Tunnel portal section construction method through traction type landslide mass

Abstract

The invention relates to the technical field of tunnels, and provides a construction method for a tunnel portal section through a traction type landslide mass, which comprises the following steps of: constructing a first reinforcing assembly, a second reinforcing assembly, a third reinforcing assembly and a fourth reinforcing assembly on the tunnel portal section to be constructed, and constructing a middle transverse support assembly and an inclined support assembly on a main influence open cut tunnel section of a landslide; constructing an open cut tunnel lining structure of a landslide main influence open cut tunnel section, constructing a bias retaining wall on the outer side of the open cut tunnel lining structure, backfilling backfill soil from the outer contour of the open cut tunnel lining structure to the top of a first reinforcing assembly and the top of a second reinforcing assembly, adopting vertical excavation at a light and shade junction interface, adopting anchor net spraying support on the junction interface, and constructing a backfill retaining wall on the outer side of the open cut tunnel lining structure; and a cover arch is constructed between the two third reinforcing assemblies, an advanced pipe shed is constructed through the cover arch, and a landslide main influence hidden hole section and a landslide secondary influence hidden hole section are excavated. According to the method, the conventional construction thought is broken, large opening and large digging are not needed, the tunnel portal section can safely pass through the traction type landslide mass, convenience is high, and construction is controllable.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnels, and particularly relates to a construction method for the tunnel entrance section passing through a traction type landslide body. Background Art

[0002] Landslides are generally classified into traction type landslides and pushing type landslides from the formation mechanism. For a traction type landslide, a free face is formed at the front part of the bottom of the slope due to excavation or scouring, resulting in unloading and relaxation of the slope body, weakening of mechanical properties, and gradual development upwards. Especially when encountering a large landslide area, the affected area of the landslide body is large. How to safely pass the tunnel entrance section through the traction type landslide body has become an urgent problem to be solved.

[0003] There are mainly the following three construction methods for a tunnel to pass through a traction type landslide body in the prior art: One is to conduct large-scale excavation of the traction type landslide body to turn the tunnel into a cutting. The treatment plan of large-scale excavation of the tunnel is too destructive to the current natural environment and is not environmentally friendly. And in the later operation stage of large-scale excavation, with the exposure of the cutting slope, affected by rain erosion and infiltration, the sliding surface of the landslide body is prone to develop deeper, seriously threatening the operation safety of the existing road.

[0004] The second is the hidden tunnel crossing and anti-slide pile reinforcement for strengthening and improving the landslide body. By strengthening and improving the landslide body and enhancing the mechanical parameters of the soil, the tunnel crosses in the form of a hidden tunnel. During the construction process, high requirements are imposed on the grouting process. The hidden tunnel construction method is cumbersome, with high cost and extremely high construction risks. And in the later operation stage, the tunnel structure is prone to cracking and water leakage.

[0005] The third is to adopt the combined construction method of anti-slide piles + open and hidden excavation. However, the existing anti-slide pile + open tunnel form requires large anti-slide pile sizes. Generally, the manual digging process is used, and the construction in the landslide body has extremely high risks. Controlled by topographic conditions, conventional anti-slide piles, as retaining structures, often have large sizes and cannot be mechanically constructed, resulting in poor construction convenience.

[0006] In view of this, it is necessary to propose a construction method for the tunnel entrance section passing through a traction type landslide body to solve or at least alleviate the above defects. Summary of the Invention

[0007] The main purpose of the present invention is to provide a construction method for the tunnel entrance section passing through a traction type landslide body, so as to solve the technical problems of high construction risks and low convenience in the existing solutions for the tunnel entrance section passing through a traction type landslide body.

[0008] To achieve the above purpose, the present invention provides a construction method for the tunnel entrance section passing through a traction type landslide body, including the following steps: S1. Determine that the tunnel entrance section includes a landslide main-influence open cut tunnel section, a landslide main-influence buried tunnel section, and a landslide secondary-influence buried tunnel section that are connected in sequence according to the positional relationship between the planned tunnel entrance section and the landslide body and the landslide range. S2. Construct a first reinforcement assembly and a second reinforcement assembly on both sides of the landslide main-influence open cut tunnel section respectively, a third reinforcement assembly on both sides of the landslide main-influence buried tunnel section respectively, and a fourth reinforcement assembly on both sides of the landslide secondary-influence buried tunnel section respectively. S3. Excavate the landslide main-influence open cut tunnel section. S4. Use vertical excavation at the interface between the landslide main-influence open cut tunnel section and the landslide main-influence buried tunnel section, apply shotcrete with wire mesh support to the interface, then construct a collar arch between the two third reinforcement assemblies, and then construct advanced pipe-roofing using the collar arch. S5. Excavate the landslide main-influence buried tunnel section. S6. Excavate the landslide secondary-influence buried tunnel section.

[0009] Preferably, the step S3 specifically includes the following steps: S31. Remove the landslide body in the landslide main-influence open cut tunnel section, and construct an intermediate cross brace assembly and a diagonal brace assembly in the landslide main-influence open cut tunnel section; wherein, the intermediate cross brace assembly is located above the contour line of the open cut tunnel, the intermediate cross brace assembly is connected between the first reinforcement assembly and the second reinforcement assembly, the diagonal brace assembly is located on the back mountain side of the landslide main-influence open cut tunnel section, and the diagonal brace assembly supports on the outside of the second reinforcement assembly. S32. Construct the open cut tunnel lining structure of the landslide main-influence open cut tunnel section and construct a bias retaining wall on the outside of the open cut tunnel lining structure, and then backfill the gap between the bias retaining wall and the second reinforcement assembly. S33. Use backfill soil to backfill from the outer contour of the open cut tunnel lining structure to the tops of the first reinforcement assembly and the second reinforcement assembly.

[0010] Preferably, the step S5 specifically includes the following steps: S51. First, grout and reinforce the surface of the back mountain side of the landslide main-influence buried tunnel section. S52. In each excavation cycle, first use the reserved core soil bench method to excavate the arch and wall area, specifically including: S521. First excavate the first upper bench, then construct the initial support of the first upper bench, and then excavate the reserved core soil of the first upper bench. S522. Construct the first temporary inverted arch at the junction of the first upper bench and the first lower bench; wherein, both ends of the first temporary inverted arch are connected to the initial support of the first upper bench. S523. After excavating the first upper bench by a first distance, excavate the first lower bench, then apply the initial support for the first lower bench, and then excavate the reserved core soil of the first lower bench. S53. After excavating the second distance of the first lower bench, excavate the first inverted arch area, and then sequentially apply the initial support for the first inverted arch and the first inverted arch filling layer. S54. Apply the secondary lining of the arch wall corresponding to the current cycle footage.

