Construction method of hollow middle wall, hollow middle wall and multi-arch tunnel construction method

Abstract

The invention discloses a hollow type middle wall construction method, a hollow type middle wall and a multi-arch tunnel construction method.The hollow type middle wall construction method comprises the steps of middle pilot tunnel excavation construction, hollow type middle wall construction and main tunnel excavation and construction, and the hollow type middle wall construction method comprises the steps that bottom and vault waterproofing is conducted in a middle pilot tunnel; an inverted trapezoidal steel reinforced concrete plate with a thick middle part and two thin ends is arranged at the junction of an upper step and a lower step of the middle pilot tunnel as a temporary inverted arch transverse support, and steel vertical support walls are arranged at the upper part and the lower part of the temporary inverted arch transverse support; breaking concrete at the middle thick part of an inverted trapezoidal steel reinforced concrete slab of the temporary inverted arch transverse support in sections, and retaining the steel in the concrete as a steel transverse support wall; reinforcing steel bars of the middle wall foundation, the wall body and the vault are bound, and a hollow structure is defined by the reinforcing steel bars of the middle wall foundation, the wall body and the vault; according to the hollow type middle wall, the structural stability can be improved, the structure is simplified, and the space utilization rate is high.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel construction, and particularly relates to a construction method for a hollow middle wall, a hollow middle wall, and a construction method for a connected-arch tunnel. Background Art

[0002] As an important part of modern transportation infrastructure, the progress of the design and construction technology of connected-arch tunnels is the key to ensuring traffic safety and efficiency. In the design of connected-arch tunnels, the form of the middle wall structure has a decisive influence on its overall performance.

[0003] Currently, the common middle wall structures of connected-arch tunnels are mainly divided into two types: integral type and composite type. However, their middle walls are all solid walls, and there is still a large room for optimization in terms of structural stress state, construction cost, construction safety, later maintenance, and functional diversity. The main disadvantages of solid middle walls include the following points: (1) Thin thickness: The thickness of the solid middle wall is relatively thin, and its overall stability and anti-overturning ability are weak. (2) Large self-weight: The self-weight of the solid structure is large, which will have an adverse impact on the stability of the tunnel. Especially in areas with poor geological conditions, additional foundation reinforcement measures are required to ensure the safety of the tunnel. (3) Single function: The distance between the left and right holes of the connected-arch tunnel is relatively close, and the structural settings required for functions such as internal pipe trenches and lines in the tunnel can be considered as a whole. The solid wall fails to fully play its functional role. (4) Structural safety: During the actual construction process, due to the slump and pouring quality of concrete, voids will occur at the top of the middle wall. Usually, the solution is to drill holes and grout from the junction of the middle pilot tunnel and the initial support of the main tunnel during the excavation of the main tunnel. This method is complex to construct and has poor effects; in addition, the steel plates embedded at the junction of the middle wall and the tunnel structure will be buried by concrete during the actual construction process, and the surface concrete needs to be chiseled off later to expose the embedded steel plates, which also destroys the integrity of the middle wall.

[0004] Based on the above considerations, the present invention designs the solid middle wall into a hollow body, which can be improved in terms of structural stress state, construction cost, construction safety, later operation and maintenance, and functional diversity. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present application provides a construction method for a hollow middle wall, a hollow middle wall, and a construction method for a connected-arch tunnel, which designs the solid middle wall into a hollow body, and can be improved in terms of structural stress state, construction cost, construction safety, later operation and maintenance, and functional diversity.

[0006] In order to achieve the above object, the present application adopts the following technical solutions:

[0007] A construction method for a hollow middle wall includes the following steps:

[0008] Apply waterproofing to the bottom and arch crown in the pilot tunnel. At the junction of the upper and lower benches of the pilot tunnel, there is an inverted trapezoidal steel-concrete slab with a thick middle and thin ends as a temporary invert transverse support. There are vertical steel support walls both above and below the temporary invert transverse support.

[0009] Segmentally break the concrete at the thick middle part of the inverted trapezoidal steel-concrete slab of the temporary invert transverse support, and retain the steel in it as a steel transverse support wall.

[0010] Bind the steel bars of the middle wall foundation, wall body and arch crown. The steel bars of the middle wall foundation, the wall body and the arch crown enclose a hollow structure; and

[0011] Pour the concrete of the middle wall foundation, the wall body and the arch crown respectively to form the hollow middle wall.

