Highway tunnel secondary lining block updating construction method

Abstract

The invention provides a road tunnel secondary lining block updating construction method, and relates to the technical field of road tunnel updating construction, the method comprises the following steps: S1, construction preparation; s2, monitoring and measuring; s3, cutting is carried out; s4, arch crown section construction; s5, haunch construction; s6, side wall construction; and S7, secondary lining concrete construction. The construction method is improved on the theoretical basis of a traditional tunnel excavation method, has the outstanding advantages of being simple in construction step, safe to operate, stable in working face, high in mechanical utilization rate and low in labor cost, and has a good reference effect on later tunnel updating.

Description

Technical Field

[0001] This invention relates to the field of highway tunnel renovation construction technology, and in particular to a method for segmented renovation construction of secondary lining of highway tunnels. Background Technology

[0002] With the surge in the number of operational tunnels in my country and the continuous expansion of newly constructed tunnels into complex geological areas, the construction technology of highway tunnels is increasingly complex, posing significant safety risks. The tunnel design under complex geological conditions rarely matches the actual exposed surrounding rock, leading to large deviations in design support parameters. This results in some tunnels developing cracks quickly during the later stages of construction or shortly after commissioning, making it difficult to meet operational safety requirements. Tunnel defects are increasing daily; cracks, leaks, and spalling in the secondary lining have a significant impact on operations, necessitating timely, efficient, and rapid treatment of these defects.

[0003] Construction period: Under adverse geological conditions, the surrounding rock of the working face exposed during construction changes significantly, resulting in a mismatch between the design support parameters and the actual working conditions. The time required for design changes to be implemented will cause the local or overall large deformation of the support structure to change from accidental to inevitable, posing a great risk. Operational period: Under adverse geological conditions, after the tunnel construction is completed, due to insufficient design support parameters or inadequate stress release in the working section, local secondary lining concrete will develop defects such as cracking, spalling, and water leakage. Tunnel defects during construction and operation require timely treatment and replacement. However, highway tunnels have large spans, and the replacement and replacement of secondary linings are risky and technically demanding. Therefore, a set of construction methods is urgently needed to ensure the quality and safety of highway tunnels with defects during the replacement and construction. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the segmented replacement of secondary lining in highway tunnels, which aims to overcome the problems of existing tunnels requiring timely treatment and replacement, while highway tunnels have large spans, high risks in secondary lining replacement and replacement, and high technical requirements.

