A tunnel primary support process for railway engineering

Abstract

The application provides a tunnel primary support process of railway engineering, and relates to the technical field of tunnel primary support.The tunnel primary support process of railway engineering comprises the following steps: immediately carrying out danger removal work after tunnel excavation, then implementing initial concrete spraying operation, carrying out mortar anchor rod or hollow anchor rod construction, reinforcing mesh laying, steel frame construction, advanced small guide pipe construction, anchor rod construction and advanced pipe shed construction;immediately removing danger and implementing initial concrete spraying after tunnel excavation can quickly close rock mass, prevent its relaxation deformation, effectively control early deformation of surrounding rock, enhance stability of the surrounding rock, provide safety guarantee for subsequent construction, the reinforcing mesh is laid and firmly connected with the anchor rod and the steel frame, which further enhances the integrity of the support structure, improves the impact resistance of the support structure, the advanced small guide pipe and the advanced pipe shed and other auxiliary construction measures are used to effectively reinforce the surrounding rock, improve the strength and stability of the surrounding rock, reduce construction risk and ensure smooth tunnel construction through adverse geological sections.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of tunnel primary support, in particular to a tunnel primary support process for railway engineering. BACKGROUND

[0002] In railway engineering, tunnel primary support is crucial for ensuring the safety of tunnel construction and the stability of the overall structure. The tunnel geological conditions in this bid section are complex, the surrounding rock is mainly grade VI and V, and most of them are micro-gas tunnels. There are toxic and harmful gases and radioactive substances in some sections, and it also faces the situation of crossing fault zones, karst development areas, and underpassing existing structures. The traditional primary support process cannot meet the support requirements under complex geological conditions, such as the timeliness, effectiveness and adaptability to special geological conditions.

[0003] Therefore, it is necessary to develop a more optimized, efficient and targeted tunnel primary support process. SUMMARY

[0004] The application aims to at least solve one of the technical problems existing in the prior art. To this end, the application provides a tunnel primary support process for railway engineering, which comprises the following steps: immediately carrying out risk removal work after tunnel excavation, then implementing initial concrete spraying operation, adopting wet spraying process, carrying out centralized mixing outside the hole, transporting the concrete into the hole by a concrete transport vehicle, and then spraying by a wet spraying machine. The initial concrete spraying should timely close the rock mass to prevent the rock mass from relaxing. Then, the mortar anchor rod or hollow anchor rod construction is performed, the hand-held air drill is used to form a hole, the anchor rod and the positioning ring are inserted into the hole after the hole is formed, then the grouting pump is used to inject early strength cement mortar or mortar into the hole, and the hole pad is installed after the cement mortar is finally set. Then, the steel mesh is laid, the steel member processing site is processed according to the design specification, the manual installation is performed after the initial concrete spraying, the steel mesh is fixed on the anchor rod or the steel frame by electric welding spot welding or binding, the steel mesh needs to follow the fluctuation of the sprayed surface and keep a certain distance, and the stones or concrete blocks that are stuck by the steel mesh should be removed in time during the spraying process. Then, the steel frame construction is performed, the steel quality and the joint position are ensured to meet the specification and design requirements, the profile steel frame adopts cold bending forming technology, the grid steel frame adopts tire membrane welding, the size is controlled by a 1:1 large sample, the full-face measurement system is established after the temporary support is removed, and the lining work is timely followed. Then, the advanced small guide pipe construction is performed, the hand-held air drill is used to drill a hole, the layout range, length and spacing of the small guide pipe are arranged according to the design, the cement slurry is selected as the grouting material, the grouting pressure is controlled in a reasonable range, the water-cement ratio meets the corresponding requirements, the cement + water glass double liquid slurry can be partially used when the surrounding rock is broken and the underground water is developed, and the slurry strength grade is required to meet the specified standard. Then, the anchor rod construction is performed, the mortar anchor rod or hollow anchor rod is used according to the design, the threaded steel is used for the mortar anchor rod, the anchor rod drill or the rock drill is used for hole drilling, the design position and the rod body insertion angle are ensured during drilling, and the water amount is controlled to prevent hole collapse. Then, the advanced pipe shed construction is performed, the pipe shed is made of hot-rolled seamless steel pipe, the hole drilling, pipe insertion or pipe drilling process is selected according to the actual stratum condition, the pipe shed joint is connected by a thread, the thread length reaches the specified size, the adjacent pipe joints are staggered by a certain distance according to the requirements, the steel pipe is punched into the surrounding rock along the design outer insertion angle of the tunnel periphery during construction, and then the cement slurry is grouted.

[0005] In addition, the tunnel primary support process for railway engineering according to the application also has the following additional technical features.

[0006] Preferably, during the initial concrete spraying, the spraying equipment should be kept in good performance state to ensure uniform and continuous concrete spraying and avoid interruption of spraying or accumulation of concrete.

[0007] Preferably, during the mortar anchor rod or hollow anchor rod construction, the hole drilling operation should ensure smooth hole wall without obvious collapse, the rod body and the positioning ring should not be damaged during the anchor rod insertion, and the grouting process should ensure that the slurry fully fills the hole space without slurry leakage.

