A tunnel construction method for steep rock and soil in complex terrain

Abstract

The present invention relates to the field of tunnel technology, and provides a method for constructing a tunnel with steep rock and soil in complex terrain. The method comprises excavating the outer mountain of the tunnel and constructing a bias retaining wall on the outer side of the tunnel, performing backfilling in 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 in the range of the main tunnel of the tunnel and constructing a lining structure, wherein the advanced middle pipe shed is located on the inner side of the bias retaining wall, and excavating and supporting the rock and soil in the order of the upper guide tunnel, the lower left guide tunnel up and down steps, and the lower right guide tunnel up and down steps, thereby reducing the influence of the mountain bias pressure. The present application forms a three-dimensional support system by adopting a bias retaining wall + a transverse pipe shed + an advanced middle pipe shed, and combines safe and reasonable construction procedures to effectively ensure the safety and construction efficiency of tunnel construction with steep rock and soil in complex terrain, and does not require large-scale excavation, thereby protecting the original terrain and ecological environment to the greatest extent.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnels, in particular to a method for constructing a tunnel in a steep rock mass with complex terrain. Background Art

[0002] With the continuous development of the economy, the requirements for expressway alignment and vehicle capacity are becoming increasingly stringent. This inevitably leads to the fact that long-span tunnel portals on expressways will pass through various ecologically sensitive areas, such as steep natural slopes (slopes > 45°), nature reserves, or water sources. Steep rock mass (i.e., rock mass with a steep frontal slope and severe lateral deflection) often presents shallow deflection and poor slope stability at the portal section, making tunnel construction difficult and prone to defects during operation. Therefore, tunnel design and construction must address the need for a tunnel portal that safely traverses the steep rock mass while avoiding large-scale excavation of the mountain surface and maximizing the preservation of the pristine terrain and ecological environment.

[0003] At present, the conventional entry method for steep rock and soil tunnels is mainly: large-scale excavation and slope reduction + open-hole construction method. This method has a great impact on the existing natural environment and is not environmentally friendly. In the later operation stage of large-scale 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 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, which is prone to induce landslides and seriously threatens the operational safety of existing roads.

[0006] To achieve the above-mentioned object, the present invention provides a method for tunnel construction in steep rock and soil with complex terrain, comprising the following steps:

[0007] 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 roof guide pipe is reserved on the top of the bias retaining wall;

[0008] S2, performing backfilling under counter pressure in the area where the bias retaining wall is located;

[0009] 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 provided along the transverse extension direction of the tunnel, the locking end being connected to the biased retaining wall, and the anchoring end being anchored into the surrounding rock;

[0010] S4, set up an advanced middle pipe shed from the front of the tunnel, and carry out excavation and support of the main tunnel of the tunnel in the order of upper pilot tunnel, upper step of lower left pilot tunnel, lower step of lower left pilot tunnel, upper step of lower right pilot tunnel, and lower step of lower right pilot tunnel, remove the temporary support and pour the secondary lining; wherein, the advanced middle pipe shed is set 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 biased retaining wall.

[0011] Preferably, the step S1 specifically includes the following steps:

[0012] 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.

[0013] Preferably, the step S4 specifically includes the following steps:

[0014] S41: Constructing a 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, installing anchor rods and a first sidewall initial support in the upper pilot tunnel area, and then constructing a first temporary invert to close the initial support in 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 sidewall initial support, and one end of the first sidewall initial support is connected to the second connecting steel plate;

[0015] 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, installing anchor rods, a second sidewall primary 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 primary support in 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 sidewall primary support;

[0016] S43: excavating the rock and soil in the lower step area of ​​the lower left pilot tunnel, constructing a third sidewall primary support and a second vertical temporary support in the lower step area of ​​the lower left pilot tunnel, and then constructing a first inverted arch to close the primary support of the lower step area of ​​the lower left pilot tunnel; wherein one end of the first inverted arch is connected to the second vertical temporary support, and the other end is connected to the third sidewall primary support;

