Anchor pulling construction method suitable for large-span high-side-wall underground excavation subway station

Abstract

The invention discloses an anchor pulling construction method suitable for a large-span high-side-wall underground excavation subway station. The anchor pulling construction method comprises the following steps that an excavation section is sequentially divided into an arch area, a middle area and a lower area from top to bottom; a first pilot tunnel, a second pilot tunnel, a third pilot tunnel and a fourth pilot tunnel of the arch area are excavated in sequence according to the section subareas; a fifth pilot tunnel, a sixth pilot tunnel and a seventh pilot tunnel in the middle area are excavated in sequence according to the section subareas; the eighth pilot tunnel, the ninth pilot tunnel and the tenth pilot tunnel of the lower area are excavated in sequence according to the section subareas; and secondary lining operation of the formwork trolley is carried out. According to the construction method, excavation and supporting of a large-span underground structure are achieved through a three-pilot-tunnel excavation and anchor-support collaborative supporting system, and the construction method is particularly suitable for urban underground engineering with large span, high side walls and complex strata.

Description

Technical Field

[0001] This invention belongs to the field of tunnel construction technology, specifically relating to an anchoring construction method suitable for subway stations with large spans and high sidewalls that are excavated by tunneling. Background Technology

[0002] The existing methods for constructing subway stations using the cut-and-cover method include the following: ① Double-sided wall pilot tunnel method: Originating in Europe and Japan, the double-sided wall pilot tunnel method was initially used primarily for tunnel projects with weak surrounding rock (such as clay and sand layers) or complex geological conditions. Its basic principle is to reduce disturbance to the surrounding rock through sectional excavation and timely support, embodying the core concepts of the New Austrian Tunneling Method (NATM) regarding the self-supporting capacity and dynamic monitoring of the surrounding rock. This method divides the cross-section into multiple small pilot tunnels (typically including left and right sidewall pilot tunnels and core soil), achieving segmented closure of the support structure, thereby controlling surrounding rock deformation and surface settlement to a certain extent. Furthermore, support parameters and construction rhythm can be adjusted based on monitoring results, providing a degree of construction flexibility.

[0003] The double-sided wall pilot tunnel method has also revealed significant limitations in practical applications. Firstly, the construction process is complex, typically involving multiple cyclical steps such as "pilot tunnel excavation → temporary support → initial support → temporary support removal → secondary lining," resulting in a long workflow and high management difficulty. Secondly, to maintain stability at each construction stage, numerous temporary support structures (such as temporary steel frames, shotcrete, horizontal braces, and vertical braces) are required, leading to high material consumption, high construction costs, and significant project waste due to the need for later dismantling of these temporary structures, resulting in poor economic efficiency. Furthermore, the small cross-section and large number of pilot tunnels limit the operating space for large machinery, hindering mechanization and reducing construction efficiency. In the context of projects with significantly larger cross-sectional dimensions, such as subway stations with ultra-large spans and high sidewalls, these problems are further exacerbated, restricting the applicability of this method under the trend of efficient and green construction.

[0004] ② Piling-Cavity Method: The Piling-Cavity Method (PBA method) is a composite construction method developed from the traditional shallow-buried tunneling method by integrating the cut-and-cover method concept. Its basic idea is "support first, excavate later": A support framework is formed by constructing cast-in-place piles and capping beams within the pilot tunnel, and an arched structure (arch-locking) is built at the top. Subsequent earthwork excavation and secondary lining construction are carried out under the protection of this rigid support system, either in the forward or reverse direction, ultimately forming a complete permanent load-bearing structure. This method falls under the category of shallow-buried tunneling and is commonly used in subway stations with poor geological conditions and large cross-sections. It is typically designed as a multi-span frame structure, with spans connected by piles, columns, and beams.

