Construction method for excavation and backfilling of pipe shed working chamber and tunnel construction method

Abstract

The invention discloses a construction method for excavation and backfilling of a pipe shed working chamber and a tunnel construction method, and relates to the technical field of tunnel construction. Excavating a pipe shed working chamber: excavating a first part close to the top of the tunnel, and reserving a part of core soil in the middle of the first part; expanding and excavating a pipe shed working chamber at the top of the first part; constructing a working chamber primary support at the periphery of the pipe shed working chamber; backfilling a pipe shed working chamber; excavating core soil; constructing a temporary cross brace; a tunnel primary support is constructed on the periphery of the first part, and a backfill cavity is defined by the tunnel primary support and the working chamber primary support; and concrete is pumped into the backfill cavity to form the protective arch. When the pipe shed working chamber is excavated, part of core soil is reserved, so that the stability of surrounding rock can be improved, the safety risk is reduced, the operation space is prevented from being occupied, and the construction efficiency is improved; when the pipe shed working chamber is backfilled, a support and a formwork do not need to be additionally erected, a secondary lining trolley does not need to be transformed, the construction cost is greatly reduced, and the construction period is shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel construction, in particular to a pipe shed working chamber excavation and backfilling construction method and a tunnel construction method. BACKGROUND

[0002] With the continuous expansion of highway traffic and urban rail transit construction scale, the tunnel design section has developed from the traditional single-hole two-lane to single-hole four-lane or even larger. At the same time, tunnel construction inevitably passes through water-bearing soil stratum, wide fracture zone and shallow buried section of densely built-up area, resulting in rapid increase of risks such as instability of working face, water and mud inrush, and excessive ground settlement.

[0003] To cope with the above challenges, advanced pipe shed is generally used for pre-support in engineering. The advanced pipe shed is formed by inserting steel flower pipes with an outer diameter of φ89-φ108mm and a wall thickness of 6-12mm along the outer 10°-15° of the tunnel excavation contour line, forming a steel pipe shed frame with a longitudinal length of 10-45m and a ring spacing of 0.3-0.5m. The strength of the steel flower pipe is used to support and reinforce the surrounding rock with low self-stability, to prevent the sinking, relaxation and collapse of soft surrounding rock, and has three functions of shed frame, anchoring and strata consolidation.

[0004] When the geological conditions are poor and multiple rows of pipe sheds need to be constructed, a pipe shed working chamber with a longitudinal length of 8-10m and a lateral expansion of 1.0-1.5m on each side needs to be set up inside the tunnel to meet the requirements of pipe shed drilling machine operation space and pipe shed positioning accuracy. After the pipe shed is constructed, the pipe shed working chamber needs to be backfilled in time to restore the standard section of the tunnel and ensure the continuity of the force of the secondary lining structure.

[0005] There are mainly two excavation methods for the existing pipe shed working chamber: 1. First, the tunnel is excavated by using the cross partition wall method, and then the pipe shed working chamber is excavated. This excavation method will occupy the operation space due to the existence of temporary vertical supports, resulting in a small operation space during the excavation of the pipe shed working chamber and low construction efficiency. After the removal of the vertical supports, the stress of the surrounding rock is redistributed, which is easy to induce local spalling. 2. First, the tunnel is excavated by using the bench method, and then the pipe shed working chamber is excavated. This excavation method has poor stability of the working face due to the large tunnel section and the large one-time exposure of the surrounding rock, which leads to high safety risks.

[0006] There are mainly two backfilling methods for the existing pipe shed working chamber: 1. The I-shaped steel formwork is used in cooperation with small block wood formwork for formwork construction. The turnover frequency of the formwork and small block formwork in this backfilling method is low, and the cost is high. 2. The secondary lining trolley is directly used for backfilling by pumping. This backfilling method needs to greatly improve the rigidity and tonnage of the trolley, and the track and walking system need to be simultaneously modified, which requires a large one-time investment. In addition, the positioning and formwork removal of the formwork are difficult, and the construction period is long.

[0007] In summary, the construction method of the existing pipe roof workshop has the chain contradictions of limited space, high cost and high risk, which has become a bottleneck link restricting large-section tunnel crossing through poor geological sections. SUMMARY

[0008] The purpose of the present application is to provide a pipe roof workshop excavation and backfill construction method and a tunnel construction method, which solves the problems of limited space, high cost and high risk in the traditional construction method.