[0005] The present invention achieves the above objectives using the following technical solution: A method for segmented replacement of secondary lining in highway tunnels includes the following steps: S1: Construction preparation; S2: Monitoring and measurement; S3: Cutting; S4: Construction of the arch section; S5: Arch construction; S6: Sidewall construction; S7: Secondary lining concrete construction; S1 includes on-site layout: the arch crown is divided into 2m sections longitudinally, and the arch waist and side walls are divided into 4m sections; the circumferential section is divided into 6 segments starting from the arch crown, 7.54m on each side, 4.95m on each side from the arch waist to the side walls, and 3.63m from the side walls to the invert surface. The 5 cutting surfaces above the side walls are cut mechanically, and the invert surface is leveled manually. S2 includes first setting up monitoring and measurement observation points within 50m of the working face and making initial records, and conducting monitoring and analysis before the start of each process to ensure the safety and stability of the working face; S3 is a special equipment for installing linear cutting. According to the layout position of the secondary lining surface of the secondary lining replacement section, it cuts and separates the secondary lining reinforced concrete. The cutting track is fixed on the secondary lining with expansion bolts. The equipment is installed in the order of first circumferential and then longitudinal. The arch crown secondary lining section is cut section by section. The arch waist and side wall sections are cut after the secondary lining is exposed. S4 includes: S41: Replace the first section of the vaulted roof; S411: First, use temporary support measures to support the right side of the first section of the secondary lining. Then, use crushing machinery to remove the reinforced concrete of the left side of the first section of the secondary lining. Finally, remove the reinforced concrete of the right side of the secondary lining. S412: Remove the initial arch frame one by one, and gradually expand the excavation outward at a 15° outward expansion angle to form the operating space for pipe roof construction. The steel arch frame uses 25b I-beams, spaced at 0.6m intervals. The longitudinal connections are made at the arch crown, left and right arch waists, using 18 I-beams for longitudinal welding. The remaining locations are connected longitudinally with φ20 steel bars, with a circumferential spacing of 1m. There are 6 sets of φ42×4mm locking foot grouting pipes on each side, each 6m long, which are firmly welded with steel plates. Install 4.5m long φ42×4mm advanced grouting pipes to consolidate the surrounding rock in front of the tunnel face. Construct the initial arch crown support one by one according to the above construction steps, and the principle of replacing one frame after another must be followed. S42: Replace the second section of the vault using the same method as the first section of the vault. S43: Weld the inner tunnel pipe roof arch below the initial support steel arch frame, and after stabilizing with C25 concrete, construct the φ108×6mm inner tunnel pipe roof with an outward expansion angle of 2°~4°. The circumferential spacing of the pipe roof is 0.4m, with a total of 32 pipe roofs and a length of 12m. The pipe roof is installed by jacking and lengthened section by section. The steel pipes are connected by thread, and the steel pipe joints are staggered according to odd and even numbers. The joints of adjacent steel pipes must be staggered by at least 1m. The lengthened steel pipes should meet the stress requirements. S44: Replace the third section of the vaulted roof; S441: First, use temporary support measures to support the right side secondary lining of the third section of the arch crown. Then, use crushing machinery to remove the reinforced concrete of the left side secondary lining of the third section of the arch crown, and finally remove the reinforced concrete of the right side secondary lining of the arch crown. S442: Replace the initial support arch frame of the arch crown segment by segment, using 3 sets of φ42×4mm locking foot small guide pipes on each side, which are firmly welded with steel plates; install 4.5m long φ42×4mm pre-grouting small guide pipes, with a circumferential spacing of 40cm and a longitudinal spacing of 2.4m. The small guide pipes are fixed to the surrounding rock with an outward insertion angle of 10-15°, and the tail end is supported in the round hole of the steel frame. The longitudinal overlap length of each row of small guide pipes is 1.5m; construct the initial support of the arch crown segment segment by segment according to the above construction steps; S45: Following the steps of S41-S44, replace the initial support and secondary lining of each section of the arch until the pipe roof is completed. S5 includes: S51: When the arch renewal construction reaches the 5th stage and exceeds 8m, construct the left arch waist and use crushing machinery to remove the secondary lining reinforced concrete, with each cycle not exceeding 2m. S52: Replace the initial support arch frame on the left arch waist, no more than 3 frames per cycle, install 4 sets of 6m long φ42×4mm locking foot grouting pipes on each frame, 2 sets on each side, and weld them firmly with steel plates; construct the shotcrete for the initial support arch waist on the left. S53: When the left arch waist is replaced for more than 4m, the right arch waist initial support is replaced in the same way as the left side, and the left and right sides are updated and constructed simultaneously and normally forward. S6 includes: S61: When the construction of the left arch waist reaches the second section and exceeds 8m, construct the left side wall section and use crushing machinery to remove the secondary lining reinforced concrete, with each cycle not exceeding 2m; the part above the invert arch is removed manually in conjunction with machinery, retaining the initial support arch frame below the C unit invert arch, and adding a B joint at an appropriate position; the size and spacing of the initial support I-beams replaced above the joint have changed, and the channel steel at the joint is used to bolt them with connecting plates. If there is a conflict between the upper and lower hole positions, the spacing is adjusted appropriately on site so that the original C unit below and the C unit after replacement above form a closed loop; 3 frames are replaced in each cycle, and the segmented channel steel is bolted with connecting plates; S62: Replace the initial support arch frame of the left side wall, no more than 3 frames per cycle, and construct the initial support shotcrete of the left side wall; S63: When the left side wall is replaced for more than 4m, the initial support of the right side wall is replaced using the same method as the left side, and the left and right sides are updated and constructed simultaneously and normally. S7 includes manually chiseling out the secondary lining reinforcement when the secondary lining concrete is removed to 1m from the invert arch, ensuring the lap length of the secondary lining reinforcement; after the initial support reaches or exceeds the length of the secondary lining trolley, the monitoring and measurement data are analyzed and monitored in real time. After the surrounding rock reaches stability, waterproofing is carried out as soon as possible to ensure effective welding of the new and old waterproofing boards, with an lap length of not less than 12cm; if the chiseled secondary lining reinforcement is too short or the staggered joints in the same section cannot reach 1m, the method of rebar installation and extension is adopted to meet the specification requirements, and the secondary lining concrete is poured in a timely manner.

[0006] To verify the construction effect, after removing the original initial support, the displacement rate was used to determine the following: when the rate was greater than 1 mm / d, the surrounding rock was in a state of rapid deformation, and support measures were strengthened; when the rate was between 0.2 mm / d and 1 mm / d, monitoring was strengthened and preparations for reinforcement were made; when the rate was less than 0.2 mm / d, the surrounding rock reached basic stability.

