Starting hole staged lining method capable of meeting shield starting requirement

Abstract

The invention relates to a starting hole stage lining method meeting the shield starting requirement, which comprises the following steps: advance support of a pipe shed: carrying out advance support on the top arch part of an excavated tunnel before a shield starting section is excavated, and filling a gap between pipe shed steel pipes of the advance support through grouting to form a waterproof curtain; after excavation, steel fiber concrete spraying layer supporting, steel arch supporting and hollow grouting anchor rod supporting are carried out in time; tunnel lining structure construction is conducted, specifically, a tunnel first-stage lining and a tunnel second-stage lining are constructed, the initial position of the tunnel first-stage lining is the intersection point of the tunnel waist and the vertical shaft peripheral diaphragm wall, the end point of the tunnel first-stage lining is the inner surface of steel fiber reinforced concrete of the tail end excavation face, and an embedded steel ring is arranged at the initial position of the first-stage lining; and shield launching is conducted, specifically, a shield tunneling machine is installed in the vertical shaft, and the shield tunneling machine is propelled into the launching tunnel after being installed. According to the staging lining method for the starting hole, the stress of the whole lining system is more balanced, so that the construction safety of the tunnel is better guaranteed.

Description

Technical Field

[0001] This application relates to the field of tunnel construction technology, specifically to a phased lining method for a starting tunnel that meets the requirements for shield tunneling. Background Technology

[0002] In shield tunneling of deep-buried tunnels, the launching tunnel serves as a crucial transition section for the tunnel boring machine (TBM) as it enters the ground from the vertical shaft. Its lining structure must simultaneously meet multiple requirements, including high impermeability, rapid construction, ability to withstand complex loads, and adaptability to various working conditions. Adopting a reasonable phased lining construction approach is of great significance for safe tunnel construction and successful launching. Traditional single-layer linings rely solely on the segments themselves to resist ground loads (earth pressure, water pressure) and structural self-weight. Their load-bearing capacity, crack resistance, and durability depend entirely on the performance of the segment materials (such as concrete strength and steel yield strength) and the quality of assembly. During the TBM launching stage, if complex geological conditions (such as soft soil or high-water-pressure strata) are encountered, the segments may crack due to concentrated loads or excessive deformation, affecting the long-term stability of the structure. Furthermore, the launching stage often faces complex geological conditions at the tunnel entrance (such as water-rich sand layers or soft plastic soil layers), resulting in significant ground deformation. Single lining has high rigidity but insufficient flexibility, making it difficult to adapt to uneven ground settlement. It is prone to additional stress due to deformation differences, which can lead to segment cracking. Summary of the Invention

[0003] This application provides a phased lining method for the starting tunnel that meets the requirements of shield tunneling. This phased lining method for the starting tunnel seals the surrounding rock through a composite structural system that combines initial support and secondary lining, quickly restrains the loosening and deformation of the surrounding rock, and makes the entire lining system more evenly stressed, thereby better ensuring the safety of tunnel construction.

[0004] The phased lining method for the launch tunnel that meets the requirements for shield tunneling launch provided in this application includes the following steps: 1) Advance support of pipe roof: Before the shield tunneling start section is excavated, the arch of the tunnel is supported in advance. The gaps between the steel pipes of the pipe roof are filled by grouting to form a water-stop curtain. 2) Initial support after excavation: Steel fiber reinforced concrete spraying support, steel arch support and hollow grouting anchor support should be carried out in a timely manner after excavation. 3) Tunnel lining structure construction: The first-stage lining and the second-stage lining of the tunnel are constructed separately. The starting position of the first-stage lining is the intersection of the tunnel waist and the diaphragm wall of the shaft, and the ending point is the inner surface of the steel fiber concrete of the end excavation face. A pre-embedded steel ring is set at the starting point of the first-stage lining. 4) Tunneling launch: The tunnel boring machine is installed inside the shaft and then advanced into the launching tunnel.

[0005] In one alternative approach, step 1) of providing pre-support includes: First, construct the outer diaphragm wall of the shaft, the inner lining of the water intake shaft, the ring beam of the water intake shaft, the bottom plate of the water intake shaft, and the chamfered lining of the shaft. Within the shield tunneling starting range, reserve openings are set in the side walls of the water intake shaft, and multiple concrete ring beams are set within the range of the reserved openings. During the construction of the water intake shaft lining, a water-stop copper sheet is installed at the reserved opening, and a guide steel pipe is pre-embedded within a 180° range at the top of the reserved opening. The guide steel pipe is inclined outward at an angle of 1.5°, and a preset distance is left between the guide steel pipe and the reserved opening. The guide steel pipe is driven into the rock mass, and grouting is performed using cement grout with a water-cement ratio of 0.5:1 to 1:1 at a pressure of 0.5 to 1 MPa. After grouting, the guide steel pipe is filled with M30 cement mortar.

[0006] In one optional embodiment, the pipe roof steel pipe is made of hot-rolled seamless steel pipe, and the pipe roof steel pipe includes a grout-stopping section, a grout overflow section and a conical section arranged in sequence. The pipe wall of the grout overflow section is provided with multiple grout overflow holes at intervals. The conical section has a conical structure and is used for forward drilling. The length of the grout-stopping section is defined as L1, the length of the grout overflow section is L2, and the length of the conical section is L3. Then: L2>L1+L3.

[0007] In one alternative scheme, in step 2), before excavation, the water intake shaft ring beam within the reserved opening area and the diaphragm wall surrounding the shaft within the projection range along the forward direction are first removed. Reliable measures should be taken during the removal process to prevent excessive removal. The excavation cross-section before the tunnel centerline intersects with the outer edge of the diaphragm wall surrounding the shaft is in the shape of a city gate, and the excavation cross-section after the intersection is in the shape of a horseshoe. The tunnel excavation adopts a step-by-step short-step or reserved core soil excavation method to ensure the safety of the tunnel excavation section. After the tunnel is excavated, steel fiber concrete should be used to seal it in time, and steel arches should be erected in the city gate-shaped excavation section and in the horseshoe-shaped excavation section. During tunnel excavation, the cycle advance is 0.5m, and a steel arch frame is erected every 0.5m. The base and waist of the steel arch frame are firmly fixed with ordinary mortar anchors, and the ordinary mortar anchors extend into the rock to a depth of not less than 4m.

