Method and structure for adding entrance of underground station by pipe jacking and tunneling

Abstract

This invention belongs to the field of subway engineering design and construction technology, and relates to a method and structure for adding entrances and exits in underground stations using pipe jacking and tunneling methods. In particular, it relates to a pipe jacking and tunneling receiving method applicable to adding entrances and exits in existing subway stations with water-rich soft soil strata. When adding entrances and exits to existing subway stations with water-rich soft soil strata, the pipe jacking method is used, with the receiving end on one side of the station. In this location, the station side wall is a complex combination of an angled structure and a retaining wall. By reusing the pipe jacking machine shell (which serves as both initial support and permanent structure), circumferential grouting for water sealing, ribbed steel plate pre-support, special safety measures, and the coordinated operation of tunneling construction, the problems of traditional receiving technology being limited by site, having a high risk of water seepage, and posing significant safety hazards are solved, achieving safe and efficient construction. This method is applicable to similar subway projects in water-rich soft soil strata.

Description

Technical Field

[0001] This invention belongs to the field of subway engineering construction technology, and relates to a method and structure for adding entrances and exits in underground stations using pipe jacking and tunneling. In particular, it relates to a method and structure for adding entrances and exits in existing underground stations with water-rich soft soil strata using pipe jacking and tunneling, which is especially suitable for engineering scenarios where the receiving end is in a folded working condition, the surrounding pipelines are dense, and the requirements for construction safety and environmental interference are high. Background Technology

[0002] Adding pedestrian crossings to existing subway stations in water-rich soft soil strata can effectively alleviate surrounding traffic pressure and improve residents' travel experience. However, its implementation faces several severe challenges: First, existing stations are surrounded by high traffic volume, dense buildings and structures, and stable residents' lives. Underground pipelines (such as gas pipelines and water supply pipelines) are dense and difficult to alter, requiring special protection during construction. Limited traffic guidance space makes the selection of entrance / exit sites and the layout of construction sites extremely difficult, and the construction site for the pipe jacking receiving end is also limited. Second, the main structure of the receiving end station is irregularly zigzag-shaped. Third, water-rich soft soil strata have a high risk of water seepage, which can easily lead to soil instability, piping, quicksand, and other accidents, thereby interfering with the normal operation of the subway and even threatening the safety of surrounding buildings and pipelines. In existing technologies, some construction methods attempt to improve construction conditions through simple grouting reinforcement or temporary support, but they have not formed a coordinated system of "water stop-support-shell disposal-cut-excavation" and lack targeted safety control measures. They cannot fundamentally solve the problems of water leakage, spatial adaptability and construction safety. Therefore, there is an urgent need for a new type of pipe jacking receiving method that is safe, efficient and highly adaptable. This invention aims to address three core challenges that traditional pipe jacking receiving technology struggles to overcome when adding entrances and exits to subway stations in water-rich soft soil strata, particularly under angled conditions at the receiving end. Specifically: 1. Insufficient spatial adaptability under angled working conditions: The main body of the receiving station is an irregular zigzag structure. The construction space layout and equipment docking path of traditional pipe jacking receiving technology are fixed and cannot be adapted to the non-linear working space in the angled area, which makes it difficult to connect the pipe jacking machine with the receiving structure and difficult to implement.

[0003] 2. Water seepage risk in water-rich strata is difficult to control: Water-rich soft soil strata have high water content and poor soil stability. Traditional technologies rely only on single grouting or temporary support, without forming a systematic water-stopping system. Water and sand inrush are likely to occur during pipe jacking and subsequent operations, directly threatening the operation of the subway and the safety of surrounding pipelines.

[0004] 3. Safety of abandoned shell construction under the dual conditions of angled and water-rich conditions is not guaranteed: Traditional abandoned shell technology has not been specifically designed for the complex scenario of "angled irregular space + water-rich strata with high water and soil pressure". As a result, the surrounding rock between the pipe jacking machine and the station cannot be effectively sealed and constrained, which can easily induce stress concentration, instability and collapse of the surrounding rock, and failure of the supporting water-stopping system, making it difficult to guarantee the safety of the operation and the surrounding environment. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method and structure for adding entrances and exits to underground stations using pipe jacking and tunneling methods. Specifically, for adding entrances and exits to existing subway stations in water-rich soft soil strata, where the receiving end is located on one side of the station and the station side wall is a complex combination of an angled structure and a retaining wall, this invention solves the problems of traditional receiving technologies being limited by site conditions, having a high risk of water seepage, and posing significant safety hazards by reusing the pipe jacking machine casing (serving as both initial support and permanent structure), circumferential grouting for water sealing, ribbed steel plate pre-support, specialized safety measures, and coordinated tunneling operations. This achieves safe and efficient construction and is applicable to similar subway projects in water-rich soft soil strata.

