground to connect the connecting passage, and the connecting passage is excavated by the mining method.

[0029] As Figures 1-5 shown, a construction method for vertical and horizontal freezing of a connecting passage between upper and lower overlapping tunnels in a water-rich stratum, the method comprising the following steps:

[0030] 1. Construction preparation: Clean the ground site, install the refrigerating machine, brine tank, brine pump, clean water pump, cooling tower, and power distribution control cabinet. Reasonably arrange the circuit pipelines, inlet and drainage pipelines according to the on-site terrain, and determine the drilling positions. Two sets of W-YSLGF300Ⅱ type units are selected for the shaft, upper and lower connecting passages, installed in parallel, and refrigeration stations are set up respectively. The designed refrigerating capacity of a single unit is 8.7×104Kcal / h, and the maximum power of a single unit is 30KW to meet the refrigeration requirements. One unit operates and one is reserved.

[0031] 2. Construction of the bottom-sealing freezing pipes: The bottom-sealing freezing pipes with a 15° inclination are advanced ahead from the designed elevation of the bottom slab of the lower connecting passage. There are 8 low-carbon steel freezing pipes with an outer diameter of 108mm and a wall thickness of 10mm in a single row. The spacing between the freezing pipes is less than 1000mm, and the deflection amount is monitored in real time during the drilling process.

[0032] 3. Construction of vertical freezing pipes: After the inner pipe hoop of the screw thread joint between the freezing steel pipes is tightened, manual arc welding is used to ensure the welding strength. Low-carbon steel pipes with an outer diameter of 108 mm and a wall thickness of 10 mm (2 - 2.5 m per single pipe) are drilled at different designed positions. During the drilling process, the deflection is monitored in real time. If the deflection is found to be greater than 150 mm, the drilling should be stopped immediately and deviation correction should be carried out. After the drilling is completed, the length of the freezing pipe is checked. After each drilling is completed, grouting is carried out in a timely manner to ensure the stable combination of the steel pipe, the grout, and the soil body. A pressure test for leakage is carried out on the vertical freezing pipes, with the pressure maintained at 0.8 MPa. If it is stable for more than 15 minutes, it is considered that the freezing pipes have no leakage. The refrigeration system, brine circulation system, and detection system are debugged, and dynamic parameters such as pressure and temperature are monitored. Freon F-22 is selected as the refrigerant, and calcium chloride solution is used as the refrigeration brine.

[0033] 4. Construction of horizontal freezing pipes: In the upper tunnel, the soil around the connection passage is reinforced by using horizontal freezing pipe holes and some inclined freezing pipes with upward and downward dips, in combination with the vertical freezing pipes on one side of the connection passage that have been constructed, to form a freezing curtain with high-strength water stop. The construction of the horizontal freezing pipes for the lower connection passage is the same, and the horizontal freezing pipes for the upper and lower lines are drilled simultaneously. The horizontal freezing pipes are divided into two layers, which are low-carbon steel pipes with an outer diameter of 89 mm and a wall thickness of 8 mm (1 - 1.5 m per single pipe). After the inner pipe hoop of the screw thread joint between the freezing steel pipes is tightened, manual arc welding is used to ensure the welding strength. The net distance between the end of the horizontal freezing pipe and the vertical freezing pipe at the portal is controlled within 0.5 m to ensure that the freezing walls intersect and the strength of the freezing curtain at the weak points meets the design requirements. The spacing of the outer-layer freezing pipes is 1000 mm, the spacing of the inner-layer freezing pipes is 1300 mm, and the deflection is controlled within 150 mm.

[0034] 5. Active freezing in the vertical direction: The designed active freezing time is 40 days, and the single-hole flow rate of the freezing holes is greater than 5 m 3 / h. The brine temperature drops below -20°C after 7 days of active freezing, below -24°C after 24 days of active freezing, and below -28°C during excavation. The designed time for the freezing curtain to intersect is 30 days. The designed thickness of the freezing wall is 2 m.

