A method for reinforcing the foundation of a tunnel pile foundation plus ribbed slab span structure in operation period

Abstract

The application provides a foundation reinforcement method for operating period tunnel pile foundation plus ribbed slab span structure, belongs to the technical field of tunnel foundation reinforcement, and is used for rock-embedded pile construction, foot lock anchor rod setting, steel pipe temporary cross support erection, pavement excavation and beam pouring, secondary lining cross support plate pouring, prestressed anchor rod and steel plate pasting reinforcement, pavement recovery and reinforcement completion. Compared with the traditional lining inverted arch replacement, the application innovatively uses the embedded rib structure to better repair the tunnel. The embedded rib plate beam structure transfers the original tunnel vertical load borne by the inverted arch to the plate beam through the embedded rib and the structural rigidity of the plate beam itself. The safety of the inverted arch replacement during construction is improved, and the construction difficulty is reduced. The application innovatively uses the artificial hole digging pilot hole and then impact drilling hole process in the rock-embedded pile construction process, which can effectively overcome the difficulty of using impact drilling hole under the condition of low tunnel clearance.

Description

Technical Field

[0001] This invention relates to the field of tunnel foundation reinforcement technology, and in particular to a method for foundation reinforcement of tunnel pile foundation with supporting rib plate span structure during operation. Background Technology

[0002] During the operational phase, tunnels often experience problems such as insufficient foundation bearing capacity and excessive deformation due to increased usage time, traffic volume exceeding design values, and construction defects. Current technologies commonly employ methods like replacing the initial lining invert or replacing the invert with beams for tunnel repair. Replacing the invert requires large-scale road excavation, resulting in a large workload, high risk, and generally limited effectiveness. Replacing the invert with beams damages the tunnel's original arch structure, leading to subsidence at the arch foot and compromising long-term operational stability. Therefore, a simple, effective, safe, and reliable mature technical solution is needed to address the foundation treatment issues of tunnels during the operational phase. Summary of the Invention

[0003] The purpose of this invention is to provide a method for foundation reinforcement of tunnel pile foundation with ribbed span structure during operation, which solves the technical problems of existing methods for tunnel maintenance, such as replacing the initial lining invert and replacing the invert with beams, which require large-volume road excavation for invert replacement, resulting in a large amount of construction work and a high risk factor.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for foundation reinforcement of tunnel pile foundation with supporting ribs during operation involves the following steps: rock-socketed pile construction, installation of foot-lock anchor rods, erection of temporary steel pipe cross bracing, road excavation and pouring of cross beams, pouring of secondary lining cross bracing plates, reinforcement with prestressed anchor rods and bonded steel plates, road restoration, and completion of reinforcement.

[0006] Furthermore, the specific process of rock-socketed pile construction is as follows:

[0007] The method of first manually excavating and then drilling with an impact drill is adopted. Due to the clearance limitations inside the tunnel, it is not possible to directly use an impact drill for drilling. After manually excavating to the appropriate depth, the hole depth plus the tunnel height can meet the height required for impact drilling. Let the pile diameter be d, the pile depth be l, and the number of piles be n. The piles should meet the strength and stiffness requirements to transfer the load to the foundation. The piles should be evenly distributed so that each pile is subjected to approximately equal stress. The piles should be constructed using steel pipe piles or steel casings. The drilling process should be recorded during construction. Drill cuttings should be blown out during drilling. The integrity, strength, and bearing capacity of the piles should be tested.

[0008] Furthermore, the specific process of installing the foot-lock anchor bolts is as follows:

[0009] After the pile foundation construction is completed, enlarged anchor rods are driven into the arch foot to support the arch ring. The anchor rods are placed in the gap between the ribs. Let the distance between adjacent anchor rods be d1, the width of the rib be s, and the width of the rib gap be s1. That is, d1 is greater than the rib width and s is less than s+s1. The anchor rods are driven in obliquely downwards, and the locking anchor rods are driven in the general section to avoid the ribs of subsequent construction from being affected.

[0010] Furthermore, the specific process for erecting temporary steel pipe cross braces is as follows:

[0011] After the anchor bolts are installed, temporary horizontal bracing is set at the arch waist, which is 0.5h to 0.8h above the ground. The temporary horizontal bracing is installed every 0.5-5 meters in the longitudinal direction, and the two ends are connected to the arch ring through pads or connectors. The steel pipe horizontal bracing at the arch waist provides temporary support for the force system transfer between the invert arch and the slab beam, avoiding the risk of structural instability during the excavation of the invert arch. The temporary horizontal bracing is removed after the construction is completed.