[0012] Furthermore, it also includes:

[0013] Segmentally break the lower part below the vertical steel support wall of the temporary invert transverse support, and cast in-situ cover plates.

[0014] Furthermore, it also includes:

[0015] Remove the concrete at the thin ends of the inverted trapezoidal steel-concrete slab of the temporary invert transverse support, and cut off the steel at the thin ends of the inverted trapezoidal steel-concrete slab of the temporary invert transverse support along the surface of the wall body of the hollow middle wall.

[0016] Furthermore, it also includes:

[0017] When pouring the concrete of the middle wall foundation, the wall body and the arch crown, the hollow structure has four corners. Reserve steel plate embedding grooves at the four corners of the hollow structure, and evenly arrange embedded steel bars in the grooves. After the concrete pouring of the middle wall foundation, the wall body and the arch crown is completed, the embedded steel bars are flush with the outer surface of the hollow middle wall;

[0018] Apply adhesive to the periphery and bottom of the perforated steel plate and insert it into the embedded steel bars; and

[0019] Weld the steel plate and the embedded steel bars into one body by means of perforated plug welding.

[0020] In addition, the present application also provides a hollow middle wall, including:

[0021] Middle wall foundation concrete, wall body concrete and arch crown concrete. The middle wall foundation concrete, wall body concrete and arch crown concrete enclose a hollow structure;

[0022] A steel transverse support wall is located in the vertical middle of the hollow structure and extends left and right to the outer surface of the wall concrete; and

[0023] The steel vertical supporting wall is located in the horizontal middle part of the hollow structure, and the upper part extends to the upper surface of the vault concrete and the lower part extends to the lower surface of the middle wall foundation concrete.

[0024] Furthermore, it also includes:

[0025] The cover plate is located at the lower part of the hollow structure.

[0026] A drainage area is formed below the cover plate, a weak current area and a fire protection area are formed between the cover plate and the steel transverse supporting wall, and a strong current area is formed above the steel transverse supporting wall.

[0027] Furthermore, a drainage pipe and a vault grouting pipe are arranged in the steel vertical supporting wall, and the drainage pipe connects the vault and the drainage area.

[0028] Furthermore, fire main pipe channel steel supports are arranged on the cover plate at longitudinal intervals, the fire main pipe channel steel supports are fixed to the cover plate by expansion bolts, and fire main pipes are arranged on the fire main pipe channel steel supports by using arc-shaped double-headed threaded rods and bolts.

[0029] Furthermore, a bracket is provided on the inner wall of the hollow structure, and an electric power equipment box is provided on the bracket;

[0030] A pre-buried galvanized steel pipe is arranged in the wall concrete, and the pre-buried galvanized steel pipe is connected to the power equipment box to transport wires and cables.

[0031] In addition, the present application also provides a method for constructing a hollow middle wall multi-arch tunnel, comprising:

[0032] The excavation construction of the middle guide tunnel includes the excavation construction of the upper step and the excavation construction of the lower step; wherein, the excavation construction of the upper step includes excavating the soil body by adopting the circular method, constructing an advanced small guide tube in the middle, constructing drug-coiled anchor rods on both sides, erecting a steel arch frame, constructing locking anchor rods and spraying concrete, excavating the reserved core soil, constructing an inverted trapezoidal steel concrete slab with a thick middle and thin ends as a temporary inverted arch transverse support at the junction of the upper and lower steps, and constructing a steel vertical support wall on the upper part of the temporary inverted arch transverse support; the excavation construction of the lower step starts after the upper step is excavated for a predetermined distance, including excavating the soil body by adopting the circular method, reserving core soil, constructing drug-coiled anchor rods, erecting a steel arch frame, constructing locking anchor rods and spraying concrete, excavating the reserved core soil, constructing a leveling layer at the bottom, and constructing a steel vertical support wall in the middle of the leveling layer; the excavation construction of the upper step and the excavation construction of the lower step are synchronously excavated with a construction step distance of 5-6m until the middle guide tunnel is formed;

[0033] Construction of the hollow middle wall, and the construction of the hollow middle wall is carried out by using the construction method as described above; and

[0034] The main tunnel is excavated and constructed by using the CRD method.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] The present application improves the stress state, construction cost and construction safety of the middle wall, reduces the maintenance cost during the tunnel operation period, improves the utilization efficiency of the middle wall space, and strengthens the multifunctionality of the middle wall.