[0008] Preferably, during the laying of the reinforcement mesh, the processing of the reinforcement mesh should ensure accurate dimensions and regular shape, and during the installation process, the reinforcement mesh should be firmly connected with the anchor rod or steel frame, without loosening or displacement.

[0009] Preferably, during the construction of the steel frame, the cold-bent steel frame should have good arc consistency, the grid steel frame welded by the membrane should ensure reliable welding quality and tight connection of components, and during the process of temporary support removal and measurement system establishment, the completed support structure should be avoided from being damaged.

[0010] Preferably, during the advanced small duct grouting, the grouting parameters should be adjusted in time according to the actual situation of surrounding rock and grouting effect feedback, to ensure uniform diffusion of the slurry in the surrounding rock and achieve the expected reinforcement effect, while avoiding excessive disturbance of the surrounding rock caused by excessive grouting pressure.

[0011] Preferably, during the construction of the anchor rod, the hole drilling operation should be accurately positioned to ensure that the anchor rod can be smoothly inserted into the hole and closely fit the hole wall, the anchoring length of the mortar anchor rod should ensure that the design anchoring force requirement is met, and the length of the hollow anchor rod body should meet the design requirements to ensure that its supporting effect is effectively exerted.

[0012] Preferably, during the construction of the advanced pipe roof, the pre-drilling and post-pipe inserting process should ensure that the drilling accuracy and pipe inserting depth meet the design requirements, the pipe following drilling process should ensure that the casing follows smoothly and cooperates well with the drill rod, and after the pipe roof installation is completed, grouting should ensure that the slurry in the pipe roof is densely filled and the pipe roof structure is stable.

[0013] Preferably, during the entire initial support construction period, a perfect surrounding rock deformation monitoring system should be established, the monitoring equipment should be stable and reliable, the data acquisition should be accurate and timely, and the support parameters should be adjusted in time and scientifically according to the monitoring data to ensure the safety of tunnel construction.

[0014] Preferably, the raw materials used for shotcrete should be strictly selected to ensure quality compliance, and the mix proportion of the concrete should be reasonably adjusted according to the actual construction conditions and design requirements to ensure that the performance of the concrete meets the requirements of the initial support.

[0015] According to the tunnel initial support process of the railway engineering, the beneficial effects are:

[0016] 1. Improve the timeliness and effectiveness of support

[0017] Immediately after tunnel excavation, danger is removed and initial shotcrete is performed, which can quickly close the rock mass, prevent its relaxation and deformation, effectively control the early deformation of the surrounding rock, and enhance the stability of the surrounding rock, providing safety protection for subsequent construction.

[0018] The wet spraying process allows the concrete to better adhere to the surrounding rock, improving the load-bearing capacity of the support structure and the surrounding rock, fully utilizing the support function, effectively reducing the risk of surrounding rock collapse and other accidents, and ensuring construction safety.

[0019] 2. Enhancing the stability of the support structure

[0020] The anchor rod (mortar anchor rod or hollow anchor rod) construction increases the anchoring force of the surrounding rock through reasonable drilling, anchor rod insertion, and grouting operations, forming a whole with the surrounding rock and the support structure, improving the self-bearing capacity of the surrounding rock, and effectively controlling the deformation and displacement of the surrounding rock.

[0021] The steel mesh is laid and firmly connected with the anchor rod and steel frame, further enhancing the integrity of the support structure, preventing local rock from falling, evenly dispersing the surrounding rock pressure, and improving the impact resistance of the support structure, which can better maintain the stability of the tunnel structure under complex geological conditions.

[0022] The steel frame construction strictly controls the quality of steel, processing technology, and installation precision to ensure that the steel frame has sufficient strength and stiffness to effectively withstand the surrounding rock pressure, prevent the support structure from deforming too much, and ensure safety and structural stability during tunnel construction, especially in soft surrounding rock sections.

[0023] 3. Adapt to complex geological conditions

[0024] For different surrounding rock conditions such as broken, weak, and water-rich, through auxiliary construction measures such as advanced small pipes and advanced pipe sheds, and by using appropriate construction techniques and parameters such as adjusting grouting materials and pressure, the surrounding rock can be effectively reinforced, the strength and stability of the surrounding rock can be improved, the construction risk can be reduced, and the tunnel construction can smoothly pass through unfavorable geological sections.

[0025] For tunnels that may contain toxic and harmful gases and radioactive substances, such as the Youping Tunnel and the Lijiacun Tunnel, measures such as strengthening ventilation and detection during construction, combined with effective initial support technology, can ensure the safety of construction personnel, avoid safety accidents caused by special geological conditions, and ensure the durability of the support structure.

[0026] 4. Ensure construction quality and efficiency

[0027] Each construction process has clear technical requirements and quality control standards, such as raw material selection, equipment commissioning, and construction process parameter control, to ensure the quality of each process and thus the quality of the entire initial support structure, reducing rework and delays caused by quality problems, and improving construction efficiency.