[0009] The technical solution adopted by the present application to solve its technical problems is: In a first aspect, a pipe roof workshop excavation and backfill construction method is provided, comprising: Pipe roof workshop excavation: excavate the first part near the top of the hole under the advanced support of the previous cycle, reserve part of the core soil in the middle of the first part; excavate the pipe roof workshop at the top of the first part; and construct the initial support of the workshop around the pipe roof workshop; Pipe roof workshop backfill: excavate the core soil of the first part; construct temporary cross braces connecting both ends of the initial support of the workshop; construct the initial support of the tunnel around the first part, and form a backfill cavity between the initial support of the workshop and the initial support of the tunnel; pump concrete into the backfill cavity, and form an arch after the concrete solidifies.

[0010] Further, the construction method of the initial support of the workshop comprises: initially spraying expansion concrete on the surface of the surrounding rock, constructing expansion anchor rods in the surrounding rock, laying expansion reinforcement mesh on the surface of the expansion concrete and connecting with the expansion anchor rods, erecting a plurality of arc-shaped expansion steel frames on the surface of the expansion reinforcement mesh, constructing expansion locking anchor pipes in the surrounding rock and connecting with the expansion steel frames, and re-spraying concrete to the designed thickness.

[0011] Further, the excavation footage of the first part meets the following requirements: V-class surrounding rock ≤ 1 steel frame spacing, and VI-class surrounding rock ≤ 2 steel frame spacing.

[0012] Further, after the core soil excavation is completed, the bottom surface of the first part forms a downwardly concave negative arch structure.

[0013] Further, the temporary cross brace is a negative arch structure with low middle and high ends, and the bottom of the temporary cross brace is attached to the bottom surface of the first part.

[0014] Further, the construction method of the initial support of the tunnel comprises: erecting arc-shaped tunnel steel frames, laying tunnel reinforcement mesh on the tunnel steel frames, and spraying concrete on the tunnel reinforcement mesh to the designed thickness.

[0015] Further, the tunnel steel frames are connected with the temporary cross braces.

[0016] In a second aspect, a tunnel construction method is provided, comprising: Under the advanced support of the previous cycle, excavate a first part close to the top of the hole, and reserve part of the core soil in the middle of the first part; excavate a pipe shed working chamber at the top of the first part; construct a working chamber initial support on the periphery of the pipe shed working chamber; and construct an advanced pipe shed in the pipe shed working chamber; Excavate the core soil of the first part; construct temporary cross braces connecting the two ends of the working chamber initial support; construct a tunnel initial support on the periphery of the first part, and form a backfill cavity between the working chamber initial support and the tunnel initial support; pump concrete into the backfill cavity, and form an arch after the concrete solidifies; Excavate a second part below the first part at a predetermined distance behind the first part; and construct a second part initial support on the periphery of the second part; Excavate a third part below the second part at a predetermined distance behind the second part; and construct a third part initial support on the periphery of the third part; Remove the temporary cross braces, and sequentially construct a inverted arch, inverted arch filling, and a secondary lining arch wall.

[0017] Further, the second part and the third part are excavated in a left-right split frame and staggered manner.

[0018] Further, the construction methods of the second part initial support and the third part initial support both include: initial spraying of concrete, construction of anchor rods, laying of a steel mesh and connection with the anchor rods, erection of a steel frame, construction of a locking foot anchor pipe and connection with the steel frame, and re-spraying of concrete to a designed thickness.

[0019] The application has the following beneficial effects: The tunnel construction method provided by the application can reduce the one-time exposure area of the surrounding rock, inhibit the deformation of the surrounding rock, improve the stability of the surrounding rock, reduce the safety risk, and provide a stable working platform for the outward expansion of the pipe shed working chamber, thereby avoiding the occupation of working space and improving the construction efficiency. When the pipe shed working chamber is backfilled, the working chamber initial support and the tunnel initial support are used to form the inner and outer forms of the pipe shed working chamber backfill concrete, without the need for additional scaffolding and forms, and without the need for modification of the secondary lining trolley, thereby greatly reducing the construction cost, and without the need for form removal in the later period, thereby shortening the construction period. The method solves the space limitation, high cost, and large risk chain contradiction of the traditional construction method. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings only illustrate some of the embodiments of the present application, and should not be considered as a limitation of the scope. All other drawings obtained by those skilled in the art without creative effort based on the drawings are within the scope of the present application. The embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0021] Figure 1 is a structural schematic diagram of a tunnel cross section; Figure 2 is a structural schematic diagram of a pipe roof working chamber longitudinal section; Figure 3 is a structural schematic diagram of a pipe roof working chamber longitudinal section; Figure 4 is a structural schematic diagram of a pipe roof working chamber longitudinal section.