[0005] Although the tunnel-pile method possesses a certain degree of structural stability control under specific conditions, its practical application faces numerous constraints. Firstly, the construction process is extremely complex, involving multiple pilot tunnel excavations, pile foundation drilling, rebar cage hoisting, concrete pouring, beam-slab connections, and the installation and removal of temporary supports. Frequent process transitions and significant organizational and coordination challenges arise. Secondly, pile foundation construction must be completed within narrow pilot tunnels, demanding extremely high precision in drilling, verticality control, and structural connection reliability. Construction quality is significantly affected by the working space and geological conditions, making deviations or defects prone to occur. Furthermore, the small cross-section of the pilot tunnels and the dispersed working surfaces hinder the deployment of large machinery, resulting in low mechanization, high reliance on manual labor, and low efficiency. Simultaneously, the formation of a stable support framework requires numerous temporary structures and support systems, leading to substantial material input and the need for later dismantling of some structures, resulting in resource waste and poor economic efficiency. These problems are particularly pronounced when facing subway station projects with ultra-large spans and high sidewalls. The increased structural span makes the stress distribution in the pile-beam system more complex, requiring higher standards for overall stiffness and reliability of connection nodes, further exacerbating construction difficulties and quality control risks. Therefore, the applicability of the tunnel-pile method in large-span, high-side-wall underground railway stations is significantly limited, making it difficult to meet the development needs of efficient, safe, and green construction.

[0006] ③ Initial Support Arch Method: The initial support arch method is a tunneling technique developed from the traditional arch method and the tunnel-pile method. It was initially mainly used in mountain tunnels and urban subway projects. This method borrows the "arch first, wall later" concept from the traditional arch method, forming a load-bearing arch by constructing initial support at the arch section first, and utilizing the synergistic effect of the surrounding rock and the support structure to provide stability. Compared to the tunnel-pile method, the initial support arch method eliminates temporary side piles and central column structures, replacing them with a large arch foot design to enhance the arch foot embedment effect. The excavation and construction of the lower main structure are carried out after the arch support is completed.

[0007] However, the initial support arch method has significant limitations in practical applications. First, it is highly dependent on geological conditions, requiring intact bedrock with high bearing capacity in the arch foot area, making it suitable for strata with a "soft upper layer and hard lower layer" or relatively good overall integrity. In weak, fractured, or groundwater-rich strata, the stability of the arch foot is difficult to guarantee, often requiring additional ground reinforcement, increasing construction complexity and cost. Second, the construction precision and structural quality requirements for large arch feet are extremely high; deviations during excavation and support can easily lead to stress concentration or arch instability. Furthermore, although it eliminates some temporary support structures, the initial support of the arch itself has a large cross-section and complex stress, placing higher demands on the quality control of shotcrete, anchor bolts, and steel frames, making it technically challenging. In subway stations with ultra-large spans and high sidewalls, the arch span increases significantly, further exacerbating the bearing pressure on the arch foot and the risk of structural deformation, severely limiting the applicability of this method and making it difficult to widely apply to urban underground engineering projects with complex or variable geological conditions.

[0008] Therefore, the existing methods for constructing subway stations using the cut-and-cover method have the following main drawbacks: a. Existing methods for constructing mined tunnels are complex and difficult, with delayed ring formation of the support structure, significantly increasing the difficulty of stability control: Ultra-large span tunnels have large excavation cross-sections and extensive exposed areas, resulting in rapid and uneven release of surrounding rock stress. Traditional methods rely on sectional excavation and temporary supports to maintain stability, but the multi-tunnel, multi-stage construction process leads to a severe delay in the closure of the main support structure (especially the bottom and sidewalls). Under high sidewall conditions, lateral pressure increases significantly with height, and the support system remains in a non-closed stress state for extended periods, easily leading to risks of large deformations such as arch foot instability and sidewall inward squeezing, making it difficult to guarantee overall stability.

[0009] b. Existing cut-and-cover tunnel construction methods involve a large amount of temporary work, severely limiting economic efficiency and construction effectiveness: To control the instability risks caused by large-section excavation, traditional methods require a large number of temporary support structures (such as horizontal braces, vertical braces, and temporary side piles). With increasing span and height, the number and scale of temporary structures grow non-linearly, resulting in large material inputs, long construction periods, and the need for large-scale dismantling later, leading to significant resource waste and increased costs. In densely populated urban areas, this problem further restricts the economic viability and sustainability of the project.

[0010] c. Severely fragmented workspace hinders mechanization and construction efficiency: The ultra-large cross-section is divided into multiple narrow pilot tunnels, which, while facilitating phased unloading, severely restricts the working space for large tunneling, support, and muck removal equipment. Under high sidewall conditions, vertical transportation and high-altitude operations become more difficult, construction organization becomes complex, mechanization is low, and manual labor dependence is high, making it difficult to achieve efficient and rapid construction, which contradicts the modern tunnel engineering development direction of "less manpower and intelligent operation."