[0011] Preferably, the step S6 specifically includes the following steps: S61. First, perform radial grouting reinforcement on the mountain side outside the contour line of the secondary affected hidden tunnel section of the landslide. S62. In each cycle footage, first use the reserved core soil bench method to excavate the arch wall area, specifically including: S621. First, excavate the second upper bench, then apply the initial support for the second upper bench, and then excavate the reserved core soil of the second upper bench. S622. Apply the second temporary inverted arch at the junction of the second upper bench and the second lower bench; wherein, both ends of the second temporary inverted arch are respectively connected to the initial support of the second upper bench. S623. After excavating the third distance of the second upper bench, excavate the second lower bench, then apply the initial support for the second lower bench, and then excavate the reserved core soil of the second lower bench. S63. After excavating the fourth distance of the second lower bench, excavate the second inverted arch area, and then sequentially apply the initial support for the second inverted arch and the second inverted arch filling layer. S64. Apply the secondary lining of the arch wall corresponding to the current cycle footage.

[0012] Preferably, the inverted arch lining structure in the step S32 is specifically obtained through the following design steps: S321. Select the first reinforcement component of the main affected inverted arch section of the landslide as the object, determine the lowest position of the inverted arch lining structure, simplify the connection between the first reinforcement component and the soil body corresponding to the lowest position as a fixed support, simplify the connection between the first reinforcement component and the intermediate cross brace component as a first hinge support, simplify the connection between the first reinforcement component and the adjacent part of the inverted arch lining structure as a second hinge support, and apply the remaining sliding force P of the landslide body to the first reinforcement component. S322. Use the formula Ph0 ≤ K(F1h1 + F2h2) to calculate the lateral pressure F2 received by the second hinge support, where h0 is the vertical distance from the position where the remaining sliding force P acts to the fixed support, K is the safety factor of the landslide, F1 is the axial force of the cross brace of the first hinge support, h1 is the vertical distance from the intermediate cross brace component to the fixed support, and h2 is the vertical distance from the second hinge support to the fixed support. S323. Simplify the lateral pressure F2 into a uniformly distributed load acting on the open cut tunnel lining structure, calculate the lateral uniformly distributed pressure received by the second hinge support, and then calculate the backfill soil pressure on the upper part of the open cut tunnel lining structure; S324. Adopt the finite element method, simplify the connection between the periphery of the open cut tunnel lining structure and the soil mass into a compression-only foundation spring, and calculate the internal force received by the open cut tunnel lining structure; S325. Adopt the comprehensive safety factor method to check the bearing capacity and reinforcement of the open cut tunnel lining structure, so as to obtain the design dimensions and reinforcement of the open cut tunnel lining structure.

[0013] Preferably, the first reinforcement assembly includes a first capping beam and a plurality of first reinforcement pile units arranged in a bite pattern along the tunnel extension direction. The plurality of first reinforcement pile units together form a reinforcement wall on the mountain side, and the first capping beam is connected to the top of the reinforcement wall on the mountain side; wherein, the bottom of each first reinforcement pile unit is embedded in the rock and soil mass by not less than 0.3 times the excavation depth, and the top of the first reinforcement pile unit extends to the ground surface; and / or each third reinforcement assembly includes a second capping beam and a plurality of second reinforcement pile units arranged in a bite pattern along the tunnel extension direction. The plurality of second reinforcement pile units together form a reinforcement wall, and the second capping beam is connected to the top of the reinforcement wall; wherein, the bottom of each second reinforcement pile unit is embedded in the rock and soil mass by not less than 0.3 times the excavation depth, and the top of the second reinforcement pile unit extends to the ground surface.

[0014] Preferably, the second reinforcement assembly includes a plurality of pile-column units arranged at intervals along the tunnel extension direction. Each pile-column unit includes a drilled cast-in-place pile with overlapping joints and a reinforced concrete column connected to the top of the drilled cast-in-place pile with overlapping joints; wherein, the top of the reinforced concrete column is higher than the middle cross-brace assembly by not less than 1 m, and the bottom of the drilled cast-in-place pile with overlapping joints is embedded in the rock and soil mass by not less than 0.3 times the excavation depth.

[0015] Preferably, the diagonal bracing assembly includes a plurality of diagonal bracing units arranged in one-to-one correspondence with the pile-column units. Each diagonal bracing unit includes a diagonal bracing and a reinforced concrete pier; wherein, the depth of the reinforced concrete pier embedded in the rock and soil mass is not less than 2 m, the lower end of the diagonal bracing is connected to the reinforced concrete pier, and the upper end of the diagonal bracing is connected to the reinforced concrete column.

[0016] Preferably, the following steps are further included between step S2 and step S3: S21. Construct three rows of anchor cables from top to bottom in sequence; wherein, each row of anchor cables includes anchor cables arranged in one-to-one correspondence with the first reinforcement pile units. Each anchor cable includes an anchoring end and a connecting end arranged opposite to each other along its own extension direction. The connecting end is connected to the corresponding first reinforcement pile unit, and the anchoring end extends obliquely downward from the connecting end towards the inside of the rock and soil mass on the mountain side and is anchored into the rock and soil mass. S22. In the first reinforcement pile unit, a through hole for the drainage pipe to penetrate is drilled, and the drainage pipe is buried; wherein, the drainage pipe penetrates through the through hole and is inclined, the low end of the drainage pipe is located on the back mountain side of the first reinforcement pile unit and is communicated with the tunnel drainage system, and the high end of the drainage pipe is located on the mountain side of the first reinforcement pile unit.

[0017] Preferably, the open cut tunnel lining structure is a special-shaped structure, the open cut tunnel lining structure includes an arch wall lining on the mountain side and an arch wall lining on the back mountain side, the thickness of the arch wall lining on the mountain side is greater than the thickness of the arch wall lining on the back mountain side, and the thickness of the arch wall lining on the mountain side gradually increases from the arch crown to the first reinforcement pile unit.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a construction method for the tunnel entrance section passing through the traction type landslide body. By constructing the first reinforcement component, the second reinforcement component, the third reinforcement component, and the fourth reinforcement component in the proposed tunnel entrance section, constructing the intermediate cross brace component and the diagonal brace component in the open cut tunnel section affected by the main landslide, constructing the open cut tunnel lining structure of the open cut tunnel section affected by the main landslide and constructing the bias pressure retaining wall on the outer side of the open cut tunnel lining structure, using backfill soil to backfill from the outer contour of the open cut tunnel lining structure to the top of the first reinforcement component and the top of the second reinforcement component, vertically excavating at the interface between the open cut and the closed cut, adopting bolt-mesh-shotcrete support for the interface, then constructing a collar arch between the two third reinforcement components, and then using the collar arch to construct the advanced pipe shed, excavating the dark tunnel section affected by the main landslide and the dark tunnel section affected by the secondary landslide, so as to pass through the traction type landslide body.