[0037] The specific advantages are as follows:

[0038] 1. Reducing self-weight: Compared with the solid wall, the design of the hollow wall can significantly reduce the self-weight of the structure, reduce the pressure on the foundation, and is beneficial to reducing the project cost and construction difficulty. It is calculated that the self-weight can be reduced by about 30%.

[0039] 2. Improving structural stability: The hollow wall can effectively disperse the load and improve the overall structural stability. During natural disasters such as earthquakes, the hollow wall can absorb part of the energy and reduce the impact on the tunnel structure.

[0040] 3. Simplifying the structure: After reducing the cable trench and drainage ditch, the internal structure of the tunnel is simpler, reducing the construction complexity and cost.

[0041] 4. High space utilization rate: By canceling the trench under the tunnel pavement, the available space inside the tunnel increases, which can be used for other facilities or to expand the driving space. Or the design elevation of the tunnel internal pavement can be reduced, and at the same time, the invert and arch crown contour lines can be adjusted accordingly. On the basis of ensuring the building clearance, the cross-sectional dimension can be reduced, thereby reducing the consumption of materials such as surrounding rock excavation and support. Among them, the surrounding rock excavation volume can be reduced by about 13%. Description of the Drawings

[0042] The drawings described herein are used to provide a further understanding of the present application, and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application, but do not constitute an improper limitation to the present application. In the drawings:

[0043] Figure 1 is a schematic diagram of the construction process of the hollow middle wall;

[0044] Figure 2 is a schematic diagram of the construction process of the middle pilot tunnel excavation;

[0045] Figure 3 is a schematic diagram of the embedded steel plate;

[0046] Figure 4Schematic diagram of steel plate embedment with steel plate inlay groove + perforation plug welding;

[0047] Figure 5 Schematic diagram of integral hollow middle wall;

[0048] Figure 6 Schematic diagram of composite hollow middle wall;

[0049] Figure 7(a) shows the schematic diagram of the central drainage ditch in the drainage area Figure 1 ;

[0050] Figure 7(b) shows the schematic diagram of the central drainage ditch in the drainage area Figure 2 ;

[0051] Figure 8 Schematic diagram of the construction process of the middle pilot tunnel excavation

[0052] Figure 9 Schematic diagram of the fire protection area of the integral hollow middle wall;

[0053] Figure 10 Schematic diagram of the fire protection area of the composite hollow middle wall;

[0054] Figure 11 Schematic diagram of the fixation of the main fire protection pipe and channel steel in the fire protection area

[0055] Figure 12 Schematic diagram of the design of the equipment box in the power area of the integral hollow middle wall;

[0056] Figure 13 Schematic diagram of the design of the equipment box in the power area of the composite hollow middle wall;

[0057] Figure 14 Schematic diagram of the entrance and exit of the hollow middle wall;

[0058] Figure 15 Schematic diagram of the design of grouting for the embedded steel pipe in the arch crown. Detailed implementation manners

[0059] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application.

[0060] In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device, element, module, system, platform or device referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application. The following description of the present application is only understood as a description of individual embodiments of the technical solution of the present application. Other embodiments are not reflected in the following description, but this does not mean that the present application excludes these other embodiments. The technical solution of the present application is not limited to the specific implementation manners described below, and the protection scope of the present application is not limited to only the specific implementation manners described below. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0061] It should be noted that if terms such as "first", "second", etc. appear in the specification, claims and the above-mentioned drawings of the present application, such descriptions are only used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0062] In some embodiments, as Figures 1 - 15 shown, a construction method of a hollow middle wall includes the following steps:

[0063] Construct bottom and arch waterproofing in the middle pilot tunnel. At the junction of the upper and lower benches of the middle pilot tunnel, an inverted trapezoidal steel-concrete slab with a thick middle and thin ends is provided as a temporary inverted arch transverse support, and steel vertical support walls are provided both above and below the temporary inverted arch transverse support;

[0064] Among them, the temporary inverted arch transverse support and the steel vertical support wall are as Figure 2 shown. At the junction of the upper and lower benches, an inverted trapezoidal steel-concrete slab with a thickness of 38 cm in the middle and 20 cm at both ends is constructed as the first temporary inverted arch transverse support 6 and the second temporary inverted arch transverse support 7; a first steel vertical support wall 8 with a thickness of 20 cm is constructed above the first temporary inverted arch transverse support 6, and a second steel vertical support wall 14 with a thickness of 20 cm is constructed at the middle position of the leveling layer 13.

