Freezing reinforcement structure and freezing reinforcement method for combined pipe roofing tunnel

Abstract

The invention relates to the field of tunnel engineering. The invention relates to the technical field of tunnel construction, in particular to a freezing reinforcing structure and a freezing reinforcing method of a combined pipe-roofing tunnel, in the freezing reinforcing structure, the area, located between adjacent steel pipe sets, of a freezing ring of the combined pipe-roofing tunnel is a strong cold junction area, and the areas, located on the two sides of the strong cold junction area, of the freezing ring of the combined pipe-roofing tunnel are weak cold junction areas. The transverse width of the strong cold junction area is larger than that of the exposed area of the stratum when the steel pipe set is cut open, the temperature of the freezing body in the strong cold junction area is lower than that of the freezing body in the weak cold junction area, construction safety of the opening portion of the steel pipe is guaranteed, meanwhile, engineering investment is saved, and the construction requirement of the pipe-roofing structure is met.

Description

Technical Field

[0001] The present invention relates to the field of tunnel engineering, and more specifically, to a frozen reinforcement structure and a frozen reinforcement method for a combined pipe-roof tunnel. Background Art

[0002] With the continuous advancement of urbanization in my country, the number of large-span shallow buried tunnels is increasing. Among them, there are more and more cases of tunnels passing under railways, roads, subway stations and other structures, and the requirements for settlement control in tunnel construction are getting higher and higher. Therefore, a dark-cut tunnel construction method with annular pre-excavation and advanced support cycle is proposed. Multiple pipe jacking machines arranged along the annular direction of the tunnel are used to excavate and form a tunnel pre-support structure. The excavation contours of adjacent pipe jacking machine cutters are overlapped and interlocked. The existing pipe curtain method, pipe curtain structure method and combined interlocking pipe curtain structure method are all supplemented with freezing measures during construction, and the soil between pipes is reinforced by freezing the strata between pipes.

[0003] The pipe curtain method is a dark excavation construction method that uses large diameter steel pipes to bear water and soil pressure and conducts excavation construction under the protection of the steel pipe pre-support structure. Generally, it is necessary to take measures such as reinforcement and water stopping for the soil between pipes to avoid soil instability during excavation. In water-rich strata, the freezing method is often used to reinforce the soil between pipes, and the dark excavation of the tunnel is carried out under the protection of pipe curtain advance support and frozen soil. Figure 1 As shown, the steel pipe 1 is first pushed in, and then the freezing pipe 2 is arranged between the steel pipes 1 (or inside the steel pipe 1). After the stable freezing circle 3 is formed by freezing, the soil 4 inside the pipe curtain is excavated and the corresponding lining construction is carried out.

[0004] From the characteristics of the above construction methods, the existing inter-pipe soil freezing reinforcement measures are carried out along the tunnel section for full ring reinforcement, and the frozen body needs to meet the functional requirements of strength and water stopping, that is, the strength of the frozen reinforcement body is high and the average temperature of the frozen wall is low. The existing technology can meet the tunnel construction method when the pipe curtain is only used as an advance support structure. The pipe curtain freezing advance support method has the following problems:

[0005] 1. The ground between pipes is exposed for a long time. The ground between pipes is completely sealed after tunnel excavation, initial support construction and reinforced concrete lining pouring. At the same time, the tunnel excavation range is large, the exposed range is large, and a large area needs to be frozen at the same time.

[0006] 2. This method is difficult to achieve time-sharing thawing. The tunnel is excavated from the entrance, and its construction sequence is consistent with the direction of the freezing liquid. In the tunnel section constructed earlier, the freezing liquid still needs to flow from this section to the unexcavated section, resulting in long-term freezing.

[0007] The pipe-curtain structure method is to cut adjacent steel pipes, connect them into a ring with steel plates to form a pipe curtain, and use the pipe curtain and the concrete filled inside to form a composite structure. It serves as both an advance support structure for the dark-cut tunnel and a bearing structure for the construction and operation of the dark-cut tunnel. It is a newer dark-cut tunnel construction method. In the process of cutting and connecting the steel pipes mentioned above, the strata between the pipes are exposed, and there is a risk of groundwater influx and stratum collapse. Therefore, it is necessary to reinforce the strata between the pipes. In construction environments such as highly permeable strata, freezing can be used to reinforce the soil between pipes. As shown in the attached figure Figure 2 As shown, after the steel pipe 1 is pushed in, the freezing pipe 2 is arranged between the steel pipes 1. After freezing to form a stable freezing circle 3, the steel plate 5 at the corresponding position is cut off, the soil 6 between the pipes is excavated, and the opening parts of the steel pipes on both sides are connected with the steel plate 7. In this way, the two adjacent steel pipes are connected to form a closed ring pipe curtain structure. After pouring concrete inside the pipe curtain structure, the soil 4 within the tunnel range is excavated.