[0017] S44, excavating the rock and soil in the upper step area of ​​the lower right pilot tunnel, and constructing a third temporary inverted arch in the upper step area of ​​the lower right pilot tunnel; wherein one end of the third temporary inverted arch is connected to the steel arch frame, and the other end is connected to the second temporary inverted arch;

[0018] S45, excavating the rock and soil in the lower step area of ​​the lower right pilot tunnel, and constructing a second inverted arch in the lower step area of ​​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;

[0019] S46, dismantle the second vertical temporary support, construct the secondary lining of the inverted arch, then dismantle the first vertical temporary support, the second temporary inverted arch, the third temporary inverted arch, and the first temporary inverted arch, and construct the secondary lining of all side walls.

[0020] 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 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.

[0021] Preferably, 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.

[0022] 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 rod and a second steel pipe pile.

[0023] 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-section area of ​​the second side wall initial support is smaller than the bottom cross-section area of ​​the first side wall initial support.

[0024] 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.

[0025] 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 to be 1-3°.

[0026] Preferably, the top of the primary support arch section is a reinforced concrete structure.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a tunnel construction method for steep rock and soil in complex terrain. The method comprises excavating the outer mountain of the tunnel and constructing a biased retaining wall on the outer side of the tunnel. Backfilling is performed in the area where the biased retaining wall is located. A transverse pipe shed is installed along the pipe shed guide pipe. An advanced middle pipe shed is installed from the front of the tunnel. The rock and soil within the main tunnel area is excavated and a lining structure is constructed. The advanced middle pipe shed is located between the lining structure and the transverse pipe shed, and the advanced middle pipe shed is located on the inner side of the biased retaining wall. The main tunnel is excavated and supported in the order of the upper pilot tunnel, the upper step of the lower left pilot tunnel, the lower step of the lower left pilot tunnel, the upper step of the lower right pilot tunnel, and the lower step of the lower right pilot tunnel. The temporary support is removed and the secondary lining is poured.

[0029] This application forms a three-dimensional support system by adopting a 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 effectively replaces the soil to effectively resist the lateral earth pressure of the mountain and ensure the stability of the steep slope. At the same time, the large horizontal 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 greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0031] Figure 1 It is a schematic flow chart of a construction method in one embodiment of the present invention.

[0032] Figure 2 This is a flow chart showing the specific steps included in step S4 in one embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the structure after step S2 is completed in one embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the structure after step S3 is completed in one embodiment of the present invention;

[0035] Figure 5 Schematic diagram of the connection between the transverse pipe rack and the first connecting steel plate in one embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of the structure after step S4 is completed in one embodiment of the present invention;

[0037] Figure 7 A schematic plan view of a construction method for a main tunnel in one embodiment of the present invention;

[0038] Figure 8 for Figure 6 Schematic diagram of the longitudinal section;

[0039] Figure 9 for Figure 6 A is an enlarged schematic diagram;

[0040] Figure 10 Schematic diagram of the connection between a tunnel and a bridge in one embodiment of the present invention;

[0041] Figure 11 is a schematic structural diagram of a first connecting assembly in one embodiment of the present invention;

[0042] Figure 12 Schematic diagram of the connection between the steel arch frame and the temporary inverted arch steel frame in one embodiment of the present invention;

[0043] Figure 13 is a schematic diagram of a reinforced concrete structure of a biased retaining wall in one embodiment of the present invention;

[0044] Figure 14 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.

[0045] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments.