[0019] This application breaks the conventional construction idea, does not require large-scale excavation, nor does it require large-area grouting reinforcement of the landslide body, realizes the safe passage of the tunnel entrance section through the traction type landslide body, has high convenience and controllable construction. The first reinforcement component, the second reinforcement component, the third reinforcement component, and the fourth reinforcement component of this application are convenient for mechanized construction, have high convenience and controllable construction, and the increased structural strength and stiffness can make up for the deficiencies of the conventional anti-slide pile construction. In addition, the dark tunnel section affected by the main landslide and the dark tunnel section affected by the secondary landslide rely on the innovative dark tunnel construction method combined with the excavation support system to effectively resist the lateral thrust of the traction type landslide on the mountain side, ensuring the construction safety of the tunnel entrance section in the traction type landslide section. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0021] Figure 1 Schematic diagram of a process in an embodiment of the present invention; Figure 2 Schematic diagram of the influence range of a traction type landslide body in an embodiment of the present invention; Figure 3 Schematic plan layout diagram after completion of step S7 in an embodiment of the present invention; Figure 4 Elevation view of the main influence open tunnel section of the landslide after completion of step S7 in an embodiment of the present invention; Figure 5 Elevation view of the main influence hidden tunnel section of the landslide in an embodiment of the present invention; Figure 6 Elevation view of the secondary influence hidden tunnel section of the landslide in an embodiment of the present invention; Figure 7 Elevation view of the excavation of the main influence hidden tunnel section of the landslide in an embodiment of the present invention; Figure 8 Elevation view after completion of step S4 in an embodiment of the present invention; Figure 9 Schematic diagram of the force on the first reinforcement assembly in an embodiment of the present invention; Figure 10 Schematic diagram of the force on the open tunnel lining structure in an embodiment of the present invention.

[0022] The realization of the object, functional features and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings.

[0023] Explanation of the reference numerals in the drawings: 110. First reinforcement assembly; 111. First capping beam; 112. First reinforcement pile unit; 120. Second reinforcement assembly; 1211. Drilled cast-in-place pile; 1212. Reinforced concrete column; 130. Intermediate cross brace assembly; 131. Inclined brace assembly; 1311. Inclined support; 1312. Reinforced concrete pier; 140. Open tunnel lining structure; 141. Arch wall lining on the mountain side; 142. Arch wall lining on the back mountain side; 150. Bias retaining wall; 160. Backfill soil; 170. Anchor cable; 210. Third reinforcement assembly; 211. Second capping beam; 212. Second reinforcement pile unit; 220. Socket arch; 230. Advanced pipe shed; 241. First upper bench; 242. Initial support of the first upper bench; 243. Reserved core soil of the first upper bench; 244. First temporary invert; 245. First lower bench; 246. Initial support of the first lower bench; 247. Initial support of the first invert; 248. First invert filling layer; 249. Secondary lining of the arch wall; 250. Steel pipe; 310. Fourth reinforcement assembly; 320. Grouting small duct. Detailed implementation manners

[0024] It should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] In the present invention, the descriptions involving "first", "second", etc. are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0027] Please refer to the attached Figures 1 to 10 , a construction method for the tunnel portal section passing through a traction type landslide body in an embodiment provided by the present invention includes the following steps: S1. According to the positional relationship between the planned tunnel portal section and the landslide body and the landslide range, determine that the tunnel portal section includes a landslide main influence open cut tunnel section, a landslide main influence hidden tunnel section, and a landslide secondary influence hidden tunnel section that are connected in sequence; It should be noted that the application scenario targeted by this application is a relatively serious traction type landslide scenario on the slope of the planned tunnel portal section. Such a traction type landslide has an obvious impact on the portal section, specifically manifested in that the entire open cut tunnel section is within the main influence area of the landslide, and at the same time, part of the hidden tunnel section is within the main influence area of the landslide and part is within the general influence area. The length of the section in the general influence area is usually taken as three to five times the tunnel excavation width B, that is, 3B~5B. For the tunnel portal section passing through this scenario, the construction method for the tunnel portal section passing through a traction type landslide body of this application is proposed.

[0028] S2. Construct a first reinforcement component 110 and a second reinforcement component 120 on both sides of the landslide main influence open cut tunnel section respectively, a third reinforcement component 210 on both sides of the landslide main influence hidden tunnel section respectively, and a fourth reinforcement component 310 on both sides of the landslide secondary influence hidden tunnel section respectively; S3. Excavate the landslide main influence open cut tunnel section; As a preferred implementation manner, the step S3 specifically includes the following steps: S31. Remove the landslide mass within the main landslide - affected open - cut tunnel section, and install the intermediate cross - brace assembly 130 and the diagonal - brace assembly 131 in the main landslide - affected open - cut tunnel section. Among them, the intermediate cross - brace assembly 130 is located above the contour line of the open - cut tunnel, the intermediate cross - brace assembly 130 is connected between the first reinforcement assembly 110 and the second reinforcement assembly 120, the diagonal - brace assembly 131 is located on the mountain - backing side of the main landslide - affected open - cut tunnel section, and the diagonal - brace assembly 131 supports on the outside of the second reinforcement assembly 120. Specifically, after completing step S2, there is a continuous reinforcement wall on the mountain - backing side of the planned tunnel entrance section. At this time, the landslide mass within the main landslide - affected open - cut tunnel section can be gradually removed to provide construction space for subsequent components. To accurately describe the positions of different components, the mountain - backing side referred to in this application is the side close to the mountain where the landslide occurred, and the mountain - facing side is the side far from the mountain where the landslide occurred.

[0029] As a preferred example, the intermediate cross - brace assembly 130 can be set 2 m away from the tunnel crown in the main landslide - affected open - cut tunnel section. Preferably, the intermediate cross - brace assembly 130 includes multiple reinforced - concrete cross - braces arranged at intervals along the tunnel extension direction, and the width × height of each reinforced - concrete cross - brace is 0.7 m × 0.9 m. The intermediate cross - brace assembly 130 can transfer part of the traction - type landslide thrust to the outer second reinforcement assembly 120 and the diagonal - brace assembly 131, effectively sharing part of the traction - type landslide thrust by the second reinforcement assembly 120 and the diagonal - brace assembly 131, improving the stress system. Moreover, the first reinforcement assembly 110 and the intermediate cross - brace assembly 130 together form a three - dimensional support system, effectively improving the safety of the tunnel.

[0030] S32. Install the open - cut tunnel lining structure 140 in the main landslide - affected open - cut tunnel section and install the bias - pressure retaining wall 150 on the outside of the open - cut tunnel lining structure 140, and then backfill the gap between the bias - pressure retaining wall 150 and the second reinforcement assembly 120. S33. Use backfill soil 160 to backfill from the outer contour of the open - cut tunnel lining structure 140 to the tops of the first reinforcement assembly 110 and the second reinforcement assembly 120.

[0031] As a preferred example, backfill soil 160 with a cement content of 8% can be used to backfill from the outer contour of the open - cut tunnel lining structure 140 to the tops of the first reinforcement assembly 110 and the second reinforcement assembly 120.

[0032] S4. Use vertical excavation at the interface between the main landslide - affected open - cut tunnel section and the main landslide - affected buried - tunnel section, adopt shotcrete - with - wire - mesh support for the interface, then install a collar arch 220 between two third - reinforcement assemblies 210, and then use the collar arch 220 to install advanced pipe - shed 230. Such as Figure 8As shown in the figure, for construction safety, considering that the traction landslide mainly exerts a thrust along the transverse direction of the tunnel and the longitudinal tunnel is less stressed, preferably, at the interface between the open-cut tunnel section mainly affected by the landslide and the hidden tunnel section mainly affected by the landslide (i.e., the interface between the open-cut and hidden parts), the third reinforcement components 210 are arranged on both sides + the anchor mesh shotcrete support for the free face of the longitudinal slope. Preferably, the third reinforcement components 210 are bored piles with a pile diameter of 1.2 m, a lap of 0.4 m between piles, and the bored piles are embedded in the rock and soil mass by no less than 0.3 times the excavation depth. The anchor mesh shotcrete uses 10 cm thick C20 steel fiber shotcrete, φ8 mm steel mesh, and mortar bolts with a length of 4 m and a diameter of φ22.