[0065] Segmentally break the concrete at the middle-thick part of the inverted trapezoidal steel-concrete slab of the first temporary inverted-arch transverse support 6 and the second temporary inverted-arch transverse support 7, and retain the steel shapes therein as the steel transverse support walls;

[0066] Among them, as Figure 1 shown, segmentally break the concrete of the 6-1 and 6-2 parts of the first temporary inverted-arch transverse support 6, and retain the steel shapes therein. The 6-1 of the first temporary inverted-arch transverse support 6 is 55 cm wide, and the 6-2 of the first temporary inverted-arch transverse support 6 is 20 cm wide.

[0067] Bind the steel bars of the middle-wall foundation 15, the wall body 16, and the arch top 17. The steel bars of the middle-wall foundation 15, the wall body 16, and the arch top 17 enclose a hollow structure;

[0068] Pour the concrete of the middle-wall foundation 15, the wall body 16, and the arch top 17 respectively to form the hollow middle wall.

[0069] In some embodiments, it further includes the steps of:

[0070] Segmentally break the lower part below the second steel vertical support wall 14 at the lower part of the first temporary inverted-arch transverse support 6, and cast the cover plate 18 in situ, as shown in Fig. 7(b).

[0071] In some embodiments, it further includes the steps of:

[0072] Demolish the concrete at the thin parts at both ends of the second temporary inverted-arch transverse support 7, that is, the inverted trapezoidal steel-concrete slab, and cut off the steel shape of the second temporary inverted-arch transverse support 7 along the surface of the wall body 16 of the hollow middle wall, as Figure 1 shown, that is, demolish the second temporary inverted-arch transverse support 7 and cut off its steel shape along the surface of the middle wall 16.

[0073] In some embodiments, it further includes the steps of:

[0074] When pouring the concrete of the middle-wall foundation 15, the wall body 16, and the arch top 17, the hollow structure has four corners. Reserve steel plate embedding grooves 24 at the four corners of the hollow structure, and evenly arrange embedded steel bars 23 in the steel plate embedding grooves 24. After the concrete pouring of the middle-wall foundation 15, the wall body 16, and the arch top 17 is completed, the embedded steel bars 23 are flush with the outer surface of the hollow middle wall;

[0075] Apply adhesive to the periphery and lower part of the perforated steel plate 21 and insert it into the embedded steel bars 23; and

[0076] Weld the steel plate 21 and the embedded steel bars 23 into one body by means of perforated plug welding.

[0077] Specifically, as Figure 3As shown, taking the composite hollow middle wall as an example, it is necessary to pre-embed steel plates 21 with a size of 36×36×1 cm (length×width×thickness) at the four corners of the middle wall foundation 15 for connection with the primary support steel arch of the main tunnel. In actual construction, generally, after welding and fixing the steel plate 21 on the pre-embedded middle wall foundation 15 to the steel reinforcement cage of the middle wall, formwork is erected and filled with cement concrete. However, in this case, the pre-embedded steel plate 21 is usually buried in the concrete, and it is very difficult to make the surface of the steel plate 21 exactly flush with the surface of the concrete. Moreover, when connecting with the primary support steel arch of the main tunnel in the later stage, the surface concrete needs to be chiseled to expose the steel plate 21, which is not conducive to the integrity and strength of the structure.

[0078] Therefore, this application proposes a steel plate pre-embedding technology of reserved steel plate embedding groove + perforated plug welding. As Figure 4 shown, when pouring the middle wall foundation 15, a steel plate embedding groove 24 with a size of 36×36×1 cm (length×width×depth) is left vacant at the position of the pre-embedded steel plate 21. Nine pre-embedded steel bars 23 with a diameter of 20 mm, an embedding length of 50 cm, and an exposed length of 1 cm are evenly arranged in the groove at intervals of 10 cm and a distance of 8 cm from the groove wall. The pre-embedded steel bars 23 are just flush with the outer surface of the middle wall foundation 15, and perforations 22 are provided on the steel plate 21. When welding the steel plate 21, A-level glue is applied to the periphery and the lower part of the steel plate 21 with perforations 22, and then the steel plate 21 is inserted into the pre-embedded steel bars 23 and welded into one body by means of perforated plug welding. In this way, it can fully ensure that the pre-embedded steel plate 21 is welded into a whole with the middle wall foundation 15, and it will not damage the structural integrity and strength of the middle wall foundation 15, and can solve the problem that the pre-embedded steel plate 21 at the lap joint of the middle wall foundation 15 and the tunnel structure will be buried by concrete during the actual construction process.