[0011] d. The structure is subjected to complex stresses, posing challenges to the load-bearing capacity of key components: the ultra-large span leads to a significant increase in arch bending moment and deflection, while the high side walls exacerbate lateral pressure and arch foot thrust. In traditional construction methods, such as the pile-beam joints in the tunnel-pile method and the large arch foot in the initial support arch cap method, these become critical stress points. Under large-scale loads, these joints are prone to stress concentration, requiring extremely high construction precision and connection quality. If not properly controlled, they can easily lead to localized damage and induce overall instability.

[0012] e. Poor geological adaptability and strong dependence on surrounding rock conditions: Most traditional construction methods (such as the initial support arch cap method) require the arch foot or bottom surrounding rock to have high bearing capacity to support large-span arch structures. However, in complex urban strata, there are often "soft upper and hard lower" or weak interlayers, making it difficult to meet the arch foot embedment conditions, requiring additional stratum reinforcement, which increases construction uncertainty and technical risks. At the same time, the large cross-section excavation has a wide disturbance range, requiring higher self-stabilizing capacity of the surrounding rock, further limiting its applicability in soft and fractured strata. Summary of the Invention

[0013] The purpose of this invention is to provide an anchoring construction method suitable for large-span, high-side-wall, underground subway stations, in order to solve the above-mentioned problems existing in the prior art.

[0014] To achieve the above objectives, the present invention adopts the following technical solution: an anchoring construction method suitable for large-span, high-side-wall underground subway stations, comprising the following steps: Step A: Divide the excavation section from top to bottom into an arch region, a middle region, and a lower region. The arch region is equipped with pilot tunnels ①, ②, ③, and ④. Pilot tunnels ③ and ④ are both located between pilot tunnels ① and ②, with pilot tunnel ③ located above pilot tunnel ④. The middle region is equipped with pilot tunnels ⑤, ⑥, and ⑦. Pilot tunnel ⑦ is located between pilot tunnels ⑤ and ⑥, and is located below pilot tunnel ④. Pilot tunnel ⑤ is located below pilot tunnel ①, and pilot tunnel ⑥ is located below pilot tunnel ②. The lower region is equipped with pilot tunnels ⑧, ⑨, and ⑩. Pilot tunnel ⑩ is located between pilot tunnels ⑧ and ⑨, and is located below pilot tunnel ⑦. Pilot tunnel ⑧ is located below pilot tunnel ⑤, and pilot tunnel ⑨ is located below pilot tunnel ⑥. Step B: Excavate the station arch area through the No. 1 construction passage. According to the cross-section, excavate the No. 1, No. 2, No. 3 and No. 4 guide tunnels in the arch area in sequence. After each guide tunnel is excavated, sprayed anchor support and arch anchor cable support are carried out. Temporary support structures are also constructed. After the No. 1, No. 2, No. 3 and No. 4 guide tunnels are excavated and the initial support is closed in the circumferential direction, the temporary support structures are removed. Step C: After the arch area has been excavated beyond the location of construction passage No. 2 by a certain distance, the No. 5, No. 6 and No. 7 pilot tunnels in the middle area are excavated in sequence according to the cross-section. After the excavation is completed, the sprayed anchor support, side wall anchor cable support, temporary horizontal support, retaining plate and vertical column are constructed. After the support is stable, the retaining plate is gradually removed, and the temporary horizontal support is retained. Step D: After the central area has been excavated beyond the location of construction passage No. 3 by a certain distance, the No. 8, No. 9, and No. 10 pilot tunnels in the lower area will be excavated in sequence according to the cross-sectional zoning. After the excavation is completed, the construction of shotcrete and anchor support, sidewall anchor cable support, temporary horizontal support, retaining plate and vertical column will be carried out. After the support is stable, the retaining plate will be gradually removed, and the temporary horizontal support will be retained. Step E: After the rock excavation within the main body of the station is completed, the temporary horizontal supports and vertical columns are removed, and the secondary lining operation of the formwork trolley is carried out.

[0015] As an optional implementation of the above technical solution, in step B, the arch anchor cable support operation includes: a number of parallel boreholes are arranged at intervals on the outside of the excavated tunnel, and the arch prestressed anchor cables are driven into the boreholes, with the length direction of the arch prestressed anchor cables perpendicular to the rock stratum surface.