[0033] Furthermore, as Figure 8 shown, an arch ring 220 and φ108 advanced long pipe-roof can be adopted, and the length of the long pipe-roof is 30 m. Further, steel bars can be planted in the bored piles, and connecting steel plates are arranged at both ends of the arch ring 220 to realize the connection between the two.

[0034] S5, Excavate the hidden tunnel section mainly affected by the landslide; S6, Excavate the hidden tunnel section secondarily affected by the landslide.

[0035] In the solution of this application, according to the influence degree of the traction landslide body on different sections of the tunnel, it is divided into the open-cut tunnel section mainly affected, the hidden tunnel section mainly affected, and the hidden tunnel section secondarily affected. The first reinforcement components 110, the second reinforcement components 120, the third reinforcement components 210, and the fourth reinforcement components 310 are constructed specifically in different paragraphs. The middle cross bracing components 130, the diagonal bracing components 131, and the second reinforcement components 120 form a three-dimensional spatial support structure, transferring part of the traction landslide thrust to the second reinforcement components 120 and the diagonal bracing components 131 to form a decentralized stress structure. The open-cut tunnel lining structure 140 is located between the reinforcement components, avoiding all the traction landslide thrust directly acting on the open-cut tunnel lining structure 140 and effectively protecting the open-cut tunnel lining structure 140.

[0036] At the interface between the open-cut tunnel section mainly affected by the landslide and the hidden tunnel section mainly affected by the landslide, vertical excavation + anchor mesh shotcrete support is adopted to avoid disturbing the traction landslide body by the traditional bench cut method. At the same time, the arch ring 220 and the advanced pipe-roof 230 are used to form a shell protection, providing safe conditions for the excavation of the hidden tunnel section. The bias retaining wall 150 can resist the remaining landslide thrust, and the backfill soil 160 balances the earth pressure behind the bias retaining wall 150 by its own weight, and the bias retaining wall 150 can prevent the offset of the open-cut tunnel lining structure 140.

[0037] The solution of this application breaks the conventional construction idea, does not require large-scale excavation, nor does it require large-area grouting reinforcement of the landslide body. It can not only enable the tunnel entrance section to safely pass through the pulling landslide body, but also the first reinforcement component 110, the second reinforcement component 120, the third reinforcement component 210, and the fourth reinforcement component 310 of this application are convenient for mechanized construction, with high convenience, controllable construction, and the increased structural strength and stiffness can make up for the deficiencies of conventional anti-slide pile construction. In addition, the main influence blind tunnel section and the secondary influence blind tunnel section can combine innovative construction methods and excavation support systems to effectively resist the lateral thrust of the pulling landslide on the mountain side, ensuring the construction safety of the tunnel entrance section in the pulling landslide section.

[0038] As a preferred implementation manner, the step S5 specifically includes the following steps: S51, first grout and reinforce the surface of the back mountain side of the blind tunnel section mainly affected by the landslide; S52, in each cycle of the advance footage, first use the reserved core soil bench method to excavate the arch wall area, specifically including: S521, first excavate the first upper bench 241, then apply the initial support 242 for the first upper bench, and then excavate the reserved core soil 243 for the first upper bench; preferably, the initial support 242 for the first upper bench can use shotcrete with wire mesh + 22b I-beam, and the longitudinal spacing of the 22b I-beam is 0.5m.

[0039] S522, apply the first temporary inverted arch 244 at the junction of the first upper bench 241 and the first lower bench 245; wherein, both ends of the first temporary inverted arch 244 are respectively connected to the initial support 242 for the first upper bench; preferably, the first temporary inverted arch 244 uses 20b I-beam, and the longitudinal spacing is 0.5m.

[0040] S523, after excavating the first distance in the first upper bench 241, excavate the first lower bench 245, then apply the initial support 246 for the first lower bench, and then excavate the reserved core soil for the first lower bench; preferably, the first distance is 5m, and the initial support 246 for the first lower bench can use shotcrete with wire mesh + 22b I-beam, and the longitudinal spacing is 0.5m.

[0041] S53, after excavating the second distance in the first lower bench 245, excavate the first inverted arch area, and then successively apply the initial support 247 for the first inverted arch and the first inverted arch filling layer 248; preferably, the second distance is preferably 6m.

[0042] S54, apply the secondary lining 249 of the arch wall corresponding to the current cycle of the advance footage.

[0043] Furthermore, two φ50mm lock-foot steel pipes with a length of 4m can be respectively used at the connection of the upper and lower benches and the bottom of the side wall, with a longitudinal spacing of 0.5m, to enhance the overall force of the steel frame.

[0044] In this embodiment, grout (such as cement grout, chemical grout, etc.) is injected into the ground surface on the mountain side of the main affected hidden tunnel section of the landslide to fill the cracks in the rock and soil mass, improve the strength of the ground surface soil, reduce the ground settlement caused by excavation disturbance, reduce the groundwater seepage channels, and enhance the overall anti-slide ability.

[0045] To simplify the construction process, this embodiment describes the construction steps for each cycle footage. The entire main affected hidden tunnel section of the landslide can repeat multiple cycle footages until completion. This idea is a conventional idea in the field and will not be elaborated here. In this embodiment, the heading face is divided into upper and lower benches, and the excavation is carried out step by step to reduce the disturbance of the surrounding rock by single excavation, and the unexcavated core soil is used to maintain the stability of the heading face. Immediately after each excavation step, primary support (such as bolts, steel frames, shotcrete) is applied to form a load-bearing structure and control the deformation of the surrounding rock. The first temporary inverted arch 244 is used to connect the primary support of the first upper bench 242 to form the closure of the first upper bench 241 area, enhance the structural integrity, and prevent the crown settlement and convergence deformation. After the first lower bench 245 is advanced a certain distance, the inverted arch is excavated to form a complete tunnel inverted arch area structure, which together with the primary support constitutes a closed load-bearing ring, significantly improving the structural stability.

[0046] As a preferred embodiment, step S6 specifically includes the following steps: S61, first, radially grout and reinforce the mountain side outside the contour line of the secondary affected hidden tunnel section of the landslide; preferably, a grouting small duct 320 can be used for grouting and reinforcement.

[0047] S62, in each cycle footage, first use the reserved core soil bench method to excavate the arch wall area, specifically including: S621, first excavate the second upper bench, then apply the primary support of the second upper bench, and then excavate the reserved core soil of the second upper bench; preferably, the primary support of the second upper bench can adopt bolt-net-shotcrete + 22b I-beam, and the longitudinal spacing of the 22b I-beam is 0.5 m.