[0008] In one alternative, when spraying steel fiber concrete, first spray a 10cm thick layer, then lay a layer of steel mesh, then erect a steel arch frame, and finally spray CF30 steel fiber concrete to seal it. 10cm of steel fiber concrete is sprayed between the steel arch frames, and the thickness of the steel fiber concrete protective layer at the steel arch frame part is 3cm. When water seepage occurs during tunnel excavation, after spraying CF30 steel fiber concrete, drainage holes are arranged at the water seepage point. The drainage holes are 5m deep and 65mm in diameter. At the end section of the tunnel excavation, a 10cm thick layer of sprayed steel fiber concrete is sprayed first, and then glass fiber anchors are installed to ensure the safety of the end excavation face. The spacing of the glass fiber anchors is 1.5m. Drainage holes are installed when water seepage occurs.

[0009] In one alternative embodiment, step 3) involves the following during the construction of the tunnel lining structure: The tunnel lining from the starting point of the first phase of tunnel lining to the structural joint section is shaped like a city gate, and the tunnel lining from the structural joint to the end point of the first phase of tunnel lining is shaped like a horseshoe. A horizontal construction joint is set at a preset distance from the bottom edge of the city gate-shaped tunnel, and a horizontal construction joint is set at a preset distance from the bottom edge of the horseshoe-shaped tunnel. Water-stop copper sheets are set in the horizontal construction joints. The horizontal construction joints of the city gate-shaped tunnel and the horseshoe-shaped tunnel have the same height, and the water-stop copper sheets are arranged along the entire length. The first-stage lining is circular, with the thickness varying at both corners according to the shape of the outer edge. Lining reinforcement is installed on the inner and outer surfaces of the first-stage lining concrete, including circumferential reinforcement and horizontally distributed reinforcement. To facilitate the advancement of the tunnel boring machine, multiple embedded steel rails are installed at the bottom of the first-stage lining concrete, and the embedded steel rails are fixed by embedded parts; a concrete guide platform of preset thickness is set within a 100° range at the bottom.

[0010] In one alternative scheme, during construction, the pre-embedded steel ring is firmly fixed to the reinforcing steel of the first-stage lining concrete. The pre-embedded steel ring includes an L-shaped steel plate and two anchoring steel bars. The anchoring steel bars are set at 2.5° intervals. The L-shaped steel plate is provided with bolt holes, one bolt hole at 2.5° intervals, and the bolt holes are staggered with the anchoring steel bars. Before the tunnel boring machine enters the tunnel, water-stop curtains should be installed in the bolt holes. Construction also includes backfill grouting and consolidation grouting. For backfill grouting, multiple backfill grouting guide steel pipes are pre-embedded within a 120° range at the top of the first phase lining of the tunnel-shaped section. Backfill grouting of the first phase lining of the horseshoe-shaped section is carried out using consolidation grouting guide steel pipes. Consolidation grouting is carried out at the section where the tunnel excavation face contacts the rock.

[0011] In one optional scheme, the backfill grouting is carried out after the first-stage lining concrete reaches 70% of its design strength. The backfill grouting is carried out in sequence from low to high and from the side arches to the top arches. The water-cement ratio of the backfill grouting is 0.5, the grouting pressure is 0.2~0.4MPa, and after the grouting hole stops sucking grout, grouting continues for at least 10 minutes before it ends. Backfill grouting is inspected 7 days and 28 days after the end of backfill grouting, and the number of inspection holes is not less than 5% of the total number of grouting holes. The consolidation grouting is carried out 7 days after the completion of the backfill grouting at the corresponding location. The consolidation grouting material is ordinary Portland cement with a strength grade of 42.5. The water-cement ratio at the start of grouting is 2:1. The grouting pressure for 2-6m of consolidation grouting is 1.5MPa, and the grouting pressure for 0-2m is 0.5-1MPa. After the grouting hole stops grouting, grouting continues for at least 10 minutes before it ends. Three days after the completion of consolidation grouting, a single-point water pressure test is used to check whether the consolidation grouting is qualified. The number of test holes is not less than 5% of the total number of grouting holes. The qualification standard is that the permeability of test holes above 85% is not greater than 3Lu. The water pressure test pressure should be greater than the grouting pressure, but not greater than 80% of the grouting pressure. Unqualified sections should be re-grouted.

[0012] In one optional embodiment, the water-stopping curtain includes a rubber sheet curtain, a pad, M20 bolts, and a flap. The rubber sheet curtain serves to seal, stop water, and stop grouting during the shield tunneling grouting process. The pad is connected to the pre-embedded steel ring via the M20 bolts to force the rubber sheet curtain to fit tightly against the tunnel opening, enhancing the sealing effect. The flap is installed on a circular plate. During shield tunneling, the flap can flip and hold the rubber sheet curtain in place, preventing the curtain rubber sheet from flipping backward due to excessive water and soil pressure ahead, thereby improving the sealing performance of the water-stopping curtain.

[0013] In one alternative scheme, in step 4), the tunnel boring machine (TBM) begins assembling tunnel segments during its advancement. The segments assembled before the structural joint are temporary segments, while the segments assembled after the structural joint are permanent segments. After the TBM penetrates the fiberglass reinforced end wall, it tunnels into the surrounding rock, forming the tunnel excavation section. After tunneling a certain distance, the temporary segments in the shaft are removed as appropriate. After removal, reinforcing bars are tied, and the second-stage lining concrete at the tunnel entrance is poured to ensure a firm connection with the inner lining of the water intake shaft. The second-stage lining concrete is poured to ensure a firm connection with the chamfered corner of the shaft. Two water-swellable sealing strips are used at the contact surface between the cast-in-place second-stage lining concrete and the permanent segments to prevent water from seeping into the surrounding rock during tunnel operation. Shrinkage will occur during the concrete setting process. Backfilling and grouting will be carried out within a 180° range of the top of the cast-in-place second-stage lining concrete. Lining reinforcement bars will be set on the inner and outer surfaces of the second-stage lining concrete. During the reinforcement binding process, two rows of backfilling and grouting guide steel pipes will be pre-embedded within a 120° range of the top arch. The permanent pipe segment will be backfilled and grouted through the grouting holes reserved on the precast pipe segment.

