Tunnel entering construction method for steep rock-soil body tunnel in complex terrain

Abstract

The invention relates to the technical field of tunnels, and provides a complex terrain steep rock-soil body tunnel entering construction method which comprises the following steps: excavating a mountain body on the outer side of a tunnel, constructing an unsymmetrical pressure retaining wall on the outer side of the tunnel, performing back pressure backfilling in the area where the unsymmetrical pressure retaining wall is located, arranging a transverse pipe shed along a pipe shed guide pipe, and arranging an advanced middle pipe shed from the front side of the tunnel. A rock-soil body in the range of a tunnel main hole is excavated, a lining structure is constructed, an advanced middle pipe shed is located on the inner side of a bias pressure retaining wall, excavation and supporting are conducted in sequence according to the sequence of an upper pilot tunnel, upper and lower steps of a lower left pilot tunnel and upper and lower steps of a lower right pilot tunnel, and the influence of mountain bias pressure is reduced. The three-dimensional supporting system is formed by adopting the bias retaining wall, the transverse pipe shed and the advanced middle pipe shed, safe and reasonable construction procedures are combined, the safety and construction efficiency of tunnel entering construction of the steep rock-soil body tunnel in the complex terrain can be effectively guaranteed, large digging is not needed, and the original terrain and the ecological environment are protected to the maximum extent.

Description

Technical Field

[0001] The invention relates to the technical field of tunnels, in particular to a tunnel entry construction method for steep rock and soil bodies in complex terrain. Background Art

[0002] With the continuous development of the economy, the requirements for the linear indicators and vehicle traffic capacity of highways are getting higher and higher, which leads to the fact that the entrances of large-span tunnels of highways will inevitably pass through various steep natural slopes (slope>45°), nature reserves or water sources and other ecologically sensitive areas. Steep rock and soil, that is, the rock form with steep front and severe lateral bias of the tunnel, often has the problems of shallow buried bias and poor slope stability in the entrance section of this type of tunnel. The construction process of the tunnel is difficult, and there are many diseases in the operation stage. Therefore, the tunnel entrance can not only safely pass through the steep rock and soil, but also avoid large-scale excavation on the surface of the mountain, and maximize the protection of the original terrain and ecological environment, which is a problem that needs to be solved in tunnel design and construction.

[0003] At present, the conventional entry method for steep rock and soil tunnels is mainly: large excavation and slope reduction + open hole construction method. This method has too much impact on the existing natural conditions and is not environmentally friendly. In addition, in the later operation stage of large excavation, as the slopes are exposed, they are easily eroded and infiltrated by rainwater, which can easily induce landslides and seriously threaten the operational safety of existing roads.

[0004] In view of this, it is necessary to propose a tunnel construction method for steep rock and soil in complex terrain to solve or at least alleviate the above defects. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for constructing tunnels in steep rock and soil bodies with complex terrain, so as to solve the technical problem in the prior art that large excavation and slope reduction are used for tunnel construction in steep rock and soil bodies, which is prone to induce landslides and seriously threatens the operational safety of existing roads.

[0006] To achieve the above object, the present invention provides a method for tunnel construction in steep rock and soil with complex terrain, comprising the following steps: S1, excavating the outer side slope of the tunnel and constructing a bias retaining wall on the outer side of the tunnel; wherein a transverse pipe shed guide pipe is reserved on the top of the bias retaining wall; S2, performing backfilling with counter pressure in the area where the bias retaining wall is located; S3, installing a transverse pipe rack along the transverse pipe rack guide pipe; wherein the transverse pipe rack includes a locking end and an anchoring end arranged along the transverse extension direction of the tunnel, the locking end is connected to the bias retaining wall, and the anchoring end is anchored into the surrounding rock; S4, set up an advanced middle pipe shed from the front of the tunnel, and excavate and support the main tunnel of the tunnel in the order of upper guide tunnel, upper step of lower left guide tunnel, lower step of lower left guide tunnel, upper step of lower right guide tunnel, and lower step of lower right guide tunnel, remove the temporary support and pour the secondary lining; wherein, the advanced middle pipe shed is arranged between the main tunnel of the tunnel and the transverse pipe shed, and the advanced middle pipe shed is located on the inner side of the bias retaining wall.

[0007] Preferably, the step S1 specifically includes the following steps: The rock and soil in the area where the bias retaining wall is located is excavated according to the temporary slope, and the bias retaining wall is constructed; wherein the bias retaining wall includes an initial support arch section and a pipe-roof connection section located above the initial support arch section; wherein the pipe-roof connection section is pre-reserved with the transverse pipe-roof guide pipe, the outer wall surface of the pipe-roof connection section is pre-embedded with a first connecting steel plate, and the locking end is connected to the first connecting steel plate; the inner wall surface of the initial support arch section is pre-embedded with a steel arch frame matching the tunnel contour line, and a step surface for overlapping the lining structure is formed between the initial support arch section and the pipe-roof connection section, and a second connecting steel plate is reserved at the step surface.