[0008] Combined interlocking pipe jacking is a newly proposed method to realize continuous steel pipe curtain. It adopts combined pipe jacking machine, sets multiple groups of combined pipe bodies, and N (N≥1) continuously interlocking steel pipes form a combined pipe body. Taking the case of three round steel pipes interlocking to form a group of combined pipe bodies as an example, it is also necessary to cut the adjacent steel pipe groups and connect them with steel plates. The freezing method can also be used to reinforce the soil between the pipes. Figure 3 As shown, after the steel pipe group 8 is pushed in, freezing pipes 2 are arranged between the steel pipe groups 8. After freezing to form a stable freezing circle 3, the steel plates 5 at the corresponding positions are cut off, the soil 6 between the pipes is excavated, and the openings of the steel pipes on both sides are connected with connecting steel plates 7. In this way, the two adjacent steel pipe groups are connected to form a closed ring pipe curtain structure. After pouring concrete inside the pipe curtain structure, the soil 4 within the tunnel range is excavated.

[0009] In the pipe-roof structure method, especially the combined pipe-roof structure method, the requirements for freezing reinforcement of the ground between pipes have changed significantly:

[0010] 1. In the pipe-curtain structure method, the time for cutting, welding and closing the steel pipe is much shorter than the time for full-section excavation, support and pouring of lining concrete when the pipe-curtain is used as an advance support. In addition, cutting and welding operations can be carried out in different areas along the tunnel. After welding in one area, the steel pipe-curtain structure in that area is closed and no longer requires freezing reinforcement. Therefore, the existing freezing measures are not suitable for the flexible construction of the pipe-curtain structure.

[0011] 2. In the combined pipe curtain structure method, multiple groups of steel pipes are used, each of which includes at least one steel pipe, and a structure using multiple groups of steel pipes is used in combination. The steel pipe groups can be prefabricated in the factory, and only cutting and welding are required between adjacent steel pipe groups or between steel pipe groups or steel pipes. The ground exposure operation is greatly reduced, and the existing full-ring freezing measures will result in construction waste.

[0012] Therefore, there is an urgent need to develop a frozen reinforcement structure and a construction method suitable for the pipe-roof structure method, especially the combined interlocking pipe-roof structure method. Summary of the invention

[0013] The purpose of the present invention is to provide a frozen reinforcement structure and a frozen reinforcement method for a combined pipe-roof tunnel in order to solve the above problems, thereby ensuring the construction safety of the steel pipe opening and saving engineering investment to meet the requirements of pipe-roof structure construction.

[0014] In order to achieve these purposes and other advantages according to the present invention, a freezing reinforcement structure of a combined pipe curtain tunnel is provided, including a first freezing device and a second freezing device, and both are in multiple groups. The first freezing device and the second freezing device are arranged in sequence around the circumference of the tunnel, the first freezing device is placed on the freezing circle in the area between adjacent steel pipe groups to form a strong cold junction area, the second freezing device forms a weak cold junction area on the tunnel stratum, the weak cold junction areas are respectively arranged on both sides of the strong cold junction area, and the strong cold junction areas and the weak cold junction areas form a freezing circle in the freezing circle stratum.

[0015] Furthermore, in the freezing reinforcement structure of a combined pipe-curtain tunnel, the first freezing device and the second freezing device both include multiple freezing pipes, and the distribution density of the multiple freezing pipes of the first freezing device within the freezing circle is greater than the distribution density of the multiple freezing pipes of the second freezing device within the freezing circle.

[0016] Furthermore, in the freezing reinforcement structure of a combined pipe curtain tunnel, when the spacing between the strong cold junction areas on both sides of the same steel pipe group is smaller than the spacing between two adjacent freezing pipes in the second freezing device, the first freezing device is arranged in the partial freezing circle between the two to form a combined strong cold junction area on the freezing circle.