[0006] The technical solution adopted by the present invention to solve this problem is as follows: A method for adding entrances and exits to underground railway stations using the pipe jacking and tunneling method includes the following steps: S1. Pre-construction preparation and pipe jacking Reinforce the soil at the receiving end of the station. Drill exploratory holes in the reinforced soil at the receiving end inside the station to observe water leakage. Control the pipe jacking machine to advance towards the station. During the advancement, inject thixotropic mud into the soil outside the pipe wall circumferentially through the rear of the pipe jacking machine casing and the grouting holes of the pipe sections until the pipe jacking machine head touches the station retaining wall and then stop advancing. After stopping the machine, immediately inject bentonite-cement composite grout into the soil around the machine body through the pre-set grouting holes of the pipe jacking machine to form a waterproof and water-stopping ring. S2, Demolition of the upper retaining wall and advanced support A waterproof and water-stopping ring and a soil plug formed by reinforcing the soil are used as a protective system. The retaining wall is broken down in sections from top to bottom and from the middle to both sides inside the station. During the demolition process, ribbed steel plates are simultaneously led out from the top and sides of the pre-opened doorway of the station, extended to the casing of the pipe jacking machine and fixed. S3, Demolition of the lower retaining wall and advanced support The soil between the retaining wall and the pipe jacking machine head is removed in stages; the lower retaining wall is broken, and ribbed steel plates are used to connect the lower part of the station's pre-opened doorway with the bottom of the machine casing, and the outer soil is sealed. The ribbed steel plates at the bottom and the ribbed steel plates at the top and on both sides together form a circumferential closed advanced support system. S4, Transportation of the pipe jacking shell disposal equipment. The casing of the pipe jacking machine is retained, while the internal components are disassembled and transported out via the pipe jacking channel. S5, Secondary Lining Structure Construction A steel reinforcement skeleton was tied inside the pipe jacking machine casing and the ribbed steel plate advanced support system, and a waterproof concrete secondary lining structure for the entrance and exit passage was poured. S6. Structural Preservation and Post-Stage Stability After the secondary lining structure reaches its design strength, the jacking machine casing and ribbed steel plates are retained as part of the permanent structure, forming the initial support. Together with the secondary lining structure, they form a collaborative load-bearing system to jointly bear the surrounding rock load. Through the grouting holes reserved in the initial support and the grouting pipes reserved in the cast-in-place concrete secondary lining structure, secondary grouting is carried out to the soil outside the initial support and between the initial support and the secondary lining structure, forming a systematic water-stopping system.

[0007] In the above technical solution, in step S1, the underground receiving end is located on one side of the main structure of the station, and the side wall of the station where the receiving end is located is irregularly folded.

[0008] In the above technical solution, in step S1, a geological survey is conducted before construction to verify whether the soil condition is abnormal; the soil at the receiving end of the station is reinforced with high-pressure jet grouting piles to form a receiving reinforced soil body. After the reinforcement is completed, in addition to confirming the reinforcement effect through core sampling, exploratory holes are drilled in the receiving end reinforced soil body inside the station to observe the water leakage in the holes; after the above preparatory work is completed and it is confirmed that the reinforced body no longer seeps water, the pipe jacking machine is controlled to advance towards the station. During the advancement, thixotropic mud is injected circumferentially into the soil outside the pipe wall through the grouting holes of the pipe jacking machine shell and the pipe section until the pipe jacking machine head touches the station retaining wall and the jacking stops; after the machine stops, bentonite-cement composite grout is immediately injected into the soil around the machine body through the pipe jacking machine shell to form a waterproof and water-stopping ring.

[0009] In the above technical solution, in step S1, the probe holes are horizontally distributed in a grid pattern, with a hole spacing of 2.0m-3.5m, ensuring that the probe holes completely cover the reinforced area of ​​the tunnel entrance to ensure verification without blind spots; if there is no obvious water seepage for 30 minutes, the seepage volume is ≤0.1L / min, and there is no sand or mud flow, the retaining wall demolition process can proceed; if there is water seepage, a double-liquid grout must be injected through the probe holes to seal it first. The double-liquid grout includes cement grout and water glass with a volume ratio of 1:1. After the seepage stops, the water seepage is re-tested.

[0010] In the above technical solution, in step S1, the thixotropic mud injection pressure is controlled at 0.3-0.5MPa, which is slightly higher than the static water pressure of the formation. This ensures that the mud can squeeze the annular gap between the pipe jacking machine and the soil and form a complete mud cake. The pipe jacking and the soil outside the pipe are dense and without gaps. At the same time, excessive pressure is avoided to prevent the formation from being disturbed.

[0011] In the above technical solution, in step S1, after the pipe jacking machine body enters the reinforced soil at the receiving end, it continues to advance until the pipe jacking machine head touches the station retaining wall, at which point the jacking stops. Then, through the pre-set special grouting holes in the pipe jacking machine head and casing, bentonite-cement composite grout is injected into the soil surrounding the machine body to form a waterproof sealing ring. This waterproof sealing ring forms a closed ring structure around the pipe jacking machine within the surrounding soil area. The bentonite-cement composite grout used has the following proportions: 5%-7% bentonite, 15%-18% P.O42.5 cement, 75%-80% water, with an additional 0.5% early-strength agent added. After grouting, the permeability coefficient of the formed sealing ring is ≤1×10^ -6 cm / s; the overlap width between the waterproof sealing ring and the reinforcement body shall not be less than 300mm.