[0048] S622, apply the second temporary inverted arch at the junction of the second upper bench and the second lower bench; wherein, both ends of the second temporary inverted arch are respectively connected to the primary support of the second upper bench; preferably, the second temporary inverted arch adopts 20b I-beam, and the longitudinal spacing is 0.5 m.

[0049] S623, after excavating the third distance in the second upper bench, excavate the second lower bench, then apply the primary support of the second lower bench, and then excavate the reserved core soil of the second lower bench; preferably, the third distance is 5 m, and the primary support of the second lower bench can adopt bolt-net-shotcrete + 22b I-beam, and the longitudinal spacing is 0.5 m.

[0050] S63. After excavating the fourth distance at the second lower bench, excavate the second inverted arch area, and then successively construct the primary support for the second inverted arch and the filling layer of the second inverted arch; preferably, the second distance is preferably 6 m.

[0051] S64. Construct the secondary lining 249 of the arch wall corresponding to the current cycle footage.

[0052] To simplify the construction process, the construction steps for each cycle footage are described in this embodiment. The entire landslide secondary-influenced blind tunnel section can be repeated for multiple cycle footages until completion. This idea is a conventional idea in the art and will not be elaborated here. In this embodiment, grout is injected into the mountain side outside the contour line of the landslide secondary-influenced blind tunnel section to fill the fissures in the rock and soil mass, improve the strength and self-stability of the rock and soil mass between the fourth reinforcement components 310, reduce the landslide risk caused by excavation disturbance, and jointly form a three-dimensional reinforcement structure with the fourth reinforcement components 310.

[0053] By dividing the heading face into upper and lower benches and excavating step by step to reduce the disturbance of the surrounding rock during single excavation, the unexcavated core soil is used to maintain the stability of the heading face. Immediately after each excavation step, construct the primary support (such as bolts, steel frames, shotcrete) to form a load-bearing structure and control the deformation of the surrounding rock. Connect the primary support of the second upper bench through the second temporary inverted arch to form the closure of the second upper bench area, enhance the integrity of the structure, and prevent the crown settlement and convergence deformation. After the second lower bench advances a certain distance, excavate the inverted arch to form a complete tunnel inverted arch area structure, which together with the primary support constitutes a closed load-bearing ring, significantly improving the structural stability.

[0054] As a preferred embodiment, the first reinforcement component 110 includes a first crown beam 111 and a plurality of first reinforcement pile units 112 arranged in an interlocking manner along the tunnel extension direction. The plurality of first reinforcement pile units 112 together form a reinforcement wall on the mountain side, and the first crown beam 111 is connected to the top of the reinforcement wall on the mountain side; wherein, the bottom of each first reinforcement pile unit 112 is embedded in the rock and soil mass by not less than 0.3 times the excavation depth, the top of the first reinforcement pile unit 112 extends to the ground surface, and the excavation depth is the maximum depth from the ground surface to the bottom of the open cut tunnel lining structure 140.

[0055] And / or each third reinforcement component 210 includes a second crown beam 211 and a plurality of second reinforcement pile units 212 arranged in an interlocking manner along the tunnel extension direction. The plurality of second reinforcement pile units 212 together form a reinforcement wall, and the second crown beam 211 is connected to the top of the reinforcement wall; wherein, the bottom of each second reinforcement pile unit 212 is embedded in the rock and soil mass by not less than 0.3 times the excavation depth, the top of the second reinforcement pile unit 212 extends to the ground surface, and the excavation depth is the maximum depth from the ground surface to the bottom of the open cut tunnel lining structure 140.

[0056] Such as Figure 3As shown in the figure, the first reinforcement pile unit 112 is arranged on the mountainside outside the tunnel outline. Preferably, each first reinforcement pile unit 112 includes a reinforced concrete pile and a plain pile. The first reinforcement pile unit 112 adopts a bored secant pile 1211. By connecting the piles along the tunnel extension direction in a secant manner, a continuous and airtight reinforcement wall on the mountainside is formed, effectively blocking the potential slip surface, significantly enhancing the anti-sliding ability of the slope, and preventing the landslide of the mountain body.

[0057] As Figure 5 shown in the figure, third reinforcement components 210 are respectively arranged on both sides of the main affected hidden tunnel section of the landslide. Preferably, the third reinforcement component 210 preferably adopts a bored secant pile 1211 to form a reinforcement wall. Further, cement slurry surface grouting reinforcement can also be carried out on the shallow-buried side tunnel rock and soil mass by using φ50mm steel pipes 250 on the back mountain side of the main affected hidden tunnel section of the landslide: the spacing of the φ50mm steel pipes 250 is set to 1.5m×1.5m, and the length of the steel pipes 250 is 10m, strengthening the strength of the rock and soil mass in the main affected hidden tunnel section and ensuring the safety and stability of the tunnel during construction.

[0058] Preferably, the pile diameters of the reinforced concrete pile and the plain pile are 1.2m, and the width×height of the first capping beam 111 = 1.6m×1m. The first capping beam 111 is used to enhance the integrity of the piles. The depth of the pile bottom embedded in the rock and soil mass ≥ 0.3 times the excavation depth, ensuring that the pile body has sufficient uplift bearing capacity to resist the uplift risk caused by the groundwater buoyancy and the lateral pressure of the mountain body. The pile top extends to the ground surface, forming a full-height support from the ground surface to the deep part, effectively restricting the deformation of the shallow loose soil body and preventing the ground surface from collapsing. In addition, the first reinforcement pile unit 112 adopts a bored secant pile 1211, which can also play the role of a water-stop curtain, reducing the additional load of the pore water pressure on the support structure. In addition, the bored secant pile 1211 process is mature and can be mechanized, effectively improving the construction convenience.

[0059] As a preferred embodiment, the second reinforcement component 120 includes a plurality of pile-column units arranged at intervals along the tunnel extension direction. Each pile-column unit includes a bored secant pile 1211 and a reinforced concrete column 1212 connected to the top of the bored secant pile 1211; wherein, the top of the reinforced concrete column 1212 is not less than 1m higher than the middle cross brace component 130, and the bottom of the bored secant pile 1211 is embedded in the rock and soil mass not less than 0.3 times the excavation depth, and the excavation depth is the maximum depth from the ground surface to the bottom of the open tunnel lining structure 140.

[0060] As Figure 3As shown in the figure, the pile-column units are arranged on the mountainside side outside the outer contour of the tunnel, that is, on the opposite side of the first reinforced pile unit 112. Each of the pile-column units includes a drilled secant pile 1211 and a reinforced concrete column 1212 connected to the top of the drilled secant pile 1211. Preferably, the reinforced concrete column 1212 is rigidly connected to the drilled secant pile 1211 to directly transfer the upper load (such as part of the traction landslide thrust transmitted by the middle cross brace assembly 130) to the pile foundation, forming a three-dimensional force-bearing system of pile-column-cross brace, significantly enhancing the overall anti-overturning and anti-sliding capabilities of the structure.