[0028] Perfect construction monitoring and adjustment mechanism can master the deformation of surrounding rock in real time, find problems in time and adjust the supporting parameters, so that the supporting structure is always in a reasonable stress state, avoiding excessive support or insufficient support, ensuring the construction quality, optimizing the construction process, improving the scientificity and rationality of construction, and effectively shortening the construction period. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0030] Figure 1 is a flow chart of a tunnel primary support process of a railway engineering according to an embodiment of the present application;

[0031] Figure 2 is a section view of a composite lining of grade II surrounding rock according to an embodiment of the present application;

[0032] Figure 3 is a section view of a composite lining of grade III surrounding rock according to an embodiment of the present application;

[0033] Figure 4 is a section view of a composite lining of grade IV surrounding rock according to an embodiment of the present application;

[0034] Figure 5 is a section view of a composite lining of grade V surrounding rock according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0036] The following will describe in detail a tunnel primary support process of a railway engineering of the present application through specific embodiments, including a construction preparation stage, primary concrete construction, mortar anchor rod or hollow anchor rod construction, steel mesh laying, steel frame construction, advanced small guide pipe construction, anchor rod construction, advanced pipe shed construction, construction monitoring and adjustment, and quality control and inspection.

[0037] 1. Construction preparation stage

[0038] Assemble a professional primary support construction team, and provide comprehensive technical training to the construction personnel to make them familiar with the process, technical points, quality standards and safety precautions of the tunnel primary support technology, and also provide detailed safety briefing to improve the safety awareness and operation standardization of the construction personnel.

[0039] Prepare advanced and stable performance construction equipment, such as handheld wind drill, wet sprayer, grouting pump, anchor rod drill, electric welder, etc. Before the equipment arrives, conduct strict inspection and debugging to ensure that the equipment is in good working condition and the performance indicators meet the construction requirements. Reasonably plan the equipment parking and operation area on the construction site to ensure convenient use and orderly operation of the equipment during construction.

[0040] Strictly select and test the raw materials. The steel shall meet the national standard, and its material quality, specification and other parameters shall meet the design requirements. The mechanical properties of the steel are tested to ensure the reliability of the steel quality. The cement selected is ordinary portland cement with stable quality and strength grade not less than 42.5. The stability, setting time and strength of the cement are tested. The sand is medium-coarse sand with hard texture and cleanliness, and the clay content is not more than 3%. The particle size distribution of the sand is determined to meet the requirements through the screening test. The stone particle size is not more than 15mm, with hard texture and good gradation, and the crushing index is not more than the specified value. The needle-like particle content and clay content of the stone are strictly controlled. The accelerator and other additives shall be strictly selected and tested to ensure their stable performance, good compatibility with raw materials such as cement, and the dosage is determined according to the test results and design requirements, generally 3%-5% of the weight of cement. A special material storage site is set up on the construction site to store different types and specifications of raw materials, and effective measures are taken to prevent moisture, rain and rust to ensure that the quality of raw materials is not affected during storage.

[0041] 2. Initial concrete spraying construction

[0042] After the tunnel excavation is completed, experienced risk removal personnel are quickly organized to enter the work site. The risk removal personnel wear complete safety protection articles, use appropriate tools such as crowbar and air pick, and carefully remove the loose rock blocks on the surface of the surrounding rock in the order of from outside to inside, top first and then both sides. During the risk removal process, the changes of the surrounding rock are closely observed, and if any abnormal sound or rock falling is found, the work is immediately stopped, and appropriate safety protection measures are taken to ensure the safety of the construction personnel.

[0043] The initial concrete operation is carried out immediately after the risk removal operation. A special concrete mixing station is set up outside the tunnel, and a forced mixer is used for centralized mixing. According to the mixing ratio of the designed concrete, the amount of cement, sand, gravel, water and accelerator is accurately measured to ensure that the workability, strength and durability of the concrete meet the requirements of the initial support. During the mixing process, the mixing time is strictly controlled to ensure that the raw materials are fully mixed and uniform, and the concrete color is consistent and there is no segregation phenomenon.

[0044] The concrete transport vehicle is selected to have good condition and good tank sealing performance. During transportation, the tank is kept rotating at a uniform speed to prevent segregation and excessive loss of slump during transportation. After the concrete is transported to the construction site in the tunnel, the slump is immediately detected. If the slump does not meet the requirements, it is adjusted or treated in time, and unqualified concrete is strictly prohibited.

[0045] The wet spraying machine is fully inspected and adjusted before spraying to ensure stable spraying pressure and flexible adjustment of spraying angle. During the spraying operation, the spraying pressure is adjusted according to the surface condition of the surrounding rock and the spraying distance, generally controlled between 0.3-0.5MPa, the spraying angle is kept perpendicular or slightly inclined to the sprayed surface, and the nozzle distance from the sprayed surface is 0.8-1.2m. According to the order from bottom to top and from both sides to the middle, the concrete is sprayed in layers, the thickness of each layer is controlled between 3-5cm, and the interval time of each layer is 3-5 minutes to ensure that the concrete of the previous layer is fully cured before the next layer is sprayed to avoid concrete hollowing, falling off and other phenomena. During the spraying process, the operator closely observes the concrete spraying situation and adjusts the spraying parameters in time according to the spraying effect to ensure that the concrete is sprayed uniformly and densely, there is no interruption or concrete accumulation, the initial concrete thickness is not less than the design value, and the rock mass is effectively sealed to prevent relaxation deformation.