[0007] Compared with the prior art, the present invention has the following advantages: 1. The present invention provides a complete set of mature and reliable construction methods for the secondary lining renovation of highway tunnels. It makes detailed provisions on various aspects such as construction preparation, time and personnel organization, and tools and equipment, providing a reliable decision-making basis and construction technical indicators for future tunnel secondary lining renovation. The novel and mature construction method will promote the progress of tunnel renovation technology and has significant social benefits.

[0008] 2. Safety aspects of the construction method of this invention: After the tunnel secondary lining is divided into longitudinal and circumferential sections, it will not cause secondary collapse of the secondary lining concrete, primary support and surrounding rock due to the mutual pulling of the double-layer steel reinforcement skeleton inside the secondary lining during demolition; it can also avoid manual cutting of the secondary lining steel reinforcement at height on the working face, which greatly reduces the safety risks of construction personnel and machinery.

[0009] 3. Regarding the quality of the construction method of this invention: After being divided into sections, the external force caused by the mutual pulling of the secondary lining steel bars during demolition is avoided, which could lead to large-scale loosening and instability of the primary support and surrounding rock. This can effectively ensure the quality of the tunnel after construction and even during the operation phase.

[0010] 4. Regarding the progress of the construction method of this invention: After cutting and segmenting, there are no exposed secondary lining steel bars left on the dismantling and replacement working surface. The mechanical utilization rate is high during dismantling, and there is no need for workers to cut steel bars on site, which improves the dismantling speed of secondary lining concrete and thus shortens the time for secondary lining section replacement.

[0011] 5. Regarding the cost of the construction method of this invention: After cutting and segmenting, the steel bars in the secondary lining concrete have been cut into sections, which can save the steel bar cutting costs for workers on the secondary lining demolition site, reduce the construction difficulty of mechanical demolition of the secondary lining reinforced concrete, improve the efficiency of machinery use, and thus effectively save construction costs.

[0012] 6. The construction method of this invention is an improvement on the traditional tunnel excavation method. Its outstanding advantages are simple construction steps, safe operation, stable working face, high machinery utilization rate, and low labor cost. It has a good reference value for future tunnel renovation. Attached Figure Description

[0013] Figure 1 A schematic diagram of the cross-section for the renovation construction of the secondary lining section of a highway tunnel. Figure 2 Update the circumferential block diagram for the tunnel secondary lining section; Figure 3 Update the construction flow chart for the tunnel secondary lining section; Figure 4 This is an updated schematic diagram of the first section of the vault. Figure 5 This is an updated schematic diagram of the second section of the vault. Figure 6 This is a schematic diagram of an arched pipe roof; Figure 7 This is an updated schematic diagram of the third section of the vault. Figure 8 This is a schematic diagram of a normal arch replacement section at the arch crown; Figure 9 An updated schematic diagram of the arched waist on the left side; Figure 10 This is a diagram illustrating the normal update process for arched backs. Figure 11 Schematic diagram of the construction joint of the I-beam for the initial support of the side wall; Figure 12 Schematic diagram of the sidewall renovation; Figure 13 This is a schematic diagram of a normal wall update. Figure 14 A schematic diagram of the demolition of the secondary lining concrete of the lower step; Figure 15 A schematic diagram showing the layout of monitoring points; Figure 16 The following diagrams are shown: (1) is the subsidence analysis diagram of the left arch waist; (2) is the subsidence analysis diagram of the arch top; (3) is the subsidence analysis diagram of the arch top; and (4) is the perimeter displacement analysis diagram. Detailed Implementation

[0014] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0015] Example: A method for segmented replacement of secondary lining in highway tunnels; The characteristics of this method are: 1. For the same cross-section of a highway tunnel, construction and treatment are carried out in three parts along the circumference: the arch crown, the arch waist, and the sidewalls. Sections ① through ⑤ are updated and constructed block by block (e.g., Figure 1 As shown), the construction distance between the arch crown section and the arch waist section shall not be less than 8m, the construction distance between the arch waist section and the side wall section on each side shall not be less than 4m, and the construction distance between the left and right sides shall not be less than 4m.

[0016] 2. During the renovation of the arch section, the construction is carried out in longitudinal sections with a working length of 2m. After one section is completed, the next section is renovated. When excavating and removing the secondary lining, the left side is first filled with caving debris as temporary support, and a 0.5m space is reserved on the right side. Starting from the arch, the secondary lining concrete on the right side ① is broken off using a crushing machine. Then, the remaining secondary lining concrete on the right side ① is excavated and removed, and the caving debris is backfilled.