[0079] In some embodiments, as Figure 5 、 Figure 6 shown, this application also provides a specific hollow middle wall 301, including:

[0080] Middle wall foundation concrete, wall body concrete and arch top concrete, and the middle wall foundation concrete, wall body concrete and arch top concrete enclose a hollow structure;

[0081] Steel section horizontal support wall, located at the vertical middle part of the hollow structure and extending left and right to the outer surface of the wall body concrete; and

[0082] Steel section vertical support wall, located at the horizontal middle part of the hollow structure, with the upper part extending to the upper surface of the arch top concrete and the lower part extending to the lower surface of the middle wall foundation 15 concrete; specifically, it can be the first steel section vertical support wall 8 and the second steel section vertical support wall 14.

[0083] Specifically, as Figure 5 and Figure 6 shown, it is divided into Figure 5The overall hollow middle wall and Figure 6 The composite hollow middle wall. The plane size of the overall hollow middle wall is 650×300 cm (height × width), and the plane size of the composite hollow middle wall is 700×290 cm (height × width). The functional zones of the hollow middle wall from bottom to top are: the drainage zone 309, the weak electricity zone and the fire protection zone 307, and the strong electricity zone 306, with a clear height size of 510×170 cm (height × width).

[0084] Among them, the cast-in-place cover plate 308 of the drainage ditch can be used as the floor of the lower weak electricity zone and the fire protection zone 307, and also as the transverse support of the hollow middle wall; the first temporary inverted arch transverse support 6 constructed during the excavation of the upper soil body in the middle pilot tunnel can be used as the floor slab of the upper strong electricity zone 306 and the transverse support of the hollow middle wall. The above structures can all serve multiple functions and increase the overall strength of the middle wall structure. Among them, the first steel vertical support wall 8 is embedded with a drain pipe 304 and a crown grouting pipe. The drain pipe 304 can drain the surrounding rock water at the crown 17 to the bottom drainage zone 309, and the embedded crown grouting pipe can solve the problem of voids in the crown of the pilot tunnel.

[0085] In some embodiments, it further includes:

[0086] A cover plate 18, located at the lower part inside the hollow structure.

[0087] A drainage zone 309 is formed below the cover plate 18, a weak electricity zone and a fire protection zone 307 are formed between the cover plate 18 and the steel transverse support wall, and a strong electricity zone is formed above the steel transverse support wall.

[0088] Specifically, as Figure 7(a) and 7(b) shown, the drainage zone 309 is a rectangular drainage ditch, separately arranged as 3091 and 3092 on the left and right tunnels, with a clear height size of 70×65 cm (height × width), and separated by the second steel vertical support wall 14 in the middle; the cover of the drainage ditch can be cast in place with reinforced concrete and also serve as the transverse support of the middle wall, as shown in Fig. 7(a). The cover of the drainage ditch can also be replaced by the cover plate 18 with holes reserved every 10 m for the maintenance of the drainage ditch. The size of the cover plate 18 is 149×50×12 cm, as shown in Fig. 7(b).

[0089] As Figure 8 shown, HPDE drain pipes 304 are embedded at a longitudinal spacing of 10 m in the first steel vertical support wall 8 and the second steel vertical support wall 14, and crown grouting pipes 81 are embedded at a longitudinal spacing of 3 m at the top of the first steel vertical support wall 8, which can effectively solve the problems of imperfect grouting at the top 17 of the middle wall and voids in the lining.

[0090] ​In some embodiments, fire main channel steel supports 85 are longitudinally spaced on the cover plate 18, and the fire main channel steel supports 85 are fixed to the cover plate 18 by expansion bolts. A fire main 84 is arranged on the fire main channel steel supports 85 by means of arc-shaped double-headed threaded rods 86 and bolts 87.