[0012] Furthermore, the specific process of road excavation and beam pouring is as follows:

[0013] After all temporary supports are erected, road excavation begins. The road surface and invert arch of the construction section are removed. The removal of the invert arch and the replacement of the secondary lining arch are all carried out using a skip-slot construction method. The rib section is excavated first, followed by the general section. The space required for the slab beam is excavated downwards. The slab beam height h1 is 0.5-3m. The embedded beam structure consists of alternating rib section and general section. The rib section achieves cantilever of the tunnel secondary lining by embedding itself into the bottom of the sidewall. Let the length of the rib section be Lt and the length of the general section be D. t L t 50-100cm, D t For L t 1-4 times the depth of the rib support S t It is equal to the width of the arch foot, and the supporting rib is a triangular prism with a triangular cross-section;

[0014] The platform is located at both ends of the treatment section, connecting the beam and slab to the normal tunnel section. Before the beam and slab are poured, verification holes are drilled to verify the bottom of the platform to ensure that the bottom of the platform is complete and continuous moderately weathered bedrock. Before the platform is poured, the soil attached to the rock should be removed to ensure that the bottom of the platform is supported on complete moderately weathered bedrock. During the construction of the platform, steel mesh should be installed to improve the overall integrity.

[0015] During beam and slab pouring, the central drainage ditch of the defective section is replaced with an HDPE drainage pipe and connected to the central drainage ditch of the normal sections at both ends. HDPE drainage pipes are pre-embedded when tying the reinforcing bars. The beam and slab are poured using the skip-slot construction method. The site is leveled, the reinforcing bars are tied, and the formwork is erected. The rib section is poured first, then the formwork is removed, and then the general section is poured. The interval between two adjacent sections is no less than 7 days. The skip-slot construction divides the large-area concrete planar structure into several areas to avoid the intense temperature difference and drying effect in the early stage of concrete construction.

[0016] Furthermore, the specific process of casting the secondary lining cross bracing is as follows:

[0017] The secondary lining cross bracing plate serves to provide horizontal reaction force to compensate for the removal of the invert arch. The secondary lining cross bracing plate applies a horizontal force to the arch foot to open the arch foot, making the secondary lining force system closed loop. The road surface structure is on the secondary lining cross bracing plate.

[0018] Furthermore, the specific process of road surface restoration is as follows:

[0019] After the concrete of the secondary lining cross bracing plate reaches the design strength, the temporary cross bracing is removed, and then the road surface is laid. Construction is completed after the road surface is restored.

[0020] Furthermore, the foundation reinforcement construction process is as follows:

[0021] Step 1: Rock-socketed pile construction. The method of manual excavation followed by drilling with an impact drill is adopted. The pile diameter d is 2m. The piles are evenly arranged in two rows with an interval of 15m between adjacent piles. Steel pipe piles are used for follow-up construction. The drilling process should be recorded during construction. The drilling should penetrate into the intact bedrock for no less than 3m. Drill cuttings should be blown out during the drilling process. After drilling is completed, concrete is poured.

[0022] Step 2: Install anchor bolts. Drive 108mm diameter anchor bolts at a 45° downward angle at the arch foot to support the arch ring. The distance between adjacent anchor bolts is 2m. Weld the end of the anchor bolt to the steel frame.

[0023] Step 3: Erect temporary cross bracing. Set up temporary cross bracing at the arch waist to improve the support capacity of the arch and ensure personnel safety. Temporary cross bracing is set every 2 meters in the longitudinal direction, and the two ends are connected to the arch through pads.

[0024] Step 4: Road excavation. The road surface and invert arch of the construction section are removed. The invert arch is broken and embedded in the rib section. The replacement of the secondary lining arch ring is carried out by skipping the trench. The rib section is excavated first, and then the general section is excavated. The space required for each section of the slab beam is excavated. The height of the slab beam is 2m. The length of the rib section is 1m and the length of the general section is 2m. When setting the rib section, care should be taken to avoid the already driven anchor rods. The anchor rods and the ribs are staggered and do not affect each other.