[0017] Furthermore, in the freezing reinforcement structure of a combined pipe curtain tunnel, when the spacing between the weak cold junction areas on both sides of the same steel pipe group is smaller than the spacing between two adjacent freezing pipes in the second freezing device, the second freezing device is arranged in the partial freezing circle between the two to form a combined weak cold junction area on the freezing circle.

[0018] Furthermore, in the freezing reinforcement structure of the combined pipe-roof tunnel, the freezing circle of the combined pipe-roof tunnel is divided into a plurality of freezing work areas connected end to end, and both ends of the freezing work areas are weak cold junction areas.

[0019] Furthermore, in the freezing reinforcement structure of the combined pipe-roof tunnel, the freezing area adopts an independent freezing device.

[0020] The present invention also provides a freezing reinforcement method for a combined pipe-roof tunnel, comprising the following steps:

[0021] S1. Complete the jacking construction of the steel pipe group of the combined pipe-roof tunnel;

[0022] S2, the area between adjacent steel pipe groups on the freezing circle of the combined pipe curtain tunnel is used as the strong cold junction area, and the areas on both sides of the freezing circle of the combined pipe curtain tunnel are used as the weak cold junction area, and the installation of freezing pipes in the cold junction area, the weak cold junction area and the steel pipe group is completed respectively, and the distribution density of freezing pipes in the strong cold junction area is greater than the distribution density of freezing pipes in the weak cold junction area;

[0023] S3. After the freezing of the cold junction area, the weak cold junction area and the steel pipe group is completed, they are overlapped into a freezing circle, the opening part of the steel pipe group is cut, the soil between the pipes is excavated, and finally the adjacent steel pipe groups are connected and closed.

[0024] Furthermore, in the freezing reinforcement method of a combined pipe-roof tunnel, the freezing circle of the combined pipe-roof tunnel is divided into a plurality of freezing work areas connected end to end, and both ends of the freezing work areas are weak cold junction areas, and independent freezing devices are used in the freezing work areas, and each of the freezing work areas in S3 is constructed independently.

[0025] Furthermore, in the freezing reinforcement method of the combined pipe-roof tunnel, the freezing circle of the combined pipe-roof tunnel is located at the top, the side walls on both sides and the bottom of the combined pipe-roof tunnel as the freezing work areas respectively.

[0026] Furthermore, in the freezing reinforcement method for a combined pipe-roof tunnel, in S2:

[0027] When two adjacent strong cold junction areas overlap or the distance between them is smaller than the distance between two adjacent freezing pipes in the weak cold junction area, the two are merged or the area between them is replaced with a strong cold junction area to form a combined strong cold junction area;

[0028] When two adjacent weak cold junction areas overlap or the spacing between them is smaller than the spacing between two adjacent freezing tubes in the weak cold junction area, the two are merged or the area between them is replaced with a weak cold junction area to form a combined weak cold junction area.

[0029] The beneficial effects of the present invention are:

[0030] 1. The frozen reinforcement structure and frozen reinforcement method of the combined pipe-curtain tunnel of the present invention set frozen reinforcement areas of different strengths on the tunnel section according to the distribution of steel pipes and steel pipes in the combined pipe-curtain structure to meet the needs of flexible construction of the combined pipe-curtain structure method, while ensuring the construction safety of the steel pipe opening part, saving project investment and meeting the requirements of pipe-curtain structure construction.

[0031] 2. The freezing reinforcement structure and freezing reinforcement method of the combined pipe-curtain tunnel of the present invention can meet the requirement of only partially cutting the steel pipes and steel pipe groups in the combined pipe-curtain structure, and perform local strong freezing, while weakly freezing or not freezing the remaining sections, so as to save energy while achieving the reinforcement and water-stopping effects.

[0032] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a cross-sectional schematic diagram of the pipe curtain method + freezing auxiliary measures described in the background technology;

[0034] Figure 2 It is a cross-sectional schematic diagram of the pipe-roof structure method + freezing auxiliary measures described in the background technology;

[0035] Figure 3 It is a cross-sectional schematic diagram of the combined pipe-roof structure method + freezing auxiliary measures described in the background technology;

[0036] Figure 4 It is a schematic diagram of the arrangement of the partitioned freezing cross-section in the freezing reinforcement structure of the combined pipe-roof tunnel described in the present invention;

[0037] Figure 5 It is a schematic diagram of the arrangement of the partitioned freezing cross-section in the freezing reinforcement structure of the combined pipe-roof tunnel described in the present invention;

[0038] Figure 6 It is a schematic diagram of the division of the zoned freezing construction work area in the freezing reinforcement structure of the combined pipe-roof tunnel described in the present invention.