[0012] In the above technical solution, in step S2, under the waterproof and seepage-proof soil-stabilized protection body jointly formed by the waterproof and seepage-stopping ring and the reinforced soil, the retaining wall at the entrance opening location inside the station is demolished in sections and blocks; the retaining wall is demolished in sections along the width of the wall into 4-5 sections, with the width of each section controlled at 1.5-2m; and along the height of the wall into 3-4 sections, with the height of each section controlled at 1.2-1.5m.

[0013] In the above technical solution, in step S2, the ribbed steel plate is made of Q355B steel plate, with a main plate thickness of 12mm and a rib plate thickness of 10mm; one end of the ribbed steel plate is welded and fixed to the pre-embedded steel plate around the pre-opened doorway of the station, and the other end extends to the outer wall of the jacking machine casing and is welded, and all welds must be continuous and fully welded; after construction, if there are gaps between the steel plate and the soil and the casing, quick-setting cement grout is used to fill and compact them to block the seepage channels of the outer soil.

[0014] In the above technical solution, the following should be noted during and after the construction of steps S2 and S3: During the construction of the upper retaining wall demolition and the installation of the ribbed steel plate advanced support, as well as after the support construction is completed, 24-hour continuous monitoring should be implemented. The monitoring objects are the ribbed steel plate advanced support system and the surrounding rock within the support range. Only when the monitoring data meets the condition that the deformation is ≤3mm and the stable state of the deformation within 3mm is maintained for 3 consecutive days can the lower retaining wall demolition and subsequent related procedures be carried out.

[0015] In the above technical solution, in step S4, the internal device is disassembled and then transported through the jacking pipe channel to a preset hoisting port for hoisting and external transport.

[0016] In the above technical solution, in step S6, the casing of the pipe jacking machine and the ribbed steel plate are retained as the initial support structure and incorporated into the permanent structural system to share the load with the secondary lining concrete structure. After the initial support construction is completed, grouting is promptly injected into the soil behind the outer side of the initial support through the reserved grouting holes. Ordinary silicate cement grout should be used as the grout. Before the secondary lining concrete is poured, grouting pipes are pre-embedded. After the concrete strength reaches 75% of the design strength, the gap between the initial support and the secondary lining structure is filled with grout according to the principle of close fit and equal strength to ensure the interlayer compactness.

[0017] In the above technical solution, the leakage of water, soil deformation and instability, and sealing failure are monitored and reported in real time throughout the construction process in steps S1-S6. The second objective of this invention is to provide a structure constructed using the aforementioned method of adding entrances and exits through pipe jacking and excavation in underground stations. This structure includes a receiving end located on one side of the main station structure, a pipe jacking machine casing located in the corner area of ​​the receiving end, and a systematic water-stopping system constructed from the pipe jacking machine casing, ribbed steel plate pre-support, and secondary lining structure through multiple grouting injections into the surrounding soil, between the secondary lining structure and the initial support. Wherein: The side wall of the station where the receiving end is located is irregularly folded, and the soil at the receiving end is reinforced by high-pressure jet grouting piles to form the receiving reinforced soil. The casing of the pipe jacking machine (which is pushed into place along with the pipe jacking machine) is positioned in the direction of the station and serves as a temporary support system during the construction phase. During the segmented demolition of the retaining wall, the ribbed steel plate extended from inside the station is rigidly connected to the casing of the pipe jacking machine to form a circumferential closed advanced support system. After the secondary lining structure is completed, the casing of the pipe jacking machine, the ribbed steel plate, and the secondary lining structure form a collaborative load-bearing system.

[0018] Combining all the above technical solutions, the advantages and positive effects of this invention are as follows: 1. High adaptability to corner working conditions and high space utilization: This invention utilizes a compact support system combining the reuse of the pipe jacking machine casing with advanced steel plate support, eliminating the need for additional space around the receiving end and allowing for precise adaptation to angled working conditions. It effectively avoids the challenges of protecting surrounding pipelines (such as gas and water supply lines) and managing traffic around existing stations, enabling safe construction in areas with dense pipelines and confined spaces.

[0019] 2. Significant safety protection effect and high risk controllability: This invention relies on the synergistic effect of a systematic water-stopping system and advanced steel plate support to reduce the risk of water seepage; the deformation of the surrounding rock and the settlement of surrounding buildings and pipelines are effectively controlled; the construction process does not interfere with the normal operation of the subway; and it fully meets the requirements for safe construction and operation protection of water-rich soft soil strata.

[0020] 3. Outstanding advantages in economic efficiency and construction efficiency: This invention utilizes the reuse of pipe jacking machine casing to reduce the consumption of materials such as steel and concrete; steel plate pre-support simplifies the construction process, reduces procedures, and shortens the construction cycle compared to traditional technologies, significantly reducing engineering material and time costs.