[0016] As an optional implementation of the above technical solution, the prestressed anchor cable includes anchor cable strands, smooth sleeves, shear reinforcement bars, and anchor cable heads. The prestressed anchor cable is fixed by anchor cable adhesive after being driven into the borehole.

[0017] As an optional implementation of the above technical solution, the shotcrete and anchor support includes initial shotcrete, erection of steel mesh, driving in anchor bolts, and re-shotcrete. One end of the anchor bolt is inserted into the rock strata, and the other end of the anchor bolt is connected to the steel mesh.

[0018] As an optional implementation of the above technical solution, the prestressed anchor cable of the arch is fixedly connected to the steel mesh through a steel pad.

[0019] As an optional implementation of the above technical solution, in step C, the excavation of the No. 5, No. 6 and No. 7 guide tunnels in the central area according to the cross-sectional partition includes: after the construction team enters the middle of the No. 2 construction channel, they first excavate a central foundation trench downwards, and then carry out construction in the central foundation trench in both front and back directions at the same time, and excavate the No. 5, No. 6 and No. 7 guide tunnels in sequence.

[0020] As an optional implementation of the above technical solution, in step D, the excavation of the No. 8, No. 9, and No. 10 guide tunnels in the lower area according to the cross-sectional partition includes: after the construction team enters the middle of the No. 3 construction channel, they first excavate a lower foundation trench downwards, and then carry out construction in the lower foundation trench in both front and rear directions simultaneously, and excavate the No. 8, No. 9, and No. 10 guide tunnels in sequence.

[0021] As an optional implementation of the above technical solution, in step E, the removal of temporary horizontal supports and vertical columns and the secondary lining operation of the formwork trolley include: removing temporary horizontal supports and vertical columns at intervals of 0.5 times the station span, and performing secondary lining operation of the formwork trolley at intervals of 1 time the station span.

[0022] The beneficial effects of this invention are as follows: This invention creatively proposes a "pull-anchor-and-arch" collaborative support system. By implementing a "large pilot tunnel, fewer sub-sections" excavation in ultra-large span, ultra-high sidewall tunnels, and combining prestressed anchor cables for overall anchoring of the arch and high straight wall areas, it achieves full-section active support with "arch-anchor synergy and wall-anchor linkage." This construction method replaces the large arch foot, temporary side piles, and numerous steel and timber supports in traditional construction methods with a prestressed pull-anchor system. This not only strengthens the arch's load-bearing capacity but also effectively controls the convergence deformation of the high sidewall through anchor cables in the straight wall area, significantly improving the integrity and deformation resistance of the support structure. With the synergistic effect of "pulling anchors" providing active constraint and "arch-and-arch" forming rigid protection of the roof slab, early support closure, fewer temporary supports, and highly mechanized operations are achieved. It is particularly suitable for urban underground engineering projects with large spans, high sidewalls, and complex geological formations, achieving a technological breakthrough in the safe, efficient, and green construction of ultra-large cross-section cut-and-cover tunnels. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the excavation section in one embodiment of the present invention; Figure 2 This is a schematic diagram of the construction steps in one embodiment of the present invention; Figure 3 This is a spatial relationship diagram between the construction passage and the main station structure in one embodiment of the present invention.

[0024] In the diagram: 1-arch prestressed anchor cable; 2-anchor rod; 3-sidewall prestressed anchor cable. Detailed Implementation

[0025] like Figures 1-3 As shown, this embodiment provides an anchoring construction method suitable for subway stations with large spans and high side walls, including the following steps: Step A involves dividing the excavation section into an arch region, a middle region, and a lower region from top to bottom. The arch region is located inside the arc at the top of the tunnel, while the middle and lower regions are located inside the high sidewalls of the tunnel sidewalls. The middle region is located below the arch region, and the lower region is located below the middle region. By constructing the tunnel in layers, the impact of rock excavation on the surrounding rock above is reduced.

