Support structure and construction method of tunnel with mushroom-shaped cross section

Abstract

The application provides a supporting structure of a mushroom-shaped cross-section tunnel and a construction method thereof, and belongs to the technical field of tunnel engineering. The supporting structure of the mushroom-shaped cross-section tunnel comprises an arch initial support located in an arch space, an arch secondary lining located in the inner side of the arch initial support, an arch foot supporting beam, a side wall initial support located at the two sides of a wall inner space, and a side wall secondary lining located in the inner side of the side wall initial support. The lower end of the arch secondary lining acts on the arch foot supporting beam on the two sides, and the distance between the two arch foot supporting beams is greater than the distance between the two side wall secondary linings. The ribbed plate type anchor rod retaining wall is used as the side wall initial support, and the vertical pressure that can be resisted is greater than that of the conventional spray anchor support. Therefore, the acting force transferred to the side wall secondary lining is smaller, the side wall secondary lining can be weakened, and the investment is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tunnel engineering and relates to a support structure of a mushroom-shaped section tunnel and a construction method of the mushroom-shaped section tunnel. BACKGROUND

[0002] With continuous breakthroughs in shield technology, the application field of shield technology is becoming more and more extensive. Meanwhile, with continuous improvement of infrastructure, engineering construction conditions are becoming more and more complex, and the requirements for engineering construction are becoming higher and higher. Because shield technology has advantages such as control of surface settlement and small construction vibration, large-diameter shield tunnels are being used more and more widely. However, the space for large-diameter shield tunnels to serve as starting or receiving shafts is becoming less and less, and even none. Therefore, tunnel-in-tunnel starting or receiving for large-diameter shield tunnels will be used more and more widely.

[0003] When a large-diameter shield tunnel is started or received in a tunnel, in order to meet the space requirements of assembly or disassembly work, if a conventional horseshoe-shaped or circular section is used, the section excavation and support area is large, and the section space is wasted, which is not economical. Meanwhile, a separate bent structure or gantry crane needs to be provided to meet the operation requirements of assembly or disassembly of the shield machine. The use of a mushroom-shaped section can reduce the excavation and support structure and reduce the support structure of the hoisting trolley, which has obvious economic efficiency. At present, mushroom-shaped section tunnels are commonly used in underground powerhouses in the water industry, and the geology is generally good. The mushroom-shaped section support structure can meet the stress requirements by using ordinary shotcrete and anchor support. If necessary, steel fibers or steel frames are added in the sprayed concrete. Meanwhile, because the geology is good, the mushroom-shaped lining is mainly excavated by the bench method.

[0004] Therefore, for complex geological conditions, especially for strata with obvious inclination, when a large-diameter shield tunnel is started or received in a tunnel, how to use a support system and a construction method is a problem that needs to be solved urgently. SUMMARY

[0005] The application aims to solve the above problems of the prior art and provides a safe and reasonable support structure of a mushroom-shaped section tunnel.

[0006] A convenient and fast construction method of a mushroom-shaped section tunnel is also provided.

[0007] The application can be implemented by the following technical solutions.

[0008] The support structure of the tunnel with mushroom-shaped cross section comprises arch initial support in the arch space, arch secondary lining inside the arch initial support, arch foot beam, side wall initial support at both sides of the wall space, and side wall secondary lining inside the side wall initial support, the lower end of the arch secondary lining acts on the arch foot beam at both sides, the distance between the arch foot beams at both sides is greater than the distance between the side wall secondary linings at both sides. The height of the arch foot beam is 1.2-2 times the thickness of the arch secondary lining.

[0009] In the support structure of the tunnel with mushroom-shaped cross section, the side wall initial support is a plate-rib type anchor rod retaining wall, which comprises rib columns arranged in sequence along the length direction of the wall space, a compression beam arranged at the top of the rib columns, and face plates arranged inside the rib columns, the rib columns and the compression beam are fixed to the side of the wall space by a plurality of side wall anchor rods.