[0025] Step 5: Inspect the platform and drill verification holes to verify the bottom of the platform to ensure that the bottom of the platform is a complete and continuous moderately weathered bedrock. Before pouring the platform, the soil attached to the rock should be removed to ensure that the bottom of the platform is supported on a complete moderately weathered bedrock.

[0026] Step 6: Tie the reinforcing bars and pre-embed the drainage pipes. Tie the reinforcing bars, lay the reinforcing mesh at the platform to improve the overall integrity, and pre-embed 3 HDPE drainage pipes in the middle.

[0027] Step 7: Beam and slab pouring. The beam and slab are poured using the skip-slot construction method. The site is leveled, the formwork for the rib section is erected, the beam and slab with the rib section is poured, the formwork is then removed, and the general section of the beam and slab is poured. The interval between the two sections is no less than 7 days. The rib section is 1m long and the general section is 2m long.

[0028] Step 8: Casting of secondary lining cross bracing plates. After the beam and slab concrete has been solidified, tie stiffeners, support formwork, and cast secondary lining cross bracing plates on them.

[0029] Step 9: Reinforcement with prestressed anchor rods and bonded steel plates; install prestressed anchor rods and steel plates, and remove temporary cross braces;

[0030] Step 10: Road surface restoration and paving are carried out. Construction is completed after paving is finished.

[0031] The design concept of a slab beam with alternating embedded rib plates. The rib sections and general sections are alternately arranged, with anchor bolts placed in the general sections, allowing the ribs and anchor bolts to function simultaneously without interfering with each other. The ribs can also be embedded in the arch ring, enabling cantilevering of the secondary lining.

[0032] The technique of using a combination of manual drilling and impact drilling for pile foundation driving in tunnels. The support system composed of ribs, anchor pipes, and arch waist braces effectively reduces the safety risks of excavating the invert arch and constructing the slab beam.

[0033] The present invention, by adopting the above-described technical solution, has the following beneficial effects:

[0034] (1) Compared to traditional invert lining replacement, this invention innovatively utilizes a rib-embedded structure for better tunnel repair. The rib-embedded plate-beam structure transfers the vertical load of the tunnel, originally borne by the invert arch, to the plate beam through the ribs and the structural rigidity of the plate beam itself. This ensures a complete force transmission path between the plate beam and the tunnel, while also reducing construction difficulty and safety risks.

[0035] (2) This technology innovatively adopts a process of first manually excavating and guiding the hole in the construction process of rock-socketed piles, and then using impact drilling to form the hole, which can effectively overcome the difficulty of using impact drilling to form the hole under the low clearance conditions of the tunnel.

[0036] (3) Compared with the traditional replacement of the inverted arch lining, the present invention effectively reduces the safety risks of excavating the inverted arch and constructing the slab beam by means of measures such as rib embedding, lateral support, and anchor pipe locking. The anchor pipe locking at the arch foot and the steel pipe lateral bracing at the arch waist provide temporary support for the force system conversion between the inverted arch and the slab beam, avoiding the risk of structural instability during the excavation of the inverted arch.

[0037] (4) Improved the safety of invert replacement during construction and reduced construction difficulty. This technology innovatively adopts a process of first manually excavating and then drilling holes in the rock-socketed pile construction process, which can effectively overcome the difficulty of using impact drilling to form holes under the low clearance conditions of the tunnel. Attached Figure Description

[0038] Figure 1 This is a flowchart of the method of the present invention;

[0039] Figure 2 This is a schematic diagram illustrating the combined use of manual drilling and impact drilling in this invention;

[0040] Figure 3 This is a plan view of the pile foundation with supporting ribs across the structure according to the present invention;

[0041] Figure 4 This is an elevation view of the cross-structure rib support section of the rib support plate of the present invention;

[0042] Figure 5 This is an elevation view of a general section of the rib support plate spanning the structure according to the present invention;

[0043] Figure 6 This is a construction process diagram of the rib support plate spanning the structural rib support section of the present invention.

[0044] In the attached diagram, 1-embedded rib, 2-pad, 3-verification hole, 4-pile foundation, 5-secondary lining cross brace, 6-plate beam, 7-existing steel frame, 8-existing arch ring, 9-temporary steel pipe cross brace, 10-replacement arch anchor bolt, 11-longitudinal steel waler. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the present invention, and these aspects of the invention can be implemented even without these specific details.