[0021] 4. Excellent structural durability and strong long-term stability: The casing of the pipe jacking machine, the secondary lining structure, and the reinforced concrete inner lining form a collaborative load-bearing system, which significantly improves the overall rigidity and strength of the structure and ensures long-term durability and stability. Attached Figure Description

[0022] Figure 1 This is a plan view of the structure for adding entrances and exits to underground stations using the pipe jacking and excavation method in this invention. Figure 2 This is an elevation view of the structure for adding entrances and exits to underground stations using the pipe jacking and excavation method in this invention. Figure 3 This is a structural diagram of the ribbed steel plate in this invention; Figure 4 This is a front view of the wall being broken down in this invention; In the diagram: 1-Pipe jacking machine casing; 2-Pipe jacking section; 3-Retaining wall; 4-Ribped steel plate; 401-Ribped steel plate main board; 402-Ribped steel plate rib; 5-Station side wall; 6-Receiving and reinforcing soil; 7-Secondary lining structure. Detailed Implementation

[0023] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0024] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Example 1

[0025] A method for adding entrances and exits to underground stations using the pipe jacking and cut-and-cover method, specifically: a method for receiving and implementing the pipe jacking and cut-and-cover method for adding entrances and exits to subway stations in water-rich soft soil strata, wherein a pipe jacking machine shell is arranged in the corner area of ​​the receiving end, the pipe jacking machine shell is reused as a temporary support structure, and steel plate advance support is set on the outside of the pipe jacking machine shell to form a compact support system, including the following steps: (1) Pre-construction preparation and pipe jacking: Before construction, geological surveys were conducted to verify whether the soil conditions were abnormal; high-pressure jet grouting piles were used to reinforce the soil at the receiving end of the station. After the reinforcement was completed, the reinforcement effect was confirmed by core sampling; exploratory holes were drilled in the reinforced soil at the receiving end inside the station to observe the water leakage in the holes; after the above preparations were completed, the pipe jacking machine was controlled to advance towards the station. During the advancement, thixotropic mud was injected circumferentially into the soil outside the pipe wall through the grouting holes of the rear of the pipe jacking machine casing 1 and the pipe section 2 until the pipe jacking machine head touched the station retaining wall 3 and then the jacking was stopped; after the machine was stopped, bentonite-cement composite grout was injected into the soil around the machine body through the pre-set grouting holes of the pipe jacking machine to form a waterproof and water-stopping ring.

[0026] (2) Demolition and advance support of the upper retaining wall: The “soil plug” formed by waterproof sealing ring and high-pressure jet grouting pile to reinforce the soil is used as the protection system; the retaining wall 3 is demolished in sections and blocks from the station according to the principle of “from top to bottom and from the middle to both sides”. During the demolition process, ribbed steel plates are simultaneously led out from the top and sides of the pre-opened doorway of the station, and the ribbed steel plates are extended to the casing of the pipe jacking machine and fixed.

[0027] (3) Demolition and advance support of the lower retaining wall: Remove the soil between the retaining wall and the jacking machine head in stages; then demolish the lower retaining wall of the passage, use ribbed steel plates to connect the lower part of the station's pre-opened doorway with the bottom of the machine casing, seal the outer soil, and form a circumferential closed advance support together with the top and side ribbed steel plates.

[0028] (4) Transport of the jacking machine casing: Keep the jacking machine casing, dismantle the tunneling and soil removal equipment, motors and hydraulic pumps inside the jacking machine; after being transported to the preset hoisting port (starting shaft) through the jacking channel, small hoisting equipment is used for the transport operation.

[0029] (5) Construction of the secondary lining structure: Tie the steel reinforcement skeleton in the casing of the pipe jacking machine and the ribbed steel plate advanced support system, and pour the waterproof concrete secondary lining structure of the entrance and exit passage. (6) Structural retention and post-construction stability: After the secondary lining concrete has reached the design strength, the jacking machine casing and ribbed steel plate are retained as part of the permanent structure and share the surrounding rock load with the secondary lining structure. The retained jacking machine casing and ribbed steel plate form the initial support. Through the grouting holes reserved in the initial support and the grouting pipes reserved in the cast-in-place concrete secondary lining structure, secondary grouting is carried out to the soil outside the initial support and between the initial support and the secondary lining structure, respectively. Micro-expansion early strength cement-based grout is injected to further enhance the sealing and stability of the structure.