[0022] Reference signs: 1-first part; 11-core soil; 2-pipe roof working chamber; 3-working chamber primary support; 31-temporary cross brace; 32-excavation concrete; 33-excavation anchor rod; 34-excavation steel mesh; 35-excavation steel frame; 36-excavation anchor pipe; 4-tunnel primary support; 41-tunnel steel frame; 42-tunnel steel mesh; 5-backfill cavity; 51-arch protection; 6-advance pipe roof; 7-second part; 71-second part primary support; 8-third part; 81-third part primary support; 9-inverted arch; 91-inverted arch filling; 10-second lining arch wall. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of the present application. The embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0024] In the description of the present application, the terms "upper", "lower", "left", "right", "front", "back", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise specified, the above orientation description can be flexibly arranged in the actual application process under the condition of meeting the relative positional relationship shown in the drawings.

[0025] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] Referring to Figure 1 , Figure 2 , Figure 3 , Figure 4 , the present application provides a construction method for pipe shed working chamber excavation and backfilling, comprising: S1, pipe shed working chamber excavation: under the advanced support of the last cycle, excavate the first part 1 close to the top of the hole, and reserve part of the core soil 11 in the middle of the first part 1; excavate the pipe shed working chamber 2 at the top of the first part 1; and make the working chamber initial support 3 around the pipe shed working chamber 2.

[0027] When the advanced support of the last cycle is completed, the surrounding rock is reinforced by the advanced support to prevent relaxation or collapse during subsequent excavation of the surrounding rock. The first part 1 is arranged at the position close to the top of the tunnel section, and part of the core soil 11 is reserved in the center during the excavation of the first part 1. When the excavation is completed, the bottom surface of the first part 1 forms a structure with high middle and low sides, which serves as an operation platform for subsequent expansion, so as to excavate the pipe shed working chamber 2 at the top of the first part 1. When the pipe shed working chamber 2 is excavated, the working chamber initial support 3 is made around the pipe shed working chamber 2 to seal the surrounding rock and provide a safe operation surface for subsequent advanced pipe shed 6 construction. Referring to Figure 2 When the pipe shed working chamber 2 is completed, the advanced pipe shed 6 can be constructed in the pipe shed working chamber 2 by using the pipe shed drilling machine. The advanced pipe shed 6 can be constructed according to the existing construction method, which will not be described here. In order to simplify the view, Figure 2 The pipe shed drilling machine and other supporting equipment or invisible structures are not shown in the middle of the figure.

[0028] S2, backfilling of the pipe roof working chamber: excavating the core soil 11 of the first part 1; constructing temporary cross braces 31 connecting the two ends of the working chamber primary support 3; constructing the tunnel primary support 4 around the first part 1, and enclosing the backfilling cavity 5 between the working chamber primary support 3 and the tunnel primary support 4; pumping concrete into the backfilling cavity 5, and forming the arch 51 after the concrete solidifies.

[0029] When the advanced pipe roof 6 is completely constructed, the pipe roof working chamber 2 can be backfilled. First, the core soil 11 reserved in the first part 1 is excavated to provide space for the subsequent construction of the tunnel primary support 4. After the core soil 11 is excavated, the temporary cross braces 31 are set up, and the two ends of the temporary cross braces 31 are respectively connected to the two lower ends of the working chamber primary support 3. In this way, a temporary closed loop is formed between the temporary cross braces 31 and the working chamber primary support 3, which improves the overall rigidity of the working chamber primary support 3, effectively suppresses the inward convergence of the working chamber primary support 3, and weakens the deformation of the surrounding rock caused by the excavation of the core soil 11. After the temporary cross braces 31 are constructed, the tunnel primary support 4 is constructed around the first part 1. Referring to Figure 3 When the tunnel primary support 4 is constructed, the backfilling cavity 5 can be enclosed between the working chamber primary support 3 and the tunnel primary support 4. The tunnel primary support 4 can be pre-drilled with pumping holes, through which concrete can be pumped into the backfilling cavity 5, and the arch 51 can be formed after the concrete solidifies, as shown in Figure 4 .