[0046] like Figure 1-6 As shown, a method for foundation reinforcement of a tunnel pile foundation with supporting ribs during operation is characterized by the use of embedded ribs in the arch ring to transfer the upper load to the pile foundation, preventing arch ring deformation and settlement. Simultaneously, measures such as lateral supports and anchor pipes are implemented to effectively reduce the safety risks associated with the excavation of the invert arch construction beam. The method includes the following steps:

[0047] Step 1: Pile Foundation Construction. The method of manual excavation followed by drilling with an impact drill is adopted. Due to the clearance limitations within the tunnel, direct drilling with an impact drill is not possible. After manually excavating to a sufficient depth, the hole depth plus the tunnel height is sufficient to meet the working height of the impact drill. See [link to manual and mechanical drilling method] for details. Figure 1Let the pile diameter be d, the pile depth be l, and the number of piles be n. d and l should be calculated according to specifications to ensure the piles meet the strength and stiffness requirements and transfer the load to the foundation. The piles should be evenly distributed so that each pile experiences approximately equal stress. The piles can be constructed using steel pipe piles or steel casings. The drilling process should be recorded, and drill cuttings should be blown out during drilling. The integrity, strength, and bearing capacity of the piles should be inspected. The construction process and inspection should comply with the requirements of relevant specifications such as the "Code for Design of Highway Bridge and Culvert Foundations" (JTG3363-2019) and the "Technical Specification for Pile Measurement of Building Foundations" (JGJ106-2014).

[0048] Step 2: Install anchor bolts at the arch foot. After the pile foundation construction is completed, drive enlarged anchor bolts at the arch foot to support the arch ring. The anchor bolts are placed in the gaps between the ribs. Let the distance between adjacent anchor bolts be d1, the rib width be s, and the rib gap width be s1, i.e., d1 is greater than the rib width s and less than s+s1. The anchor bolts are driven diagonally downwards, and the anchor bolt angle and depth are designed according to the specifications. The anchor bolts are driven in the general section to avoid affecting the ribs constructed later.

[0049] Step 3: Road Excavation. Road excavation begins after all temporary supports are erected. The road surface and invert arch of the construction section are removed. The removal of the invert arch and the replacement of the secondary lining arch are carried out using a skip-slot construction method, excavating the rib section first, then the general section. The space required for the slab beam is excavated downwards; the slab beam height h1 is 0.5-3m. The rib-embedded beam structure consists of alternating rib-embedded and general sections. The rib-embedded sections achieve cantilever support of the tunnel secondary lining by embedding themselves into the bottom of the sidewall. The length of the rib-embedded section can be set as L. t The typical segment length is D. t L t 50-100cm, D t For L t 1-4 times the depth of the rib support S t It equals the width of the arch foot. The supporting rib is a triangular prism with a triangular cross-section, such as... Figure 3-4 As shown.

[0050] Step 4: Platform 2. Platforms are placed at both ends of the treatment section, connecting the beams and slabs to the normal tunnel sections. Before pouring the beams and slabs, verification holes 3 are drilled to verify the bottom of platform 2, ensuring that the bottom of platform 2 is intact and continuous moderately weathered bedrock. Before pouring platform 2, any soil adhering to the rock should be removed to ensure that the bottom of platform 2 is supported on intact moderately weathered bedrock. During the construction of platform 2, a steel mesh should be installed to improve its overall integrity.

[0051] Step 5: Beam and Slab Casting. The central drainage ditch in the damaged section is replaced with an HDPE drainage pipe and connected to the central drainage ditches in the normal sections at both ends. HDPE drainage pipes are pre-embedded during rebar tying. A skip-slot construction method is used for beam and slab casting. The site is leveled, rebar is tied, formwork is erected, the ribbed section is cast first, then the formwork is removed, and then the normal section is cast, with an interval of no less than 7 days between adjacent sections. Skip-slot construction divides the large-area concrete planar structure into several areas, avoiding intense temperature differences and drying effects in the early stages of concrete construction.

[0052] Step 6: Casting of the secondary lining cross bracing. The secondary lining cross bracing provides horizontal reaction force, compensating for the removal of the invert arch. The cross bracing applies a horizontal force to the arch foot, opening it up and creating a closed-loop stress system for the secondary lining. The pavement structure is located on top of the secondary lining cross bracing.