[0026] The arch area has pilot tunnels ①, ②, ③, and ④. Pilot tunnels ③ and ④ are both located between pilot tunnels ① and ②, with pilot tunnel ③ above pilot tunnel ④. The middle area has pilot tunnels ⑤, ⑥, and ⑦. Pilot tunnel ⑦ is located between pilot tunnels ⑤ and ⑥, and is below pilot tunnel ④. Pilot tunnel ⑤ is below pilot tunnel ①, and pilot tunnel ⑥ is below pilot tunnel ②. The lower area has pilot tunnels ⑧, ⑨, and ⑩. Pilot tunnel ⑩ is located between pilot tunnels ⑧ and ⑨, and is below pilot tunnel ⑦. Pilot tunnel ⑧ is below pilot tunnel ⑤, and pilot tunnel ⑨ is below pilot tunnel ⑥.

[0027] Step B involves excavating the station arch area through the No. 1 construction passage using a jacking method. Based on the cross-sectional divisions, pilot tunnels ①, ②, ③, and ④ in the arch area are excavated sequentially. After excavation of each pilot tunnel, shotcrete and anchor support, as well as arch anchor cable support, are immediately implemented, and temporary support structures are constructed. These temporary support structures are removed after the excavation of pilot tunnels ①, ②, ③, and ④ is completed and the initial support circumferentially closed. The arch anchor cable support operation includes: several parallel boreholes are spaced at intervals on the outer side of the excavated tunnel, and prestressed anchor cables 1 are driven into these boreholes. The length direction of the prestressed anchor cables 1 is perpendicular to the rock strata surface. Specifically, the prestressed anchor cable includes anchor cable strands, a smooth sleeve, shear reinforcement, and an anchor head. After being driven into the borehole, the prestressed anchor cable is fixed using anchor cable adhesive.

[0028] Shotcrete and anchor support includes initial shotcrete application, installation of steel mesh, driving in anchor bolts 2, and subsequent shotcrete application. One end of the anchor bolt 2 is inserted into the rock strata, and the other end is connected to the steel mesh. The prestressed anchor cable 1 in the arch is fixedly connected to the steel mesh through steel pads. The prestressed anchor cable 1 and the anchor bolts 2 in the arch are used to improve the support effect.

[0029] Step C: After the arch area has been excavated a certain distance beyond the location of construction passage #2, the pilot tunnels ⑤, ⑥, and ⑦ in the central area are excavated sequentially according to the cross-sectional zoning. After excavation, the shotcrete and anchor support, sidewall anchor cable support, temporary lateral supports, retaining walls, and vertical columns are constructed immediately. After the support is stable, the retaining walls are gradually removed, while the temporary lateral supports are retained. The construction method of shotcrete and anchor support is the same as in step B, and the sidewall anchor cable support uses prestressed anchor cables 3. Specifically, the excavation of pilot tunnels ⑤, ⑥, and ⑦ in the central area according to the cross-sectional zoning includes: after the construction team enters the middle of construction passage #2, a central foundation trench is first excavated downwards, and then construction is carried out simultaneously in both front and rear directions within the central foundation trench, excavating pilot tunnels ⑤, ⑥, and ⑦ in sequence.

[0030] Step D: After the excavation in the central area exceeds the location of construction passage #3 by a certain distance, excavate pilot tunnels #8, #9, and #10 in the lower area according to the cross-sectional zoning. After excavation, immediately proceed with the construction of shotcrete and anchor support, sidewall anchor cable support, temporary lateral supports, retaining walls, and vertical columns. After the support is stable, gradually remove the retaining walls, retaining the temporary lateral supports. The construction method of shotcrete and anchor support is the same as in step B, and the sidewall anchor cable support uses prestressed anchor cables 3. Specifically, the excavation of pilot tunnels #8, #9, and #10 in the lower area according to the cross-sectional zoning includes: after the construction team enters the middle of construction passage #3, first excavate a lower foundation trench downwards, and then simultaneously construct in both front and rear directions within the lower foundation trench, excavating pilot tunnels #8, #9, and #10 in sequence.

[0031] Step E: After the rock excavation within the main body of the station is completed, the temporary horizontal supports and vertical columns are dismantled at intervals of 0.5 times the station span, and the secondary lining of the formwork trolley is carried out at intervals of 1 time the station span.