[0035] 6. Maintenance freezing in the vertical direction: The maintenance freezing time is 30 days. During the maintenance period, shaft excavation, dewatering and drainage in the shaft, shaft support, waterproofing, and structure construction are carried out in parallel.

[0036] 7. Shaft construction: The shaft excavation is carried out in a segmented manner, with each segment being 0.5 m. The in-shaft support, structure, and waterproof construction are carried out successively from top to bottom. After the shaft excavation is completed, a grid mesh is hung around the shaft wall, and concrete is sprayed from top to bottom. After the sprayed concrete reaches the design strength, steel supports are installed. Repeat the above steps of excavation, reinforcement, concrete spraying, and steel support until the shaft is constructed to the design elevation of the bottom slab of the lower connecting passage, and then the secondary lining structure is constructed.

[0037] 8. Active freezing in the horizontal direction: While the shaft excavation is in progress, the horizontal freezing pipes start active freezing. The freezing sequence is as follows: The horizontal freezing pipes of the upper connecting passage are actively frozen for 15 days first, then maintained for 10 days, and then the horizontal freezing pipes of the lower connecting passage are frozen to reduce the frost heave impact between the upper and lower connecting passages.

[0038] 9. Cut-and-cover connecting passage construction: When the temperature at the interface between the freezing curtain and the segment is lower than -5°C, the temperature difference between the supply and return brine is less than 2°C, and the temperature at the outer boundary of the frozen wall is lower than 0°C, it can be considered that the designed freezing curtain has been formed and meets the cut-and-cover conditions for the connecting passage. A working scaffold is built with steel pipes with an outer diameter of 48 mm and a wall thickness of 4 mm. To prevent sand gushing and water inrush from the curtain and cause engineering hazards, safety protection doors should be installed before the tunnel segments are removed. Two 5t jacks and 5t and 2t chain hoists are used to remove the segments. During operation, pay attention to the force condition of the segments to prevent deformation. Since the soil strength is high after being reinforced by the freezing method, the cut-and-cover excavation of the connecting passage can be carried out by the top-down bench method. The spacing of the internal supports in the passage is 0.45 m. Then, wooden backboards are laid, steel supports are erected, and the excavation step distance at the bell mouth is controlled at about 0.4 m, and the deviation of the excavation center line is less than 20 mm. The initial support is C25 shotcrete (250 mm thick). After completion, a 4-mm-thick double-sided self-adhesive waterproof coiled material is laid, and the secondary lining is constructed. The cut-and-cover excavation of the lower connecting passage is the same.

[0039] 10. Cutting of freezing pipes: After the shaft structure is completed and the cut-and-cover excavation of the connecting passage is completed, before breaking through the portal, the vertical freezing pipes on the side of the upper and lower connecting passages within the portal range are cut off in advance by acetylene gas cutting. During cutting preheating, the cutting nozzle is perpendicular to the surface of the steel pipe. During cutting, ensure that the angle between the cutting nozzle and the surface of the steel pipe is 70° - 80°. Since the vertical freezing pipes use steel pipes with an outer diameter of 108 mm and a wall thickness of 10 mm, and the pipe wall is relatively thick, the gas cutting is carried out in three times.

[0040] 11. Plugging of freezing pipes: Mix double-fast cement with a certain hardness and knead it into a spherical shape for plugging into the freezing pipes. Tamp it. After the plugging is completed, level the plugging surface to be consistent with the structural surface.

[0041] 12. Portal construction: Advance small pipes with an outer diameter of 32 mm and a wall thickness of 3.5 mm are driven in a double row 1 m above the portal, with a spacing of 0.4 m. The soil above the portal is grouted and reinforced, and the direction is parallel to the center line of the passage. A circular blind box is constructed 10 cm outside the portal structure, the spacing of the shaft grids is adjusted, channel steel is embedded in layers, and preparations for portal demolition construction are made. The top-down bench method is used to excavate the connection passage, which can avoid the disassembly and assembly of the scaffolding in the connection passage and bring convenience. The portal is demolished in three times, and the grids and supports at the top of the portal arch are erected in sequence. The steel bars are welded firmly to the grids of the shaft wall, and C25 concrete is sprayed. First, demolish the portal of the lower connection passage, and then erect a scaffolding in the shaft to cooperate with the demolition of the portal of the upper connection passage. The steel pipes of the scaffolding use steel pipes with an outer diameter of 48 mm and a wall thickness of 3.6 mm.