[0008] Preferably, the step S4 specifically includes the following steps: S41, constructing the first left-side advanced middle pipe shed in the upper pilot tunnel area from the front of the tunnel, excavating the rock and soil in the upper pilot tunnel area, constructing anchor rods and the first side wall initial support in the upper pilot tunnel area, and then constructing a first temporary invert to close the initial support of the upper pilot tunnel area; wherein one end of the first temporary invert is connected to the steel arch frame, and the other end is connected to the first side wall initial support, and one end of the first side wall initial support is connected to the second connecting steel plate; S42, constructing a second left-side advanced middle pipe shed in the upper step area of ​​the lower left pilot tunnel from the front of the tunnel, excavating the rock and soil in the upper step area of ​​the lower left pilot tunnel, constructing anchor rods, a second side wall initial support and a first vertical temporary support in the upper step area of ​​the lower left pilot tunnel, and then constructing a second temporary invert to close the initial support of the upper step area of ​​the lower left pilot tunnel; wherein one end of the second temporary invert is connected to the first vertical temporary support, and the other end is connected to the second side wall initial support; S43, excavating the rock and soil mass in the step area below the lower left guide tunnel, constructing the third side wall initial support and the second vertical temporary support in the step area below the lower left guide tunnel, and then constructing the first invert to close the initial support of the step area below the lower left guide tunnel; wherein one end of the first invert is connected to the second vertical temporary support, and the other end is connected to the third side wall initial support; S44, excavating the rock and soil mass in the upper step area of ​​the lower right guide tunnel, and constructing a third temporary invert in the upper step area of ​​the lower right guide tunnel; wherein one end of the third temporary invert is connected to the steel arch frame, and the other end is connected to the second temporary invert; S45, excavating the rock and soil mass in the step area below the lower right pilot tunnel, and constructing a second inverted arch in the step area below the lower right pilot tunnel; wherein one end of the second inverted arch is connected to the steel arch frame, and the other end is connected to the first inverted arch; S46, dismantle the second vertical temporary support, construct the secondary lining of the invert, then dismantle the first vertical temporary support, the second temporary invert, the third temporary invert, and the first temporary invert, and construct the secondary lining of all the side walls.

[0009] Preferably, the step S2 specifically includes the steps of backfilling soil and rocks in the area where the bias retaining wall is located, manually compacting in layers, covering the surface with a clay layer, and backfilling concrete in the area along the terrain outside the current bias for counter-pressure.

[0010] Preferably, the step S41 further includes the step of: locking the arch foot position of the initial support of the first side wall with a first prestressed expansion shell anchor and a first steel pipe pile.

[0011] Preferably, the step S42 further includes the step of: locking the arch foot position of the initial support of the second side wall with a second prestressed expansion shell anchor and a second steel pipe pile.

[0012] Preferably, the cross-section of the arch foot end of the first side wall initial support gradually increases from top to bottom, and the top cross-sectional area of ​​the second side wall initial support is smaller than the bottom cross-sectional area of ​​the first side wall initial support.

[0013] Preferably, the cross-section of the arch foot end of the second side wall initial support gradually increases from top to bottom, and the top cross-sectional area of ​​the third side wall initial support is smaller than the bottom cross-sectional area of ​​the second side wall initial support.

[0014] Preferably, the transverse pipe-roof guide pipe is anchored obliquely upward from the locking end into the surrounding rock, and the inclination angle of the transverse pipe-roof guide pipe is controlled within 1-3°.

[0015] Preferably, the top of the initial support arch section is a reinforced concrete structure.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a tunnel construction method for steep rock and soil bodies in complex terrain, which includes excavating the outer mountain of the tunnel and constructing a bias retaining wall on the outer side of the tunnel, backfilling the area where the bias retaining wall is located, laying a transverse pipe shed along the pipe shed guide pipe, laying an advanced middle pipe shed from the front of the tunnel, excavating the rock and soil body within the range of the main tunnel of the tunnel and constructing a lining structure, wherein the advanced middle pipe shed is arranged between the lining structure and the transverse pipe shed, and the advanced middle pipe shed is located on the inner side of the bias retaining wall. The main tunnel of the tunnel is excavated and supported in the order of the upper guide tunnel, the upper step of the lower left guide tunnel, the lower step of the lower left guide tunnel, the upper step of the lower right guide tunnel, and the lower step of the lower right guide tunnel, and the temporary support is removed and the secondary lining is poured.