[0061] The embedding depth of the secant pile is ≥ 0.3 times the excavation depth to ensure that the pile bottom is located in the stable rock and soil layer, and the resistance of the rock and soil mass is used to limit the deformation of the pile body, effectively controlling the surface settlement caused by tunnel excavation. The top of the reinforced concrete column 1212 is higher than the middle cross brace assembly 130 by ≥ 1 m to form a rigid frame structure. The stable stress-bearing areas of the middle cross brace assembly 130 and the reinforced concrete column 1212 are connected to improve the lateral stiffness. At the same time, a vertical backfill space can be formed, and backfill soil 160 is used for backfilling in the later stage, which can improve the lateral resistance effect of the overall structure. In addition, the technologies of the drilled secant pile 1211 and the reinforced concrete column 1212 are mature and can be mechanized, effectively improving the construction convenience.

[0062] Furthermore, fourth reinforcement components 310 are respectively arranged on both sides of the secondary influence dark tunnel section of the landslide. Preferably, the fourth reinforcement components 310 adopt bored piles with a pile diameter of 1.2 m and a pile spacing of 1.6 m. The piles are embedded in the rock and soil mass by not less than 0.3 times the excavation depth. At the same time, after excavation, radial grouting reinforcement is carried out on the arch wall on the mountainside side of the rock and soil mass in the tunnel, as Figure 6 shown. Preferably, φ50 mm steel pipes 250 with a length of 5 m are used, and the reinforcement spacing is 1 m × 1.5 m to strengthen the strength of the rock and soil mass between the piles and ensure the safety of construction.

[0063] Furthermore, the diagonal brace assembly 131 includes a plurality of diagonal brace units arranged in one-to-one correspondence with the pile-column units. Each of the diagonal brace units includes a diagonal brace 1311 and a reinforced concrete pier 1312. Among them, the depth of the reinforced concrete pier 1312 buried in the rock and soil mass is not less than 2 m. The low end of the diagonal brace 1311 is connected to the reinforced concrete pier 1312, and the high end of the diagonal brace 1311 is connected to the reinforced concrete column 1212.

[0064] The diagonal bracing assembly 131 in this embodiment includes multiple diagonal bracing units arranged in one-to-one correspondence with the pile column units. Specifically, the buried depth of the reinforced concrete pier 1312 is ≥ 2 m. Such a deep burial form can significantly increase the frictional resistance on the pier side and the passive earth pressure at the end, effectively resisting the horizontal force of the landslide mass. The diagonal bracing assembly 131 of the present application can transfer part of the traction landslide thrust to the reinforced concrete pier 1312 embedded in the soil mass, improve the overall stress, and enhance the safety of the tunnel portal section. Preferably, the reinforced concrete pier 1312 is in the form of a square pier, and one side close to the reinforced concrete column 1212 is set as an inclined plane. The lower end of the diagonal brace 1311 is connected to the inclined plane. Preferably, the size of the diagonal brace 1311 is width × height = 0.7 m × 0.9 m.

[0065] As a preferred implementation manner, the following steps are further included between step S2 and step S3: S21, construct three rows of anchor cables from top to bottom in sequence; wherein, each row of anchor cables includes anchor cables 170 arranged in one-to-one correspondence with the first reinforcement pile unit 112. Each anchor cable 170 includes an anchoring end and a connecting end arranged oppositely along its own extending direction. The connecting end is connected to the corresponding first reinforcement pile unit 112, and the anchoring end extends obliquely downward from the connecting end towards the interior of the rock and soil mass on the mountain side and is anchored into the rock and soil mass. S22, drill a through hole for the drain pipe to penetrate in the first reinforcement pile unit 112 and bury the drain pipe; wherein, the drain pipe penetrates through the through hole and is obliquely arranged. The lower end of the drain pipe is located on the mountain-back side of the first reinforcement pile unit 112 and is communicated with the tunnel drainage system, and the upper end of the drain pipe is located on the mountain side of the first reinforcement pile unit 112.

[0066] In this embodiment, three rows of prestressed anchor cables 170 are arranged downward from the pile top in the main affected open cut tunnel section of the landslide, and part of the traction landslide thrust of the pile body is transferred to the deep rock stratum on the mountain side. Preferably, the anchoring end is anchored into the strongly weathered rock stratum not less than 5 m, the vertical spacing of the anchor cables 170 is 4 m, and the horizontal spacing is 3 m.

[0067] The drain pipe is obliquely arranged and drains naturally by the action of gravity, effectively reducing the pore water pressure of the rock and soil mass on the mountain side and reducing the additional water load. The drain pipe can be communicated with the tunnel drainage network to form a complete drainage path, for example, communicated with the tunnel side ditch or intercepting ditch to drain the water body on the mountain side in time.

[0068] Furthermore, the open cut tunnel lining structure 140 is a special-shaped structure. The open cut tunnel lining structure 140 includes an arch wall lining 141 on the mountain side and an arch wall lining 142 on the mountain-back side. The thickness of the arch wall lining 141 on the mountain side is greater than the thickness of the arch wall lining 142 on the mountain-back side, and the thickness of the arch wall lining 141 on the mountain side gradually increases from the arch top to the first reinforcement pile unit 112.

[0069] As Figure 4 shown, to ensure that the tunnel structure in the main affected segment of the landslide during the operation period can resist the landslide traction force for a long time and prevent the structure from being damaged or destroyed, the open cut tunnel lining structure 140 adopts an asymmetric structure with a thin arch and thick wall on the inner side against the mountain, that is, the thickness of the arch wall lining 141 on the mountain side is greater than the thickness of the arch wall lining 142 on the back mountain side, and the thickness of the arch wall lining 141 on the mountain side gradually increases from the arch crown to the reinforcement pile unit. For example, the thickness of the arch wall lining 142 on the back mountain side is set to 1.1 m, and the thickness of the arch wall lining 141 on the mountain side is set to 2.6 m. A bias retaining wall 150 is adopted on the outer side (back mountain side) to prevent the offset of the open cut tunnel lining, further dispersing the traction thrust of the landslide mass. Finally, the soil body is backfilled from the arch crown of the open cut tunnel lining structure 140 to further resist the traction thrust of the landslide mass. The special-shaped open cut tunnel lining structure 140 with a thin arch and thick wall in this embodiment can strengthen the structural stiffness on the mountain side of the tunnel, make up for the damage or destruction of the open cut tunnel lining structure 140 caused by the increase in the traction landslide thrust due to adverse factors such as extreme weather during the operation period of the tunnel, improve the safety toughness of the tunnel structure, and ensure the long-term safety of the tunnel structure.

[0070] As Figure 9 and Figure 10 shown, as a preferred embodiment, the open cut tunnel lining structure 140 in the step S32 is specifically obtained through the following design steps: S321, Select the first reinforcement component 110 in the main affected segment of the landslide as the object, determine the lowest position of the open cut tunnel lining structure 140, simplify the soil connection part corresponding to the lowest position of the first reinforcement component 110 as a fixed support, simplify the connection part between the first reinforcement component 110 and the intermediate cross brace component 130 as a first hinge support, simplify the adjacent part between the first reinforcement component 110 and the open cut tunnel lining structure 140 as a second hinge support, and apply the remaining sliding force P of the landslide mass to the first reinforcement component 110; Specifically, the limit equilibrium method is usually used for slope stability calculation. According to different assumptions about the forces between slices, landslide calculation theories such as the Bishop method, the simple slice method, and the transfer coefficient method can be adopted. The transfer coefficient method is used to conduct landslide stability analysis and calculate the remaining sliding force P = T - F (T is the slope sliding force, and F is the slope anti-sliding force). The specific slope calculation can be based on the slope stability calculation methods for different slip surface forms in Appendix A of the Technical Code for Building Slope Engineering (GB 50330 - 2013). Therefore, the remaining sliding force P of the landslide mass can be obtained by the methods of the existing technology and will not be elaborated here.