[0042] 13. Extraction of freezing pipes: First, circulate brine at 30 - 40 °C for about 5 minutes, and then circulate brine at 60 - 80 °C for about 30 minutes. When the temperature of the return brine reaches 25 - 30 °C, try to extract while circulating. The hook is connected to the end of the freezing pipe, and a jack is used for trial extraction. When extracting the pipe, it should be rotated and extracted at the same time, slowly at first and then quickly.

[0043] 14. Filling grouting: The grouting pipes for filling grouting are embedded during the construction of the connection passage, and the embedded depth of the grouting pipes penetrates the structural layer. Filling grouting behind the lining can be carried out 3 - 7 days after the freezing is stopped and when the strength of the lining concrete reaches more than 60% of the design strength. The grouting slurry uses single-component cement slurry, and the grouting pressure is controlled at 0.4 Mpa. It is carried out in the order from bottom to top. When the upper grouting hole continuously returns slurry, the grouting of the lower layer can be stopped until the top of the arch is grouted and completed.

[0044] 15. Settlement grouting: The slurry is mainly single-component cement slurry and supplemented by cement-sodium silicate double slurry. The soil is reinforced through the embedded grouting pipes. The grouting pressure is determined according to the buried depth and does not exceed 0.5 Mpa. The grouting range is the entire frozen reinforcement area. The settlement grouting follows the principle of "small quantity, multiple points, multiple times, and uniformity". From the side of the structure, from shallow to deep, after all the grouting ports at each depth are grouted, the grouting at the next depth is carried out. This plan uses forced thawing, so the grouting sequence is consistent with the forced thawing sequence and is carried out in zones. Grouting is tracked while thawing.

Claims

1. A vertical and horizontal freezing construction method for a connecting passage of an overlapping tunnel in a water-rich stratum, characterized in that It includes the following steps: S1: When tunneling, the segment steel pipe for the portal of the connection passage is reserved in both the upper connection passage (4) and the lower connection passage (5) to be excavated; S2: From the ground downwards, a plurality of vertical freezing pipes (3) are vertically arranged at certain intervals within the design elevation range around the shaft (6) to be excavated. The drilling depth of each vertical freezing pipe (3) is below the design elevation of the bottom slab of the lower connection passage (5). A plurality of horizontal freezing pipes (8) for the upper connection passage are arranged at certain intervals along the transverse direction around the upper connection passage (4) to be excavated at the portal of the upper connection passage (4) to be excavated, a row of upwardly inclined freezing pipes (10) for the upper connection passage are arranged obliquely upwards, and a row of downwardly inclined freezing pipes (11) for the upper connection passage are arranged obliquely downwards, and all are close to the vertical freezing pipes (3) on the side of the upper connection passage (4) to be excavated. A plurality of horizontal freezing pipes (9) for the lower connection passage are arranged at certain intervals along the transverse direction around the lower connection passage (5) to be excavated at the portal of the lower connection passage (5), a row of upwardly inclined freezing pipes (12) for the lower connection passage are arranged obliquely upwards, and all are close to the vertical freezing pipes (3) on the side of the lower connection passage (5) to be excavated. A row of bottom sealing freezing pipes (7) are arranged obliquely below the lower connection passage (5) to be excavated, and all are close to the lower ends of the plurality of vertical freezing pipes (3); S3: Each vertical freezing pipe (3) and the bottom sealing freezing pipe (7) are actively frozen to form a vertical and bottom freezing curtain, and then the shaft (6) is excavated and the initial support is constructed. While the shaft (6) is being excavated, each horizontal freezing pipe (8) for the upper connection passage, horizontal freezing pipe (9) for the lower connection passage, upwardly inclined freezing pipe (10) for the upper connection passage, downwardly inclined freezing pipe (11) for the upper connection passage, and upwardly inclined freezing pipe (12) for the lower connection passage are actively frozen; S4: After the shaft (6) is excavated to the elevation of the lower connection passage (5) to be excavated, the secondary lining structure (24) of the shaft (6) is constructed and the grouting pipe (22) is embedded; S5: After the freezing walls (13) of the upper connection passage (4) and the lower connection passage (5) to be excavated meet the design requirements, the reserved segment steel pipe for the portal of the connection passage is removed, and the upper connection passage (4) and the lower connection passage (5) are mined by the drift method and the initial support is constructed; S6: The upper connection passage (4) and the lower connection passage (5) are excavated to the vertical freezing curtain and prepared to break through the portal; S7: First, stop the freezing of the two rows of vertical freezing pipes (14) on the side of the portal near the upper connection passage (4) and the lower connection passage (5), and cut off these two rows of vertical freezing pipes (14). After the portal of the lower connection passage (5) is breached, erect a working platform in the shaft (6) to breach the portal of the upper connection passage (4). After breaching the portal, carry out the construction of the secondary lining (21) of the upper connection passage (4) and the lower connection passage (5). After the construction is completed, stop the freezing of the horizontal freezing pipes (8) of the upper connection passage, the horizontal freezing pipes (9) of the lower connection passage, the upwardly inclined freezing pipes (10) of the upper connection passage, the downwardly inclined freezing pipes (11) of the upper connection passage, and the upwardly inclined freezing pipes (12) of the lower connection passage. S8: Stop the freezing of all freezing pipes, pull out each vertical freezing pipe (3), and seal each bottom freezing pipe (7), each horizontal freezing pipe (8) of the upper connection passage, each horizontal freezing pipe (9) of the lower connection passage, each upwardly inclined freezing pipe (10) of the upper connection passage, each downwardly inclined freezing pipe (11) of the upper connection passage, each upwardly inclined freezing pipe (12) of the lower connection passage, and the vertical freezing holes. S9: Grout for thaw settlement.