[0039] in:

[0040] Steel pipe 1; freezing pipe 2; freezing circle 3; weak cold junction area 3-1; strong cold junction area 3-2; combined weak cold junction area 3-3; combined strong cold junction area 3-4; soil 4; steel plate 5; soil between pipes 6; connecting steel plate 7; steel pipe group 8. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0042] It should be noted that, in the description of the present invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc. indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0043] like Figure 4 As shown, an embodiment of the present invention provides a freezing reinforcement structure of a combined pipe curtain tunnel, including a first freezing device and a second freezing device, and both are in multiple groups. The first freezing device and the second freezing device are arranged in sequence around the circumference of the tunnel. The first freezing device is placed on the tunnel stratum in an area between adjacent steel pipe groups 8 to form a strong cold junction area 3-2, and the second freezing device forms a weak cold junction area 3-1 on the freezing circle. The weak cold junction areas 3-1 are respectively arranged on both sides of the strong cold junction area 3-2. The strong cold junction areas 3-2 and the weak cold junction areas 3-1 form a freezing circle 8 in the freezing circle stratum, and the frozen body temperature in the strong cold junction area 3-2 is lower than the frozen body temperature in the weak cold junction area 3-1.

[0044] In this embodiment, the first freezing device and the second freezing device both include a plurality of freezing pipes, and the distribution density of the plurality of freezing pipes of the first freezing device in the freezing circle is greater than the distribution density of the plurality of freezing pipes of the second freezing device in the freezing circle. When the working parameters of each freezing pipe 2 are the same, by setting the distribution density of the freezing pipes 2 in the strong cold junction area 3-2 to be greater than the distribution density of the freezing pipes 2 in the weak cold junction area 3-1, the freezing effect of the strong cold junction area 3-2 can be higher than the freezing effect of the weak cold junction area 3-1, thereby achieving a freezing body temperature in the strong cold junction area 3-2 lower than the freezing body temperature in the weak cold junction area 3-1.

[0045] Between adjacent steel pipe groups 8 of the combined pipe curtain tunnel, the steel pipes 1 on both sides of the steel pipe group 8 are used as a combined pipe body, and a strong cold junction area 3-2 is arranged at the part where the combined pipe body needs to be cut. The outer lateral width Dq1 and the inner lateral width Dq2 of the strong cold junction area 3-2 need to be larger than the outer lateral width B1 and the inner lateral width B2 of the stratum range exposed when the steel pipe 1 is cut, so as to ensure that the stratum range exposed when the steel pipe 1 is cut is located in the strong cold junction area 3-2, and the freezing effect in the strong cold junction area 3-2 needs to meet the requirements of still ensuring the freezing performance after the heat loss caused by the construction. At the same time, weak cold junction areas 3-1 are set on both sides of each strong cold junction area 3-2. The purpose of setting the weak reinforcement area is to enable the frozen body to still play a role of sealing and stopping water under the influence of the strong heat source of cutting and welding of the steel pipe 1 and the ventilation in the steel pipe 1, so as to prevent groundwater from flowing into the steel pipe 1 along the contact surface between the strong reinforcement area and the steel pipe group 8. The outer lateral width Dr1 and the inner lateral width Dr2 of the weak cold junction area 3-1 should be determined according to the above-mentioned water-stopping requirements. The frozen body temperature in the weak cold junction area 3-1 is lower than the frozen body temperature in the strong cold junction area 3-2. The area between the adjacent weak cold junction areas 3-1 on the freezing circle 3 may not be frozen. Figure 4 This embodiment sets freezing reinforcement areas of different strengths on the tunnel section, which can meet the needs of the combined pipe curtain structure that the steel pipe 1 and the steel pipe group 8 only need to cut the steel pipe 1 locally, perform local strong freezing, and the remaining sections are weakly frozen or not frozen, so as to achieve the effect of reinforcement and water stopping while saving energy.