[0046] Description of Figure Numbers:

[0047] 10. Tunnel; 110. Upper pilot tunnel area; 111. First sidewall primary support; 1111. First sidewall steel frame; 1112. Fourth connecting steel plate; 112. First temporary invert; 120. Lower left pilot tunnel upper step area; 121. Second sidewall primary support; 122. First vertical temporary support; 123. Second temporary invert; 130. Lower right pilot tunnel upper step area; 131. Third temporary invert; 140. Lower left pilot tunnel lower step Area; 141. Primary support for the third side wall; 1411. Steel frame for the third side wall; 1412. Steel pad; 142. Secondary vertical temporary support; 143. First invert; 1431. Steel frame for the invert; 1432. Curved section; 1433. First horizontal section; 150. Lower step area of ​​the lower right pilot tunnel; 151. Secondary invert; 161. Secondary lining for the invert; 162. Secondary lining for the side wall; 170. Prestressed expansion shell anchor bolts; 180. Tunnel face;

[0048] 20. Biased retaining wall; 210. Initially supported 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. Horizontal 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. Horizontal 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

[0049] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0050] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0051] In the present invention, the descriptions of "upper portion" and "lower portion" are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "upper portion" and "lower portion" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the various embodiments may be combined with each other, but this must be based on the fact that they can be implemented by a person of ordinary skill in the art. If the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0052] Please see the attached Figures 1 to 14 In one embodiment of the present invention, a method for constructing a tunnel in a complex terrain with steep rock and soil mass comprises the following steps:

[0053] 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;

[0054] S2, performing backfilling under counter pressure in the area where the bias retaining wall 20 is located;

[0055] S3, installing a transverse pipe shed 40 along the transverse pipe shed guide tube 221; wherein the transverse pipe shed 40 includes a locking end 410 and an anchoring end 420 disposed opposite to each other along the extension direction of the tunnel 10, the locking end 410 being connected to the biased retaining wall 20, and the anchoring end 420 being anchored into the surrounding rock;

[0056] S4, an advanced middle pipe shed 50 is set up from the front of the tunnel 10, the rock and soil in the range of the main tunnel are excavated and the lining structure is constructed; wherein, the advanced middle pipe shed 50 is set between the main tunnel 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.

[0057] Specifically, by constructing a bias retaining wall 20 on the outside of the tunnel 10, the bias load on the outside of the tunnel 10 is directly resisted, 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 shed 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 shed 40; counter-pressure backfilling is carried out at the position of the bias retaining wall 20, which can basically restore the original shape of the slope, and can achieve micro-transformation of the slope without the need for large-scale excavation.

[0058] The transverse pipe shed 40 spans across the tunnel 10. Its locking end 410 is connected to the biased retaining wall 20, and its anchoring end 420 is embedded deep into the stable surrounding rock, creating a beam effect that transfers the biased load to the deeper surrounding rock on the mountain side, significantly enhancing the stability and safety of the overall structure. Preferably, the anchoring end 420 is embedded to a depth of 3-4 meters. Each guide pipe in the transverse pipe shed 40 is preferably 159 mm in diameter and 8 mm thick.

[0059] An advanced intermediate pipe shed 50 is installed at the tunnel face 10, forming a pre-support structure in the longitudinal direction of the tunnel 10. The three-dimensional support system of the advanced intermediate pipe shed 50 and the transverse pipe shed 40 can not only improve the ability to resist lateral bias pressure, but also enhance the top support capacity, effectively controlling the relaxation and deformation of the surrounding rock during main tunnel excavation. Preferably, the advanced intermediate pipe shed includes a first advanced intermediate pipe shed and a second advanced intermediate pipe shed, and the lining structure is a composite lining structure, including primary support and secondary lining.

[0060] In the present application, a three-dimensional support system is formed by adopting bias retaining wall 20 + horizontal pipe shed 40 + advanced middle pipe shed 50 + construction process, which can significantly improve the stability and safety of tunnel 10 excavation in complex terrain and steep rock and soil, 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 tunnel 10 to improve the structural durability during the operation period; this application can achieve micro-transformation of the slope without large-scale excavation. At the same time, the horizontal large 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.

[0061] As a preferred embodiment, Figure 11 As shown, the second connecting steel plate 213 can also be set in the form of a first connecting assembly, wherein the first connecting assembly 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, and the rubber pad 233 is connected between the channel steel 234 and the second connecting plate 232, and the second connecting plate 232 is provided with a second connecting hole for the second bolt 231 to pass through, and the rubber pad 233 is provided with a third connecting hole arranged one-to-one corresponding to the second connecting hole, and the depth of the second bolt 231 embedded in the initial support arch section 210 is greater than the anchoring length of the steel bar.