[0053] Step 7: Install prestressed anchor bolts and reinforce with steel plates. Applying prestress can improve the load-bearing capacity and durability of the beam. However, this technology is not the focus of this patent.

[0054] Step 8: Road Surface Restoration. After the secondary lining cross bracing concrete reaches its design strength, the temporary cross bracing is removed. Then, the road surface structure is laid, and construction is complete upon completion of road surface restoration. Construction procedures and processes. Figure 1 and Figure 6 As shown.

[0055] The construction process for this case is as follows:

[0056] Rock-socketed pile construction. The method involves manual excavation followed by drilling using an impact drill. The pile diameter (d) is 2m, and the piles are evenly arranged in two rows with a 15m interval between adjacent piles. Steel pipe piles are used in the follow-up construction. The drilling process should be recorded, and the borehole should penetrate at least 3m into intact bedrock. Drill cuttings should be blown out during drilling. Concrete is poured after drilling is completed.

[0057] Install anchor bolts. Drive 108mm diameter anchor bolts at a 45° downward angle into the arch foot to support the arch ring. The distance between adjacent anchor bolts is 2m. The ends of the anchor bolts are welded to the Ⅱ4 type steel frame.

[0058] Erect temporary cross bracing. Temporary cross bracing is installed at the arch waist (0.8h above the ground) to improve the arch's support capacity and ensure personnel safety. Temporary cross bracing is installed every 2 meters longitudinally, with both ends connected to the arch via pads.

[0059] Road excavation. The road surface and invert arch of the construction section will be removed. The removal of the invert arch and the replacement of the embedded rib section, as well as the secondary lining arch ring, will be carried out using a skip-slot construction method. The rib section will be excavated first, followed by the general section. The space required for each section of the slab beam will be excavated, with a slab beam height of 2m. The rib section will be 1m long, and the general section will be 2m long. When installing the rib section, care must be taken to avoid the already driven anchor bolts; the anchor bolts and ribs should be staggered to avoid interference.

[0060] Inspect platform 2. Drill verification holes to verify the bottom of platform 2, ensuring that the bottom of platform 2 is intact and continuous moderately weathered bedrock. Before pouring platform 2, remove any soil adhering to the rock to ensure that the bottom of platform 2 is supported on intact moderately weathered bedrock.

[0061] Reinforcing steel bars and pre-embedded drainage pipes. Reinforcing steel bars were tied, and steel mesh was laid at two points on the platform to improve the overall integrity. Three HDPE drainage pipes were pre-embedded in the middle.

[0062] Beam and slab pouring. The skip-slot construction method is used for beam and slab pouring. The site is leveled, formwork is erected for the rib section, the rib section of the beam and slab is poured, then the formwork is removed, and the general section of the beam and slab is poured. The interval between the two pours is no less than 7 days. The rib section is 1m long, and the general section is 2m long.

[0063] Secondary lining cross bracing slab pouring. After the beam and slab concrete has solidified, tie stiffeners, erect formwork, and pour the secondary lining cross bracing slab.

[0064] Prestressed anchor bolts and bonded steel plates for reinforcement. Install prestressed anchor bolts and steel plates, and remove temporary cross braces.

[0065] Road surface restoration. Road surface paving is carried out, and construction is completed after paving is finished.

[0066] The design concept employs an alternating arrangement of embedded ribs in the slab-beam configuration. The rib sections and general sections are alternately arranged, with anchor bolts positioned in the general sections, ensuring that the ribs and anchor bolts function simultaneously without interfering with each other. The ribs can also be embedded in the arch ring, allowing for cantilevering of the secondary lining.

[0067] The technology of using a combination of manual drilling and impact drilling for pile foundation driving in tunnels.

[0068] The support system, consisting of rib supports, anchor pipes, and horizontal bracing, effectively reduces the safety risks of constructing slab beams during the excavation of the inverted arch.

[0069] like Figure 3 As shown, the embedded ribs 1 are spaced apart, and the verification holes 3 are located at the positions of the pads 2. The pile foundation 4 is located at the bottom of the crossbeam. (See diagram below.) Figure 4 The embedded rib 1 extends out to support the existing arch ring 8, making the support effect better. The plate beam 6 is embedded in the rib 1 as a whole. The secondary lining cross brace 5 is set at the upper end of the plate beam 6. The existing steel frame 7 is set above the existing arch ring 8. The replacement arch locking foot anchor rod 10 is set on the inner side of the connection between the bottom of the existing arch ring 8 and the secondary lining cross brace 5. The longitudinal steel waler 11 is set on the outer side of the replacement arch locking foot anchor rod 10.