[0091] Specifically, as Figure 9 , Figure 10 , Figure 11 shown, the fire main channel steel supports 85 are fixed to the cover plate 18 of the cast-in-place drainage ditch by expansion bolts, and are arranged at a longitudinal spacing of 10 m; the fire main 84 is erected on the fire main channel steel supports 85, and is fixed to the fire main channel steel supports 85 by M16 arc-shaped double-headed threaded rods 86 through M16 bolts 87; when constructing the integral hollow middle wall, fire chambers 82 with dimensions of 280×100×30 cm need to be made every 50 m along the longitudinal direction of the tunnel; when constructing the composite hollow middle wall, there is no need to reserve fire chambers 82, and the fire chambers 82 are reserved when the secondary lining is actively constructed; fire branch pipes 83 are reserved every 50 m along the longitudinal direction of the fire main 84 for connecting the fire-fighting equipment in the fire chambers 82.

[0092] In some embodiments, as Figure 5 shown, brackets 305 are arranged on the inner wall of the hollow structure. As Figure 12 and Figure 13 shown, power equipment boxes 3051 are arranged on the brackets 305;

[0093] Embedded galvanized steel pipes 3052 are arranged in the wall concrete, and the embedded galvanized steel pipes 3052 are connected to the power equipment boxes 3051 to convey wires and cables.

[0094] Specifically, as Figure 5 , Figure 6 , Figure 12 , Figure 13 shown, in this application, only according to the actual power distribution requirements, the power equipment boxes 3051 are erected on the brackets 305, and the embedded galvanized steel pipes 3052 are arranged in the middle wall foundation 15 to convey wires and cables.

[0095] In some embodiments, as Figure 14 shown, holes are opened on both sides of the middle wall at the midpoint position of the tunnel, and the opening size is 150×256 cm (width×height). After the holes are opened, fireproof rolling doors 3053 are installed. This can be used as an entrance to the inner space of the middle wall, and can also be used as a sidewalk and escape passage during the later operation period.

[0096] In some embodiments, the present application also provides a construction method for a connected-arch tunnel with a hollow middle wall, including:

[0097] The excavation construction of the middle guide tunnel includes the excavation construction of the upper step and the excavation construction of the lower step; the excavation construction of the upper step includes excavating the soil body by adopting the circular method, constructing an advanced small guide tube in the middle, constructing drug-coiled anchor rods on both sides, erecting a steel arch frame, constructing locking anchor rods and spraying concrete, excavating the reserved core soil, constructing an inverted trapezoidal steel concrete slab with a thick middle and thin ends as a temporary inverted arch transverse support at the junction of the upper and lower steps, and constructing a steel vertical support wall on the upper part of the temporary inverted arch transverse support; the excavation construction of the lower step starts after the upper step is excavated for a predetermined distance, including excavating the soil body by adopting the circular method, reserving core soil, constructing drug-coiled anchor rods, erecting a steel arch frame, constructing locking anchor rods and spraying concrete, excavating the reserved core soil, constructing a leveling layer at the bottom, and constructing a steel vertical support wall in the middle of the leveling layer; the excavation construction of the upper step and the excavation construction of the lower step are synchronously excavated with a construction step distance of 5-6m until the middle guide tunnel is formed;

[0098] Specifically, Figure 2 As shown, the excavation construction of the upper step:

[0099] (1) The upper step uses the circular method to excavate the soil 1, leaving a core soil 2 3-4 m long;

[0100] (2) A small leading guide tube 3 is constructed in the middle, and drug-coiled anchor rods 4 are constructed on both sides;

[0101] (3) Erect the steel arch frame, construct the anchor bolts and spray concrete 5;

[0102] (4) Excavate the reserved core soil 2, and construct the first temporary inverted arch transverse support 6 and the second temporary inverted arch transverse support 7 of the inverted trapezoidal steel concrete slab with a thickness of 38 cm in the middle and 20 cm at both ends at the junction of the upper and lower steps. In the later stage, the first temporary inverted arch transverse support 6 of the steel concrete slab with a thickness of 38 cm in the middle will also serve as the transverse support of the middle area of ​​the hollow wall and the floor slab of the power area;