[0017] This application forms a three-dimensional support system by adopting bias retaining wall + horizontal pipe shed + advanced middle pipe shed. On this basis, combined with safe and reasonable construction procedures, it can effectively ensure the safety and construction efficiency of tunnel construction in complex terrain and steep rock and soil. The bias retaining wall equivalently replaces the soil to effectively resist the lateral soil pressure of the mountain and ensure the stability of the steep slope. At the same time, the horizontal large pipe shed of this application can also create advanced support for the front steep tunnel excavation. The three-dimensional support system + construction process can provide greater lateral stiffness, improve the stability of the surrounding rock, effectively control the deformation of the surrounding rock, alleviate the impact of terrain bias on the tunnel structure, and protect the original terrain and ecological environment to the maximum extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0019] Figure 1 It is a schematic flow chart of a construction method in one embodiment of the present invention.

[0020] Figure 2 This is a flow chart of the specific steps included in step S4 in one embodiment of the present invention; Figure 3 This is a schematic diagram of the structure after step S2 is completed in one embodiment of the present invention; Figure 4 It is a schematic diagram of the structure after the construction of step S3 in one embodiment of the present invention; Figure 5 It is a schematic diagram of the connection between the transverse pipe rack and the first connecting steel plate in one embodiment of the present invention; Figure 6 It is a schematic diagram of the structure after the construction of step S4 in one embodiment of the present invention; Figure 7 A schematic plan view of a construction method for a main tunnel of a tunnel in one embodiment of the present invention; Figure 8 for Figure 6 Schematic diagram of longitudinal section; Fig. 9 for Figure 6 A is an enlarged schematic diagram; Fig.10 A schematic diagram of the connection between a tunnel and a bridge in one embodiment of the present invention; Fig.11 is a schematic structural diagram of a first connecting component in one embodiment of the present invention; Fig.12 It is a schematic diagram of the connection between the steel arch frame and the temporary inverted arch steel frame in one embodiment of the present invention; Fig.13 is a schematic diagram of a reinforced concrete structure of a biased retaining wall in one embodiment of the present invention; Fig.14 It is a schematic diagram of the connection between the third side wall steel frame and the inverted arch steel frame in one embodiment of the present invention.

[0021] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments.

[0022] Description of Figure Numbers: 10. Tunnel; 110. Upper pilot tunnel area; 111. First side wall initial support; 1111. First side wall steel frame; 1112. Fourth connecting steel plate; 112. First temporary invert; 120. Upper step area of ​​lower left pilot tunnel; 121. Second side wall initial support; 122. First vertical temporary support; 123. Second temporary invert; 130. Upper step area of ​​lower right pilot tunnel; 131. Third temporary invert; 140. Lower step of lower left pilot tunnel Area; 141, initial support of the third side wall; 1411, steel frame of the third side wall; 1412, steel pad; 142, second vertical temporary support; 143, first invert; 1431, steel frame of invert; 1432, arc section; 1433, first horizontal section; 150, lower step area of ​​the lower right guide tunnel; 151, second invert; 161, secondary lining of invert; 162, secondary lining of side wall; 170, prestressed expansion shell anchor rod; 180, face; 20. biased retaining wall; 210. primary support arch section; 211. steel arch frame; 2111. main body of steel arch frame; 2112. first connecting plate; 2113. first bolt; 2114. temporary inverted arch steel frame; 2115. fifth connecting plate; 212. step surface; 213. second connecting steel plate; 220. pipe shed connecting section; 221. transverse pipe shed guide pipe; 222. first connecting steel plate; 230. first connecting assembly; 231. second bolt; 232. second connecting plate; 233. rubber pad; 234. channel steel; 240. reinforced concrete structure; 30. clay layer; 40. transverse pipe shed; 410. locking end; 420. anchoring end; 50. advanced middle pipe shed; 510. first left advanced middle pipe shed; 520. second left advanced middle pipe shed; 60. bridge. DETAILED DESCRIPTION

[0023] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In the present invention, the descriptions of "upper part", "lower part", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "upper part" and "lower part" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0026] Please refer to the attached Figures 1 to 14 In one embodiment of the present invention, a method for constructing a tunnel in a steep rock mass with complex terrain comprises the following steps: S1, excavating the outer side slope of the tunnel 10 and constructing a bias retaining wall 20 on the outer side of the tunnel 10; wherein a transverse pipe-roof guide pipe 221 is reserved on the top of the bias retaining wall 20; S2, performing backfilling with reverse pressure in the area where the bias retaining wall 20 is located; S3, laying a transverse pipe shed 40 along the transverse pipe shed guide pipe 221; wherein the transverse pipe shed 40 comprises a locking end 410 and an anchoring end 420 which are arranged opposite to each other along the extension direction of the tunnel 10 itself, the locking end 410 is connected to the bias retaining wall 20, and the anchoring end 420 is anchored into the surrounding rock; S4, an advanced middle pipe shed 50 is installed from the front of the tunnel 10, the rock and soil in the range of the tunnel main hole is excavated and a lining structure is constructed; wherein the advanced middle pipe shed 50 is arranged between the tunnel main hole and the transverse pipe shed 40, and the advanced middle pipe shed 50 is located on the inner side of the bias retaining wall 20.