[0070] Compared to traditional invert arch replacement methods, this invention effectively reduces the safety risks of excavating the invert arch for the slab beam by using measures such as rib embedding, lateral support, and anchor pipe locking. The anchor pipe locking at the arch foot and the steel pipe lateral bracing at the arch waist provide temporary support for the force transfer between the invert arch and the slab beam, avoiding the risk of structural instability during the excavation of the invert arch.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for foundation reinforcement of a tunnel pile foundation with supporting ribs spanning the tunnel during operation, characterized in that: For the construction of rock-socketed piles, foot lock anchor rods are installed, temporary steel pipe cross bracing is erected, road surface is excavated and cross beams are poured, secondary lining cross bracing plates are poured, prestressed anchor rods and bonded steel plates are used for reinforcement, road surface is restored, and reinforcement is completed. The specific process for erecting temporary steel pipe cross bracing is as follows: After the anchor bolts are installed, temporary cross bracing is set at the arch waist, which is 0.5h to 0.8h above the ground. The temporary cross bracing is installed every 0.5 to 2m in the longitudinal direction, and the two ends are connected to the arch ring through pads or connectors. The steel pipe cross bracing at the arch waist provides temporary support for the force system transfer between the invert arch and the slab beam, avoiding the risk of structural instability during the excavation of the invert arch. The temporary cross bracing is removed after the construction is completed. The specific process of road excavation and beam pouring is as follows: After all temporary supports were erected, road excavation began. The road surface and invert arch of the construction section were removed. The invert arch was broken and embedded in the rib section, and the secondary lining arch was replaced. All of these were carried out using a skip-slot construction method. The rib section was excavated first, followed by the general section. The space required for the slab beam was then excavated downwards. The height of the slab beam was determined. The span is 0.5-3m. The embedded beam structure consists of alternating embedded rib sections and general sections. The embedded rib sections achieve cantilever support of the tunnel secondary lining by embedding themselves into the bottom of the sidewall. The length of the embedded rib section is set as follows: General segment length , Take 50-100cm. for 1-4 times the depth of the rib support The supporting ribs are triangular prisms with a triangular cross-section; The platform is located at both ends of the treatment section, connecting the beam and slab to the normal tunnel section. Before the beam and slab are poured, verification holes are drilled to verify the bottom of the platform to ensure that the bottom of the platform is complete and continuous moderately weathered bedrock. Before the platform is poured, the soil attached to the rock should be removed to ensure that the bottom of the platform is supported on complete moderately weathered bedrock. During the construction of the platform, steel mesh should be installed to improve the overall integrity. When pouring beams and slabs, the central drainage ditch of the defective section is replaced with an HDPE drainage pipe and connected to the central drainage ditch of the normal sections at both ends. HDPE drainage pipes are pre-embedded when tying the reinforcing bars. The beams and slabs are poured using the skip-slot construction method. The site is leveled, the reinforcing bars are tied, and the formwork is erected. The rib section is poured first, then the formwork is removed, and then the general section is poured. The interval between two adjacent sections is no less than 7 days. The skip-slot construction divides the large-area concrete planar structure into several areas to avoid the intense temperature difference and drying effect in the early stage of concrete construction. The specific process for pouring the secondary lining cross bracing is as follows: The secondary lining cross bracing plate serves to provide horizontal reaction force, which is used to compensate for the removal of the invert arch. The secondary lining cross bracing plate applies a horizontal force to the arch foot to open the arch foot, thus making the secondary lining force system closed loop. The road surface structure is on the secondary lining cross bracing plate.