[0017] 3. Due to the relatively loose surrounding rock and poor self-stabilizing ability of the surrounding rock in the project renewal section, the three parts of the arch crown, arch waist and sidewall are all replaced by cold excavation. When replacing the arch crown section, the surrounding loose rock mass must be grouted and reinforced before the secondary lining can be excavated and replaced piece by piece, and the arch crown frame can be replaced unit by unit.

[0018] 4. After the working face is reinforced by grouting, the construction operation space for the pipe roof is reserved by excavation. After the construction of the pipe roof is completed, it is filled with secondary lining concrete. When constructing the secondary lining concrete, a grouting pipe is reserved at the highest point, and the gap between the secondary lining and the primary support is filled by grouting.

[0019] 5. After cutting the secondary lining piece by piece, the tension of the reinforcing bars between each piece of secondary lining is relieved, which provides temporary support for the removal of the secondary lining concrete. This makes the arch replacement operation both quick and safe. This not only greatly improves the utilization rate of machinery, but also effectively controls the disturbance range to the surrounding rock due to the small construction area.

[0020] 6. After the arch, waist, and sidewalls are updated, monitoring and measurement points should be set up on the secondary lining in a timely manner, and the update schedule of the defective secondary lining should be adjusted in a timely manner according to the monitoring situation.

[0021] Scope of application of this method: 1. Applicable to permanent structural defects such as collapse and stress cracks that cannot be repaired after the completion of the secondary lining construction of newly built highway tunnels.

[0022] 2. Applicable to sections of the support structure in operating highway tunnels where local repair is not possible due to secondary lining cracking, water leakage, encroachment, large deformation, etc.

[0023] The technological principle of this method is as follows: 1. Segmented Update: The secondary lining of the tunnel with defects is longitudinally segmented, with the arch crown segmented in 2m sections and the arch waist and sidewalls segmented in 4m sections; circumferential updates are performed at several locations with low stress concentration, including the arch crown, arch waist, sidewalls, and the top surface of the invert (see...). Figure 2 The arched secondary lining is divided into 6 sections, with the arch top section divided into two pieces, and the arch waist and side walls each having one piece.

[0024] 2. To establish a safe step distance, the arch crown section (steps ① to ④) will be replaced first. Once a safe step distance for excavation is achieved, the arch waist and sidewall sections (steps ⑤, ⑦, and ⑨) will be replaced. Steps ⑧ and ⑩ represent gaps in the replacement of the arch waist and sidewalls, but normal arch crown replacement will continue. The secondary lining arch-shaped block structure to be removed will be used as temporary support near the local removal points. Replacement will be carried out in sections to minimize the impact on the primary support and surrounding rock.

[0025] 3. By disconnecting the reinforcing bars between each section of the secondary lining, the pulling effect of the reinforcing bars can be avoided when removing the secondary lining, thus speeding up the construction process and increasing the utilization rate of construction machinery.

[0026] 4. By radially and pre-grouting the exposed surrounding rock, the loose surrounding rock within a 3-5m range in the direction of the working face is consolidated to form an arc-shaped hard shell. Then, through pipe roof grouting reinforcement, the area within 10-20m in front of the working face can be pre-reinforced, so that the initial support of the tunnel and the secondary lining concrete together form an integral load-bearing structure, forming a spreading effect during excavation and construction, ensuring the quality and safety of the tunnel during the treatment process and operation period.

[0027] 5. Strengthen monitoring and measurement during construction, analyze monitoring data to guide construction, dynamically determine support parameters and construction methods, and provide a basis for correcting the tunnel construction plan.

[0028] The process flow and key points of operation for this method are as follows: 1. Construction process flow: Grouting reinforcement of the surrounding rock in the affected section → Removal of the first section of secondary lining concrete at the arch crown → Enlargement and replacement of the first section of the arch crown's initial support arch frame → Removal of the second section of secondary lining concrete at the arch crown → Removal of the second section of the arch crown's initial support → Enlargement and replacement of the second section of the arch crown's initial support arch frame → Grouting support with advanced pipe roof (φ108) → Removal of the third section of secondary lining concrete at the arch crown → Removal of the third section of the arch crown's initial support → Replacement of the third section of the arch crown's initial support arch frame → Repeat the third section's steps until the arch crown pipe roof section is completed → Excavation and removal of secondary lining concrete on both sides of the arch waist → Removal of the arch waist's initial support → Replacement of the arch waist's initial support arch frame → Removal of secondary lining concrete on both side walls → Removal of the side wall's initial support → Replacement of the side wall's initial support arch frame → Hanging waterproof membrane → Installation of secondary lining reinforcement → Pouring secondary lining concrete; see Figure 3 .