[0030] (7) Safety guarantee throughout the process: Emergency materials such as quick-hardening cement, double-liquid grouting equipment, and high-power water pumps are prepared throughout the construction process. Monitoring data is fed back in real time, and corresponding emergency plans are activated for situations such as water leakage, soil instability, and sealing failure. The structure constructed using the above-mentioned method of adding entrances and exits through pipe jacking and excavation for underground stations includes a receiving end located on one side of the main structure of the station, a pipe jacking machine casing located in the corner area of ​​the receiving end, and a systematic water-stopping system formed by multiple grouting injections from the pipe jacking machine casing into the surrounding soil. The station side wall 5 at the location of the receiving end is irregularly angled. The soil at the receiving end is reinforced by high-pressure jet grouting piles to form the receiving reinforced soil 6. The pipe jacking machine casing advances towards the station with the pipe jacking machine and serves as a temporary support system during the construction phase. During the segmented demolition of the retaining wall 3, the ribbed steel plate 4 extended from inside the station is rigidly connected to the pipe jacking machine casing 1 to form a circumferential closed advanced support system. The ribbed steel plate 4 includes a ribbed steel plate main board 401 and ribbed steel plate ribs 402 set on the ribbed steel plate main board 401. The ribbed steel plate 4 is arranged around the pipe jacking machine casing 1, extending from the station side wall, and finally forming a closed ring between the pipe jacking machine head and the angled station structure. The ring-closed ribbed steel plate forms the initial support for the underground excavation. After the secondary lining structure 7 is completed, the pipe jacking machine casing 1, the ribbed steel plate 4, and the secondary lining structure 7 form a collaborative bearing system.

[0031] In the above embodiment, step (1) involves two key pre-verification operations: first, to conduct geological supplementary exploration, the core purpose of which is to obtain more detailed geological data and achieve precise control over the hydrogeological conditions of the receiving end; second, to drill exploratory boreholes, which need to be drilled in a grid-like distribution within the preset portal area of ​​the receiving end station, with the borehole spacing set at 2.0m-3.5m, and it must be ensured that the exploratory boreholes completely cover the reinforced area of ​​the portal area to ensure verification without blind spots; if the exploratory boreholes do not show obvious seepage for 30 minutes (seepage volume ≤0.1L / min), and there is no sand or mud flow, the retaining wall demolition process can proceed; if there is seepage, it is necessary to first inject double liquid grout (cement grout + water glass, volume ratio 1:1) through the exploratory boreholes to seal it, and then re-explore for verification after the seepage stops.

[0032] In the above embodiment, in step (1), when the cutterhead of the pipe jacking machine is 5-10m away from the receiving reinforcement area, the pressure inside the chamber is gradually reduced to balance with the soil pressure of the receiving well.

[0033] In the above embodiments, the injection pressure of the thixotropic mud in step (1) is controlled at 0.3-0.5 MPa, which needs to be slightly higher than the static water pressure of the formation to ensure that the mud can squeeze the annular gap between the pipe jacking machine and the soil and form a complete mud cake. The pipe jacking and the soil outside the pipe are dense and without gaps, while avoiding excessive pressure that could cause formation disturbance. The complete mud cake of the thixotropic mud has an impermeability grade ≥ P6, blocking external radial water seepage. In the above embodiment, in step (1), the receiving end is on one side of the main structure of the station, and the side wall of the station where the receiving end is located is irregularly folded. The soil of the receiving end on the station side is reinforced by high-pressure jet grouting piles to form a receiving reinforced soil. After the reinforcement is completed, in addition to confirming the reinforcement effect by core sampling, a test hole is drilled in the receiving end reinforced soil inside the station to observe the water leakage in the hole. After the above preparation work is completed and it is confirmed that the reinforced body no longer seeps water, the pipe jacking machine is controlled to advance towards the station. During the advancement, thixotropic mud is injected circumferentially into the soil outside the pipe wall through the rear of the pipe jacking machine and the grouting hole of the pipe section. After the machine stops, bentonite-cement composite grout is immediately injected into the soil around the machine body through the casing of the pipe jacking machine to form a waterproof and water-stopping ring.

[0034] In the above embodiment, after the machine body enters the MJS receiving and reinforced soil, it continues to advance until the jacking head touches the station retaining wall and stops jacking. Then, through the special grouting holes preset in the jacking head and the machine casing, bentonite-cement composite grout is injected into the soil around the machine body to form a waterproof sealing ring. The waterproof sealing ring in step (1) forms a ring-shaped closed structure around the machine body with the jacking head as the center. The bentonite-cement composite grout used has the following ratio: 5%-7% bentonite, 15%-18% P.O42.5 cement, 75%-80% water, and 0.5% early strength agent is added. After the grouting is completed, the permeability coefficient of the formed sealing ring is ≤1×10 -6 cm / s; The overlap width between the waterproof sealing ring and the high-pressure jet grouting pile reinforcement is not less than 300mm, which together form "double protection" to resist the water pressure and soil pressure of the water-rich soft soil layer and prevent soil collapse or water inrush when the retaining wall is broken.

[0035] In the above embodiment, step (2) involves breaking down the retaining wall at the entrance / exit doorway inside the station. This is done manually or with small machinery in sections, and blasting or large-scale mechanical breaking is strictly prohibited. The retaining wall is divided into 4-5 sections along the width direction, each section being 1.5-2m wide, and into 3-4 sections along the height direction, each section being 1.2-1.5m high, to avoid soil instability caused by excessively large areas being broken down in a single operation.