[0046] 3. Mortar anchor rod or hollow anchor rod construction

[0047] A handheld air drill is used for drilling operation, and the air drill operator needs to be professionally trained and familiar with the operation method and safety precautions of the air drill. Before drilling, the drilling position is accurately marked on the surface of the surrounding rock according to the design requirements of the anchor rod position, angle and depth. During drilling, the drilling speed and pressure of the air drill are controlled and adjusted in time according to the hardness of the surrounding rock to ensure smooth drilling, smooth hole wall and no obvious collapse phenomenon. The drilling depth is 3-5cm longer than the design length of the anchor rod to ensure sufficient anchoring length after the anchor rod is installed.

[0048] After the drilling is completed, the hole is thoroughly cleaned with high-pressure air or water to remove rock powder, debris and accumulated water, ensuring that the hole is clean and dry, creating good conditions for the installation of the anchor rod and grouting. The processed and quality-qualified anchor rod and positioning ring are carefully inserted into the hole. During the insertion process, the rod body and positioning ring should not be damaged, and the rod body should be positioned at the center of the hole, with a uniform spacing of the positioning ring, generally 0.5-1m, to ensure the stability of the anchor rod in the hole.

[0049] The grouting pump is debugged and checked before use to ensure that the grouting pressure is stable and the flow is adjustable. According to the design requirements, the appropriate grouting material, such as early strength cement mortar or mortar, is selected and prepared according to the specified mix ratio to ensure that the properties of the slurry, such as consistency and strength, meet the requirements. During the grouting process, the grouting pipe is inserted into the hole bottom and the slurry is slowly injected. The grouting pipe is pulled out at a uniform speed while the hole opening is closely observed to prevent slurry overflow or leakage, ensuring that the slurry fills the hole space and tightly combines with the anchor rod and surrounding rock. After the cement mortar is finally set, the hole opening pad is installed. The pad installation should be flat, firm and perpendicular to the anchor rod, and the nut should be tightened to ensure that the pad is tightly attached to the surrounding rock, and the anchoring force of the anchor rod is evenly transmitted to the surrounding rock.

[0050] 4. Steel mesh laying

[0051] In the steel member processing site, the steel mesh is carefully processed according to the accurate specifications of the design using professional equipment such as a steel cutting machine and a bending machine. The cutting tool of the steel cutting machine should be sharp to ensure accurate steel cutting length with an error of not more than ±5mm. The mold of the bending machine should be customized according to the shape and size of the steel mesh required by the design to ensure accurate steel bending angle and consistent curvature. The grid size deviation of the processed steel mesh should not exceed ±5mm, and the shape should be regular.

[0052] After the initial spraying of concrete, the processed steel mesh is manually transported to the work surface. During the transportation process, the steel mesh should be protected to avoid deformation or damage. When laying the steel mesh, according to the shape of the surrounding rock surface and the arrangement of the anchor rod and steel frame, the steel mesh is laid flat on the initial spraying concrete surface, ensuring that the steel mesh maintains a distance of 3-5cm from the sprayed surface, and the overlapping length between adjacent steel meshes is not less than 1 grid length, generally 15-20cm. The overlapping parts are connected by spot welding or firm binding, and the spot welding or binding point spacing should not be greater than 20cm to ensure that the steel mesh is firmly connected as a whole without loosening or displacement. The steel mesh should follow the natural undulations of the sprayed surface and should not be forcibly pulled or twisted to ensure that the steel mesh is tightly attached to the surrounding rock and can jointly bear the force during the spraying of concrete. During the spraying of concrete, a dedicated person is arranged to observe the condition of the steel mesh at any time. Once it is found that a stone or concrete block is stuck by the steel mesh, it should be immediately cleaned with a tool to ensure that the spraying of concrete proceeds smoothly and the steel mesh can fully play its role in reinforcing the surrounding rock.

[0053] 5. Steel frame construction

[0054] Steel procurement is strictly in accordance with the design requirements, the selection of good reputation, reliable quality suppliers to ensure that the steel material, specifications, etc. in line with national standards and design requirements. Steel into the field, according to the batch of strict sampling inspection, inspection content includes steel chemical composition analysis, mechanical properties testing (yield strength, tensile strength, elongation, impact toughness, etc.) and appearance quality inspection (surface cracks, folding, rust and other defects). The unqualified steel sampling is firmly rejected, and is strictly prohibited for construction.

[0055] Steel frame using cold bending forming technology, according to the tunnel design contour line to produce high-precision cold bending die, die radius, size should be consistent with the design requirements, to ensure that the steel frame after cold bending forming good consistency, deviation not more than ± 1 cm, closely with the tunnel design contour line. In the cold bending process, control the operating parameters of the cold bending equipment, such as bending speed, pressure, etc. to ensure that the steel frame is not damaged during cold bending, and the surface of the steel frame after cold bending is smooth, without obvious wrinkles or deformation.