[0029] 2. Key operational points, i.e., core methods and steps: The operational steps of the secondary lining renovation construction method for highway tunnels include: construction preparation, monitoring and measurement, installation of specialized linear cutting equipment, construction of the arch crown section, construction of the arch waist, construction of the sidewalls, and construction of the secondary lining concrete, as detailed below: S1: Construction preparation; 1) Be familiar with the documents, replacement plan drawings and related documents.

[0030] 2) Conduct safety technical briefings and training for construction personnel before construction, so that every person entering the tunnel is clear about the technical standards and safety precautions for construction operations.

[0031] 3) Vehicles and tools required for construction, including: transportation vehicles, work platforms, surveying and construction tools, lighting and communication tools, safety equipment and protective gear.

[0032] 4) Preparation of machinery and equipment, personnel, materials, drainage facilities and emergency supplies.

[0033] 5) Based on the implementation plan, conduct a detailed analysis and understanding of the engineering geology and current hydrogeological conditions, formulate reasonable detailed operation instructions, and develop construction monitoring and measurement schemes and settlement and displacement observation plans.

[0034] 6) On-site layout: The arch crown is divided into 2m sections longitudinally, and the arch waist and side walls are divided into 4m sections. The circumferential section is divided into 6 segments starting from the arch crown, with each side being 7.54m long. The arch waist is 4.95m long from each side wall, and the side wall is 3.63m long from each side wall to the invert surface. The 5 cutting surfaces above the side walls are cut mechanically, and the invert surface is leveled manually.

[0035] S2: Monitoring and measurement; First, set up monitoring and measurement observation points within 50m of the working face and make initial records. Before each process begins, conduct monitoring and analysis to ensure the safety and stability of the working face.

[0036] S3: Cutting (installation of dedicated linear cutting equipment); According to the layout position of the secondary lining surface of the secondary lining replacement section, the secondary lining reinforced concrete is cut and separated. The cutting track is fixed to the secondary lining with expansion bolts. The equipment is installed in the order of first circumferential and then longitudinal. The arch crown secondary lining section is cut section by section. The arch waist and side wall sections are cut after the secondary lining is exposed.

[0037] S4: Construction of the arch section; S41: Replace the first section of the vaulted roof; S411: First, use temporary support measures to support the right side of the first section of secondary lining. Then, use crushing machinery to remove the reinforced concrete of the left side of the first section of secondary lining, and then remove the reinforced concrete of the right side of secondary lining.

[0038] S412: Remove the initial arch support frame one by one, and gradually expand the excavation outward at a 15° outward expansion angle to create the operating space for pipe roof construction. The steel arch frame uses 25b I-beams, spaced 0.6m apart. Longitudinal connections are made at the arch crown, left and right arch waists (3 locations), using 18 I-beams for longitudinal welding. The remaining locations are connected longitudinally with φ20 steel bars at 1m circumferential spacing. There are 6 sets of φ42×4mm locking grouting pipes on each side, each 6m long, securely welded with steel plates. Install 4.5m long φ42×4mm pre-grouting pipes to solidify the surrounding rock ahead of the tunnel face. Construct the initial arch crown support frame by frame according to the above construction steps, adhering to the principle of replacing one frame at a time. See the schematic diagram of the first arch crown replacement. Figure 4 ; S42: Replace the second section of the vault using the same method as the first section; see the diagram for the second section update. Figure 5 ; S43: Weld the inner-cavity pipe roof arch below the initial support steel arch frame. After stabilizing with C25 concrete, construct φ108×6mm inner-cavity pipe roofs with an outward expansion angle of 2°~4°. The circumferential spacing of the pipe roofs is 0.4m, with a total of 32 roofs, each 12m long. The pipe roofs are installed using a jacking method, extending section by section. The steel pipes are connected with threaded joints, with odd and even numbers of joints staggered. Adjacent pipe joints must be staggered by at least 1m. The extended steel pipes must meet the stress requirements. See the schematic diagram of the arch-top pipe roof. Figure 6 ; S44: Replace the third section of the vaulted roof; S441: First, use temporary support measures to support the right side secondary lining of the third section of the arch crown. Then, use crushing machinery to remove the reinforced concrete of the left side secondary lining of the third section of the arch crown, and finally remove the reinforced concrete of the right side secondary lining of the arch crown. S442: Replace the initial arch support frame for the arch crown segment by segment, using 3 sets of φ42×4mm locking guide pipes on each side, securely welded with steel plates; install 4.5m long φ42×4mm pre-grouting guide pipes, with a circumferential spacing of 40cm and a longitudinal spacing of 2.4m. The guide pipes are fixed to the surrounding rock with an outward insertion angle of 10-15°, and the tail ends are supported in the circular holes of the steel frame. The longitudinal overlap length of each row of guide pipes is 1.5m; construct the initial support of the arch crown segment segment by segment according to the above construction steps; see the schematic diagram of the third arch crown replacement. Figure 7 ; S45: Following steps S41-S44, replace the initial supports and secondary linings of each section of the arch crown until the pipe roof is completed; if the next section requires pipe roof installation, resume from S41. See the schematic diagram of a normal arch replacement section for details. Figure 8 As shown; S5: Arch construction; S51: When the arch renewal construction reaches the 5th stage and exceeds 8m, construct the left arch waist and use crushing machinery to remove the secondary lining reinforced concrete, with each cycle not exceeding 2m.