[0062] Specifically, the embedded depth of the second bolt 231 exceeds the anchorage 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.

[0063] 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.

[0064] As a preferred embodiment, step S1 specifically includes the following steps:

[0065] 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.

[0066] For details, please refer to the attached Figure 3 and Figure 4 By pre-embedding a steel arch frame 211 that matches the outline of the tunnel 10, the steel arch frame 211 can serve as part of the initial support of the tunnel 10 and can also serve 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. 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, significantly improving the overall bending stiffness and bearing redundancy of the support structure.

[0067] The second connecting steel plate 213 reserved on the step surface 212 provides 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 to be in the form of a large arch foot, thereby 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 at the same time ensure the accuracy and reliability of the connection nodes.

[0068] 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 line and serves as part of the initial support of the tunnel. The first connecting plate 2112 is provided with a first connecting hole (not shown in the figure) for the first bolt 2113 to pass through.

[0069] Specifically, by pre-embedding the steel arch frame body 2111 that matches the tunnel contour line, the steel arch frame body 2111 can serve as a part of the initial support of the tunnel and can also serve as a steel structure to strengthen the structural strength of the bias retaining wall structure. Figure 12 As shown, Figure 12Schematic 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.

[0070] As a preferred embodiment, please refer to the attached Figure 6 and Figure 8 , the step S4 specifically includes the following steps:

[0071] S41, a first left-side advanced middle pipe shed 510 is installed in the upper pilot tunnel area 110 from the front of the tunnel 10, and the rock and soil of the upper pilot tunnel area 110 is excavated. Anchor rods (not shown) and a first sidewall primary support 111 are installed in the upper pilot tunnel area 110, and a first temporary invert 112 is installed to close the primary 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 sidewall primary support 111, and one end of the first sidewall primary support 111 is connected to the second connecting steel plate 213;

[0072] S42: Constructing a second left-side advanced middle pipe shed 520 in the upper step area 120 of the lower left pilot tunnel from the front of the tunnel 10, excavating the rock and soil in the upper step area 120 of the middle and lower left pilot tunnel, installing anchor rods, a second sidewall primary support 121, and a first vertical temporary support 122 in the upper step area 120 of the lower left pilot tunnel, and then constructing a second temporary invert 123 to close the primary 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 sidewall primary support 121;

[0073] S43: Excavate the rock and soil mass of the lower left pilot tunnel step area 140, construct a third sidewall primary support 141 and a second vertical temporary support 142 in the lower left pilot tunnel step area 140, and then construct a first invert 143 to close the primary support of the lower left pilot tunnel step area 140; 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 sidewall primary support 141;

[0074] S44, excavating the rock and soil in the upper step area 130 of the lower right pilot tunnel, and constructing a third temporary inverted arch 131 in the upper step area 130 of the lower right pilot tunnel; wherein one end of the third temporary inverted arch 131 is connected to the steel arch frame 211, and the other end is connected to the second temporary inverted arch 123;

[0075] S45, excavating the rock and soil mass in 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;

[0076] S46, dismantle the second vertical temporary support 142, construct the secondary lining of the inverted arch, then dismantle the first vertical temporary support 122, the second temporary inverted arch 123, the third temporary inverted arch 131, and the first temporary inverted arch 112, and construct the secondary lining 162 of all the side walls.

[0077] This 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 side wall support) is immediately applied after excavation of each area, and the initial support structure is closed into a ring through a temporary inverted arch to form a temporary bearing ring, which effectively restrains 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 pilot tunnel area and the lower pilot tunnel area to transfer the lateral pressure of the initial side wall support to the temporary inverted arch, forming a triangular support system and enhancing the structure's ability to resist lateral displacement.

[0078] In addition, this embodiment follows the principle of symmetrical demolition from bottom to top, gradually dismantling the vertical temporary supports and temporary inverts, and then applying the secondary lining. This ensures to the greatest extent that the secondary lining is applied after the deformation of the surrounding rock is basically stable, thus forming a permanent bearing structure.