[0014] The beneficial effects of this application are as follows: The phased lining method for the starting tunnel in this application, which meets the requirements for shield tunneling, uses advanced support, tunnel excavation support, primary lining, and secondary lining to seal the surrounding rock in the starting section of the deep-buried tunnel shield tunnel under complex geological conditions. This rapidly restrains the loosening and deformation of the surrounding rock, making the entire lining system more evenly stressed and thus better ensuring the safety of tunnel construction.

[0015] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the working shaft before the excavation of the shield tunneling starting section; Figure 2 for Figure 1 A schematic diagram of the cross-section along A-A'; Figure 3 for Figure 1 A schematic diagram of the cross-section along B-B'; Figure 4 for Figure 3 Cross-sectional view along line BB′; Figure 5 This is a plan view of the excavation and support for the starting section of the tunnel boring machine. Figure 6 for Figure 5 A schematic diagram of the cross-section along C-C'; Figure 7 for Figure 5 A schematic diagram of the cross-section along D-D'. Figure 8 This is a schematic diagram of the support for the end excavation face; Figure 9 This is a schematic diagram of a steel arch frame structure; Figure 10 This is a schematic diagram of another type of steel arch frame structure. Figure 11 This is a schematic diagram of the connection between the steel plates; Figure 12 This is a cross-sectional view of the connecting steel plates; Figure 13 A schematic diagram of the welding process for erecting steel plates; Figure 14 This is a schematic diagram showing the connection between the reinforcing bars and the connecting steel arch frame; Figure 15 A schematic diagram of fixing a steel arch frame to mortar anchor bolts; Figure 16 This is a schematic diagram of the first-phase lining of the shield tunnel's starting section. Figure 17 for Figure 16 A schematic diagram of the cross-section along F-F'; Figure 18 for Figure 16 A schematic diagram of the cross-section along G-G'; Figure 19 for Figure 16 A schematic diagram of the cross-section along H-H'; Figure 20 A schematic diagram of the planar structure for pre-embedded steel rings; Figure 21 A schematic diagram showing the connection between the embedded steel ring and the water-stop curtain; Figure 22 A schematic diagram of the pre-embedded parts for the guide rail; Figure 23 for Figure 22 A schematic diagram of the cross-section along b-b'; Figure 24 This is a schematic diagram of the second-phase lining of the shield tunnel's starting section; Figure 25 for Figure 24 A schematic diagram of the cross-section along J-J'; Figure 26 for Figure 24 A schematic diagram of the cross-section along K-K'; Figure 27 for Figure 24 A schematic diagram of the cross-section along L-L'; Figure 28 for Figure 24 A schematic diagram of the cross-section along M-M'.

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. Detailed Implementation

[0018] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0019] It should be understood that the described embodiments are merely some embodiments of this application, and not all embodiments. All other technical solutions obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0020] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0021] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0022] It should be noted that the directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this application are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this application. Furthermore, in the context, it should be understood that when it is mentioned that an element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0023] like Figure 1-28 As shown in the figure, this application provides a method for phased lining of the launching tunnel to meet the requirements of shield tunneling. The method mainly includes the following steps: 1) Pre-support of the pipe roof: Before the excavation of the shield tunneling starting section, pre-support is carried out on the arch of the excavated tunnel. The gaps between the steel pipes of the pre-support pipe roof are filled by grouting to form a water-stop curtain. Specifically, before the excavation of the shield tunneling starting section, pre-support is carried out on the arch of the excavated tunnel. The gaps between the steel pipes of the pipe roof are filled by grouting (such as cement grout, chemical grout, etc.) to form a water-stop curtain, which transfers the load of the surrounding rock above and around the tunnel excavation face to the unexcavated stable strata or the supported structure, reducing the deformation and collapse risk of the surrounding rock.

[0024] 2) Initial support after excavation: Steel fiber reinforced concrete sprayed layer support, steel arch frame support, and hollow grouting anchor bolt support should be implemented promptly after excavation. Specifically, these three components work together to bear the surrounding rock load, control surrounding rock deformation, ensure construction safety, and lay the foundation for subsequent secondary lining (such as concrete lining).

[0025] 3) Tunnel Lining Structure Construction: The first-phase lining and second-phase lining of the tunnel will be constructed separately. The starting point of the first-phase lining is the intersection of the tunnel waist and the diaphragm wall of the shaft, and the ending point is the inner surface of the steel fiber reinforced concrete at the end excavation face. A pre-embedded steel ring is set at the starting point of the first-phase lining. Specifically, the first-phase lining is a key link connecting construction and operation. It serves as temporary support and operational guarantee during the construction phase, and also as a permanent load-bearing structure during the operation phase. It provides initial support and positioning benchmark for the stability of the shield machine's starting posture, transmits the initial thrust of the shield machine, and avoids damage to the starting shaft structure or the shield machine due to thrust concentration. During the operation of the water conveyance tunnel, the first-phase lining structure is also the main load-bearing structure, which must withstand the soil pressure of the surrounding rock, the groundwater pressure, and the water pressure inside the tunnel for a long time.