2. The method for foundation reinforcement of a tunnel pile foundation with supporting ribs span structure during operation, as described in claim 1, is characterized in that: The specific process of rock-socketed pile construction is as follows: The method of first manually excavating and then drilling with an impact drill is adopted. Due to the clearance limitations inside the tunnel, it is not possible to directly use an impact drill for drilling. After manually excavating to the appropriate depth, the hole depth plus the tunnel height can meet the height required for impact drilling. Let the pile diameter be d, the pile depth be l, and the number of piles be n. Ensure that the pile foundation meets the requirements of strength and stiffness, transfer the load to the foundation, and the pile foundation is evenly distributed so that each pile is subjected to equal force. The pile foundation is constructed using steel pipe piles or steel casing follow-up method. The drilling process should be recorded during construction. Drill cuttings should be blown out during drilling. The integrity, strength, and bearing capacity of the pile should be tested.

3. The method for foundation reinforcement of a tunnel pile foundation with supporting ribs span structure during operation, as described in claim 1, is characterized in that: The specific process for installing foot-lock anchor bolts is as follows: After the pile foundation construction is completed, enlarged anchor bolts are driven into the arch foot to support the arch ring. The anchor bolts are placed in the gaps between the support ribs, and the distance between adjacent anchor bolts is set as follows: The width of the support rib is s, and the width of the support rib gap is... ,Right now Width greater than the support rib width s and less than The anchor bolts are driven in at an angle downwards, while the locking anchor bolts are driven in the general section to avoid affecting the support ribs in subsequent construction.

4. The foundation reinforcement method for a tunnel pile foundation with supporting rib span structure during operation, as described in claim 1, is characterized in that: The specific process of road surface restoration is as follows: After the concrete of the secondary lining cross bracing plate reaches the design strength, the temporary cross bracing is removed, and then the road surface is laid. Construction is completed after the road surface is restored.

5. The method for foundation reinforcement of a tunnel pile foundation with supporting ribs span structure during operation, as described in claim 1, is characterized in that: The foundation reinforcement construction process is as follows: Step 1: Rock-socketed pile construction. The method of manual excavation followed by drilling with an impact drill is adopted. The pile diameter d is 2m. The piles are evenly arranged in two rows with an interval of 15m between adjacent piles. Steel pipe piles are used for follow-up construction. The drilling process should be recorded during construction. The drilling should penetrate into the intact bedrock for no less than 3m. Drill cuttings should be blown out during the drilling process. After drilling is completed, concrete is poured. Step 2: Install anchor bolts. Drive 108mm diameter anchor bolts at a 45° downward angle at the arch foot to support the arch ring. The distance between adjacent anchor bolts is 2m. Weld the end of the anchor bolt to the steel section. Step 3: Erect temporary cross bracing. Set up temporary cross bracing at the arch waist to improve the support capacity of the arch and ensure personnel safety. Temporary cross bracing is set every 2 meters in the longitudinal direction, and the two ends are connected to the arch through pads. Step 4: Road excavation. The road surface and invert arch of the construction section are removed. The invert arch is broken and embedded in the rib section. The replacement of the secondary lining arch ring is carried out by skipping the trench. The rib section is excavated first, and then the general section is excavated. The space required for each section of the slab beam is excavated. The height of the slab beam is 2m. The length of the rib section is 1m and the length of the general section is 2m. When setting the rib section, care should be taken to avoid the already driven anchor rods. The anchor rods and the ribs are staggered and do not affect each other. Step 5: Inspect the platform and drill verification holes to verify the bottom of the platform to ensure that the bottom of the platform is a complete and continuous moderately weathered bedrock. Before pouring the platform, the soil attached to the rock should be removed to ensure that the bottom of the platform is supported on a complete moderately weathered bedrock. Step 6: Tie the reinforcing bars and pre-embed the drainage pipes. Tie the reinforcing bars, lay the reinforcing mesh at the platform to improve the overall integrity, and pre-embed 3 HDPE drainage pipes in the middle. Step 7: Beam and slab pouring. The beam and slab are poured using the skip-slot construction method. The site is leveled, the formwork for the rib section is erected, the beam and slab with the rib section is poured, the formwork is then removed, and the general section of the beam and slab is poured. The interval between the two sections is no less than 7 days. The rib section is 1m long and the general section is 2m long. Step 8: Casting of secondary lining cross bracing plates. After the beam and slab concrete has solidified, steel bars are tied on them, formwork is erected, and secondary lining cross bracing plates are cast. Step 9: Reinforcement with prestressed anchor rods and bonded steel plates; install prestressed anchor rods and steel plates, and remove temporary cross braces; Step 10: Road surface restoration and paving are carried out. Construction is completed after paving is finished.

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