[0010] The compression beam is a reinforced concrete structure, which serves as the top of the rib columns and the face plates, the width of the compression beam is equal to the width of the rib columns, and the height of the compression beam is 0.5-1.5 m. The rib column is a reinforced concrete structure, the thickness of the rib column is 0.3-1 m, the width of the rib column is 0.5-1.5 m, and the distance between two adjacent rib columns is 2-5 m. The face plate is a concrete structure, the thickness of the face plate is 0.15-0.5 m, and the width of the face plate is the net width between two adjacent rib columns. The distance of the side wall anchor rods in the height direction is 1.5-3 m, and the density of the anchor rods is increased in the range of 2 m from the top.

[0011] In the support structure of the tunnel with mushroom-shaped cross section, the arch initial support comprises arch steel support, arch sprayed concrete, and arch system anchor rod. The arch steel support is a steel mesh, and a steel frame can be additionally arranged if necessary.

[0012] In the support structure of the tunnel with mushroom-shaped cross section, a bottom plate secondary lining is arranged at the bottom of the wall space, and the side wall secondary lining and the bottom plate secondary lining are integrated.

[0013] In the support structure of the tunnel with mushroom-shaped cross section, the top of the side wall secondary lining has a transversely extending part extending outward, and the side wall initial support is arranged below the transversely extending part. In order to improve the structural strength, the transversely extending part can be extended to the arch foot beam, and the transversely extending part and the arch foot beam are integrated.

[0014] The construction method of the tunnel with mushroom-shaped cross section comprises the following steps:

[0015] Step 1: excavating the arch space, and timely arranging the arch initial support and temporary support. The upper end of the temporary support abuts against the arch initial support, and the lower end of the temporary support abuts against the bottom of the arch space, and the temporary support adopts 18-22 type I-beam.

[0016] Step 2: Pre-splitting blasting is performed at the inner walls of the two sides of the in-wall space, and the surrounding rock and tunnel rock bed in the range of the side wall initial support are blasted open.

[0017] Step 3: After the free deformation and stress release of the pre-splitting of the side wall initial support end, the temporary support is removed, and the secondary lining of the arch and the arch foot beam are constructed.

[0018] Step 4: Under the protection of the secondary lining of the arch, the surrounding rock in the range of the two sides of the in-wall space is excavated, and the side wall initial support is timely constructed.

[0019] Step 5: After the in-wall space is excavated and the side wall initial support is constructed, the secondary lining of the bottom plate and the side wall is constructed, and the lifting equipment is installed.

[0020] After the pre-splitting blasting of the two sides of the side wall initial support, the stress of the surrounding rock in the range of the side wall initial support can be fully released before the secondary lining of the arch is constructed, so that the deformation or cracking of the secondary lining of the arch caused by the stress release of the subsequent lower excavation is avoided; after the stress release of the surrounding rock in the range of the side wall initial support, the stress of the support structure in the range of the side wall initial support is smaller.

[0021] In the construction method of the mushroom-shaped cross-section tunnel, the arch space is formed by step-by-step excavation.

[0022] In the construction method of the mushroom-shaped cross-section tunnel, the gap cracked by the pre-splitting blasting in step 2 needs to be more than 3cm.

[0023] In the construction method of the mushroom-shaped cross-section tunnel, the surrounding rock in the range of the two sides of the in-wall space is excavated by step-by-step benching method in step 4. After each bench is excavated, a bench of the side wall initial support is constructed, and finally the entire side wall initial support is formed.

[0024] In the construction method of the mushroom-shaped cross-section tunnel, the height of the bench constructed by the step-by-step benching method in step 4 is not greater than 5m. That is, the surrounding rock is excavated layer by layer, and after the first layer is excavated, the second layer is excavated, and then the third layer is excavated, and the excavation depth of each layer is not greater than 5m.

[0025] In the construction method of the mushroom-shaped cross-section tunnel, the lifting equipment directly acts on the secondary lining of the side wall. The lifting equipment is a crane.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] The support system is reasonable and safe, and investment is reduced; the profile of the arch space is arc-shaped, the profile of the side wall of the wall inner space is straight, different initial support structures are selected by combining different line types, the ribbed anchor rod retaining wall is used as the initial support of the side wall, the vertical pressure that can be resisted is larger than that of the conventional shotcrete anchor support, the acting force transmitted to the secondary lining of the side wall is smaller, the secondary lining of the side wall can be weakened, and then the investment is reduced.