[0032] The core innovation of this invention's construction method lies in its innovative "anchor-and-arch" collaborative support system. This system achieves full-section active support through "large pilot tunnel, fewer sub-sections" excavation in ultra-large span, ultra-high sidewall tunnels, combined with the overall anchoring of prestressed anchor cables in the arch and high straight wall areas. This system replaces the large arch foot, temporary side piles, and numerous steel and timber supports found in traditional methods with a prestressed anchor system. This not only strengthens the arch's load-bearing capacity but also effectively controls the convergence deformation of the high sidewalls through prestressed anchor cables in the high straight wall areas, significantly improving the overall integrity and deformation resistance of the support structure. With the synergistic effect of "anchor" providing active constraint and "arch" forming rigid protection of the roof slab, early support closure, fewer temporary supports, and highly mechanized operations are achieved. This method is particularly suitable for urban underground engineering projects with large spans, high sidewalls, and complex geological formations, representing a technological breakthrough in the safe, efficient, and green construction of ultra-large cross-section tunnels.

[0033] In today's era where urban subway station construction is gradually becoming more mechanized and rapid, temporary support structures such as columns, piles, and beams can significantly affect the operation of large machinery. In addition, applying the above construction methods to subway stations with large spans and high side walls through underground excavation will result in complicated construction procedures, increase construction difficulty, and even cause delays in the construction period.

[0034] Based on the above background and considering the characteristics of large-span, high-side-wall, cut-and-cover subway station projects, this invention innovatively proposes a novel construction method suitable for large-span, high-side-wall, cut-and-cover subway stations. This method is based on the double-side-wall pilot tunnel method, the tunnel-pile method, and the initial support arch cover method. It combines the prestressed long anchor cable-anchor rod anchoring system with the synergistic support of the initial support structure. Building upon the original design of the double-side-wall pre-reserved rock column method, which only uses side-wall anchor cables, it adds arch anchor cables. Because the excavation and support of the upper pilot tunnel in the arch resembles the arch-locking construction in the tunnel-pile method, it is named the "anchor-locking arch method." A schematic diagram of the excavation and support sections is shown below. Figure 1 As shown. The optimization of the pilot tunnel excavation sequence using the "anchor-and-arch method" is based on two points: Firstly, there is the support effect of the excavation face on the nearby rock mass. In sectional excavation tunnel engineering, the stress and deformation of the surrounding rock beyond three times the tunnel diameter behind the pilot tunnel excavation face can be considered no longer affected by the disturbance of the pilot tunnel excavation. Therefore, the longitudinal excavation step distance between the upper and lower pilot tunnels on the same side should be reasonably controlled. If the excavation step distance is too small, the distance between the excavation faces of the upper and lower pilot tunnels is too close, and the disturbance effect on the upper surrounding rock is almost equivalent to the excavation of the same cross section, which greatly increases the surrounding rock load and aggravates the construction risk. The excavation face included in the disturbance range caused by the excavation of the uppermost pilot tunnel is considered as one step of excavation. After optimizing the excavation sequence of the anchor-and-arch method, the excavation sequence of the first and second layers of pilot tunnels on the left and right sides differs by 3 steps, and the excavation sequence of the first and second layers of pilot tunnels in the middle differs by 5 steps. This significantly increases the step distance between the excavation faces of the first and second layers of pilot tunnels, effectively reducing the impact of the lower pilot tunnel excavation on the upper rock mass, and is suitable for the construction of underground structures with high sidewalls.

[0035] Secondly, the prestressed long anchor cable-anchor rod anchoring system of the arch section designed by the anchor-anchor method, combined with the traditional initial support of shotcrete and steel arch frame, forms a composite synergistic initial support system (hereinafter referred to as the "anchor-support synergistic support system"), which has a strong primary / secondary support function. Yudaishan Station is located in a mudstone-sandstone composite stratum with the characteristics of "hard upper layer and soft lower layer". The prestressed anchor cable 1 of the arch section can mobilize the bearing capacity of the upper sandstone and form a synergistic support system with the initial support to play a "flexible span reduction" role, optimize the internal force of the initial support, and increase the cross-section of the pilot tunnel and reduce the number of pilot tunnels under the protection of the arch support structure. This is conducive to the operation of large machinery and saves the construction period, and is suitable for the construction of large-span and large-section underground structures.