[0027] Specifically, the bias retaining wall 20 is constructed on the outside of the tunnel 10 to directly resist the bias load on the outside of the tunnel 10, and the lateral earth pressure is transferred to the bias retaining wall 20. The bias retaining wall 20 equivalently replaces the soil to effectively resist the lateral earth pressure of the mountain, thereby ensuring the stability of the steep slope. A transverse pipe rack guide pipe 221 is reserved at the top of the bias retaining wall 20 to provide precise positioning and support for the subsequent construction of the transverse pipe rack 40. Backfilling at the position of the bias retaining wall 20 can basically restore the original shape of the slope, thereby achieving micro-transformation of the slope without large-scale excavation.

[0028] The transverse pipe shed 40 spans above the tunnel 10, the locking end 410 of the transverse pipe shed 40 is connected to the bias retaining wall 20, and the anchor end 420 penetrates into the stable surrounding rock to form a beam effect, which can transfer the bias load to the deep surrounding rock on the mountain side, greatly improving the stability and safety of the overall structure. Preferably, the embedding depth of the anchor end 420 is controlled at 3-4m, and each pipe shed guide pipe in the transverse pipe shed 40 preferably adopts Φ159mm and a wall thickness of 8mm.

[0029] The advanced middle pipe shed 50 is constructed from the tunnel face 10 to form a pre-support structure in the longitudinal direction of the tunnel 10. The three-dimensional spatial support system of the advanced middle pipe shed 50 and the transverse pipe shed 40 can not only improve the ability to resist lateral bias, but also improve the top support ability, and effectively control the relaxation and deformation of the surrounding rock during the excavation of the main tunnel. Preferably, the advanced middle pipe shed includes a first advanced middle pipe shed and a second advanced middle pipe shed, and the lining structure is a composite lining structure, including initial support and secondary lining.

[0030] In the present application, a three-dimensional support system is formed by using a bias retaining wall 20 + a transverse pipe shed 40 + an advanced middle pipe shed 50 + a construction process, which can significantly improve the stability and safety of the excavation of the tunnel 10 in a steep rock and soil mass with complex terrain, reduce the number of disturbances to the surrounding rock during construction, and improve construction efficiency. At the same time, it can also serve as a permanent support structure for the tunnel 10 to improve the structural durability during the operation period; the present application can achieve micro-transformation of the slope without large-scale excavation. At the same time, the large transverse pipe shed is taken into account to create advanced support for the front steep tunnel excavation. The three-dimensional support system + construction process can provide greater lateral stiffness, improve the stability of the surrounding rock, effectively control the deformation of the surrounding rock, and alleviate the impact of terrain bias on the tunnel structure.

[0031] As a preferred embodiment, Fig.11 As shown, the second connecting steel plate 213 can also be set in the form of a first connecting component, wherein the first connecting component 230 includes a second bolt 231, a second connecting plate 232, a rubber pad 233 and a channel steel 234; wherein the second connecting plate 232 is embedded in the top of the initial support arch section 210, the rubber pad 233 is connected between the channel steel 234 and the second connecting plate 232, the second connecting plate 232 is provided with a second connecting hole for the second bolt 231 to pass through, the rubber pad 233 is provided with a third connecting hole arranged one-to-one with the second connecting hole, and the second bolt 231 is embedded in the initial support arch section 210 at a depth greater than the steel bar anchoring length.

[0032] Specifically, the embedded depth of the second bolt 231 exceeds the anchoring length of the steel bar, ensuring the effective connection between the bolt and the initial support arch section 210, avoiding bolt loosening or insufficient anchoring force under long-term load; the second connecting plate 232 forms a large-area load transfer interface, disperses concentrated stress, and reduces the risk of local concrete crushing; the rubber pad 233 absorbs vibrations during tunnel operation and reduces stress concentration caused by rigid connection.

[0033] For example, the fourth connecting steel plate 1112 of the first side wall steel frame 1111 and the first connecting assembly 230 can be connected. Specifically, the second bolt 231 can pass through the bolt hole on the fourth connecting plate, and the connection between the fourth connecting plate and the second connecting plate 232 can be achieved by screwing the nut, thereby realizing the connection between the two.