[0028] The construction is convenient, the method is better, the structure is safe, the social and economic value is good; after the pre-split blasting on both sides of the initial support of the side wall, the stress of the surrounding rock in the initial support range of the side wall can be fully released before the secondary lining of the arch is constructed, and deformation or cracking caused by the stress release of the subsequent lower excavation to the secondary lining of the arch can be avoided; after the stress release of the surrounding rock in the initial support range of the side wall, the stress of the support structure in the initial support range of the side wall will be smaller, the vertical pre-split blasting operation space is larger under the action of the space of the arch, and the vertical construction is more convenient. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a mushroom-shaped cross-section tunnel support structure.

[0030] Figure 2 It is a schematic diagram of arch excavation of a mushroom-shaped cross-section tunnel.

[0031] Figure 3 It is a schematic diagram after the arch initial support and temporary support are constructed.

[0032] Figure 4 It is a schematic diagram after pre-split blasting of a mushroom-shaped cross-section tunnel.

[0033] Figure 5 It is a schematic diagram after the arch secondary support and arch foot joist are constructed.

[0034] Figure 6 It is a schematic diagram of step-by-step excavation and initial support of the side wall.

[0035] Figure 7 It is a schematic diagram after the initial support of the side wall of a mushroom-shaped cross-section tunnel is completed.

[0036] Figure 8 It is a schematic diagram after the secondary lining of the side wall and the secondary lining of the bottom plate are completed.

[0037] In the figure, a, arch space; b, wall space; 1, arch primary support; 11, arch system anchor rod; 12, arch steel support; 13, arch shotcrete; 2, side wall primary support; 21, side wall anchor rod bundle; 22, top beam; 23, rib column; 24, panel; 31, arch secondary lining; 32, side wall secondary lining; 33, bottom plate secondary lining; 34, transverse extension; 4, arch foot beam; 5, hoisting equipment; 6, shield lining; 71, arch excavation part; 72, unexcavated part; 8, temporary support; 9, pre-splitting. DETAILED DESCRIPTION

[0038] The following is a specific embodiment of the present application and further describes the technical solutions of the present application in conjunction with the drawings, but the present application is not limited to these embodiments.

[0039] As shown in the supporting structure of the mushroom-shaped cross-section tunnel, it is arranged in the mushroom-shaped cross-section tunnel, the mushroom-shaped cross-section tunnel includes an arch space a located at the upper part and a wall space b located at the lower part, the two side walls of the wall space b vertically extend, the profile of the arch space a is arc-shaped, the maximum width of the arch space a is greater than the width of the wall space b, the shape of the cross-section is mushroom-shaped, so it is called mushroom-shaped cross-section tunnel. Figure 1 As shown in the supporting structure of the mushroom-shaped cross-section tunnel, it is arranged in the mushroom-shaped cross-section tunnel, the mushroom-shaped cross-section tunnel includes an arch space a located at the upper part and a wall space b located at the lower part, the two side walls of the wall space b vertically extend, the profile of the arch space a is arc-shaped, the maximum width of the arch space a is greater than the width of the wall space b, the shape of the cross-section is mushroom-shaped, so it is called mushroom-shaped cross-section tunnel.

[0040] Figure 1 As shown in the supporting structure of the mushroom-shaped cross-section tunnel, it is arranged in the mushroom-shaped cross-section tunnel, the mushroom-shaped cross-section tunnel includes an arch space a located at the upper part and a wall space b located at the lower part, the two side walls of the wall space b vertically extend, the profile of the arch space a is arc-shaped, the maximum width of the arch space a is greater than the width of the wall space b, the shape of the cross-section is mushroom-shaped, so it is called mushroom-shaped cross-section tunnel.

[0041] Among them, the lower end of the arch secondary lining 31 acts on the two side arch foot beams 4 respectively, the height of the arch foot beam 4 is 1.2-2 times the thickness of the arch secondary lining 31.

[0042] The arch steel support 12 is a steel mesh, and a steel frame can be added as necessary.

[0043] The supporting structure further includes a side wall primary support 2 located at both sides of the wall space b and a side wall secondary lining 32 located inside the side wall primary support 2, the distance between the two side arch foot beams 4 is greater than the distance between the two side wall secondary linings 32.