[0039] S52: Replace the initial support arch frame of the left arch waist, no more than 3 frames per cycle. For each frame, install 4 sets of 6m long φ42×4mm locking grouting pipes, 2 sets on each side, and securely weld them with steel plates; construct the shotcrete for the initial support arch waist of the left arch waist. See the schematic diagram for the left arch waist replacement. Figure 9 As shown; S53: After the left arch waist has been replaced for more than 4 meters, replace the initial support of the right arch waist using the same method as the left side, and proceed with the normal forward replacement construction on both sides simultaneously. See the diagram for a normal arch waist replacement. Figure 10 As shown.

[0040] S6: Sidewall construction; S61: When the construction of the left arch waist reaches the second section and exceeds 8m, construct the left sidewall section, using a crushing machine to remove the secondary lining reinforced concrete, with each cycle not exceeding 2m; the part above the invert arch is removed manually in conjunction with machinery, retaining the initial support arch frame below the C unit invert arch, and adding a B joint at an appropriate location; the size and spacing of the initial support I-beams replaced above the joint have changed, using the channel steel at the joint and bolting with connecting plates, if there is conflict between the upper and lower hole positions, the spacing is adjusted appropriately on site so that the original C unit below and the replaced C unit initial support arch frame above form a closed loop; 3 frames are replaced each cycle, and the segmented channel steel is bolted with connecting plates; see the schematic diagram of the construction joint of the sidewall initial support I-beams. Figure 11 ; S62: Replace the initial support arch of the left side wall, no more than 3 arches per cycle, and construct the initial support shotcrete for the left side wall; see the schematic diagram of the side wall replacement. Figure 12 ; S63: After the left sidewall has been replaced for more than 4 meters, replace the initial support of the right sidewall using the same method as the left sidewall, and proceed with the normal, simultaneous upgrade work on both sides. See the diagram for a normal sidewall upgrade. Figure 13 ; S7: Secondary lining concrete construction.

[0041] When the secondary lining concrete is removed to 1m from the invert arch, the secondary lining reinforcement is slowly chiseled out manually, ensuring the lap length of the reinforcement. Once the initial support reaches or exceeds the length of the secondary lining trolley, monitoring and measurement data are continuously analyzed. After the surrounding rock stabilizes, waterproofing is constructed as soon as possible, ensuring effective welding of the old and new waterproofing membranes, with an lap length of not less than 12cm. If the chiseled secondary lining reinforcement is too short or the staggered joints on the same section cannot reach 1m, reinforcement anchoring and extension methods are used to meet the specifications, and secondary lining concrete is poured promptly. See the schematic diagram of the secondary lining concrete removal for the lower step. Figure 14 ; After removing the original initial support, the displacement rate is used to determine the following: when the rate is greater than 1 mm / d, the surrounding rock is in a state of rapid deformation, and support measures should be strengthened; when the rate changes between 0.2 mm / d and 1 mm / d, monitoring should be strengthened and preparations for reinforcement should be made; when the rate is less than 0.2 mm / d, the surrounding rock has reached basic stability.