[0030] The construction method for excavating and backfilling the pipe roof working chamber provided by the embodiments of the present application can, when the pipe roof working chamber 2 is excavated, reduce the one-time exposure area of the surrounding rock, suppress the deformation of the surrounding rock, improve the stability of the surrounding rock, reduce the safety risk, and provide a stable working platform for the outward expansion of the pipe roof working chamber 2, avoid occupying the working space, and improve the construction efficiency. When the pipe roof working chamber 2 is backfilled, the working chamber primary support 3 and the tunnel primary support 4 are used to form the inner and outer forms for backfilling concrete of the pipe roof working chamber 2, without the need for additional scaffolding and forms, and without the need for modifying the secondary lining trolley, which greatly reduces the construction cost, and at the same time, there is no need to remove the forms in the later stage, which shortens the construction period. The method solves the chain of contradictions of the traditional construction method, such as space limitation, high cost, and high risk.

[0031] In some embodiments, referring to Figure 1 , the construction method of the working chamber primary support 3 includes: initially spraying and excavating concrete 32 on the surface of the surrounding rock, constructing excavating anchor rods 33 in the surrounding rock, laying an excavating steel mesh 34 on the surface of the excavating concrete 32 and connecting it with the excavating anchor rods 33, erecting a plurality of arc-shaped excavating steel frames 35 on the surface of the excavating steel mesh 34, constructing excavating lock foot anchor pipes 36 in the surrounding rock and connecting them with the excavating steel frames 35, and re-spraying concrete to the designed thickness.

[0032] Correspondingly, the initial spraying and excavating concrete 32 can quickly close the exposed surface of the surrounding rock to form a temporary protective layer to prevent the surrounding rock from weathering and stress relaxation; the excavating anchor rod 33 is anchored in the surrounding rock, which not only can reinforce the surrounding rock, but also can transfer the loose load to the deep stable rock mass; the excavating steel mesh 34 is laid on the surface of the excavating concrete 32 and connected with the excavating anchor rod 33, which can inhibit the spalling of the concrete and improve the crack resistance of the sprayed layer; the excavating steel frame 35 provides a circumferential rigid skeleton for bearing most of the initial load, and adjacent excavating steel frames 35 can also be connected by connecting rods; the excavating lock foot anchor pipe 36 is anchored in the surrounding rock and welded with the excavating steel frame 35, which is used to firmly fix the excavating steel frame 35; after the secondary spraying concrete is formed to the designed thickness, a reinforced ring is formed to change the surface of the surrounding rock from loose to integral, thereby improving the overall reliability of the initial support 3 of the working chamber.

[0033] In some embodiments, in order to control the deformation of the surrounding rock during excavation and improve construction safety, the excavation footage of the first part 1 meets the following requirements: for V-class surrounding rock, the distance between two steel frames is 1; for VI-class surrounding rock, the distance between two steel frames is 2.

[0034] In some embodiments, referring to Figure 1 After the core soil 11 is excavated, the bottom surface of the first part 1 forms a downwardly concave negative arch structure. For example, the temporary cross brace 31 is a negative arch structure with low middle and high ends, and the bottom of the temporary cross brace 31 is attached to the bottom surface of the first part 1. For example, the bottom surface of the first part 1 is excavated into a negative arch groove with the same curvature, and the temporary cross brace 31 is embedded in the negative arch groove. The number of temporary cross braces 31 can be consistent with and one-to-one corresponding to the number of excavating steel frames 35, and the two ends of the temporary cross brace 31 are respectively welded to the two ends of the corresponding excavating steel frame 35.

[0035] Correspondingly, by excavating the bottom surface of the first part 1 into a negative arch structure, not only the working surface thereon can be increased and the working space can be enlarged, but also the bottom of the temporary cross brace 31 can be completely attached to the bottom surface of the first part 1, avoiding point contact or eccentric compression, thereby further improving the stability and load-bearing capacity of the temporary cross brace 31 and effectively inhibiting the convergence deformation and arch crown settlement of the excavating steel frame 35.

[0036] In some embodiments, referring to Figure 1 The method for constructing the tunnel initial support 4 includes erecting an arc-shaped tunnel steel frame 41, laying a tunnel steel mesh 42 on the tunnel steel frame 41, and spraying concrete on the tunnel steel mesh 42 to a designed thickness.