[0044] As shown in the supporting structure of the mushroom-shaped cross-section tunnel, it is arranged in the mushroom-shaped cross-section tunnel, the mushroom-shaped cross-section tunnel includes an arch space a located at the upper part and a wall space b located at the lower part, the two side walls of the wall space b vertically extend, the profile of the arch space a is arc-shaped, the maximum width of the arch space a is greater than the width of the wall space b, the shape of the cross-section is mushroom-shaped, so it is called mushroom-shaped cross-section tunnel. Figure 1 As shown in the supporting structure of the mushroom-shaped cross-section tunnel, it is arranged in the mushroom-shaped cross-section tunnel, the mushroom-shaped cross-section tunnel includes an arch space a located at the upper part and a wall space b located at the lower part, the two side walls of the wall space b vertically extend, the profile of the arch space a is arc-shaped, the maximum width of the arch space a is greater than the width of the wall space b, the shape of the cross-section is mushroom-shaped, so it is called mushroom-shaped cross-section tunnel.

[0045] ​In this embodiment, the top beam 22 is a reinforced concrete structure, which serves as the top of the rib column 23 and the panel 24, and has the same width as the rib column 23. The height of the top beam 22 is 0.5m-1.5m. The rib column 23 is a reinforced concrete structure, which has a thickness of 0.3m-1m, a width of 0.5m-1.5m, and a spacing of 2m-5m between two adjacent rib columns 23. The panel 24 is a concrete structure, which has a thickness of 0.15m-0.5m and a width equal to the net width between two adjacent rib columns 23. The spacing of the side wall anchor rod bundle 21 in the height direction is 1.5m-3m, and the density is increased within a range of 2m from the top.

[0046] As shown in Figure 1 , a bottom plate secondary lining 33 is arranged at the bottom of the wall space b, and the side wall secondary lining 32 is integrated with the bottom plate secondary lining 33.

[0047] As shown in Figure 1 , the top of the side wall secondary lining 32 has a transversely extending portion 34 extending outward, and the side wall primary support 2 is located below the transversely extending portion 34. In order to improve the structural strength, the transversely extending portion 34 can be extended to the arch foot support beam 4 and integrated with the arch foot support beam 4.

[0048] As shown in Figure 1 , a shield lining 6 is arranged in the wall space b.

[0049] The construction method of the mushroom-shaped cross-section tunnel comprises the following steps:

[0050] Step 1: As shown in Figure 2 , the arch space a is excavated step by step to form an arch excavation portion 71, as shown in Figure 3 , and the arch primary support 1 and the temporary support 8 are timely constructed. The upper end of the temporary support 8 abuts against the arch primary support 1, and the lower end abuts against the bottom of the arch space a. The temporary support 8 is made of I-beam of type 18-22.

[0051] Step 2: As shown in Figure 4 , pre-split blasting is performed on the inner walls of both sides of the wall space b to blast the surrounding rock and the tunnel rock wall bedrock in the unexcavated portion 72 within the range of the side wall primary support 2. The gap caused by the pre-split blasting needs to be more than 3cm.

[0052] After the pre-split blasting on both sides of the side wall primary support 2, the stress of the surrounding rock within the range of the side wall primary support 2 can be fully released before the arch secondary lining 31 is constructed, so as to avoid the deformation or cracking of the arch secondary lining 31 caused by the stress release from the subsequent lower excavation. After the stress of the surrounding rock within the range of the side wall primary support 2 is released, the stress on the support structure within the range of the side wall primary support 2 will be smaller.

[0053] Step 3: After the free deformation and stress release of the side wall primary support 2 at the pre-splitting position 9 are completed, the temporary support 8 is removed, and the secondary lining 31 of the arch portion and the arch foot joist 4 are constructed, as shown in FIG. 3. Figure 5

[0054] Step 4: Under the protection of the secondary lining 31 of the arch portion, the surrounding rock at both sides of the wall space b is excavated in steps, and the side wall primary support 2 is constructed in time, as shown in FIG. 4. Figure 6 The step height of the step-by-step method is not greater than 5 m.