[0103] (5) A 20 cm thick first steel vertical support wall 8 is constructed on the upper part of the first temporary inverted arch transverse support 6. It can be used as the vertical support for the initial support of the middle guide tunnel in the early stage, and can be used as the permanent vertical support for the middle wall of the multi-arch tunnel and the isolation wall on the left and right sides of the hollow middle wall in the later stage. HPDE drainage pipes are pre-buried in the first steel vertical support wall 8 to drain the surrounding rock water of the middle guide tunnel arch top 17 to the drainage ditch. The vault grouting pipe 81 is prepared for subsequent vault grouting;

[0104] When the upper step is excavated 5-6m, the lower step construction begins:

[0105] (1) The lower step is excavated using the circular method 9, and a core soil 10 with a length of 3-4 m is reserved;

[0106] (2) Construction of drug coil anchor rod 11;

[0107] (3) Erect the steel arch frame, construct the locking foot bolts for construction and spray concrete 12;

[0108] (4) Excavate and reserve the core soil 10, and construct a leveling layer 13 with a thickness of 20 cm at the bottom;

[0109] (5) Construct the second vertical steel support wall 14 with a thickness of 20 cm at the middle position of the leveling layer. It can be used as the vertical support for the first temporary inverted arch transverse support 6 in the early stage, and can be used as the permanent vertical support for the middle wall of the double - arch tunnel and the isolation wall on both sides of the hollow middle wall in the later stage;

[0110] Keep a construction step distance of 5 - 6 m for the upper and lower benches of the pilot tunnel and excavate synchronously until breakthrough.

[0111] For the construction of the hollow middle wall, as Figure 1 shown,

[0112] (1) Apply waterproofing at the bottom and arch crown;

[0113] (2) Demolish the concrete of parts 6 - 1 and 6 - 2 of the first temporary inverted arch transverse support 6 in sections, and retain the steel in it. Part 6 - 1 of the first temporary inverted arch transverse support 6 is 55 cm wide, and part 6 - 2 of the first temporary inverted arch transverse support 6 is 20 cm wide;

[0114] (3) Bind the steel bars of the middle wall foundation 15, wall body 16, and arch crown 17, and pour the concrete of the middle wall foundation 15, wall body 16, and arch crown 17 respectively;

[0115] (4) Demolish part 14 - 1 of the second vertical steel support 14 in sections, and cast - in - place the cover plate 18. The cover plate 18 can also serve as the transverse support for the bottom area of the hollow middle wall;

[0116] (5) Remove the second temporary inverted arch transverse support 7 and cut off the steel in it along the surface of the middle wall.

[0117] Adopt the CRD method for the excavation and construction of the main tunnel.

[0118] In the present application, compared with solid walls, the hollow wall design can significantly reduce the structural self-weight, decrease the pressure on the foundation, which is beneficial to reducing the project cost and construction difficulty, and the self-weight can be reduced by about 30%; it can effectively disperse the load and improve the stability of the overall structure. When natural disasters such as earthquakes occur, the hollow wall can absorb part of the energy and reduce the impact on the tunnel structure; after eliminating the cable trench and drainage ditch, the internal structure of the tunnel is simpler, reducing the construction complexity and cost; in this application, the trench under the tunnel pavement is cancelled, increasing the available space inside the tunnel, which can be used for other facilities or to expand the driving space, or the design elevation of the tunnel internal pavement can be reduced, and at the same time, the invert and crown contour lines can be adjusted accordingly. On the basis of ensuring the building clearance, the cross-section size can be reduced, thereby reducing the consumption of materials such as surrounding rock excavation and support. Among them, the surrounding rock excavation volume 4012 can be reduced by about 13%, as Figure 15 shown, 4010 is the original pavement surface, 4011 is the adjusted pavement surface, 4013 is the original internal contour section, 4014 is the adjusted internal contour section, 4015 is the original building clearance, and 4016 is the adjusted building clearance.

[0119] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0120] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the protection scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A construction method of a hollow middle wall, characterized in that, It includes the following steps: Apply bottom and arch waterproofing in the middle pilot tunnel. At the junction of the upper and lower benches of the middle pilot tunnel, an inverted trapezoidal steel-concrete slab with a thick middle and thin ends is provided as a temporary invert transverse support. Steel vertical support walls are provided both above and below the temporary invert transverse support. Segmentally break the concrete at the thick middle part of the inverted trapezoidal steel-concrete slab of the temporary invert transverse support, and retain the steel in it as a steel transverse support wall. Bind the steel bars of the middle wall foundation, wall body and arch top. The steel bars of the middle wall foundation, the wall body and the arch top enclose a hollow structure; and pour the concrete of the middle wall foundation, the wall body and the arch top respectively to form the hollow middle wall.