[0071] In this embodiment, according to the structural interrelationship and force characteristics of the open-cut tunnel lining structure 140 and the first reinforcement assembly 110, the connection between the first reinforcement assembly 110 and the soil body corresponding to the lowest position is simplified to a fixed support, the connection between the first reinforcement assembly 110 and the intermediate cross bracing assembly 130 is simplified to a first hinge support, the adjacent connection between the first reinforcement assembly 110 and the open-cut tunnel lining structure 140 is simplified to a second hinge support, and the remaining sliding force P of the landslide is applied to the first reinforcement assembly 110 for convenient calculation.

[0072] S322. Calculate the lateral pressure F2 on the second hinge support using the formula Ph0 ≤ K(F1h1 + F2h2), where h0 is the vertical distance from the acting point of the remaining sliding force P to the fixed support, in m, K is the safety factor of the landslide (generally taken as 1.35), F1 is the axial force of the cross bracing at the first hinge support. Preferably, F1 = EAδ / L, where E is the elastic modulus of the material (in KN / m 2 ), A is the cross-sectional area of the intermediate cross bracing assembly 130 (in m 2 ), δ is the displacement magnitude at the first hinge support, in m, which can be obtained from on-site measurements by burying displacement measuring points at this support point. h1 is the vertical distance from the intermediate cross bracing assembly 130 to the fixed support, in m, and h2 is the vertical distance from the second hinge support to the fixed support, in m; S323. Simplify the lateral pressure F2 into a uniformly distributed load acting on the open-cut tunnel lining structure 140, calculate the lateral uniformly distributed pressure on the second hinge support, and then calculate the pressure of the upper backfill soil 160 of the open-cut tunnel lining structure 140; Preferably, calculate the lateral uniformly distributed pressure e on the second hinge support using the formula F2 = e1h2 1， (in KN / m); preferably, calculate the pressure q1 of the upper backfill soil 160 of the open-cut tunnel lining structure 140 using the formula q1 = γh3 (where γ is the unit weight of the backfill soil 160, generally 15 - 18 KN / m 2 , h3 is the height of the backfill soil 160, in m, and q1 is in KN / m).

[0073] S324. Using the finite element method, simplify the connection between the periphery of the open-cut tunnel lining structure 140 and the soil body to a compression-only foundation spring, and calculate the internal forces on the open-cut tunnel lining structure 140; preferably, the internal forces include the bending moment M and the axial force N; S325. Using the comprehensive safety factor method, check the bearing capacity and reinforcement of the open-cut tunnel lining structure 140, so as to obtain the design dimensions and reinforcement of the open-cut tunnel lining structure 140.

[0074] Specifically, the preliminary dimensions and reinforcement of the open cut tunnel lining structure 140 can be initially designed according to experience, and the bearing capacity and reinforcement of the open cut tunnel lining structure 140 can be checked by the comprehensive safety factor method, and it can be determined whether the preliminary dimensions and reinforcement meet the requirements. If they meet, the current dimensions and reinforcement are taken as the final design dimensions and reinforcement; if not, the dimensions or reinforcement are readjusted until the design requirements are met. The comprehensive safety factor method can be used to check the bearing capacity and reinforcement of the open cut tunnel lining structure 140 according to Appendix N.0.8-2 of "Code for Design of Highway Tunnels Volume 1: Civil Engineering" (JTG 3370.1-2018), so as to obtain the dimensions and reinforcement of the designed structure. This part is the technical content recorded in the existing specifications and will not be elaborated here.

[0075] Since the position of the open cut tunnel lining structure 140 is relatively special, and the safety of the open cut tunnel lining structure 140 directly affects the safety inside the tunnel, in this embodiment, through the bearing capacity and reinforcement check, it can be ensured that the open cut tunnel lining structure 140 has a certain safety reserve when bearing the design load, thereby improving the safety of the design. By repeatedly checking and adjusting the design dimensions or reinforcement, the dimensions or reinforcement that meet the design requirements and are relatively economical can be found, thereby optimizing the structural design. Through precise checking and adjustment in the design stage, the uncertainty and risks during the construction process can be reduced, and the construction efficiency and quality can be improved.

[0076] The above are only the preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A construction method for the tunnel entrance section passing through a traction type landslide body, characterized in that, It includes the following steps: S1. According to the positional relationship between the tunnel portal section to be constructed and the landslide body and the landslide range, determine that the tunnel portal section includes a main landslide - affected open - cut tunnel section, a main landslide - affected hidden - cut tunnel section, and a secondary landslide - affected hidden - cut tunnel section that are connected in sequence; S2. Construct a first reinforcement assembly and a second reinforcement assembly on both sides of the main landslide - affected open - cut tunnel section respectively, a third reinforcement assembly on both sides of the main landslide - affected hidden - cut tunnel section respectively, and a fourth reinforcement assembly on both sides of the secondary landslide - affected hidden - cut tunnel section respectively; S3. Excavate the main landslide - affected open - cut tunnel section; S4. Adopt vertical excavation at the interface between the main landslide - affected open - cut tunnel section and the main landslide - affected hidden - cut tunnel section, apply shotcrete with wire mesh and bolts to the interface, then construct a collar arch between the two third reinforcement assemblies, and then construct advanced pipe - shed using the collar arch; S5. Excavate the main landslide - affected hidden - cut tunnel section; S6. Excavate the secondary landslide - affected hidden - cut tunnel section.

2. The construction method for the tunnel entrance section passing through the traction landslide body according to claim 1, characterized in that The specific steps of step S3 include the following steps: S31. Remove the landslide body in the main landslide - affected open - cut tunnel section, and construct an intermediate cross - brace assembly and a diagonal brace assembly in the main landslide - affected open - cut tunnel section; wherein, the intermediate cross - brace assembly is located above the contour line of the open - cut tunnel, the intermediate cross - brace assembly is connected between the first reinforcement assembly and the second reinforcement assembly, the diagonal brace assembly is located on the back - mountain side of the main landslide - affected open - cut tunnel section, and the diagonal brace assembly supports on the outside of the second reinforcement assembly; S32. Construct the lining structure of the open - cut tunnel in the main landslide - affected open - cut tunnel section and construct a bias retaining wall on the outside of the lining structure of the open - cut tunnel, and then backfill the gap between the bias retaining wall and the second reinforcement assembly; S33. Backfill with soil from the outer contour of the lining structure of the open - cut tunnel to the top of the first reinforcement assembly and the top of the second reinforcement assembly.