[0056] The grid steel frame adopts the membrane welding process, and the membrane should be strictly made according to the 1:1 sample to ensure the size and shape of the membrane. During welding, skilled and experienced welders are selected to operate, and welding current, voltage, welding speed and other parameters are strictly controlled to ensure reliable welding quality, full and uniform weld, no pores, slag, cracks and other defects, and the connection between parts is tight, and the node welding strength meets the design requirements.

[0057] Before the installation of the steel frame, the tunnel excavation contour is accurately measured, and the installation position of the steel frame is determined according to the measurement results. In the installation process, the distance between adjacent steel frames is strictly controlled, with an error of not more than ± 5 cm, to ensure uniform arrangement of the steel frame. The verticality of the steel frame is measured using high-precision measuring instruments such as total station, and the verticality deviation of each steel frame after installation is not more than ± 1°, to ensure that the steel frame is installed vertically and stably. High-strength bolts are used to connect between the steel frames, and the specifications and types of the bolts should meet the design requirements. During installation, the bolt tightening torque is ensured to reach the design value, and torque wrench is used for inspection to prevent bolt loosening and affect the overall stability of the steel frame.

[0058] During the removal of temporary supports, a detailed removal plan should be developed, and a reasonable removal sequence and safety protection measures should be adopted to avoid damage to the completed support structure. After removal, a full-section measurement system should be established promptly. The layout of measurement points should be representative, with a spacing of no more than 5 meters, to accurately reflect the deformation of the surrounding rock. High-precision monitoring equipment such as total stations and convergence meters should be used for data acquisition. The data acquisition frequency should be determined according to the deformation of the surrounding rock; generally, the acquisition frequency should be appropriately increased when the deformation is large to ensure accurate and timely measurement data. The collected data should be analyzed and processed promptly. Based on the analysis results, the stability of the surrounding rock and the effectiveness of the support structure should be judged, providing a reliable basis for subsequent construction and allowing for timely adjustments to the lining construction time to ensure tunnel construction safety.

[0059] 6. Advanced small-diameter pipe construction

[0060] Handheld pneumatic drills are used for pre-drilling of small guide pipes. Drill operators must possess skilled operation techniques and extensive experience. Before drilling, the drilling positions are accurately marked on the tunnel face according to the design requirements for the layout, length, spacing, and external insertion angle of the small guide pipes. During drilling, the drilling direction and angle of the pneumatic drill are strictly controlled to ensure that the drilling angle matches the designed external insertion angle with an error not exceeding ±1°. The drilling depth meets the design requirements. Hot-rolled seamless steel pipes with a diameter of 42-50mm and a length of 3-5m are used to ensure that the small guide pipes can be accurately driven into the predetermined positions in the surrounding rock, providing a good channel for subsequent grouting reinforcement.

[0061] The fabrication of the small guide pipes strictly adheres to design requirements, ensuring that parameters such as diameter, wall thickness, and length meet specifications. The front end of the steel pipe is machined into a tapered shape for easy insertion into the surrounding rock, and a grout stop valve is welded to the rear end to prevent grout backflow during the grouting process. The layout, length, and spacing of the small guide pipes should be rationally arranged based on the geological conditions of the surrounding rock and the tunnel design requirements to ensure uniform and effective grouting reinforcement.

[0062] The grouting material should be a suitable cement grout, with the water-cement ratio adjusted according to the surrounding rock conditions and design requirements, generally between 0.8:1 and 1:1. In special cases such as fractured surrounding rock or well-developed groundwater, a cement + water glass dual-liquid grout may be used, with a volume ratio of cement grout to water glass grout of 1:0.8, and the grout strength grade not less than M10. Before grouting, the grouting equipment should be thoroughly inspected and tested to ensure that the grouting pump is stable, the pressure is adjustable, and the grouting pipe connections are secure and leak-free.

[0063] During the grouting process, the grouting pipe is tightly connected with the small catheter to ensure the smooth grouting passage. When starting grouting, slowly apply pressure and gradually increase the grouting speed, control the grouting pressure between 0.5-1.0 MPa, avoid excessive grouting pressure causing excessive disturbance to the surrounding rock, and at the same time ensure that the slurry can diffuse uniformly in the surrounding rock. Observe the grouting situation closely, and adjust the grouting parameters such as grouting pressure, grouting speed, slurry ratio, etc. in time according to the slurry diffusion and surrounding rock feedback. When the surrounding rock absorbs a large amount of slurry, intermittent grouting method can be used, and the interval time between each grouting is 10-15 minutes, so that the slurry has a certain diffusion time in the surrounding rock, and the grouting reinforcement effect is improved. After grouting, check the grouting effect by drilling core taking and other methods, observe the filling situation of the slurry in the surrounding rock, and ensure that the slurry is filled fully to achieve the expected reinforcement effect.

[0064] 7. Anchor rod construction

[0065] According to the design requirements, select the mortar anchor rod or hollow anchor rod, the mortar anchor rod is processed by high-quality threaded steel, to ensure that the rod diameter is not less than 20 mm, and the length meets the design requirements. The material of the threaded steel should meet the national standard, and its mechanical properties such as yield strength and tensile strength meet the design requirements. During the processing, the length, diameter and other size accuracy of the anchor rod are strictly controlled to ensure the processing quality.