[0036] In the above embodiments, in steps (2) and (3), during and after the demolition of the upper retaining wall and the installation of the ribbed steel plate advanced support, the deformation of the surrounding rock and the displacement of the support structure under the ribbed steel plate advanced support are monitored for 24 hours. After the deformation is ≤3mm and stabilized for 3 consecutive days, the next process is carried out.

[0037] In the above embodiment, in step (2), the ribbed steel plate is made of Q355B steel plate, the main plate thickness is 12mm, and the rib plate thickness is 10mm; one end of the steel plate is welded and fixed to the pre-embedded steel plate around the opening of the side wall of the station, the other end is welded to the steel shell of the jacking pipe, and the other end extends to the outer wall of the jacking machine shell and is welded to the outer wall of the shell. The weld seam needs to be continuously and fully welded. When sealing the outer soil, if there are gaps, quick-setting cement grout (water-cement ratio 0.4) is used to fill and compact it to block the seepage channel of the outer soil.

[0038] In the above embodiment, in step (6), the casing of the pipe jacking machine and the ribbed steel plate are retained as the initial support structure and incorporated into the permanent structural system to bear load together with the secondary lining concrete structure. After the initial support construction is completed, grouting is promptly injected into the soil behind the outer side of the initial support through the reserved grouting holes. Ordinary silicate cement grout should be used as the grout. Before the secondary lining concrete is poured, grouting pipes are pre-embedded. After the concrete strength reaches 75% of the design strength, the gap between the initial support and the secondary lining structure is filled with grout according to the principle of close fit and equal strength to ensure that the interlayer is dense. Example 2

[0039] A structure constructed using the underground station pipe jacking and excavation method described in Embodiment 1 above for adding entrances and exits includes a receiving end located on one side of the main station structure, a pipe jacking machine casing located in the corner area of ​​the receiving end, and a systematic water-stopping system constructed by the pipe jacking machine casing, ribbed steel plate pre-support, and secondary lining structure with multiple grouting injections into the surrounding soil, between the secondary lining structure and the initial support. Wherein: The side wall of the station where the receiving end is located is irregularly folded, and the soil at the receiving end is reinforced by high-pressure jet grouting piles to form the receiving reinforced soil. The casing of the pipe jacking machine (which is pushed into place along with the pipe jacking machine) is positioned in the direction of the station and serves as a temporary support system during the construction phase. During the segmented demolition of the retaining wall, the ribbed steel plate extended from inside the station is rigidly connected to the casing of the pipe jacking machine to form a circumferential closed advanced support system. After the secondary lining structure is completed, the casing of the pipe jacking machine, the ribbed steel plate, and the secondary lining structure form a collaborative load-bearing system.

[0040] The core innovation of this invention lies in constructing an integrated technical system of "reusable pipe jacking machine casing - water-stop ring - ribbed steel plate advanced support - underground excavation - safety coordination", which specifically includes the following key technical aspects: Receiving end soil reinforcement and staged precision grouting water-stopping technology: The receiving end soil pretreatment scheme adopts high-pressure jet grouting pile reinforcement + borehole seepage verification; during the jacking stage, thixotropic mud is injected to form a protective drag-reducing layer; after the machine stops, bentonite-cement composite grout is immediately injected to form a waterproof water-stopping ring, realizing integrated management of "reinforcement-verification-water-stopping" and solving the risk of water leakage in the corner area.

[0041] Integrated circumferential closed advanced support technology of pipe jacking machine casing and ribbed steel plate: relying on the pipe jacking machine casing as temporary support for construction, combined with the segmented demolition process of the retaining wall from top to bottom and from the middle to both sides, the ribbed steel plate is rigidly connected to the casing at the same time to form a circumferential closed support system, which effectively disperses stress concentration in the corner area and avoids the instability of the surrounding rock during the demolition of the retaining wall.

[0042] The technology of permanent retention of the primary support and secondary lining of the pipe jacking machine casing: abandoning the traditional mode of lifting the casing out with the pipe jacking machine, the casing and ribbed steel plate are retained as permanent primary support, forming a co-support system with the cast-in-place secondary lining structure, which greatly improves the overall rigidity and long-term stability of the entrance and exit structure and reduces the construction cost of secondary support.