[0034] As a preferred implementation, step S1 specifically includes the following steps: The rock and soil in the area where the bias retaining wall 20 is located is excavated according to the temporary slope, and the bias retaining wall 20 is constructed; wherein, the bias retaining wall 20 includes an initial support arch section 210 and a pipe-roof connection section 220 located above the initial support arch section 210; wherein, the pipe-roof connection section 220 is reserved with the transverse pipe-roof guide pipe 221, and the outer wall surface of the pipe-roof connection section 220 is pre-embedded with a first connecting steel plate 222, and the locking end 410 is connected to the first connecting steel plate 222; the inner wall surface of the initial support arch section 210 is pre-embedded with a steel arch frame 211 matching the contour line of the tunnel 10, and a step surface 212 for overlapping the lining structure is formed between the initial support arch section 210 and the pipe-roof connection section 220, and a second connecting steel plate 213 is reserved at the step surface 212.

[0035] For details, please refer to the attached Figure 3 and Figure 4 By pre-embedding a steel arch frame 211 matching the contour of the tunnel 10, the steel arch frame 211 can be used as a part of the initial support of the tunnel 10, and can also be used as a steel structure to strengthen the structural strength of the bias retaining wall 20. The pipe-roof connection section 220 is rigidly connected to the locking end 410 of the transverse pipe-roof 40 through the first connecting steel plate 222, such as Figure 5 As shown, the two are connected by welding to form a composite support system of bias retaining wall 20 + transverse pipe shed 40, which can transfer the bias load to the deep stable surrounding rock and significantly improve the overall bending stiffness and bearing redundancy of the support structure.

[0036] The second connecting steel plate 213 is reserved on the step surface 212 to provide a lap platform for the lining structure, which can increase the lap area of ​​the lining structure and provide a strong guarantee for the initial support setting of the preferred embodiment as a large arch foot, avoiding stress concentration and reducing the risk of cracking at the structural mutation point; the steel arch frame 211 and the pre-buried steel plate realize factory prefabrication and rapid on-site installation, reduce the amount of wet work, shorten the support construction period, and ensure the accuracy and reliability of the connection nodes.

[0037] As a preferred embodiment, the steel arch frame 211 includes a steel arch frame body 2111 and a first connecting plate 2112 connected to the outer wall of the steel arch frame body 2111. The steel arch frame body 2111 matches the tunnel contour and serves as a partial initial support for the tunnel. The first connecting plate 2112 is provided with a first connecting hole (not shown) for the first bolt 2113 to pass through.

[0038] Specifically, by pre-embedding the steel arch frame body 2111 that matches the tunnel contour, the steel arch frame body 2111 can be used as a part of the initial support of the tunnel, and can also be used as a steel structure to strengthen the structural strength of the biased retaining wall structure. Fig.12 As shown, Fig.12It is a schematic diagram of the connection between the steel arch frame assembly, the temporary inverted arch steel frame 2114 and the fifth connecting plate 2115 through bolts.

[0039] As a preferred embodiment, please refer to the attached Figure 6 and Figure 8 , the step S4 specifically comprises the following steps: S41, constructing the first left-side advanced middle pipe shed 510 of the upper pilot tunnel area 110 from the front of the tunnel 10, excavating the rock and soil of the upper pilot tunnel area 110, constructing anchor rods (not shown) and the first side wall initial support 111 in the upper pilot tunnel area 110, and then constructing the first temporary invert 112 to close the initial support of the upper pilot tunnel area 110; wherein one end of the first temporary invert 112 is connected to the steel arch frame 211, and the other end is connected to the first side wall initial support 111, and one end of the first side wall initial support 111 is connected to the second connecting steel plate 213; S42, constructing the second left-side advanced middle pipe shed 520 of the upper step area 120 of the lower left pilot tunnel from the front of the tunnel 10, and excavating the rock and soil of the upper step area 120 of the middle and lower left pilot tunnel, constructing anchor rods, the second side wall initial support 121 and the first vertical temporary support 122 in the upper step area 120 of the lower left pilot tunnel, and then constructing the second temporary invert 123 to close the initial support of the upper step area 120 of the lower left pilot tunnel; wherein one end of the second temporary invert 123 is connected to the first vertical temporary support 122, and the other end is connected to the second side wall initial support 121; S43, excavating the rock and soil mass of the lower step area 140 of the lower left guide tunnel, constructing a third side wall initial support 141 and a second vertical temporary support 142 in the lower step area 140 of the lower left guide tunnel, and then constructing a first invert 143 to close the initial support of the lower step area 140 of the lower left guide tunnel; wherein one end of the first invert 143 is connected to the second vertical temporary support 142, and the other end is connected to the third side wall initial support 141; S44, excavating the rock and soil mass of the upper step area 130 of the lower right pilot tunnel, and constructing a third temporary invert 131 in the upper step area 130 of the lower right pilot tunnel; wherein one end of the third temporary invert 131 is connected to the steel arch frame 211, and the other end is connected to the second temporary invert 123; S45, excavating the rock and soil mass of the lower step area 150 of the lower right pilot tunnel, and constructing a second inverted arch 151 in the lower step area 150 of the lower right pilot tunnel; wherein one end of the second inverted arch 151 is connected to the steel arch frame 211, and the other end is connected to the first inverted arch 143; S46, dismantle the second vertical temporary support 142, construct the secondary lining of the invert, then dismantle the first vertical temporary support 122, the second temporary invert 123, the third temporary invert 131, and the first temporary invert 112, and construct the secondary lining 162 of all the side walls.