[0026] For the second-phase tunnel lining, the tunnel boring machine (TBM) relies on jacks to push the tunnel segments and generate reaction force. The initial tunnel segment is the first permanent structure to provide stable reaction force after the TBM gets rid of the temporary negative ring structure. As the negative ring segments are gradually removed, the second-phase lining structure of the initial section must directly bear the thrust of the jacks and evenly transfer the force to the formed tunnel structure and the surrounding strata to ensure the TBM continues to advance and avoids stagnation due to insufficient reaction force. The second-phase concrete structure inside the structural joint is the stress intersection point of the shaft and the water conveyance tunnel. It must bear the loads of the shaft's self-weight, the soil pressure of the surrounding strata, the groundwater pressure, and the internal pressure of the water conveyance. The second-phase lining structure forms a rigid ring through the integrity of reinforced concrete, which enhances the rigidity of the portal area, resists fatigue failure under long-term loads, improves the sealing and water-stopping performance of the portal, and strengthens the overall load-bearing capacity of the portal structure.

[0027] 4) Tunneling launch: The tunnel boring machine is installed inside the shaft and then advanced into the launching tunnel.

[0028] like Figure 1-4 As shown, during the pre-support construction of the pipe roof in step 1), the following should be constructed before the tunnel boring machine (TBM) launch: the outer diaphragm wall 1, the inner lining 2 of the intake shaft, the ring beam 4 of the intake shaft, the bottom plate 5 of the intake shaft, and the chamfered lining 3 of the shaft. The bottom plate 5 of the intake shaft is connected to the inner lining 2 of the intake shaft via the chamfered lining 3. Within the TBM launch area, a reserved opening 9 is set in the side wall of the intake shaft. Concrete construction is not carried out within the reserved opening 9 initially, as the height of the reserved opening 9 is approximately 15m and the width is approximately 14m. Four concrete ring beam supports 6 are installed within the reserved opening 9 to ensure its safety.

[0029] When constructing the inner lining 2 of the water intake shaft, a water-stop copper plate 7 is installed at the reserved opening 9, and the water-stop copper plate 7 is 6cm away from the inner wall of the side wall of the water intake shaft. The geological conditions of the tunnel section at the shield tunneling launch point are complex. To ensure excavation safety, pre-support is required before the shield tunneling launch point begins excavation. During the construction of the water intake shaft lining 2, guide steel pipes 8 (140mm in diameter and 5mm in wall thickness) are pre-embedded within a 180° range at the top of the reserved opening 9. The guide steel pipes 8 are 30cm away from the reserved opening 9. To prevent the pipe roof from encroaching into the tunnel interior during pre-support construction, the guide steel pipes 8 are inclined outward at an angle of 1.5°. During pre-support, pipe roof steel pipes 10 with a diameter of 108mm (6mm in wall thickness) are driven into the rock mass from the pre-embedded guide steel pipes 8. Grouting is performed using cement grout with a water-cement ratio of 0.5:1 to 1:1, with the grouting pressure controlled at 0.5 to 1MPa to enhance the rigidity and strength of the pipe roof and fill the voids in the surrounding rock mass. After grouting, M30 cement mortar is used to fill the steel pipes.

[0030] The pipe roof steel pipe 10 is made of hot-rolled seamless steel pipe. The pipe roof steel pipe 10 includes a grout-stopping section 10a, a grout overflow section 10c, and a conical section 10d arranged in sequence. The pipe wall of the grout overflow section 10c is provided with multiple grout overflow holes 10b at intervals (the hole spacing is 15cm). The conical section 10d is a conical structure and is used for forward drilling. The length of the grout-stopping section is defined as L1, the length of the grout overflow section is L2, and the length of the conical section is L3. Then: L2>L1+L3.

[0031] Only after the above construction is completed can the initial support construction of step 2), namely the excavation of the shield tunneling starting section, be carried out.

[0032] like Figure 5-15 As shown, in one specific embodiment, in step 2), before the shield excavation, the ring beam 6 within the reserved opening 9 and the diaphragm wall 1 surrounding the shaft within the projection range along the forward direction are first removed. Reliable measures should be taken during the removal process to prevent excessive removal and to avoid damaging the shaft lining, the water-stop copper sheet, and the diaphragm wall 1 surrounding the shaft outside the removal range. The excavation cross-section before the intersection of the tunnel centerline and the outer edge of the diaphragm wall 1 is arch-shaped, and the excavation cross-section after the intersection is horseshoe-shaped.

[0033] The tunnel excavation adopts a step-by-step short-step excavation method or a pre-reserved core soil method to ensure the safety of the tunnel excavation section. After the tunnel excavation, CF30 steel fiber reinforced concrete 11 should be applied for sealing in a timely manner. Steel arch frames 15 should be erected in the arch-shaped excavation section, and steel arch frames 16 should be erected in the horseshoe-shaped excavation section. When spraying steel fiber reinforced concrete 11, first spray a 10cm thickness, then lay a layer of steel mesh (8mm diameter steel bars, 15cm spacing), then erect steel arch frames 14 or 15, and finally spray CF30 steel fiber reinforced concrete 11 for sealing. A 10cm layer of steel fiber reinforced concrete 11 should be sprayed between the steel arch frames, and the thickness of the steel fiber reinforced concrete protective layer at the steel arch frame area should be 3cm.

[0034] The tunnel excavation cycle advance is 0.5m, with a steel arch frame erected every 0.5m. The base and waist of the steel arch frame are firmly fixed with ordinary mortar anchors 17 with a diameter of 28mm. The ordinary mortar anchors 17 extend into the rock to a depth of 4.2m. If water seepage occurs during tunnel excavation, after spraying CF30 steel fiber reinforced concrete 11, drainage holes 16 are arranged at the water seepage point. The drainage holes are 5m deep and 65mm in diameter. At the end section of the tunnel excavation, a 10cm thick layer of sprayed steel fiber reinforced concrete 11 is first sprayed, followed by the installation of glass fiber anchors 12 to ensure the safety of the end excavation face. The glass fiber anchors 12 are spaced 1.5m apart, and drainage holes 16 are installed if water seepage occurs.