[0042] Following the aforementioned process, after the Biqing Tunnel (a twin-bore, six-lane separated tunnel on the Dali-Nanjian Expressway (referred to as the Da-Nan Expressway) was constructed, with the left tunnel at K34+745~K35+940, a total length of 1195m and a longitudinal slope of +1.1%, and the right tunnel at K34+745~K35+995, a length of 1250m and a longitudinal slope of +1.1%, both tunnels having end-wall portals, and a maximum tunnel depth of 1158.15m) was implemented, according to... Figure 15 The monitoring points were arranged according to the diagram, and the data in Table 1-2 below were obtained. Figure 16 result: Table 1. Monitoring Measurement Data Analysis Table Table 2 Monitoring Measurement Data Analysis Table Based on the data in the table above, the conclusion issued by the third-party monitoring unit is as follows: Corresponding observation points were set up inside the left tunnel at the entrance of the Biqing Tunnel. As of June 30, 2021, the following conclusions were drawn based on the monitoring and measurement data and analysis results: (1) According to the monitoring data and curves, the average displacement rate of the surrounding area in the ZK35+089 to ZK35+115 section in the past five days is less than 0.2 mm / d and the average settlement rate of the arch is less than 0.1 mm / d, which has reached a basic stability. The surrounding rock of the tunnel in the ZK35+115 to ZK35+138 section is still changing and needs to be monitored in accordance with relevant requirements. This month, the A1 measuring point of the arch settlement in the ZK35+120 section has the largest settlement, with a cumulative settlement of 87.2 mm. The BC measuring line of the surrounding displacement in the ZK35+120 section has the largest displacement, with a cumulative displacement of 78.27 mm.

[0043] (2) Based on relevant standards and specifications, and combined with actual measurement and monitoring data analysis, the rock in the ZK35+089~ZK35+115 arch replacement section has basically stabilized and can proceed with the next construction process.

[0044] Through the implementation of the above-mentioned project, and by treating the secondary lining defects in the left tunnel of the Biqing Tunnel on the Dali-Nanjian Expressway, a relatively scientific method for treating and monitoring tunnel secondary lining defects has been basically mastered. For the defective secondary lining concrete, a method of segmented, targeted replacement is adopted, which eliminates the drag force generated during the removal of the secondary lining reinforcement. The unremoved parts serve as temporary supports, allowing large machinery to dominate the entire removal process. This method is simple, safe, and improves construction efficiency while saving labor and machinery costs. This construction method has strong reference value for the renovation of various highway tunnels. Through this secondary lining renovation, a set of easy-to-operate, simple, and practical construction techniques has been summarized, which not only ensures project quality and construction period but also achieves good economic benefits. It provides detailed technical solutions for the renovation of similar tunnels.

[0045] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and concept of this application, should be included within the scope of protection of this application.

Claims

1. A method for segmented renovation of secondary lining in highway tunnels, characterized in that: Includes the following steps: S1: Construction preparation; S2: Monitoring and measurement; S3: Cutting; S4: Construction of the arch section; S5: Arch construction; S6: Sidewall construction; S7: Secondary lining concrete construction.

2. The method for segmented replacement of secondary lining in highway tunnels according to claim 1, characterized in that: S1 includes on-site layout: the arch crown is divided into 2m sections longitudinally, and the arch waist and side walls are divided into 4m sections; the circumferential section is divided into 6 segments starting from the arch crown, 7.54m on each side, 4.95m from the arch waist to the side walls on each side, and 3.63m from the side walls to the invert surface on each side. The 5 cutting surfaces above the side walls are cut mechanically, and the invert surface is leveled manually.

3. The method for segmented renovation of secondary lining in highway tunnels according to claim 2, characterized in that: S2 includes setting up monitoring and measurement observation points within 50m of the working face and making initial records. Monitoring and analysis are carried out before each process begins to ensure the safety and stability of the working face.

4. The method for segmented replacement of secondary lining in highway tunnels according to claim 3, characterized in that: S3 is a special equipment for installing linear cutting. According to the layout position of the secondary lining surface of the secondary lining replacement section, it cuts and separates the secondary lining reinforced concrete. The cutting track is fixed on the secondary lining with expansion bolts. The equipment is installed in the order of first circumferential and then longitudinal, and the arch crown secondary lining section is cut section by section. The arch waist and side wall sections are cut after the secondary lining is exposed.