[0079] Preferably, the anchor rod of this embodiment is a forward-type resin anchor rod.

[0080] This embodiment can provide a safe and reasonable construction process. The use of advanced middle pipe shed 50+ partial excavation can significantly reduce the deformation of the surrounding rock, which is particularly suitable for weak surrounding rock or shallow buried tunnels 10. The temporary invert arch + 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.

[0081] Further, 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 meters, 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 meters, 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 meters, 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 meters, and the distance of the secondary lining from the lower step area 150 of the lower right pilot tunnel is ≤20 meters.

[0082] 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 upward-opening arc segment 1432 and a first horizontal segment 1433 connected to one end of the arc segment 1432, and the first horizontal segment 1433 is welded to the third side wall steel frame 1411.

[0083] Furthermore, the construction tunnel is adjacent to the project, such as Figure 10 As shown, if tunnel 10 connects to bridge 60, after the portal wall is constructed, the bridge piers are designed as column abutments, and the way the abutments enter the tunnel is considered. If it connects to the roadbed, the portal wall is designed as a wall-mounted end wall to avoid excavating the natural back slope.

[0084] 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, manually compacting the rocks in layers, covering the surface with a clay layer 30, and backfilling concrete in the area along the terrain outside the current bias for counter-pressure.

[0085] Specifically, layered manual compaction of the backfill ensures the density of the backfill material, thereby improving the bearing capacity and stability of the foundation. A clay layer 30, preferably 50 cm thick, is placed over the backfill to provide isolation and restore greenery. Concrete is backfilled in the area outside the biased retaining wall 20, conforming to the terrain, to provide counterpressure. The high density and strength of the concrete generate sufficient counterpressure to help offset the horizontal pressure on the biased retaining wall 20 and further enhance its stability. Preferably, C20 concrete is used.

[0086] Furthermore, after step S41, the step of locking the arch foot of the first side wall primary support 111 with a first prestressed expansion shell anchor 170 and a first steel pipe pile (not shown) is further included.

[0087] Furthermore, the step S42 further includes the step of locking the arch foot of the second side wall primary support 121 with a second prestressed expansion shell anchor (not shown) and a second steel pipe pile (not shown).

[0088] Specifically, the prestressed expansion shell anchor, through its unique tensioning device and prestressed design, provides strong pullout resistance and stability, ensuring that the arch foot is not easily displaced or deformed when subjected to external forces. The steel pipe piles, through their rigidity and strength, provide additional support for the arch foot, further enhancing its stability. The combined use of prestressed expansion shell anchors and steel pipe piles can significantly improve the overall bearing capacity of the support structure. As a specific example, the prestressed expansion shell anchor uses a Φ50mm prestressed expansion shell anchor, and the steel pipe piles use a Φ72mm steel pipe pile.

[0089] 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-section area of ​​the second side wall initial support 121 is smaller than the bottom cross-section area of ​​the first side wall initial support 111 .

[0090] 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-section area of ​​the third side wall initial support 141 is smaller than the bottom cross-section area of ​​the second side wall initial support 121 .

[0091] Specifically, such as Figure 6 As shown, the gradient of the cross-sectional area at the arch foot creates a gradual structure, which improves shear resistance, effectively supports the arch load, and effectively resists the lateral pressure caused by the lateral terrain. This embodiment uses a large arch foot + initial support buckle arch + temporary invert arch to increase support stiffness and lateral resistance, effectively solving the problem of shallow buried lateral pressure.

[0092] As a preferred example, the transverse pipe-roof guide tube 221 is anchored upwardly from the locking end 410 into the surrounding rock, with the inclination angle of the transverse pipe-roof guide tube 221 controlled between 1 and 3 degrees. This upward anchoring into the surrounding rock provides directional positioning for pipe-roof installation, allowing for more precise placement of the pipe-roof guide tube, reducing directional deviation and the number of adjustments required during construction, and improving construction efficiency. The relatively small and reasonable inclination angle range of 1 to 3 degrees ensures the guide tube is effectively anchored into the surrounding rock without increasing the difficulty of construction due to excessively large angles.