[0066] Use anchor rod drill or rock drill for hole drilling operation. Before drilling, the operator should accurately mark the drilling position on the surrounding rock surface according to the anchor rod position, angle and depth required by the design. During the hole drilling process, control the drilling speed and pressure of the drill or rock drill to ensure that the drilling position and the rod body insertion angle meet the design requirements, and strictly control the water quantity to prevent hole collapse. The drilling depth is 5-10 cm longer than the design length of the anchor rod. After inserting the anchor rod, pour the mortar with M30 or above to ensure that the anchoring length meets the design requirements. The length of the hollow anchor rod meets the design requirements. When installing, insert the anchor rod into the hole, connect the grouting pipe, inject the cement slurry, and ensure that the rod body closely fits the hole wall to play an effective supporting role.

[0067] 8. Advance pipe shed construction

[0068] The pipe shed is made of hot-rolled seamless steel pipe that meets the quality standards, and the pipe diameter is selected according to the design requirements. When the stratum conditions permit, the hole drilling and pipe insertion process is used. Before drilling, accurately determine the drilling position, angle and depth according to the pipe shed design parameters, use professional drilling equipment for construction to ensure drilling accuracy, the drilling diameter is 20-30 mm larger than the pipe diameter of the pipe shed, and the drilling depth meets the design requirements. When inserting the pipe, accurately hit the steel pipe into the surrounding rock along the design specified outer insertion angle of the tunnel periphery, the pipe shed joint uses screw connection, the screw length reaches the specified size, and the adjacent pipe joints are staggered by a certain distance as required to ensure firm connection.

[0069] When the geological conditions are complex, the pipe-roofing drilling technology is adopted. During construction, the casing and drill pipe are drilled at the same time, the drilling speed and pressure are controlled to ensure the smooth progress of the casing and the good cooperation with the drill pipe. After the hole is formed, the drill pipe is removed, the pipe shed is jacked, and the outer casing is pulled out. After the installation of the pipe shed is completed, pressure grouting is carried out, the grouting pressure and grouting volume are determined according to the design requirements to ensure that the grout in the pipe shed is filled densely, and the pipe shed structure is stable and reliable.

[0070] 9. Construction monitoring and adjustment

[0071] During the whole process of initial support construction of the tunnel, a perfect surrounding rock deformation monitoring system is established. The monitoring points are arranged reasonably around the tunnel, high-precision monitoring equipment such as total station and convergence meter is used to ensure the accuracy and timeliness of the monitoring data. The arrangement of monitoring points should cover different geological conditions and support structure parts, and can fully reflect the deformation of surrounding rock.

[0072] The monitoring is carried out according to the specified frequency. Generally, the collection frequency is appropriately increased when the surrounding rock deformation is large. The collected data is analyzed and processed in real time, professional data analysis software is used to draw deformation curves and analyze deformation trends. When the monitoring data shows that the surrounding rock deformation is abnormal, such as the displacement rate exceeds the reasonable range or the deformation curve appears mutation, the construction is immediately suspended.

[0073] Professional technicians are organized to analyze the reasons in depth, which may include geological changes, unreasonable support parameters, construction technology problems, etc. According to the analysis results, the support parameters are quickly and scientifically adjusted, such as increasing the number of anchor rods, adjusting the spacing of anchor rods, strengthening the support strength of steel frame, changing the grouting parameters, etc. The adjusted support scheme needs to be implemented after being demonstrated by experts or approved by relevant departments to ensure the safety of tunnel construction.

[0074] 10. Quality control and inspection

[0075] After each construction process is completed, the overall quality inspection is strictly carried out according to the relevant specifications and standards. The initial sprayed concrete is checked for thickness and strength, the core drilling method is used to detect the strength, the core sample is taken on the concrete structure and sent to the laboratory for compression test to ensure that the strength meets the design requirements. The thickness is checked using laser range finder and other measuring equipment to ensure that the thickness is not less than the design value.

[0076] The pullout force of anchor rod is checked, and the pullout test is carried out according to the specified number. The pullout equipment is installed on the anchor rod, the pulling force is gradually applied, and the pullout force value of the anchor rod is recorded to ensure that the pullout force meets the design standard. The mesh spacing of steel mesh, the distance from the sprayed surface, the fastness of connection, etc. are checked, the mesh spacing is measured by steel ruler, the fit of steel mesh with the sprayed surface is observed, and the fastness of welding or binding points is checked.

[0077] The steel frame is checked for installation position, spacing, verticality, connection quality, etc. A total station instrument is used to measure the position and verticality of the steel frame, a steel ruler is used to measure the spacing, and the bolt connection is checked for tightness, and the welding is checked for fullness and defects. The length, angle, and grouting effect of the advanced small conduit and pipe shed are checked, the grout filling is observed by drilling and coring, and the grouting is ensured to be full. The installation position and angle of the pipe shed and small conduit are ensured to meet the design requirements. For parts that do not meet the quality requirements, immediate corrective measures are developed, thorough correction is carried out, and after the correction is completed, strict inspection is carried out again to ensure that the initial support quality completely meets the design and specification requirements.