[0040] The present application decomposes a large section into multiple small sections to reduce the disturbance of a single excavation to the surrounding rock; initial support (anchor rods + initial support of side walls) is immediately applied after excavation of each area, and the initial support structure is closed into a ring through a temporary invert to form a temporary bearing ring, which effectively constrains the three-dimensional deformation of the surrounding rock; a first vertical temporary support 122 and a second vertical temporary support 142 are set in the middle guide tunnel area and the lower guide tunnel area to transfer the lateral pressure of the initial support of the side wall to the temporary invert, forming a triangular support system and enhancing the structure's ability to resist lateral displacement.

[0041] In addition, this embodiment follows the principle of first lower and then upper and symmetrical demolition, gradually dismantling the vertical temporary supports and temporary inverts, and then constructing the secondary lining, which ensures to the greatest extent that the secondary lining is constructed after the deformation of the surrounding rock is basically stable, forming a permanent bearing structure.

[0042] Preferably, the anchor rod of this embodiment is a forward-type resin anchor rod.

[0043] This embodiment can provide a safe and reasonable construction process. The use of advanced middle pipe shed 50+ partial excavation can greatly reduce the deformation of the surrounding rock, which is especially suitable for soft surrounding rock or shallow buried tunnel 10. The temporary invert + vertical temporary support constitutes a circumferential + triangular composite support system, which can effectively improve the structural bending stiffness, effectively disperse the eccentric load, and avoid local damage.

[0044] Furthermore, if Figure 7 As shown, Figure 7 It is a plan schematic diagram of the tunnel main tunnel construction method. As a preferred example, the front end face of the upper pilot tunnel area 110 is the heading face 180, the upper step area 120 of the lower left pilot tunnel lags behind the upper pilot tunnel area 110 by 3 to 5 m, the lower step area 140 of the lower left pilot tunnel lags behind the upper step area 120 of the lower left pilot tunnel by 3 to 5 m, the upper step area 130 of the lower right pilot tunnel lags behind the lower step area 140 of the lower left pilot tunnel by 3 to 5 m, the lower step area 150 of the lower right pilot tunnel lags behind the upper step area 130 of the lower right pilot tunnel by 3 to 5 m, and the distance of the secondary lining from the lower step area 150 of the lower right pilot tunnel is ≤20 m.

[0045] Furthermore, the third side wall initial support 141 includes a third side wall steel frame 1411 and a steel pad 1412, and the first inverted arch 143 includes an arc segment 1432 with an opening facing upward and a first horizontal segment 1433 respectively connected to one end of the arc segment 1432, and the first horizontal segment 1433 and the third side wall steel frame 1411 are welded.

[0046] Furthermore, the construction tunnel is adjacent to the project, such as Fig.10 As shown, if the tunnel 10 is connected to the bridge 60, after the portal wall is constructed, the bridge pier adopts a column abutment, and the way the abutment enters the tunnel is considered. If it is connected to the roadbed, the portal wall adopts a wall-attached end wall design to avoid excavating the natural back slope.

[0047] As a preferred embodiment, step S2 specifically includes the steps of backfilling soil and rocks in the area where the bias retaining wall 20 is located, compacting the soil in layers, covering the surface with a clay layer 30, and backfilling concrete in the area along the terrain on the outer side of the current bias for counter-pressure.

[0048] Specifically, by layering and manually compacting the backfilled soil and rocks, the density of the backfilled materials can be ensured, thereby improving the bearing capacity and stability of the foundation; the clay layer 30 is covered on the surface of the backfilled soil and rocks, preferably with a thickness of 50 cm, which can play an isolation role and restore greening. Concrete is backfilled in the area along the terrain outside the bias retaining wall 20 for counterpressure. The high density and strength of the concrete can generate sufficient counterpressure, which helps to offset the horizontal pressure borne by the bias retaining wall 20 and further enhance the stability of the retaining wall. Preferably, the concrete uses C20 concrete.