5. The method for segmented replacement of secondary lining in highway tunnels according to claim 4, characterized in that: S4 includes: S41: Replace the first section of the vaulted roof; S411: First, use temporary support measures to support the right side secondary lining of the first section, then use crushing machinery to remove the reinforced concrete of the left side secondary lining of the first section, and then remove the reinforced concrete of the right side secondary lining. S412: Remove the initial arch frame one by one, and gradually expand the excavation outward at a 15° outward expansion angle to form the operating space for pipe roof construction. The steel arch frame uses 25b I-beams, spaced at 0.6m intervals. The longitudinal connections are made at the arch crown, left and right arch waists, using 18 I-beams for longitudinal welding. The remaining locations are connected longitudinally with φ20 steel bars, with a circumferential spacing of 1m. There are 6 sets of φ42×4mm locking foot grouting pipes on each side, each 6m long, which are firmly welded with steel plates. Install 4.5m long φ42×4mm advanced grouting pipes to consolidate the surrounding rock in front of the tunnel face. Construct the initial arch crown support one by one according to the above construction steps, and the principle of replacing one frame after another must be followed. S42: Replace the second section of the vault using the same method as the first section of the vault. S43: Weld the inner tunnel pipe roof arch below the initial support steel arch frame, and after stabilizing with C25 concrete, construct the φ108×6mm inner tunnel pipe roof with an outward expansion angle of 2°~4°. The circumferential spacing of the pipe roof is 0.4m, with a total of 32 pipe roofs and a length of 12m. The pipe roof is installed by jacking and lengthened section by section. The steel pipes are connected by thread, and the steel pipe joints are staggered according to odd and even numbers. The joints of adjacent steel pipes must be staggered by at least 1m. The lengthened steel pipes should meet the stress requirements. S44: Replace the third section of the vaulted roof; S441: First, use temporary support measures to support the right side secondary lining of the third section of the arch crown. Then, use crushing machinery to remove the reinforced concrete of the left side secondary lining of the third section of the arch crown. Finally, remove the reinforced concrete of the right side secondary lining of the arch crown. S442: Replace the initial support arch frame of the arch crown segment by segment, using 3 sets of φ42×4mm locking foot small guide pipes on each side, which are firmly welded with steel plates; install 4.5m long φ42×4mm pre-grouting small guide pipes, with a circumferential spacing of 40cm and a longitudinal spacing of 2.4m. The small guide pipes are fixed to the surrounding rock with an outward insertion angle of 10-15°, and the tail end is supported in the round hole of the steel frame. The longitudinal overlap length of each row of small guide pipes is 1.5m; construct the initial support of the arch crown segment segment by segment according to the above construction steps; S45: Following steps S41-S44, replace the initial supports and secondary linings of each section of the arch until the pipe roof is completed.

6. The method for segmented replacement of secondary lining in highway tunnels according to claim 5, characterized in that: S5 include: S51: When the arch renewal construction reaches the 5th stage and exceeds 8m, construct the left arch waist and use crushing machinery to remove the secondary lining reinforced concrete, with each cycle not exceeding 2m. S52: Replace the initial support arch frame on the left arch waist, no more than 3 frames per cycle, install 4 sets of 6m long φ42×4mm locking foot grouting pipes on each frame, 2 sets on each side, and weld them firmly with steel plates; construct the shotcrete for the initial support arch waist on the left. S53: After the left arch waist has been replaced for more than 4m, replace the right arch waist initial support in the same way as the left side, and the left and right sides will be updated and constructed simultaneously and normally.

7. The method for segmented replacement of secondary lining in highway tunnels according to claim 6, characterized in that: S6 include: S61: When the construction of the left arch waist reaches the second section and exceeds 8m, construct the left side wall section and use crushing machinery to remove the secondary lining reinforced concrete, with each cycle not exceeding 2m; the part above the invert arch is removed manually in conjunction with machinery, retaining the initial support arch frame below the C unit invert arch, and adding a B joint at an appropriate position; the size and spacing of the initial support I-beams replaced above the joint have changed, and the channel steel at the joint is used to bolt them with connecting plates. If there is a conflict between the upper and lower hole positions, the spacing is adjusted appropriately on site so that the original C unit below and the C unit after replacement above form a closed loop; 3 frames are replaced in each cycle, and the segmented channel steel is bolted with connecting plates; S62: Replace the initial support arch frame of the left side wall, no more than 3 frames per cycle, and construct the initial support shotcrete of the left side wall; S63: When the left side wall is replaced for more than 4m, replace the initial support of the right side wall using the same method as the left side, and proceed with the normal forward replacement construction on both sides simultaneously.

8. The method for segmented replacement of secondary lining in highway tunnels according to claim 7, characterized in that: S7 includes manually chiseling out the secondary lining reinforcement when the secondary lining concrete is removed to 1m from the invert arch, ensuring the lap length of the secondary lining reinforcement; after the initial support reaches or exceeds the length of the secondary lining trolley, analyze and monitor the measurement data in real time, and after the surrounding rock reaches stability, construct waterproofing as soon as possible to ensure effective welding of the new and old waterproofing boards, with an lap length of not less than 12cm; if the chiseled secondary lining reinforcement is too short or the staggered joints in the same section cannot reach 1m, adopt the method of rebar installation and extension to meet the specifications, and pour the secondary lining concrete in a timely manner.

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