[0036] In summary, this invention provides a method for the fully mechanized underground excavation of extra-large cross-section subway stations in rock strata—the anchor-and-arch method—which has the following characteristics: 1. Simplified construction procedures and reduced temporary support structures: The anchor-and-arch method inherits the advantages of the traditional initial support arch method, featuring fewer pilot holes, simpler procedures, and a more concise support structure. It reduces the need for side piles and temporary supports, minimizing project waste and increasing the utilization rate of the construction work surface. This makes the construction process more efficient and reduces management difficulty and costs. 2. Enhanced structural stability and effective control of surrounding rock deformation and surface settlement: This method combines the advantages of the tunnel-pile method, using an anchor-support synergistic support system to enclose the arch support and ensure overall structural stability. It can effectively control surrounding rock deformation and surface settlement, and is particularly suitable for complex geological environments with ultra-large spans and high sidewalls, providing stronger safety guarantees.

[0037] 3. Initial support closure, minimal deformation, and high safety and reliability: Drawing on the advantages of the traditional double-sidewall pilot tunnel method, the anchor-and-arch method achieves rapid closure of the initial support for each pilot tunnel, significantly reducing surrounding rock deformation and improving the safety of the construction process. Especially in large-section excavation, this early closure mechanism helps to quickly form a stable load-bearing system.

[0038] 4. Wide adaptability to geological formations: The anchor-and-arch method has wider adaptability to geological formations, suitable for various geological conditions ranging from "soft upper and hard lower" to most rock formations. By replacing the traditional arch foot and cap beam design with prestressed anchor cables and following the principle of "sidewall first, center second, excavation and support simultaneously," the deformation of the sidewalls is effectively controlled, expanding the application range of the construction method.

[0039] 5. Flexible Cross-Section Adaptability: This method achieves excavation and support of large-span underground structures through three-tunnel excavation and an anchor-support collaborative system. Under the protection of the arch-supported structure, the lower space can be excavated and supported according to the double-side-wall pilot tunnel method, adapting to the excavation needs of rock masses with various design cross-sections. Especially in rock strata, prestressed anchor cables replace temporary horizontal and vertical braces, avoiding the high-risk process of dismantling supports, while providing greater operating space for large machinery.

[0040] 6. Increase mechanization and reduce reliance on manual labor: Under fully mechanized construction conditions, the anchor-and-arch method replaces temporary supports with prestressed anchor cables, which not only reduces the high-risk dismantling and support process, but also provides ample working space for large machinery and equipment, improves construction efficiency, and reduces reliance on manual labor.

[0041] 7. Saves construction time and reduces costs: Compared with traditional construction methods (such as the double-sided wall pilot tunnel method, the reserved central rock column method, and the initial support arch cover method), the anchor-and-arch method significantly shortens the construction cycle by increasing the area of ​​the pilot tunnel and reducing the number of pilot tunnels. The use of temporary horizontal bracing + columns to control the deformation of the sidewalls saves time and costs associated with the construction and dismantling of the shotcrete temporary support, further reducing the overall project cost.

[0042] In the description of this invention, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. They can refer to fixed connections, detachable connections, or integral connections; they can be mechanical or electrical connections; they can be direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art will understand the specific meanings of these terms in this invention. Furthermore, the specific features and structures described in the embodiments are included in at least one implementation method. Those skilled in the art can combine features from different implementation methods without contradiction. The scope of protection of this invention is not limited to the specific implementation methods described above. Based on the basic technical concept of this invention, implementation methods that can be conceived by those skilled in the art without creative effort are all within the scope of protection of this invention.