[0043] Multi-level, full-cycle systematic water-stopping system construction technology: Integrating the grouting operations of the three stages of pipe jacking, shutdown, and secondary lining formation, grouting is carried out in stages through the grouting holes of the casing, the reserved holes of the initial support, and the reserved pipes of the secondary lining, to form a closed water-stopping curtain, achieving dual protection of structural seepage prevention and load-bearing function, and completely solving the problem of water seepage in water-rich strata. Reusable Pipe Jacking Machine Casing Technology: Breaking through the limitations of traditional pipe jacking machine casings serving only as temporary construction equipment, this technology designs the casing as a dual-function carrier of "initial support + permanent structure." During the construction phase, the casing provides temporary support for the tunneling operation, resisting the pressure of surrounding water and soil. After construction, the casing does not need to be dismantled and can directly serve as part of the permanent structure, sharing the load with the secondary lining structure. This significantly reduces construction procedures and material consumption, while also being suitable for narrow, angled spaces. Advanced support and core soil protection technology: During the segmented demolition of the retaining wall (each segment ≤50cm), Q345 ribbed steel plates are simultaneously led out from the station and rigidly welded to the casing of the pipe jacking machine. Combined with the retention of 1.0m thick core soil at the receiving face, a circumferential closed advanced support structure is formed. This structure can effectively constrain soil deformation, controlling the deformation of the surrounding rock within 3mm, and preventing ground instability during the demolition of the retaining wall. Full-process safety management technology: Establish a full-cycle safety management system encompassing "preoperative preparation - process control - postoperative stabilization". Preoperatively, a solid safety foundation is established through geological remediation, foundation reinforcement, and emergency material reserves. During the process, risks are reduced through slow and stable jacking, real-time deformation monitoring, and graded sealing control. Postoperatively, secondary grouting and internal reinforcement ensure long-term structural stability. Furthermore, specific emergency plans are developed for various unforeseen circumstances, ensuring safety and controllability throughout the entire construction process. The above description is merely a preferred embodiment of the present invention. It should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments, but can be used in various other combinations, modifications, and environments. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A method for adding entrances and exits to underground stations using pipe jacking and tunneling methods, characterized in that: Includes the following steps: S1. Pre-construction preparation and pipe jacking Reinforce the soil at the receiving end of the station and control the pipe jacking machine to advance towards the station. During the advancement process, thixotropic mud is injected circumferentially into the soil outside the pipe wall through the rear of the pipe jacking machine and the grouting holes of the pipe section until the pipe jacking machine head touches the station retaining wall and then stops advancing. Then, bentonite-cement composite grout is injected into the soil around the machine body through the pre-set grouting holes of the pipe jacking machine to form a waterproof and water-stopping ring; S2, Demolition of the upper retaining wall and advanced support The retaining wall inside the station is broken down in sections from top to bottom and from the middle to both sides. At the same time, ribbed steel plates are led out from the top and sides of the pre-opened doorway of the station, extended to the casing of the pipe jacking machine and fixed. S3, Demolition of the lower retaining wall and advanced support The soil between the retaining wall and the pipe jacking machine head is removed in stages; the lower retaining wall is broken, and ribbed steel plates are used to connect the lower part of the station's pre-opened doorway with the bottom of the machine casing, forming a circumferential closed advanced support system with the top and side ribbed steel plates; S4, Pipe jacking shell disposal and equipment transportation The casing of the pipe jacking machine is retained, while the internal components are disassembled and transported out via the pipe jacking channel. S5, Secondary Lining Structure Construction A steel reinforcement skeleton was tied inside the pipe jacking machine casing and ribbed steel plate support system, and a waterproof concrete secondary lining structure for the entrance and exit passage was poured. S6. Structural Preservation and Post-Stage Stability The casing of the pipe jacking machine and the ribbed steel plate are retained to form the initial support. Through the grouting holes reserved in the initial support and the grouting pipes reserved in the cast-in-place concrete secondary lining structure, secondary grouting is carried out to the soil outside the initial support and between the initial support and the secondary lining structure to form a systematic water-stopping system.

2. The method for adding entrances and exits to underground stations using pipe jacking and tunneling methods according to claim 1, characterized in that: In step S1, the receiving end is located on one side of the main structure of the station, and the side wall of the station where the receiving end is located is irregularly folded. The soil at the receiving end on the station side is reinforced with high-pressure jet grouting piles to form a receiving and reinforced soil body. After the reinforcement is completed, in addition to confirming the reinforcement effect by core sampling, exploratory holes are drilled in the reinforced soil body at the receiving end inside the station to observe the water leakage in the holes. After the above preparations are completed and it is confirmed that the reinforced body no longer seeps water, the pipe jacking machine is controlled to advance towards the station. During the advancement, thixotropic mud is injected circumferentially into the soil outside the pipe wall through the rear of the pipe jacking machine and the grouting holes of the pipe section. After the machine stops, bentonite-cement composite grout is immediately injected into the soil around the machine body through the casing of the pipe jacking machine to form a waterproof and water-stopping ring.