2. A vertical and horizontal freezing construction method for a connecting passage of superimposed tunnels in a water-rich stratum according to claim 1, characterized in that: Multiple said vertical freezing pipes (3) form a multi-ring freezing pipe surrounding structure around the shaft (6) to be excavated, and the pipe spacing of the outer ring vertical freezing pipes (3) is smaller than that of the inner ring vertical freezing pipes (3); multiple said horizontal freezing pipes (8) of the upper connection passage form a multi-ring freezing pipe surrounding structure around the upper connection passage (4) to be excavated, and the pipe spacing of the outer ring horizontal freezing pipes (8) of the upper connection passage is smaller than that of the inner ring horizontal freezing pipes (8) of the upper connection passage; multiple said horizontal freezing pipes (9) of the lower connection passage form a multi-ring freezing pipe surrounding structure around the lower connection passage (5) to be excavated, and the pipe spacing of the outer ring horizontal freezing pipes (9) of the lower connection passage is smaller than that of the inner ring horizontal freezing pipes (9) of the lower connection passage.

3. A vertical and horizontal freezing construction method for a connecting passage of an overlapping tunnel in a water-rich stratum according to claim 1 or 2, characterized in that: The distance from the end of each said horizontal freezing pipe (8) of the upper connection passage and the end of the horizontal freezing pipe (9) of the lower connection passage to the innermost vertical freezing pipe (3) is 0.5 m. The distance from the lower end of each vertical freezing pipe (3) to the bottom freezing pipe (7) is 0.5 m. The end of each bottom freezing pipe (7) extends 0.5 m beyond the outermost side of the vertical freezing pipe (3).

4. A vertical and horizontal freezing construction method for a connecting passage of superposed tunnels in a water-rich stratum according to claim 3, characterized in that: The upward inclination angle of each said upwardly inclined freezing pipe (10) of the upper connection passage is 15°, the downward inclination angle of the downwardly inclined freezing pipe (11) of the upper connection passage is 15°, the upward inclination angle of the upwardly inclined freezing pipe (12) of the lower connection passage is 15°, and the downward inclination angle of the bottom freezing pipe (7) is 12°.

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