[0055] Step 5: After the wall space b is excavated and the side wall primary support 2 is constructed, the secondary lining 33 of the floor and the secondary lining 32 of the side wall are constructed, and the lifting equipment 5 is installed, as shown in FIG. 5. Figure 7 The lifting equipment 5 directly acts on the secondary lining 32 of the side wall, as shown in FIG. 6. Figure 8

[0056] The lifting equipment 5 in this embodiment is a crane.

[0057] The specific embodiments described herein are merely illustrative of the spirit of the present application. Those skilled in the art to which the present application belongs can make various modifications or supplements to the described specific embodiments or replace them with similar ways, without departing from the spirit of the present application or exceeding the scope defined by the appended claims.​​

Claims

1. A construction method for a mushroom-shaped cross-section tunnel, characterized in that, include: The arch initial support (1) is located in the arch space (a), the arch secondary lining (31) is located inside the arch initial support (1), the arch foot support beam (4), the side wall initial support (2) is located on both sides of the wall space (b), and the side wall secondary lining (32) is located inside the side wall initial support (2). The lower end of the arch secondary lining (31) acts on the arch foot support beam (4) on both sides respectively, and the distance between the arch foot support beam (4) on both sides is greater than the distance between the side wall secondary lining (32) on both sides. The side wall initial support (2) is a plate-rib anchor retaining wall, including rib columns (23) arranged sequentially along the length direction of the wall space (b), a capping beam (22) set at the top of the rib column (23), and a panel (24) set inside several rib columns (23). The ribs (23) and the capping beam (22) are fixed to the side of the wall space (b) by several side wall anchor bundles (21); the ribs (23) are reinforced concrete structures with a thickness of 0.3m to 1m and a width of 0.5m to 1.5m, and the spacing between two adjacent ribs (23) is 2m to 5m; the panel (24) is a concrete structure with a thickness of 0.15m to 0.5m and a width equal to the net width between two adjacent ribs (23); the spacing of the side wall anchor bundles (21) in the height direction is 1.5m to 3m, with the top 2m range being denser; the bottom of the wall space (b) is provided with a secondary lining (33), and the secondary lining (32) of the side wall is integrated with the secondary lining (33); It also includes the following steps: Step 1: Excavate the arch space (a) and promptly implement the initial arch support (1) and temporary support (8). Step 2: Perform pre-splitting blasting on the inner walls of both sides of the space (b) to blast open the surrounding rock and tunnel bedrock of the unexcavated part (72) within the initial support (2) of the side wall; Step 3: After the initial support (2) of the side wall has been free-deformed and the stress has been released at the pre-cracked part (9), remove the temporary support (8) and construct the secondary lining (31) of the arch and the arch foot support beam (4). Step 4: Under the protection of the secondary lining (31) of the arch, the unexcavated part (72) within the space (b) inside the wall is excavated using the distributed step method, and the initial support of the side wall is applied in a timely manner (2): the initial support of the side wall is applied for each step excavated, and finally the entire initial support of the side wall is formed as a whole (2). Step 5: After the excavation of the space inside the wall (b) is completed and the initial support of the side wall (2) is completed, the secondary lining of the bottom plate (33) and the secondary lining of the side wall (32) are constructed, and the lifting equipment (5) is installed.

2. The construction method for a mushroom-shaped cross-section tunnel according to claim 1, characterized in that, The initial arch support (1) includes arch steel support (12), arch shotcrete (13) and system anchor bolts (11).

3. The construction method for a mushroom-shaped cross-section tunnel according to claim 1, characterized in that, The top of the secondary lining (32) of the sidewall has an outwardly extending transverse extension (34), and the initial support (2) of the sidewall is located below the transverse extension (34).

4. The construction method for a mushroom-shaped cross-section tunnel according to claim 1, characterized in that, In step 1, the arch space (a) was excavated in stages.

5. The construction method for a mushroom-shaped cross-section tunnel according to claim 1, characterized in that, In step 2, the crack created by pre-splitting blasting must exceed 3cm.

6. The construction method for a mushroom-shaped cross-section tunnel according to claim 1, characterized in that, In step 4, the height of the steps constructed using the step-by-step method shall not exceed 5m.

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