[0078] In the specific embodiments of the present application, the full-tunnel portal is divided into four types: end wall type, double-line double-ear wall type A, single-line double-ear wall type, and single-pressure type. The Bai-lang tunnel portal is connected with the large mileage of the Hongshuihe super-large bridge and the small mileage of the Longna bridge tunnel, the Bai-lang tunnel portal open cut is 17 m, and the exit open cut is 23 m. The Youping tunnel exit and the Lijiacun tunnel portal are respectively connected with the small and large mileage of the Masancun bridge tunnel, the Youping tunnel exit open cut is 11 m, and the Lijiacun tunnel portal open cut is 15 m.

[0079] The total length of the open tunnel and the excavated section is 32.926 km, among which the proportion of grade II surrounding rock in the excavated section is 7.6%, the proportion of grade III surrounding rock is 33%, the proportion of grade IV surrounding rock is 55%, and the proportion of grade V surrounding rock is 11.2%. The construction methods include bench method, bench method + temporary inverted arch, three-bench method + temporary inverted arch, micro-bench method, and full-face method. The portal section is shallowly buried and is supported by two specifications of Φ89 and Φ108 pipe sheds. The Bai-lang tunnel DK186+681~+688 section passes under the existing rural road, is supported by the Φ89 pipe shed inside the tunnel, the surface of the Shangli tunnel DK214+973 is the Changsha river, is supported by the Φ89 pipe shed inside the tunnel + surface channeling paving reinforcement, and the Shangli tunnel DK214+790~930 section passes under the Yinbai expressway, is supported by the Φ159 large pipe shed inside the tunnel.

[0080] The auxiliary caverns for the tunnel construction of the project mainly include small parking caverns, large parking caverns, and ladder car caverns, with sizes of 2 m wide, 1 m deep, and 2.2 m high, 4 m wide, 2.5 m deep, and 2.8 m high, and 2.5 m wide, 7.53 m deep, respectively, which meet the construction organization requirements. The auxiliary caverns are all designed to be supported by steel arches and lined with concrete structures, and during the construction, only the initial support part of the caverns is completed to meet the spatial requirements of the construction organization.

[0081] The above implementation manners are only used to illustrate the specific embodiments of the present application, and are not limited thereto. According to the idea of the present application, various similar modifications and changes can be made by those skilled in the art, and these modifications and changes should be considered as the protection scope of the present application.

Claims

1. A railway engineering tunnel primary support process, characterized by, The method comprises the following steps: Immediately after tunnel excavation, risk elimination work is carried out, and then initial concrete spraying operation is implemented, wet spraying process is adopted, centralized mixing is carried out outside the tunnel, a concrete transport vehicle is used to transport concrete into the tunnel, and then a wet spraying machine is used for spraying; the initial concrete spraying should timely close the rock mass to prevent the rock mass from relaxing; the wet spraying machine is comprehensively checked and debugged before spraying to ensure that the spraying pressure is stable and the spraying angle can be flexibly adjusted; during spraying operation, the spraying pressure is reasonably adjusted according to the surrounding rock surface condition and the spraying distance and is controlled to be between 0.3-0.5MPa, the spraying angle is kept perpendicular or slightly inclined to the sprayed surface, the nozzle distance to the sprayed surface is 0.8-1.2m, the spraying is carried out in layers according to the sequence from bottom to top and from both sides to the middle, the thickness of each layer is controlled to be 3-5cm, the interval time of each layer is 3-5min, the next layer is sprayed after the previous layer is completely cured to avoid the phenomenon of hollowing, falling and the like of the concrete; The mortar anchor rod or hollow anchor rod construction is carried out, a handheld air drill is used to form a hole, the anchor rod and the positioning ring are inserted into the hole, and then the grouting pump is used to inject early strength cement mortar or mortar into the hole; after the cement mortar is completely cured, the hole pad is installed; The steel mesh is laid out, is processed and formed according to the design specification at the steel member processing site, is manually installed after the initial concrete spraying, is fixed on the anchor rod or the steel frame by means of electric spot welding or binding, the steel mesh needs to follow the undulation of the sprayed surface and maintain a certain distance, and the stones or concrete blocks that are stuck by the steel mesh during the spraying process should be timely removed; during the laying of the steel mesh, the steel mesh is laid flat on the initial concrete surface according to the shape of the surrounding rock surface and the arrangement of the anchor rod and the steel frame to ensure that the steel mesh maintains a distance of 3-5cm from the sprayed surface, the overlapping length between adjacent steel meshes is not less than 1 grid length, generally 15-20cm, and the overlapping parts are connected by means of electric spot welding or firm binding, the spot welding or binding point spacing is not greater than 20cm, and the overall connection of the steel mesh is firm without loosening or displacement phenomenon; The steel frame construction is implemented, the steel quality and the joint position meet the specification and design requirements, the steel frame is formed by cold bending technology, the grid steel frame is welded by a tire membrane, and a 1:1 sample is used to control the size; after the temporary support is removed, a full-section measurement system is established, and the lining work is timely followed up. The small pilot pipe is drilled by hand-held air drill, the layout range, length and spacing of the small pilot pipe are arranged according to the design, the grouting material is cement slurry, the grouting pressure is controlled in a reasonable range, the water-cement ratio meets the corresponding requirements, when the surrounding rock is broken and the groundwater is developed, the cement + sodium silicate double liquid slurry can be partially used, the slurry strength grade is required to meet the specified standard, before drilling, the drilling position is accurately marked on the tunnel face according to the design requirements of the small pilot pipe layout range, length, spacing and external insertion angle; during drilling, the drilling direction and angle of the air drill are strictly controlled to ensure that the drilling angle is consistent with the design external insertion angle, the error is not more than ± 1°, the drilling depth meets the design requirements, the small pilot pipe is made of hot-rolled seamless steel pipe with a diameter of 42-50 mm and a length of 3-5 m, which can ensure that the small pilot pipe can be accurately punched into the predetermined position of the surrounding rock to provide a good channel for subsequent grouting reinforcement; The anchor rod is constructed according to the design by using mortar anchor rod or hollow anchor rod, the mortar anchor rod is processed by using threaded steel, the hole is drilled by using anchor rod drill or rock drill, and the position and rod body external insertion angle are ensured during drilling, and the water quantity is controlled to prevent hole collapse; The pipe shed is made of hot-rolled seamless steel pipe, and the drilling first and pipe inserting later or pipe drilling process is selected according to the actual stratum condition, the pipe shed joint is connected by using thread, the thread length reaches the specified size, the adjacent steel pipe joints are staggered by a certain distance according to the requirements, and the steel pipe is punched into the surrounding rock along the design external insertion angle of the tunnel periphery, and then the cement slurry is poured.