[0037] Correspondingly, the tunnel steel frame 41 provides a ring-shaped rigid framework for bearing most of the initial load, and the adjacent tunnel steel frames 41 can be connected by welding connection rods; the tunnel steel mesh 42 is laid on the tunnel steel frame 41 and connected with the tunnel steel frame 41, and the tunnel steel mesh 42 is used as a spraying matrix for subsequent sprayed concrete to prevent the concrete from falling; after the sprayed concrete reaches the designed thickness, a reinforced ring is formed by mechanical interlocking of the tunnel steel frame 41, the tunnel steel mesh 42 and the concrete, thereby ensuring the overall reliability of the tunnel initial support 4. To further improve the reliability of the support structure, the tunnel steel frame 41 is welded with the temporary cross brace 31.

[0038] The embodiment of the present application also provides a tunnel construction method, which comprises the following steps: S1, under the advanced support of the previous cycle, excavate a first part 1 close to the top of the hole, and reserve a core soil 11 in the middle of the first part 1; excavate a pipe shed working chamber 2 at the top of the first part 1; construct a working chamber initial support 3 around the pipe shed working chamber 2; and construct an advanced pipe shed 6 in the pipe shed working chamber 2.

[0039] S2, excavate the core soil 11 of the first part 1; construct a temporary cross brace 31 connecting the two ends of the working chamber initial support 3; construct a tunnel initial support 4 around the first part 1, and form a backfill cavity 5 between the working chamber initial support 3 and the tunnel initial support 4; pump concrete into the backfill cavity 5, and form an arch 51 after the concrete solidifies.

[0040] S3, excavate a second part below the first part 1 at a predetermined distance behind the first part 1; and construct a second part initial support 71 around the second part 7.

[0041] S4, excavate a third part 8 below the second part 7 at a predetermined distance behind the second part 7; and construct a third part initial support 81 around the third part 8.

[0042] S5, remove the temporary cross brace 31, and sequentially construct an inverted arch 9, an inverted arch filling 91 and a secondary lining arch wall 10.

[0043] The second part 7 and the third part 8 are both constructed by using the construction method of left-right framing and staggered excavation. Correspondingly, by using the construction method of framing and staggered excavation, the exposure time of the surrounding rock is shortened by more than half, the construction requirements of strong support and fast closure are met, and the construction safety is improved. The construction methods of the second part initial support 71 and the third part initial support 81 both comprise the following steps: initial spraying of concrete, construction of anchor rods, laying of a steel mesh and connection with the anchor rods, erection of a steel frame, construction of a lock foot anchor pipe and connection with the steel frame, and secondary spraying of concrete to the designed thickness.

[0044] Correspondingly, the initial shotcrete can quickly seal the exposed surface of the surrounding rock to form a temporary protective layer, preventing weathering and stress relaxation of the surrounding rock; the anchor rod is anchored in the surrounding rock, which not only reinforces the surrounding rock, but also transfers the loose load to the deep stable rock mass; the steel mesh is laid on the surface of the initial shotcrete and connected with the anchor rod, which can inhibit the spalling of the concrete and improve the crack resistance of the sprayed layer; the steel frame provides a circumferential rigid skeleton for bearing most of the initial load, and adjacent steel frames can also be connected by connecting rods; the locking foot anchor pipe is anchored in the surrounding rock and connected with the steel frame by welding, which is used to firmly fix the steel frame; after the secondary shotcrete reaches the designed thickness, a reinforced ring is formed to change the surface of the surrounding rock from loose to integral, improving the overall reliability of the initial support.

[0045] The tunnel construction method provided by the embodiments of the present application can reduce the one-time exposure area of the surrounding rock, inhibit the deformation of the surrounding rock, improve the stability of the surrounding rock, and reduce the safety risk when the pipe shed working chamber 2 is excavated by reserving part of the core soil 11 in the middle of the first part 1. In addition, the method can provide a stable operation platform for the expansion of the pipe shed working chamber 2, avoid occupying operation space, and improve construction efficiency. When the pipe shed working chamber 2 is backfilled, the initial support 3 of the working chamber and the initial support 4 of the tunnel respectively form the inner and outer templates of the backfilled concrete of the pipe shed working chamber 2, without the need for additional scaffolding and templates, and without the need for modification of the secondary lining trolley, which greatly reduces the construction cost, and at the same time, there is no need to remove the formwork in the later stage, shortening the construction period. The method solves the chain reaction contradiction of limited space, high cost and high risk in the traditional construction method.

[0046] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements within the technical scope disclosed in the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application.