[0035] The steel arch frame 14 consists of three I20 I-beams 14a, four connecting steel plates 14b, and two supporting steel plates 14c. The I-beams are securely welded to the connecting and supporting steel plates. Adjacent connecting steel plates are connected by four bolts 14d. The supporting steel plates are in close contact with the tunnel excavation floor. The steel arch frame 15 consists of six I20 I-beams 15a, ten connecting steel plates 15b, and two supporting steel plates 15c. The I-beams are securely welded to the connecting and supporting steel plates. Adjacent connecting steel plates are connected by four bolts 14d. The supporting steel plates are securely in close contact with the tunnel excavation floor. The steel arch frames are connected by 22mm diameter connecting steel bars 18, spaced 1m apart.

[0036] This embodiment combines pre-excavation support and anchor bolt support during excavation. Pre-excavation support is used to reinforce unfavorable geological sections such as weak, broken, water-rich, and high-stress areas in advance, controlling the deformation and collapse of the surrounding rock caused by excavation. Anchor bolt support is used to connect the loosened surrounding rock after excavation with the deep stable rock mass to form an integrated force-bearing system, preventing further deformation or collapse of the surrounding rock.

[0037] After the above construction is completed, step 3) should be carried out in a timely manner, that is, the first-stage lining of the tunnel in the shield tunneling starting section should be carried out to ensure the safety and stability of the tunnel.

[0038] like Figure 16-23 As shown, in one specific embodiment, during the construction of step 3), the starting position of the first-stage lining of the shield tunnel is the intersection of the tunnel waist and the diaphragm wall, and the ending point is the inner surface of the steel fiber concrete 12 at the end excavation face. Water-stop copper plates 25 are installed in the middle of the first-stage lining concrete 19 on both sides of the structural joint, with the ends of the copper plates 25 sealed. The tunnel lining from the starting point of the first-stage lining to the structural joint is arch-shaped, while the tunnel lining from the structural joint to the end point of the first-stage lining is horseshoe-shaped. Due to the large tunnel cross-section, the tunnel cross-section cannot be cast in one go. A horizontal construction joint 28 is set at 3.8m from the bottom edge of the arch-shaped tunnel, with a water-stop copper plate 25 installed inside the joint. A horizontal construction joint 28 is set at 2.9m from the bottom edge of the horseshoe-shaped tunnel, with a water-stop copper plate 25 installed inside the joint. The horizontal construction joints 25 of the arch-shaped and horseshoe-shaped tunnels have the same height, and the water-stop copper plates 25 are arranged along the entire length.

[0039] Since the tunnel is mainly subjected to axial force and the shaft is mainly subjected to vertical force, structural joints are set at the interface. The structural joints of the first-phase lining structure are equipped with closed-loop water-stop copper sheets, and the structural joints of the second-phase lining structure are equipped with closed-loop water-swellable water-stop strips. The structural joints are used to avoid cracking of the concrete at the interface due to additional stress caused by the differential deformation of the two structures under forced constraint. The water-stop copper sheets and the expandable water-stop strips are used to form a continuous water-stop barrier in the gap of the structural joint to block the seepage path of groundwater or water transport medium along the joint surface.

[0040] The first-stage lining is circular, with a thickness of 60cm at the top arch. The thickness varies at the two corners according to the outer shape. Lining reinforcement is installed on the inner and outer surfaces of the first-stage lining concrete 19. The circumferential reinforcement is 32mm in diameter and spaced 15cm apart, while the horizontally distributed reinforcement is 25mm in diameter and spaced 20cm apart. To facilitate the tunnel boring machine's (TBM) advancement, four pre-embedded rails 29 are installed at the bottom, secured by pre-embedded parts 24. The anchoring reinforcement 24b of the pre-embedded parts 24 is firmly welded to the reinforcement of the first-stage lining concrete 19. To ensure the rails do not break during TBM travel, a 17cm thick concrete guide platform 26 is installed within a 100° range at the bottom, with 3cm of the rail protruding to ensure good stress conditions on the rails and not affecting the TBM's advancement.

[0041] The concrete guide platform provides a rigid support surface for the main body of the tunnel boring machine (including the shield body and the subsequent trolley). By constraining the trajectory of the tunnel boring machine through the preset axial slope and elevation, it ensures that the tunnel boring machine excavates along the design axis to avoid deviating from the center line of the tunnel lining. The concrete guide platform is equipped with embedded parts, which are used to embed steel rails and firmly anchor the steel rails to the concrete guide platform. This allows the vertical load (including its own weight and equipment weight), longitudinal thrust, and lateral torque generated during tunnel boring machine excavation to be transmitted to the embedded parts through the steel rails and then evenly distributed into the concrete of the guide platform. This prevents the steel rails from loosening, warping, or shifting due to excessive local stress, and avoids cracking and peeling damage on the surface of the guide platform.

[0042] At the starting point of the first-phase lining, a pre-embedded steel ring 21 is set at the tunnel entrance. The pre-embedded steel ring consists of an L-shaped steel plate 21a and two anchoring steel bars 21c with a diameter of 28mm. One set of anchoring steel bars is set every 2.5°. The pre-embedded steel ring at the tunnel entrance is firmly fixed to the lining steel bars of the first-phase lining concrete 19. Bolt holes 21b are set on the L-shaped steel plate 21a. One bolt hole is arranged every 2.5°. The bolt holes 21b should be staggered with the anchoring steel bars 21b. Before the tunnel boring machine enters the tunnel, the water-stop curtain 22 should be fixed through the bolt holes.

[0043] In addition, to ensure the stability and safety of the surrounding rock mass of the initial tunnel section, consolidation grouting holes are drilled into the rock on the side where the tunnel contacts the surrounding rock for consolidation grouting. Consolidation grouting is carried out after the completion of the first-stage lining concrete 19. To avoid damaging the lining reinforcement during the drilling of the consolidation grouting holes, a consolidation grouting guide steel pipe 30 (76mm diameter, 5mm wall thickness) is embedded during the reinforcement binding process inside the first-stage lining concrete 19. During the later consolidation grouting, holes 23 are drilled from inside the guide steel pipe to form consolidation grouting holes. Shrinkage will occur during the setting of the first-stage lining concrete 19, forming shrinkage joints at the top of the tunnel. Therefore, backfill grouting is carried out within a 180° range at the top of the tunnel.