[0046] Preferably, as another embodiment of the present invention, Figure 4 Based on the embodiment shown, it also includes:

[0047] When the spacing between the strong cold junction areas 3-2 on both sides of the same steel pipe group 8 is smaller than the spacing between two adjacent freezing pipes 2 in the second freezing device, the first freezing device is arranged in the partial freezing circle 3 between the two to form a combined strong cold junction area 3-4 on the freezing circle 3.

[0048] In this embodiment, if Figure 5 In the embodiment, when the steel pipe group 8 has only one steel pipe 1, the distance between the openings on both sides of the steel pipe group 8 is relatively close, and the two strong cold junction areas 3-2 on both sides may overlap, or overlap with the weak freezing area between the two. At this time, the two strong cold junction areas 3-2 are merged into a large combined strong cold junction area 3-4, or the area between the two is set as a strong cold junction area 3-2 to form a combined strong cold junction area 3-4. The outer lateral width Dq3 and the inner lateral width Dq4 of the combined strong cold junction area 3-4 should be able to envelop the stratum ranges B1 and B2 exposed by adjacent cuts, and should be able to meet the requirement of ensuring freezing performance after heat loss caused by construction.

[0049] Preferably, as another embodiment of the present invention, Figure 4Based on the embodiment shown, it also includes:

[0050] When the spacing between the weak cold junction areas 3-1 on both sides of the same steel pipe group 8 is smaller than the spacing between two adjacent freezing pipes in the second freezing device, the second freezing device is arranged in the partial freezing circle 3 between the two to form a combined weak cold junction area 3-3 on the freezing circle 3.

[0051] In this embodiment, when two adjacent weak cold junction areas 3-1 overlap or the spacing between them is smaller than the spacing between two adjacent freezing tubes 2 in the weak cold junction area 3-1, the two are merged or the area between them is replaced with the weak cold junction area 3-1 to form a combined weak cold junction area 3-3.

[0052] Preferably, as another embodiment of the present invention, Figure 4 Based on the embodiment shown, it also includes:

[0053] The freezing circle 3 of the combined pipe-roof tunnel is divided into a plurality of freezing work areas connected end to end, and both ends of the freezing work areas are weak cold junction areas 3-1.

[0054] In this embodiment, if Figure 6 As shown, the top freezing area M1, the side wall freezing areas M2 and M3, and the bottom freezing area M4 are divided according to the top, side wall, bottom plate and other positions. Both ends of each freezing area are weak cold junction areas 3-1. At the same time, each freezing area adopts an independent freezing device to achieve the effect of zoned freezing and zoned thawing, and is combined with the pipe curtain construction process and zone division to achieve the purpose of shortening the freezing time as much as possible.

[0055] An embodiment of the present invention further provides a freezing reinforcement method for a combined pipe-roof tunnel, comprising the following steps:

[0056] S1, completing the jacking construction of the steel pipe group 8 of the combined pipe-curtain tunnel;

[0057] S2. The freezing circle 3 of the combined pipe-roof tunnel is divided into a plurality of freezing work areas connected end to end, and both ends of the freezing work area are weak cold junction areas 3-1, and independent freezing devices are used in the freezing work area, and each freezing work area is constructed independently.

[0058] Specific:

[0059] The area between adjacent steel pipe groups 8 on the freezing circle 3 of the combined pipe curtain tunnel is used as the strong cold junction area 3-2, and the areas on both sides of the freezing circle 3 of the combined pipe curtain tunnel are used as the weak cold junction area 3-1, and the installation of the freezing pipes 2 in the cold junction area, the weak cold junction area 3-1 and the steel pipe group 8 is completed respectively, and the distribution density of the freezing pipes 2 in the strong cold junction area 3-2 is greater than the distribution density of the freezing pipes 2 in the weak cold junction area 3-1;

[0060] In addition, as an extension:

[0061] When two adjacent strong cold junction areas 3-2 overlap or the distance between them is smaller than the distance between two adjacent freezing pipes 2 in the weak cold junction area 3-1, the two are merged or the area between them is replaced with the strong cold junction area 3-2 to form a combined strong cold junction area 3-4;

[0062] When two adjacent weak cold junction areas 3-1 overlap or the spacing between them is smaller than the spacing between two adjacent freezing tubes 2 in the weak cold junction area 3-1, the two are merged or the area between them is replaced with the weak cold junction area 3-1 to form a combined weak cold junction area 3-3.