[0093] Furthermore, if Figure 13 As shown, the top of the primary support arch section 210 is a reinforced concrete structure 240. Reinforced concrete structure 240 combines the tensile strength of steel and the compressive strength of concrete, resulting in a high load-bearing capacity. Preferably, while ensuring structural safety, the remaining portions of the bias retaining wall 20 can be constructed of plain concrete.

[0094] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, 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 method for tunnel construction in steep rock and soil with complex terrain, characterized by: 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 roof guide pipe is reserved on the top of the bias retaining wall; S2, performing backfilling under counter pressure in the area where the bias retaining wall is located; S3, installing a transverse pipe rack along the pipe rack guide pipe; wherein the transverse pipe rack includes a locking end and an anchoring end extending in the transverse direction of the tunnel, the locking end is connected to the biased retaining wall, and the anchoring end is anchored into the surrounding rock; S4, setting up an advanced middle pipe shed from the front of the tunnel, and excavating and supporting the main tunnel in the order of upper pilot tunnel, upper step of lower left pilot tunnel, lower step of lower left pilot tunnel, upper step of lower right pilot tunnel, and lower step of lower right pilot tunnel, removing the temporary support and pouring the secondary lining; wherein the advanced middle pipe shed is set between the main tunnel and the transverse pipe shed, and the advanced middle pipe shed is located on the inner side of the bias retaining wall; 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.

2. The method for tunnel construction in complex terrain and steep rock and soil according to claim 1 is characterized in that: The step S4 specifically includes the following steps: S41: Constructing a 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, installing anchor rods and a first sidewall initial support in the upper pilot tunnel area, and then constructing a first temporary invert to close the initial support in 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 sidewall initial support, and one end of the first sidewall 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, installing anchor rods, a second sidewall primary 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 primary support in 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 sidewall primary support; S43: excavating the rock and soil in the lower step area of ​​the lower left pilot tunnel, constructing a third sidewall primary support and a second vertical temporary support in the lower step area of ​​the lower left pilot tunnel, and then constructing a first inverted arch to close the primary support of the lower step area of ​​the lower left pilot tunnel; wherein one end of the first inverted arch is connected to the second vertical temporary support, and the other end is connected to the third sidewall primary support; S44, excavating the rock and soil in the upper step area of ​​the lower right pilot tunnel, and constructing a third temporary inverted arch in the upper step area of ​​the lower right pilot tunnel; wherein one end of the third temporary inverted arch is connected to the steel arch frame, and the other end is connected to the second temporary inverted arch; S45, excavating the rock and soil in the lower step area of ​​the lower right pilot tunnel, and constructing a second inverted arch in the lower step area of ​​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 inverted arch, then dismantle the first vertical temporary support, the second temporary inverted arch, the third temporary inverted arch, and the first temporary inverted arch, and construct the secondary lining of all side walls.

3. The method for tunnel construction in complex terrain and steep rock and soil 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 outside the bias retaining wall along the terrain for counter-pressure.

4. The method for tunnel construction in complex terrain and steep rock mass according to claim 2 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.

5. The method for tunnel construction in complex terrain and steep rock mass according to claim 2 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.

6. The method for tunnel construction in complex terrain and steep rock mass according to claim 2 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.

7. The method for tunnel construction in complex terrain and steep rock mass according to claim 2, characterized in that: The cross-section of the arch foot end of the second side wall primary support gradually increases from top to bottom, and the top cross-section area of ​​the third side wall primary support is smaller than the bottom cross-section area of ​​the second side wall primary support.

8. The method for tunnel construction in complex terrain and steep rock mass according to claim 1 is 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 degrees.

9. The method for tunnel construction in complex terrain and steep rock mass according to claim 1, characterized in that: The top of the primary support arch section is a reinforced concrete structure.

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