3. The construction method of the tunnel entrance section passing through the traction type landslide body according to claim 1, characterized in that, The specific steps of step S5 include the following steps: S51. First, grout and reinforce the surface of the back - mountain side of the main landslide - affected hidden - cut tunnel section; S52. In each cycle of advance, first adopt the reserved - core - soil bench method to excavate the arch - wall area, specifically including: S521. First excavate the first upper bench, then construct the initial support for the first upper bench, and then excavate the reserved core soil of the first upper bench; S522. Construct the first temporary invert at the junction of the first upper bench and the first lower bench; wherein, both ends of the first temporary invert are respectively connected to the initial support of the first upper bench; S523. After excavating a first distance in the first upper bench, excavate the first lower bench, then construct the initial support for the first lower bench, and then excavate the reserved core soil of the first lower bench; S53. After excavating a second distance in the first lower bench, excavate the first invert area, and then successively construct the initial support for the first invert and the first invert filling layer; S54. Construct the secondary lining of the arch - wall corresponding to the current cycle of advance.

4. The construction method for the tunnel entrance section passing through the traction landslide body according to claim 3, characterized in that, The specific steps of step S6 include the following steps: S61. First, conduct radial grouting reinforcement on the mountain - side close to the contour line of the secondary landslide - affected hidden - cut tunnel section; S62. In each cycle of advance, first adopt the reserved - core - soil bench method to excavate the arch - wall area, specifically including: S621. First excavate the second upper bench, then construct the initial support for the second upper bench, and then excavate the reserved core soil of the second upper bench; S622, construct a second temporary inverted arch at the junction of the second upper bench and the second lower bench; wherein, both ends of the second temporary inverted arch are respectively connected to the initial support of the second upper bench; S623, after excavating a third distance on the second upper bench, excavate the second lower bench, then construct the initial support of the second lower bench, and then excavate the reserved core soil of the second lower bench; S63, after excavating a fourth distance on the second lower bench, excavate the second inverted arch area, and then successively construct the initial support of the second inverted arch and the filling layer of the second inverted arch; S64, construct the secondary lining of the arch wall corresponding to the current cycle footage.

5. The construction method for the tunnel entrance section passing through the traction landslide body according to claim 2, characterized in that, The inverted arch lining structure in the step S32 is specifically obtained through the following design steps: S321, select the first reinforcement component of the main influence inverted arch section of the landslide as the object, determine the lowest position of the inverted arch lining structure, simplify the connection between the first reinforcement component and the soil body corresponding to the lowest position as a fixed support, simplify the connection between the first reinforcement component and the intermediate cross brace component as a first hinge support, simplify the connection between the first reinforcement component and the adjacent part of the inverted arch lining structure as a second hinge support, and apply the remaining landslide thrust P to the first reinforcement component; S322, use the formula Ph0≤K(F1h1+F2h2) to calculate the lateral pressure F2 received by the second hinge support, where h0 is the vertical distance from the acting point of the remaining landslide thrust P to the fixed support, K is the safety factor of the landslide, F1 is the axial force of the cross brace of the first hinge support, h1 is the vertical distance from the intermediate cross brace component to the fixed support, and h2 is the vertical distance from the second hinge support to the fixed support; S323, simplify the lateral pressure F2 as a uniformly distributed load acting on the inverted arch lining structure, calculate the lateral uniformly distributed pressure received by the second hinge support, and then calculate the backfill soil pressure on the upper part of the inverted arch lining structure; S324, adopt the finite element method, simplify the connection between the periphery of the inverted arch lining structure and the soil body as a foundation spring only under compression, and calculate the internal force received by the inverted arch lining structure; S325, adopt the comprehensive safety factor method to check the bearing capacity and reinforcement of the inverted arch lining structure, so as to obtain the design dimensions and reinforcement of the inverted arch lining structure.

6. The construction method for the tunnel portal section passing through the traction landslide body according to claim 2, characterized in that, The first reinforcement component includes a first crown beam and a plurality of first reinforcement pile units arranged in a meshing manner along the tunnel extension direction. The plurality of first reinforcement pile units jointly form a reinforcement wall on the mountain side, and the first crown beam is connected to the top of the reinforcement wall on the mountain side; wherein, the bottom of each first reinforcement pile unit is embedded in the rock and soil body not less than 0.3 times the excavation depth, and the top of the first reinforcement pile unit extends to the ground surface; and / or each of the third reinforcement components includes a second crown beam and a plurality of second reinforcement pile units arranged in a meshing manner along the tunnel extension direction. The plurality of second reinforcement pile units jointly form a reinforcement wall, and the second crown beam is connected to the top of the reinforcement wall; wherein, the bottom of each second reinforcement pile unit is embedded in the rock and soil body not less than 0.3 times the excavation depth, and the top of the second reinforcement pile unit extends to the ground surface.

7. The construction method for the tunnel entrance section passing through the traction landslide body according to claim 2, characterized in that The second reinforcement component includes a plurality of pile-column units arranged at intervals along the tunnel extension direction. Each pile-column unit includes a secant pile and a reinforced concrete column connected to the top of the secant pile. Among them, the top of the reinforced concrete column is not less than 1 m higher than the intermediate cross-brace component, and the bottom of the secant pile is embedded in the rock and soil mass not less than 0.3 times the excavation depth.

8. The construction method for the tunnel portal section passing through the traction landslide body according to claim 7, characterized in that, The inclined bracing component includes a plurality of inclined bracing units arranged in one-to-one correspondence with the pile-column units. Each inclined bracing unit includes an inclined support and a reinforced concrete pier. Among them, the depth of the reinforced concrete pier buried in the rock and soil mass is not less than 2 m. The lower end of the inclined support is connected to the reinforced concrete pier, and the upper end of the inclined support is connected to the reinforced concrete column.

9. The construction method of the tunnel entrance section passing through the traction landslide body according to claim 6, characterized in that, The following steps are further included between step S2 and step S3: S21, construct three cable anchor rows successively from top to bottom. Among them, each cable anchor row includes a cable anchor corresponding to the first reinforcement pile unit one by one. Each cable anchor includes an anchoring end and a connecting end arranged oppositely along its own extension direction. The connecting end is connected to the corresponding first reinforcement pile unit, and the anchoring end extends obliquely downward from the connecting end towards the inside of the rock and soil mass on the mountain side and is anchored into the rock and soil mass. S22, drill a through hole for the drainage pipe to penetrate in the first reinforcement pile unit and bury the drainage pipe. Among them, the drainage pipe penetrates through the through hole and is obliquely arranged. The lower end of the drainage pipe is located on the back mountain side of the first reinforcement pile unit and is connected to the tunnel drainage system, and the upper end of the drainage pipe is located on the mountain side of the first reinforcement pile unit.

10. The construction method for the tunnel portal section passing through the traction landslide body according to claim 6, characterized in that, The open cut tunnel lining structure is a special-shaped structure. The open cut tunnel lining structure includes an arch wall lining on the mountain side and an arch wall lining on the back mountain side. The thickness of the arch wall lining on the mountain side is greater than that of the arch wall lining on the back mountain side, and the thickness of the arch wall lining on the mountain side gradually increases from the arch crown to the first reinforcement pile unit.

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