Claims

1. An anchoring construction method suitable for underground subway stations with large spans and high sidewalls, characterized in that, Includes the following steps: Step A: Divide the excavation section from top to bottom into an arch region, a middle region, and a lower region. The arch region is equipped with pilot tunnels ①, ②, ③, and ④. Pilot tunnels ③ and ④ are both located between pilot tunnels ① and ②, with pilot tunnel ③ located above pilot tunnel ④. The middle region is equipped with pilot tunnels ⑤, ⑥, and ⑦. Pilot tunnel ⑦ is located between pilot tunnels ⑤ and ⑥, and is located below pilot tunnel ④. Pilot tunnel ⑤ is located below pilot tunnel ①, and pilot tunnel ⑥ is located below pilot tunnel ②. The lower region is equipped with pilot tunnels ⑧, ⑨, and ⑩. Pilot tunnel ⑩ is located between pilot tunnels ⑧ and ⑨, and is located below pilot tunnel ⑦. Pilot tunnel ⑧ is located below pilot tunnel ⑤, and pilot tunnel ⑨ is located below pilot tunnel ⑥. Step B: Excavate the station arch area through the No. 1 construction passage. According to the cross-section, excavate the No. 1, No. 2, No. 3 and No. 4 guide tunnels in the arch area in sequence. After each guide tunnel is excavated, sprayed anchor support and arch anchor cable support are carried out. Temporary support structures are also constructed. After the No. 1, No. 2, No. 3 and No. 4 guide tunnels are excavated and the initial support is closed in the circumferential direction, the temporary support structures are removed. Step C: After the arch area has been excavated beyond the location of construction passage No. 2 by a certain distance, the No. 5, No. 6 and No. 7 pilot tunnels in the middle area are excavated in sequence according to the cross-section. After the excavation is completed, the sprayed anchor support, side wall anchor cable support, temporary horizontal support, retaining plate and vertical column are constructed. After the support is stable, the retaining plate is gradually removed, and the temporary horizontal support is retained. Step D: After the central area has been excavated beyond the location of construction passage No. 3 by a certain distance, the No. 8, No. 9, and No. 10 pilot tunnels in the lower area will be excavated in sequence according to the cross-sectional zoning. After the excavation is completed, the construction of shotcrete and anchor support, sidewall anchor cable support, temporary horizontal support, retaining plate and vertical column will be carried out. After the support is stable, the retaining plate will be gradually removed, and the temporary horizontal support will be retained. Step E: After the rock excavation within the main body of the station is completed, the temporary horizontal supports and vertical columns are removed, and the secondary lining operation of the formwork trolley is carried out.

2. The anchoring construction method for large-span, high-side-wall underground subway stations according to claim 1, characterized in that, In step B, the arch anchor cable support operation includes: several parallel boreholes are arranged at intervals on the outside of the excavated tunnel, and the arch prestressed anchor cable (1) is installed in the borehole. The length direction of the arch prestressed anchor cable (1) is perpendicular to the rock stratum surface.

3. The anchoring construction method for large-span, high-side-wall underground subway stations according to claim 2, characterized in that, The prestressed anchor cable includes anchor cable strands, smooth sleeves, shear reinforcement bars, and anchor cable heads. After the prestressed anchor cable is driven into the drilled hole, it is fixed by anchor cable adhesive.

4. The anchoring construction method for large-span, high-sidewall tunnel subway stations according to claim 2, characterized in that, The shotcrete and anchor support includes initial shotcrete, erection of steel mesh, driving in anchor rods (2) and re-shotcrete. One end of the anchor rod (2) is inserted into the rock strata, and the other end of the anchor rod (2) is connected to the steel mesh.

5. The anchoring construction method for large-span, high-side-wall tunnel subway stations according to claim 4, characterized in that, The prestressed anchor cable (1) of the arch is fixedly connected to the steel mesh through a steel pad.

6. The anchoring construction method for large-span, high-sidewall tunnel subway stations according to claim 1, characterized in that, In step C, the excavation of pilot tunnels ⑤, ⑥ and ⑦ in the central area according to the cross-sectional zoning includes: after the construction team enters the middle of the No. 2 construction channel, they first excavate a central foundation trench downwards, and then carry out construction in the central foundation trench in both front and back directions simultaneously, and excavate pilot tunnels ⑤, ⑥ and ⑦ in sequence.

7. The anchoring construction method for large-span, high-side-wall tunnel subway stations according to claim 1, characterized in that, In step D, the excavation of pilot tunnels ⑧, ⑨ and ⑩ in the lower area according to the cross-sectional zoning includes: after the construction team enters the middle of the No. 3 construction channel, they first excavate a lower foundation trench downwards, and then carry out construction in the lower foundation trench in both front and back directions at the same time, and excavate pilot tunnels ⑧, ⑨ and ⑩ in sequence.

8. The anchoring construction method for large-span, high-side-wall tunnel subway stations according to claim 1, characterized in that, In step E, the removal of temporary horizontal supports and vertical columns and the secondary lining operation of the formwork trolley include: removing temporary horizontal supports and vertical columns at intervals of 0.5 times the station span, and performing secondary lining operation of the formwork trolley at intervals of 1 time the station span.

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