[0044] For backfill grouting, seven backfill grouting guide steel pipes 27 (diameter 32mm, wall thickness 5mm) are pre-embedded within a 120° range at the top of the first phase lining 19 in the city gate-shaped section. For backfill grouting of the first phase lining 19 in the horseshoe-shaped section, the consolidation grouting guide steel pipe 30 is used for backfill grouting. After the first-phase lining concrete reaches 70% of its design strength, backfilling and grouting will be carried out. Backfilling and grouting will be carried out in the order of low to high and from the side arches to the top arches. The water-cement ratio of the backfilling grout is 0.5, and the grouting pressure is 0.2~0.4MPa. Under this pressure, after the grouting hole stops grouting, grouting will continue for 10 minutes before stopping. Backfilling and grouting will be checked 7 days and 28 days after completion. The number of check holes should be 5% of the total number of grouting holes. The check method is as follows: inject cement grout with a water-cement ratio of 2:1 into the top arch of the grouting part. Under a pressure of 0.2~0.4MPa, the injection volume should not exceed 10L in the first 10 minutes to be considered qualified. If it is not qualified, each hole should be re-grouted.

[0045] Consolidation grouting is carried out at the section where the tunnel excavation face contacts the rock. Specifically, the consolidation grouting holes for the tunnel lining in the city gate section are located on both sides of the tunnel. The lining of the water intake shafts at the top and bottom of the tunnel (2), the bottom plate of the water intake shaft (55), and the diaphragm wall (1) do not require consolidation grouting. The entire cross-section of the horseshoe-shaped lining is grouted, with a spacing of 2m between the grouting holes. Consolidation grouting is carried out 7 days after the completion of backfill grouting in the corresponding areas. The consolidation grouting material is ordinary Portland cement with a strength grade of 42.5. The initial water-cement ratio is 2:1. The grouting pressure for 2-6m is 1.5MPa, and the grouting pressure for 0-2m is 0.5-1MPa. Under this pressure, after the grouting hole stops grouting, grouting continues for 10 minutes before ending. Three days after the completion of consolidation grouting, a single-point water pressure test method is used to check whether the consolidation grouting is qualified. The number of inspection holes shall not be less than 5% of the total number of grouting holes. The qualification standard is that the permeability of inspection holes above 85% shall not be greater than 3Lu. The water pressure test pressure shall be greater than the grouting pressure, but not greater than 80% of the grouting pressure. Unqualified sections shall be supplemented with grout.

[0046] The consolidation grouting after the first-stage lining concrete construction enhances the bonding between the lining and the surrounding rock by filling the gaps between them, forming an integrated structure of "lining-grouting body-surrounding rock" that works together to improve the load-bearing capacity. The grout also penetrates and cements the cracks in the surrounding rock to improve the integrity and strength of weak and broken surrounding rock, and reduce its compressibility and permeability. Together with pre-support and anchor bolt support, it forms a complete technical chain from "pre-reinforcement" to "immediate support" and then to "post-reinforcement", which reduces uneven settlement between the water conveyance tunnel and the water conveyance shaft.

[0047] During tunnel excavation, a 40cm thick end wall 20 is constructed at the end section. Fiberglass reinforcement is installed on the outer surface of the end wall 40, with an 8cm thick protective layer for the reinforcing steel. The end wall will eventually be worn through by the tunnel boring machine (TBM). Using steel reinforcement would significantly increase the difficulty of TBM tunneling; therefore, fiberglass reinforcement is used inside the end wall.

[0048] The water-stop curtain 22 consists of a rubber sheet curtain 22a, a pad 22b, M20 bolts 22c, and a flap 22d. The rubber sheet curtain 22a serves to seal, stop water, and stop grouting during the shield tunneling grouting process. The pad 22b is connected to the pre-embedded steel ring 22 at the tunnel entrance via M20 bolts 22c, which forces the rubber sheet curtain 22a to fit tightly against the tunnel entrance, enhancing the sealing effect. The flap 22d is installed on the circular ring plate. During shield tunneling, the flap 22d flips and holds the rubber sheet curtain 22a in place, preventing the curtain from flipping backwards due to excessive water and soil pressure ahead, further improving the sealing performance of the water-stop curtain 22.

[0049] The embedded part 24 consists of a Q235B steel plate, two anchor bars 24b (165cm long and 20mm in diameter), two pressure plates 24c, and M20 bolts 24d. The embedded rail 29 is firmly fixed by the pressure plates 24c and M20 bolts 24d.

[0050] After the above construction process is completed, the shield tunneling can be launched in step 4).

[0051] like Figure 24-28 As shown, in one specific embodiment, during the construction of step 4), the tunnel boring machine (TBM) is installed inside the shaft and then advanced into the starting tunnel. During the advancement process, the tunnel segments 29 are assembled. The tunnel segments 29 assembled before the structural joint are temporary segments, while the tunnel segments 29 assembled after the structural joint are permanent segments. The space between the outer surface of the tunnel segment 29 and the inner surface of the primary lining concrete 19 is the wall thickness grouting section 30. Grouting of the tunnel segment begins from the pre-embedded steel ring, with a grouting thickness of 0.4m. After the tunnel boring machine (TBM) penetrates the fiberglass reinforced end wall, it advances into the surrounding rock, forming the tunnel section. After advancing a certain distance, the temporary segments in the shaft are removed as appropriate. After removal, the steel bars are tied, and the second-stage lining concrete 32 at the tunnel entrance is poured to firmly connect with the inner lining 2 of the water intake shaft. The second-stage lining concrete 33 is poured to firmly connect with the chamfer 3 of the shaft. Two water-swellable sealing strips 34 are used at the contact surface between the cast-in-place second-stage lining concrete 32 and the permanent segment 31 to prevent water from seeping into the surrounding rock during tunnel operation.