[0049] Furthermore, the step S41 further includes the step of: locking the arch foot position of the first side wall initial support 111 with a first prestressed expansion shell anchor rod 170 and a first steel pipe pile (not shown).

[0050] Furthermore, the step S42 further includes the step of: locking the arch foot position of the second side wall initial support 121 with a second prestressed expansion shell anchor (not shown) and a second steel pipe pile (not shown).

[0051] Specifically, the prestressed shell anchor rod can provide strong pull-out resistance and stability through its unique tensioning device and prestressed design, ensuring that the arch foot is not easily displaced or deformed when subjected to external forces. The steel pipe pile provides additional support for the arch foot through its rigidity and strength, further enhancing the stability of the arch foot. The combined use of prestressed shell anchor rod and steel pipe pile can significantly improve the overall bearing capacity of the support structure. As a specific example, the prestressed shell anchor rod uses a Φ50mm prestressed shell anchor rod, and the steel pipe pile uses a Φ72mm steel pipe pile.

[0052] Furthermore, the cross-section of the arch foot end of the first side wall initial support 111 gradually increases from top to bottom, and the top cross-sectional area of ​​the second side wall initial support 121 is smaller than the bottom cross-sectional area of ​​the first side wall initial support 111 .

[0053] Furthermore, the cross-section of the arch foot end of the second side wall initial support 121 gradually increases from top to bottom, and the top cross-sectional area of ​​the third side wall initial support 141 is smaller than the bottom cross-sectional area of ​​the second side wall initial support 121 .

[0054] Specifically, Figure 6 As shown, the cross-sectional area gradient of the arch foot end increases to form a gradual structure, which can improve the shear bearing capacity, effectively support the arch load, and effectively resist the bias caused by the side terrain. This embodiment uses a large arch foot + initial support buckle arch + temporary inverted arch to increase the lateral resistance of the support stiffness, which can well solve the problem of shallow buried bias.

[0055] As a preferred example, the transverse pipe-roof guide tube 221 is tilted upward from the locking end 410 and anchored into the surrounding rock, and the tilt angle of the transverse pipe-roof guide tube 221 is controlled at 1~3°. The setting of tilting upward anchoring into the surrounding rock provides directional positioning for the installation of the pipe-roof, and can more accurately place the pipe-roof guide tube in place, reduce directional deviation and adjustment times during the construction process, and improve construction efficiency. The tilt angle range of 1~3° is relatively small and reasonable, which ensures that the guide tube can be effectively anchored into the surrounding rock without increasing the difficulty of construction due to excessive angles.

[0056] Furthermore, if Fig.13 As shown, the top of the primary support arch section 210 is a reinforced concrete structure 240. The reinforced concrete structure 240 combines the tensile properties of the steel bar and the compressive properties of the concrete, and has a high bearing capacity. Preferably, on the basis of ensuring structural safety, the other parts of the bias retaining wall 20 can be made of plain concrete structure.

[0057] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent structure or equivalent process transformation made by using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A tunnel construction method for steep rock and soil with complex terrain, characterized in that: The following steps are involved: S1, excavating the outer mountain of the tunnel and constructing a bias retaining wall on the outer side of the tunnel; wherein a transverse pipe shed guide pipe is reserved on the top of the bias retaining wall; S2, performing backfilling with counter pressure in the area where the bias retaining wall is located; S3, laying a transverse pipe rack along the pipe rack guide pipe; wherein the transverse pipe rack comprises a locking end and an anchoring end extending in the transverse direction of the tunnel, the locking end is connected to the bias retaining wall, and the anchoring end is anchored into the surrounding rock; S4, set up an advanced middle pipe shed from the front of the tunnel, and excavate and support the main tunnel of the tunnel in the order of upper guide tunnel, upper step of lower left guide tunnel, lower step of lower left guide tunnel, upper step of lower right guide tunnel, and lower step of lower right guide tunnel, remove the temporary support and pour the secondary lining; wherein, the advanced middle pipe shed is arranged between the main tunnel of the tunnel and the transverse pipe shed, and the advanced middle pipe shed is located on the inner side of the bias retaining wall.