[0063] S3, after completing the freezing of the cold junction area, the weak cold junction area 3-1 and the steel pipe group 8, overlap them into a freezing circle 3, cut at the opening of the steel pipe group 8, excavate the soil 4 between the pipes, and finally connect and close the adjacent steel pipe groups 8.

[0064] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A freezing reinforcement structure of a combined pipe-roof tunnel, characterized in that: It includes a first freezing device and a second freezing device, and both are in multiple groups. The first freezing device and the second freezing device are arranged in sequence around the circumference of the tunnel. The first freezing device is placed on the tunnel stratum in an area between adjacent steel pipe groups to form a strong cold junction area. The second freezing device forms a weak cold junction area on the freezing circle. The weak cold junction areas are respectively arranged on both sides of the strong cold junction area. The strong cold junction areas and the weak cold junction areas form freezing circles in the freezing circle stratum.

2. A freezing reinforcement structure for a combined pipe-roof tunnel according to claim 1, characterized in that: The first freezing device and the second freezing device both include a plurality of freezing pipes, and a distribution density of the plurality of freezing pipes of the first freezing device in the freezing circle is greater than a distribution density of the plurality of freezing pipes of the second freezing device in the freezing circle.

3. A freezing reinforcement structure for a combined pipe-roof tunnel as claimed in claim 2, characterized in that: When the spacing between the strong cold junctions on both sides of the same steel pipe group is smaller than the spacing between two adjacent freezing pipes in the second freezing device, the first freezing device is arranged in the partial freezing circle between the two to form a combined strong cold junction on the freezing circle.

4. A freezing reinforcement structure for a combined pipe-roof tunnel as claimed in claim 2, characterized in that: When the spacing between the weak cold junction zones on both sides of the same steel pipe group is smaller than the spacing between two adjacent freezing pipes in the second freezing device, the second freezing device is arranged in the partial freezing circle between the two to form a combined weak cold junction zone on the freezing circle.

5. The freezing reinforcement structure of a combined pipe-roof tunnel according to claim 1, characterized in that: The freezing circle of the combined pipe-roof tunnel is divided into a plurality of freezing work areas connected end to end, and both ends of the freezing work areas are weak cold junction areas.

6. The freezing reinforcement structure of a combined pipe-roof tunnel according to claim 1, characterized in that: The freezing area adopts an independent freezing device.

7. A freezing reinforcement method for a combined pipe-roof tunnel, characterized in that: The following steps are involved: S1. Complete the jacking construction of the steel pipe group of the combined pipe-roof tunnel; S2. The area between adjacent steel pipe groups on the freezing circle of the combined pipe-curtain tunnel is used as a strong cold junction area, and the areas on both sides of the freezing circle of the combined pipe-curtain tunnel are used as weak cold junction areas, and the installation of freezing pipes in the cold junction area, the weak cold junction area and the steel pipe group is completed respectively, and the distribution density of freezing pipes in the strong cold junction area is greater than the distribution density of freezing pipes in the weak cold junction area; S3. After the freezing of the cold junction area, the weak cold junction area and the steel pipe group is completed, they are overlapped into a freezing circle, the opening part of the steel pipe group is cut, the soil between the pipes is excavated, and finally the adjacent steel pipe groups are connected and closed.

8. A freezing reinforcement method for a combined pipe-roof tunnel according to claim 7, characterized in that: The freezing circle of the combined pipe-roof tunnel is divided into a plurality of freezing work areas connected end to end, and both ends of the freezing work area are weak cold junction areas, and independent freezing devices are used in the freezing work area, and each of the freezing work areas in S3 is constructed independently.

9. A freezing reinforcement method for a combined pipe-roof tunnel according to claim 8, characterized in that: The freezing circle of the combined pipe-roof tunnel is located at the top, the side walls on both sides and the bottom of the combined pipe-roof tunnel as the freezing work areas.

10. A freezing reinforcement method for a combined pipe-roof tunnel according to claim 7, characterized in that: In S2: When two adjacent strong cold junction areas overlap or the distance between them is smaller than the distance between two adjacent freezing pipes in the weak cold junction area, the two are merged or the area between them is replaced with a strong cold junction area to form a combined strong cold junction area; When two adjacent weak cold junction areas overlap or the spacing between them is smaller than the spacing between two adjacent freezing tubes in the weak cold junction area, the two are merged or the area between them is replaced with a weak cold junction area to form a combined weak cold junction area.

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