2. A process for initial support of a tunnel in railway engineering according to claim 1, characterized in that, When the initial concrete is sprayed, the spraying equipment should be in good performance state to ensure that the concrete is uniformly and continuously sprayed, and the interruption or accumulation of the concrete is avoided.

3. A process for initial support of a tunnel in railway engineering according to claim 1, characterized in that, During the construction of the mortar anchor rod or hollow anchor rod, the drilling operation should ensure that the hole wall is smooth and has no obvious collapse, the rod body and positioning ring should not be damaged during the insertion of the anchor rod, and the grouting process should ensure that the slurry fully fills the hole space and has no slurry leakage.

4. A process for initial support of a tunnel in railway engineering according to claim 1, characterized in that, When the steel mesh is laid, the processing of the steel mesh should ensure the size accuracy and shape regularity, and the installation process should ensure that it is firmly connected with the anchor rod or steel frame, and the loosening or displacement phenomenon should not occur.

5. A process for initial support of a tunnel in railway engineering according to claim 1, characterized in that, During the construction of the steel frame, the cold-bent steel frame should have good arc consistency, the grid steel frame welded by the membrane should ensure reliable welding quality and close connection of the components, and the completed support structure should not be damaged during the temporary support removal and the establishment of the measurement system.

6. A process for initial support of a tunnel in railway engineering according to claim 1, characterized in that, During the grouting of the small pilot pipe, the grouting parameters should be adjusted in time according to the actual situation of the surrounding rock and the feedback of the grouting effect to ensure that the slurry uniformly diffuses in the surrounding rock and achieves the expected reinforcement effect, and the excessive disturbance of the surrounding rock caused by the excessive grouting pressure is avoided.

7. A process for initial support of a tunnel in railway engineering according to claim 1, characterized in that, During the construction of the anchor rod, the hole drilling operation should be accurately positioned to ensure that the anchor rod can be smoothly inserted into the hole and closely fit with the hole wall, the anchoring length of the mortar anchor rod should ensure that the anchoring force meets the design requirements, and the length of the rod body of the hollow anchor rod should meet the design requirements to ensure that the support effect is effectively exerted.

8. A process for initial support of a tunnel in railway engineering according to claim 1, characterized in that, In the construction of the advanced pipe roof, the drilling and pipe inserting process should ensure the drilling accuracy and pipe inserting depth to meet the design requirements, the pipe following drilling process should ensure the smooth pipe following and good cooperation with the drill rod, and the grouting after the pipe roof installation should ensure the dense filling of the grout in the pipe roof and the stable structure of the pipe roof.

9. A process for initial support of a tunnel in railway engineering according to claim 1, characterized in that, During the whole initial support construction, a perfect surrounding rock deformation monitoring system should be established, the monitoring equipment should be stable and reliable, the data acquisition should be accurate and timely, the support parameters should be adjusted timely and scientifically according to the monitoring data, and the tunnel construction safety should be ensured.

10. A process for initial support of a tunnel in railway engineering according to claim 1, characterized in that, The raw materials for the shotcrete should be strictly selected to ensure the quality, and the mix proportion of the concrete should be reasonably adjusted according to the actual construction conditions and design requirements to ensure that the performance of the concrete meets the requirements of the initial support.

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