2. The method for tunnel construction in steep rock and soil with complex terrain according to claim 1 is characterized in that: The step S1 specifically includes the following steps: The rock and soil in the area where the bias retaining wall is located is excavated according to the temporary slope, and the bias retaining wall is constructed; wherein the bias retaining wall includes an initial support arch section and a pipe-roof connection section located above the initial support arch section; wherein the pipe-roof connection section is pre-reserved with the transverse pipe-roof guide pipe, the outer wall surface of the pipe-roof connection section is pre-embedded with a first connecting steel plate, and the locking end is connected to the first connecting steel plate; the inner wall surface of the initial support arch section is pre-embedded with a steel arch frame matching the tunnel contour line, and a step surface for overlapping the lining structure is formed between the initial support arch section and the pipe-roof connection section, and a second connecting steel plate is reserved at the step surface.

3. The method for tunnel construction in steep rock and soil with complex terrain according to claim 2 is characterized in that: The step S4 specifically comprises the following steps: S41, constructing the first left-side advanced middle pipe shed in the upper pilot tunnel area from the front of the tunnel, excavating the rock and soil in the upper pilot tunnel area, constructing anchor rods and the first side wall initial support in the upper pilot tunnel area, and then constructing a first temporary invert to close the initial support of the upper pilot tunnel area; wherein one end of the first temporary invert is connected to the steel arch frame, and the other end is connected to the first side wall initial support, and one end of the first side wall initial support is connected to the second connecting steel plate; S42, constructing a second left-side advanced middle pipe shed in the upper step area of ​​the lower left pilot tunnel from the front of the tunnel, excavating the rock and soil in the upper step area of ​​the lower left pilot tunnel, constructing anchor rods, a second side wall initial support and a first vertical temporary support in the upper step area of ​​the lower left pilot tunnel, and then constructing a second temporary invert to close the initial support of the upper step area of ​​the lower left pilot tunnel; wherein one end of the second temporary invert is connected to the first vertical temporary support, and the other end is connected to the second side wall initial support; S43, excavating the rock and soil mass in the step area below the lower left guide tunnel, constructing the third side wall initial support and the second vertical temporary support in the step area below the lower left guide tunnel, and then constructing the first invert to close the initial support of the step area below the lower left guide tunnel; wherein one end of the first invert is connected to the second vertical temporary support, and the other end is connected to the third side wall initial support; S44, excavating the rock and soil mass in the upper step area of ​​the lower right guide tunnel, and constructing a third temporary invert in the upper step area of ​​the lower right guide tunnel; wherein one end of the third temporary invert is connected to the steel arch frame, and the other end is connected to the second temporary invert; S45, excavating the rock and soil mass in the step area below the lower right pilot tunnel, and constructing a second inverted arch in the step area below the lower right pilot tunnel; wherein one end of the second inverted arch is connected to the steel arch frame, and the other end is connected to the first inverted arch; S46, dismantle the second vertical temporary support, construct the secondary lining of the invert, then dismantle the first vertical temporary support, the second temporary invert, the third temporary invert, and the first temporary invert, and construct the secondary lining of all the side walls.

4. The method for tunnel construction in steep rock and soil with complex terrain according to claim 1 is characterized in that: The step S2 specifically includes the steps of backfilling soil and rocks in the area where the bias retaining wall is located, manually compacting the soil in layers, covering the surface with a clay layer, and backfilling concrete in the area along the terrain outside the current bias for counter-pressure.

5. The method for tunnel construction in steep rock and soil with complex terrain according to claim 3 is characterized in that: The step S41 is followed by the step of: locking the arch foot position of the initial support of the first side wall with a first prestressed expansion shell anchor rod and a first steel pipe pile.

6. The method for tunnel construction in steep rock and soil with complex terrain according to claim 3 is characterized in that: The step S42 also includes the following steps: locking the arch foot position of the initial support of the second side wall with a second prestressed expansion shell anchor rod and a second steel pipe pile.

7. The method for tunnel construction in steep rock and soil with complex terrain according to claim 3 is characterized in that: The cross-section of the arch foot end of the first side wall initial support gradually increases from top to bottom, and the top cross-section area of ​​the second side wall initial support is smaller than the bottom cross-section area of ​​the first side wall initial support.

8. The method for tunnel construction in steep rock and soil with complex terrain according to claim 3 is characterized in that: The cross-section of the arch foot end of the second side wall initial support gradually increases from top to bottom, and the top cross-section area of ​​the third side wall initial support is smaller than the bottom cross-section area of ​​the second side wall initial support.

9. The method for tunnel construction in steep rock and soil with complex terrain according to claim 1, characterized in that: The transverse pipe-roof guide pipe is anchored obliquely upward from the locking end into the surrounding rock, and the inclination angle of the transverse pipe-roof guide pipe is controlled within 1-3°.

10. The method for tunnel construction in steep rock and soil with complex terrain according to claim 2, characterized in that: The top of the initial support arch section is a reinforced concrete structure.

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