[0052] Shrinkage occurs during the concrete setting process. Backfilling and grouting are carried out within a 180° range at the top of the cast-in-place second-stage lining concrete 27. Lining reinforcement is installed on the inner and outer surfaces of the second-stage lining concrete 32. The circumferential reinforcement has a diameter of 32mm and a spacing of 15cm, while the horizontally distributed reinforcement has a diameter of 25mm and a spacing of 20cm. During the reinforcement binding process, two rows of backfilling and grouting guide steel pipes 33 (diameter 32mm, wall thickness 5mm) are pre-embedded within a 120° range of the top arch, with 7 pipes in each row. The permanent pipe segments are backfilled and grouted through pre-drilled grouting holes on the precast pipe segments.

[0053] This phased lining method for the starting tunnel is used in deep-buried tunnels and shield tunneling starting sections with complex surrounding geological conditions. Before starting, the geological conditions of the starting tunnel are pre-treated. During excavation, timely support is provided at the excavation location, and hollow grouting anchors are installed in the rock mass. During the first-stage lining, consolidation grouting is carried out around the tunnel, which makes the voids in the surrounding rock mass of the starting tunnel densely filled, and the lining is firm and reliable. The horseshoe-shaped cross-section of the diaphragm wall on the outside of the shaft helps to stabilize the tunnel under stress. After the first-stage lining, the shield tunneling starting is safe and reliable.

[0054] As can be seen from this embodiment, the phased lining method for the starting tunnel that meets the requirements of shield tunneling can achieve the following by setting up advanced support, tunnel excavation support, primary lining and secondary lining. Under complex geological conditions, the starting section of the shield tunnel in the deep-buried tunnel can seal the surrounding rock through a composite structural system, quickly restrain the loosening and deformation of the surrounding rock, and make the entire lining system more evenly stressed, thereby better ensuring the safety of tunnel construction.

[0055] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for phased lining of a launch tunnel to meet the requirements of shield tunneling launch, characterized in that, Includes the following steps: 1) Advance support of pipe roof: Before the shield tunneling start section is excavated, the arch of the tunnel is supported in advance. The gaps between the steel pipes of the pipe roof are filled by grouting to form a water-stop curtain. 2) Initial support after excavation: Steel fiber reinforced concrete spraying support, steel arch support and hollow grouting anchor support should be carried out in a timely manner after excavation. 3) Tunnel lining structure construction: The first-stage lining and the second-stage lining of the tunnel are constructed separately. The starting position of the first-stage lining is the intersection of the tunnel waist and the diaphragm wall of the shaft, and the ending point is the inner surface of the steel fiber concrete of the end excavation face. A pre-embedded steel ring is set at the starting point of the first-stage lining. 4) Tunneling launch: The tunnel boring machine is installed inside the shaft and then advanced into the launching tunnel.

2. The method for phased lining of the launching tunnel to meet the requirements of shield tunneling as described in claim 1, characterized in that, In step 1), the pre-support procedure includes: First, construct the outer diaphragm wall of the shaft, the inner lining of the water intake shaft, the ring beam of the water intake shaft, the bottom plate of the water intake shaft, and the chamfered lining of the shaft. Within the shield tunneling starting range, reserve openings are set in the side walls of the water intake shaft, and multiple concrete ring beams are set within the range of the reserved openings. During the construction of the water intake shaft lining, a water-stop copper sheet is installed at the reserved opening, and a guide steel pipe is pre-embedded within a 180° range at the top of the reserved opening. The guide steel pipe is inclined outward at an angle of 1.5°, and a preset distance is left between the guide steel pipe and the reserved opening. The guide steel pipe is driven into the rock mass, and grouting is performed using cement grout with a water-cement ratio of 0.5:1 to 1:1 at a pressure of 0.5 to 1 MPa. After grouting, the guide steel pipe is filled with M30 cement mortar.

3. The method for phased lining of the launching tunnel to meet the requirements of shield tunneling as described in claim 2, characterized in that, The steel pipe for the pipe roof is made of hot-rolled seamless steel pipe. The steel pipe for the pipe roof includes a grout-stopping section, a grout overflow section and a conical section arranged in sequence. The pipe wall of the grout overflow section is provided with multiple grout overflow holes at intervals. The conical section is a conical structure and is used for forward drilling. The length of the grout-stopping section is defined as L1, the length of the grout overflow section is L2, and the length of the conical section is L3. Then: L2>L1+L3.

4. The method for phased lining of the launching tunnel to meet the requirements of shield tunneling launch according to any one of claims 1-3, characterized in that, In step 2), before excavation, the water intake shaft ring beam within the reserved opening area and the diaphragm wall surrounding the shaft within the projection range along the forward direction should be removed. Reliable measures should be taken during the demolition process to prevent excessive demolition. The excavation section before the tunnel centerline intersects with the outer edge of the diaphragm wall surrounding the shaft is in the shape of a city gate, and the excavation section after the intersection is in the shape of a horseshoe. The tunnel excavation adopts a step-by-step short-step or reserved core soil excavation method to ensure the safety of the tunnel excavation section. After the tunnel is excavated, steel fiber concrete should be used to seal it in time, and steel arches should be erected in the city gate-shaped excavation section and in the horseshoe-shaped excavation section. During tunnel excavation, the cycle advance is 0.5m, and a steel arch frame is erected every 0.5m. The base and waist of the steel arch frame are firmly fixed with ordinary mortar anchors, and the ordinary mortar anchors extend into the rock to a depth of not less than 4m.

5. The method for phased lining of the launching tunnel to meet the requirements of shield tunneling as described in claim 4, characterized in that, When spraying steel fiber concrete, first spray a 10cm thick layer, then lay a layer of steel mesh, then erect a steel arch frame, and finally spray CF30 steel fiber concrete to seal it. Spray 10cm of steel fiber concrete between the steel arch frames, and the thickness of the steel fiber concrete protective layer at the steel arch frame part is 3cm. When water seepage occurs during tunnel excavation, after spraying CF30 steel fiber concrete, drainage holes are arranged at the water seepage point. The drainage holes are 5m deep and 65mm in diameter. At the end section of the tunnel excavation, a 10cm thick layer of sprayed steel fiber concrete is sprayed first, and then glass fiber anchors are installed to ensure the safety of the end excavation face. The spacing of the glass fiber anchors is 1.5m. Drainage holes are installed when water seepage occurs.