3. The method for adding entrances and exits to underground stations using pipe jacking and tunneling methods according to claim 2, characterized in that: In step S1, the probe holes are horizontally arranged in a grid pattern; the spacing between the probe holes is controlled at 2.0m to 3.5m to ensure that the probe holes completely cover the reinforced area of ​​the tunnel entrance and achieve verification without blind spots; after the probe hole construction is completed, seepage detection is carried out. If the following conditions are met, the subsequent retaining wall demolition process can proceed: no obvious seepage is observed in the probe holes for 30 minutes, the measured seepage volume is ≤0.1L / min, and there is no sand or mud flow, then the retaining wall demolition process can proceed; if seepage exists, a double-liquid grout must be injected through the probe holes to seal it. The double-liquid grout includes cement grout and water glass with a volume ratio of 1:

1. After the seepage stops, the seepage detection is repeated.

4. The method for adding entrances and exits to underground stations using pipe jacking and tunneling methods according to claim 2, characterized in that: In step S1, after the pipe jacking machine body enters the reinforced soil at the receiving end, it continues to advance until the pipe jacking machine head touches the station retaining wall, at which point the jacking stops. Then, through the pre-set dedicated grouting holes in the pipe jacking machine head and casing, bentonite-cement composite grout is injected into the soil surrounding the machine body to form a waterproof sealing ring. This waterproof sealing ring forms a closed ring structure around the pipe jacking machine, with the bentonite-cement composite grout having the following proportions: 5%-7% bentonite, 15%-18% P.O42.5 cement, and 75%-80% water, with an additional 0.5% early-strength agent added. After grouting and curing for 24 hours, the permeability coefficient of the formed sealing ring is ≤1×10⁻⁶. -6 cm / s; the overlap width between the waterproof sealing ring and the high-pressure jet grouting pile reinforcement body shall not be less than 300mm.

5. The method for adding entrances and exits to underground stations using pipe jacking and tunneling methods according to claim 1, characterized in that: In step S2, under the waterproof and seepage-proof soil stabilization protection body jointly formed by the waterproof and seepage-stopping ring and the reinforced soil, the retaining wall at the entrance opening location inside the station is demolished in sections and blocks. The retaining wall is demolished in sections along the width of the wall, which are divided into 4-5 sections, with the width of each section controlled at 1.5-2m; and along the height of the wall, it is divided into 3-4 sections, with the height of each section controlled at 1.2-1.5m.

6. The method for adding entrances and exits to underground stations using pipe jacking and tunneling methods according to claim 1, characterized in that: In step S2, the ribbed steel plate is made of Q355B material, with a main plate thickness of 12mm and a rib plate thickness of 10mm. One end of the ribbed steel plate is welded and fixed to the pre-embedded steel plate around the pre-opened doorway of the station, and the other end extends to the outer wall of the jacking machine casing and is welded. All welds must be continuous and fully welded. After construction, if there are gaps between the steel plate and the soil and the casing, quick-setting cement grout is used to fill and compact them to block the seepage channels of the outer soil.

7. The method for adding entrances and exits to underground stations using pipe jacking and tunneling methods according to claim 1, characterized in that: During and after the construction of steps S2 and S3, the following should be noted: During the construction of the upper retaining wall demolition and the installation of the ribbed steel plate pre-support, as well as after the support construction is completed, 24-hour continuous monitoring should be implemented. The monitoring objects are the ribbed steel plate pre-support system and the surrounding rock within the support range. Only when the monitoring data meets the condition that the deformation is ≤3mm and the stable state of the deformation within 3mm is maintained for 3 consecutive days can the lower retaining wall demolition and subsequent related procedures be carried out.

8. The method for adding entrances and exits to underground stations using pipe jacking and tunneling methods according to claim 1, characterized in that: In step S4, the internal device is disassembled and then transported through the jacking pipe channel to the preset hoisting port for hoisting and external transport.

9. A method for adding entrances and exits to an underground station using the pipe jacking and tunneling method according to claim 1, characterized in that: In step S6, the casing of the pipe jacking machine and the ribbed steel plate are retained as the initial support structure and incorporated into the permanent structural system to share the load with the secondary lining concrete structure. After the initial support construction is completed, grouting is promptly performed behind the soil outside the initial support through the reserved grouting holes. Ordinary silicate cement grout should be used as the grout. Before the secondary lining concrete is poured, grouting pipes are pre-embedded. After the concrete strength reaches 75% of the design strength, the gap between the initial support and the secondary lining structure is filled with grout according to the principle of close fit and equal strength to ensure the interlayer compactness.

10. A structure constructed using the method of adding entrances and exits through pipe jacking and tunneling as described in any one of claims 1-9, characterized in that: include: The receiving end is installed on one side of the main structure of the station. The side wall of the station where the receiving end is located is irregularly folded. The soil at the receiving end is reinforced to form a receiving and reinforced soil. The casing of the pipe jacking machine is installed in the corner area of ​​the receiving end. The casing of the pipe jacking machine is advanced towards the station with the pipe jacking machine. During the construction phase, it serves as a temporary support system. During the segmented demolition of the retaining wall, the ribbed steel plate led out from inside the station is rigidly connected to the casing of the pipe jacking machine to form a circumferential closed advanced support system. After the secondary lining structure is completed, the casing of the pipe jacking machine, the ribbed steel plate, and the secondary lining structure form a collaborative load-bearing system. And a systematic water-stopping system is formed by grouting the surrounding soil, the secondary lining structure and the initial support in stages from the casing of the pipe jacking machine, the ribbed steel plate and the secondary lining structure.

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