2. The construction method of a hollow middle wall according to claim 1, characterized in that It also includes the step: Segmentally break the lower part below the steel vertical support wall of the temporary invert transverse support and cast the cover plate in-situ.

3. The construction method of a hollow middle wall according to claim 2, characterized in that, It also includes the step: Remove the concrete at the thin ends of the inverted trapezoidal steel-concrete slab of the temporary invert transverse support and cut off the steel at the thin ends of the inverted trapezoidal steel-concrete slab of the temporary invert transverse support along the surface of the wall body of the hollow middle wall.

4. The construction method of a hollow middle wall according to any one of claims 1-3, characterized in that, It also includes the step: When pouring the concrete of the middle wall foundation, the wall body and the arch top, the hollow structure has four corners. Reserve steel plate embedding grooves at the four corners of the hollow structure, and evenly arrange embedded steel bars in the grooves. After the concrete pouring of the middle wall foundation, the wall body and the arch top is completed, the embedded steel bars are flush with the outer surface of the hollow middle wall. Apply adhesive around and below the perforated steel plate and insert it into the embedded steel bars; and weld the steel plate and the embedded steel bars into one by means of perforated plug welding.

5. A hollow middle wall, characterized in that, It includes: Middle wall foundation concrete, wall body concrete and arch top concrete. The middle wall foundation concrete, wall body concrete and arch top concrete enclose a hollow structure. Steel transverse support wall, located at the vertical middle part of the hollow structure and extending left and right to the outer surface of the wall body concrete. And Steel vertical support wall, located at the horizontal middle part of the hollow structure, with the upper part extending to the upper surface of the arch top concrete and the lower part extending to the lower surface of the middle wall foundation concrete.

6. The hollow middle wall according to claim 5, characterized in that, It also includes: Cover plate, located at the lower part inside the hollow structure. A drainage area is formed below the cover plate, a weak current area and a fire protection area are formed between the cover plate and the steel transverse support wall, and a strong current area is formed above the steel transverse support wall.

7. A hollow middle wall according to claim 6, wherein: A drain pipe and an arch top grouting pipe are arranged in the steel vertical support wall, and the drain pipe communicates the arch top and the drainage area.

8. A hollow middle wall according to claim 6, wherein: Fire main channel steel supports are longitudinally spaced on the cover plate. The fire main channel steel supports are fixed on the cover plate by expansion bolts, and a fire main is arranged on the fire main channel steel supports by means of arc-shaped double-headed threaded rods and bolts.

9. A hollow middle wall according to claim 6, wherein: Brackets are arranged on the inner wall of the hollow structure, and power equipment boxes are arranged on the brackets. Embedded galvanized steel pipes are provided in the wall concrete, and the embedded galvanized steel pipes are connected to the power equipment box to convey wires and cables.

10. A construction method for a multi-arch tunnel with a hollow middle wall, characterized in that, It includes the following steps: Excavation construction of the middle pilot tunnel, including upper bench excavation construction and lower bench excavation construction; wherein, the upper bench excavation construction includes excavating the soil body by the circular method, constructing advanced small pipes in the middle, constructing cartridge bolts on both sides, erecting steel arch frames, constructing locking foot bolts and spraying concrete, excavating and reserving the core soil, constructing an inverted trapezoidal steel-concrete slab with a thick middle and thin ends as a temporary inverted arch transverse support at the junction of the upper and lower benches, and constructing a steel vertical support wall on the upper part of the temporary inverted arch transverse support; the lower bench excavation construction starts after a predetermined distance of the upper bench excavation, including excavating the soil body by the circular method, reserving the core soil, constructing cartridge bolts, erecting steel arch frames, constructing locking foot bolts and spraying concrete, excavating and reserving the core soil, and constructing a leveling layer at the bottom, and constructing a steel vertical support wall at the middle position of the leveling layer; the upper bench excavation construction and the lower bench excavation construction are synchronously excavated with a construction step distance of 5-6 m until the middle pilot tunnel is formed through; Construction of the hollow middle wall, and the construction of the hollow middle wall is carried out by using the construction method described in any one of claims 1-4; and the main tunnel is excavated and constructed by using the CRD method.

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