6. The method for phased lining of the launching tunnel to meet the requirements of shield tunneling launch according to any one of claims 1-3 or 5, characterized in that, In step 3), the tunnel lining structure includes the following during construction: The tunnel lining from the starting point of the first phase of tunnel lining to the structural joint section is shaped like a city gate, and the tunnel lining from the structural joint to the end point of the first phase of tunnel lining is shaped like a horseshoe. A horizontal construction joint is set at a preset distance from the bottom edge of the city gate-shaped tunnel, and a horizontal construction joint is set at a preset distance from the bottom edge of the horseshoe-shaped tunnel. Water-stop copper sheets are set in the horizontal construction joints. The horizontal construction joints of the city gate-shaped tunnel and the horseshoe-shaped tunnel have the same height, and the water-stop copper sheets are arranged along the entire length. The first-stage lining is circular, with the thickness varying at both corners according to the shape of the outer edge. Lining reinforcement is installed on the inner and outer surfaces of the first-stage lining concrete, including circumferential reinforcement and horizontally distributed reinforcement. To facilitate the advancement of the tunnel boring machine, multiple embedded steel rails are installed at the bottom of the first-stage lining concrete, and the embedded steel rails are fixed by embedded parts; a concrete guide platform of preset thickness is set within a 100° range at the bottom.

7. The method for phased lining of the launching tunnel to meet the requirements of shield tunneling as described in claim 6, characterized in that, During construction, the pre-embedded steel ring is firmly fixed to the reinforcing steel of the first-phase lining concrete. The pre-embedded steel ring includes an L-shaped steel plate and two anchoring steel bars. The anchoring steel bars are set at 2.5° intervals. The L-shaped steel plate is provided with bolt holes, one at 2.5° intervals, and the bolt holes are staggered with the anchoring steel bars. A water-stop curtain should be installed before the tunnel boring machine enters the tunnel, and the water-stop curtain should be fixed through the bolt holes. Construction also includes backfill grouting and consolidation grouting. For backfill grouting, multiple backfill grouting guide steel pipes are pre-embedded within a 120° range at the top of the first phase lining of the tunnel-shaped section. Backfill grouting of the first phase lining of the horseshoe-shaped section is carried out using consolidation grouting guide steel pipes. Consolidation grouting is carried out at the section where the tunnel excavation face contacts the rock.

8. The method for phased lining of the launching tunnel to meet the requirements of shield tunneling as described in claim 7, characterized in that, The backfill grouting is carried out after the first-stage lining concrete reaches 70% of its design strength. The backfill grouting is carried out in the order of low to high and from the side arch to the top arch. The water-cement ratio of the backfill grouting is 0.5, and the grouting pressure is 0.2~0.4MPa. After the grouting hole stops sucking grout, the grouting continues for at least 10 minutes before it ends. Backfill grouting is inspected 7 days and 28 days after the completion of backfill grouting. The number of inspection holes is not less than 5% of the total number of grouting holes. The consolidation grouting is carried out 7 days after the completion of the backfill grouting at the corresponding location. The consolidation grouting material is ordinary Portland cement with a strength grade of 42.

5. The water-cement ratio at the start of grouting is 2:

1. The grouting pressure for 2-6m of consolidation grouting is 1.5MPa, and the grouting pressure for 0-2m is 0.5-1MPa. After the grouting hole stops grouting, grouting continues for at least 10 minutes before it ends. Three days after the completion of consolidation grouting, a single-point water pressure test is used to check whether the consolidation grouting is qualified. The number of test holes is not less than 5% of the total number of grouting holes. The qualification standard is that the permeability of test holes above 85% is not greater than 3Lu. The water pressure test pressure should be greater than the grouting pressure, but not greater than 80% of the grouting pressure. Unqualified sections should be re-grouted.

9. The method for phased lining of the launching tunnel to meet the requirements of shield tunneling as described in claim 7, characterized in that, The water-stop curtain includes a rubber sheet curtain, a pad, M20 bolts, and a flap. The rubber sheet curtain plays a sealing, water-stopping, and grout-stopping role during shield tunneling grouting. The pad is connected to the pre-embedded steel ring through the M20 bolts to force the rubber sheet curtain to fit tightly against the tunnel opening, enhancing the sealing effect. The flap is installed on a circular plate. During shield tunneling, the flap can flip and hold the rubber sheet curtain in place, preventing the curtain rubber sheet from flipping in reverse due to excessive water and soil pressure in front, thereby improving the sealing performance of the water-stop curtain.

10. The method for phased lining of the launching tunnel to meet the requirements of shield tunneling launch according to any one of claims 1-3 or 7-9, characterized in that, In step 4), the tunnel boring machine (TBM) begins assembling tunnel segments during its advancement. The segments assembled before the structural joint are temporary segments, while the segments assembled after the structural joint are permanent segments. After the TBM penetrates the fiberglass reinforced end wall, it tunnels into the surrounding rock, forming the tunnel excavation section. After tunneling a certain distance, the temporary segments in the shaft are removed as appropriate. After removal, the reinforcing bars are tied, and the second-stage lining concrete at the tunnel entrance is poured to ensure a firm connection with the water intake shaft lining. The second-stage lining concrete is poured to ensure a firm connection with the shaft chamfer and the shaft lining. Two water-swellable sealing strips are used at the contact surface between the cast-in-place second-stage lining concrete and the permanent segments to prevent water from seeping into the surrounding rock during tunnel operation. Shrinkage will occur during the concrete setting process. Backfilling and grouting will be carried out within a 180° range of the top of the cast-in-place second-stage lining concrete. Lining reinforcement bars will be set on the inner and outer surfaces of the second-stage lining concrete. During the reinforcement binding process, two rows of backfilling and grouting guide steel pipes will be pre-embedded within a 120° range of the top arch. The permanent pipe segment will be backfilled and grouted through the grouting holes reserved on the precast pipe segment.

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