Claims

1. A construction method for excavation and backfilling of a pipe shed working chamber, characterized in that, include: Pipe shed chamber excavation: Under the advance support of the previous cycle, the first part (1) near the top of the tunnel is excavated, and the core soil (11) is reserved in the middle of the first part (1); the pipe shed chamber (2) is expanded at the top of the tunnel of the first part (1); the initial support (3) of the chamber is constructed around the pipe shed chamber (2). Backfilling of the pipe shed chamber: excavate the core soil (11) of the first part (1); construct temporary cross bracing (31) connecting the two ends of the initial support (3) of the chamber; construct the initial support (4) of the tunnel around the first part (1) and form a backfill cavity (5) between the initial support (3) of the chamber and the initial support (4) of the tunnel; pump concrete into the backfill cavity (5) and form a protective arch (51) after the concrete solidifies.

2. The construction method for excavation and backfilling of the pipe shed working chamber according to claim 1, characterized in that, The method for constructing the initial support (3) of the workshop includes: spraying excavation concrete (32) on the surface of the surrounding rock, constructing excavation anchors (33) in the surrounding rock, laying excavation steel mesh (34) on the surface of the excavation concrete (32) and connecting it with the excavation anchors (33), erecting several arc-shaped excavation steel frames (35) on the surface of the excavation steel mesh (34), constructing excavation locking anchor pipes (36) in the surrounding rock and connecting them with the excavation steel frames (35), and spraying concrete to the designed thickness.

3. The construction method for excavation and backfilling of the pipe shed working chamber according to claim 1, characterized in that, The excavation advance of the first part (1) meets the following requirements: Class V surrounding rock ≤ 1 steel frame spacing, Class VI surrounding rock ≤ 2 steel frame spacing.

4. The construction method for excavation and backfilling of the pipe shed working chamber according to claim 1, characterized in that, After the core soil (11) is excavated, the bottom surface of the first part (1) forms a downward-concave negative arch structure.

5. The construction method for excavation and backfilling of the pipe shed working chamber according to claim 1, characterized in that, The temporary cross brace (31) is a negative arch structure with a low middle and high ends, and the bottom of the temporary cross brace (31) is in contact with the bottom surface of the first part (1).

6. The construction method for excavation and backfilling of the pipe shed working chamber according to claim 1, characterized in that, The construction method of the initial support (4) of the tunnel includes: erecting an arc-shaped tunnel steel frame (41), laying a tunnel steel mesh (42) on the tunnel steel frame (41), and spraying concrete on the tunnel steel mesh (42) to the designed thickness.

7. The construction method for excavation and backfilling of the pipe shed working chamber according to claim 6, characterized in that, The tunnel steel frame (41) is connected to the temporary cross brace (31).

8. A tunnel construction method, characterized in that, include: Under the advance support of the previous cycle, the first part (1) near the top of the tunnel is excavated, and the core soil (11) is reserved in the middle of the first part (1); the pipe shed studio (2) is expanded at the top of the tunnel of the first part (1); the initial support (3) of the studio is constructed around the pipe shed studio (2); and the advance pipe shed (6) is constructed in the pipe shed studio (2). Excavate the core soil (11) of the first part (1); construct temporary cross bracing (31) connecting the two ends of the initial support (3) of the working chamber; construct the initial support (4) of the tunnel around the first part (1) and form a backfill cavity (5) between the initial support (3) of the working chamber and the initial support (4) of the tunnel; pump concrete into the backfill cavity (5) and form a protective arch (51) after the concrete solidifies. Delaying the first part (1) by a predetermined distance, excavate the second part (7) below the first part (1); and construct the second part initial support (71) around the second part (7). Delaying the second part (7) by a predetermined distance, excavate the third part (8) below the second part (7); and construct the initial support (81) for the third part around the third part (8). Remove the temporary cross bracing (31), and then construct the inverted arch (9), inverted arch filling (91), and secondary lining arch wall (10) in sequence.

9. The tunnel construction method according to claim 8, characterized in that, Both the second part (7) and the third part (8) adopt the construction method of left and right split and staggered excavation.

10. The tunnel construction method according to claim 8, characterized in that, The construction methods for the second part of the initial support (71) and the third part of the initial support (81) both include: initial shotcreting, installation of anchor rods, laying of steel mesh and connecting it with the anchor rods, erection of steel frame, installation of locking foot anchor pipes and connection with the steel frame, and re-shotcreting of concrete to the design thickness.

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