Guide pipe embedding method for tunnel pipe shed

Abstract

The invention provides a guide pipe embedding method for a tunnel pipe shed, and belongs to the technical field of tunnel pipe shed construction.The guide pipe embedding method comprises the steps that an I-shaped steel frame composed of seven rigid connecting units is installed in a guide wall to serve as a positioning benchmark, and a guide pipe is welded to the I-shaped steel frame through the welding line energy control and reversible deformation presetting technology; reinforcing ribs are welded to the outer wall of the guide pipe to form a space truss connecting system to improve the anti-buoyancy capacity, positive-pressure protective gas is filled into the guide pipe, concrete grout is prevented from invading by means of pressure difference, a stress diffusion cushion layer is arranged during arch foot foundation construction, and the drilling direction is restrained through a guide sleeve. During layered concrete pouring, a low-frequency vibrating rod is used for avoiding the inherent frequency of the guide pipe, the position deviation value of the guide pipe is monitored in real time, and when the position deviation value exceeds a threshold value, a jack is immediately adopted for applying reverse torque for position correction, so that the problem that the position precision of the guide pipe is difficult to control in the concrete pouring process is solved.

Description

Technical Field

[0001] This invention belongs to the field of tunnel pipe roof construction technology, and more specifically, relates to a method for laying guide pipes for tunnel pipe roofs. Background Technology

[0002] In tunnel construction, pipe roof support technology requires the pre-installation of guide pipes within the guide wall to control the direction of subsequent drilling. Traditionally, the guide pipes are fixed to a steel mesh or simple support before concrete is poured. However, in existing technologies, the buoyancy generated during concrete pouring acts on the guide pipe surface, the vibration energy of the vibrator is transmitted to the guide pipe structure through the concrete medium, and welding thermal deformation causes initial positional shifts in the guide pipe. These three factors combined cause positional shifts in the guide pipe during pouring. Traditional techniques control positional deviations by increasing the number of binding points or improving the rigidity of the support, but these measures only mitigate, not eliminate, the tendency for positional shifts. When the accumulated positional deviation of the guide pipe exceeds the allowable range, the subsequent drilling axis deviates from the design position, affecting the quality of the pipe roof construction. In other words, existing technologies suffer from the technical problem of difficulty in controlling the positional accuracy of the guide pipe during concrete pouring. Summary of the Invention

[0003] In view of this, the present invention provides a method for laying guide pipes for tunnel pipe sheds, which can solve the technical problem in the prior art that the positional accuracy of the guide pipe is difficult to control during the concrete pouring process.

[0004] This invention is implemented as follows: A method for burying guide pipes for tunnel pipe roofs includes establishing a guide wall positioning benchmark by marking the tunnel centerline and outer arch elevation on the slope surface based on tunnel centerline control piles and elevation control points; installing an I-beam frame inside the guide wall and placing the bottom of the I-beam frame on stable bedrock; welding the guide pipe to the I-beam frame using a segmented symmetrical welding process; welding reinforcing ribs to the outer wall of the guide pipe to form a spatial truss connection system with the I-beam frame; filling the guide pipe with positive pressure protective gas; setting a stress diffusion pad at the bottom of the arch foot foundation during construction and using a guide sleeve to constrain the drilling direction of the anchor bolts; using a low-frequency vibrator when pouring the guide wall concrete in layers; monitoring the guide pipe's position deviation in real time and immediately stopping pouring when it exceeds the position deviation control threshold; applying a reverse torque with a jack for position correction; and releasing the positive pressure protective gas inside the guide pipe after the concrete has initially set to complete the guide pipe burial construction.

[0005] The I-beam frame is divided into seven connection units, and each connection unit is rigidly connected by welded connection plates and bolts.

[0006] The height of the arch foot at the bottom of the I-beam frame is 15 to 20 cm lower than the bottom line of the upper excavation.

[0007] The thickness of the concrete protective layer reserved between the bottom of the I-beam frame and the top surface of the inner formwork of the guide wall is 21cm.

[0008] The welding heat input is controlled within the range of 15 to 20 kJ / cm, and the welding process adopts the skip welding method and performs reverse deformation pre-setting.

[0009] Among them, the reverse deformation presetting refers to calculating the expected deformation value based on the welding shrinkage amount before welding and setting a deviation value opposite to the welding shrinkage direction on the I-beam frame or guide tube in advance.

[0010] Among them, the skip welding method refers to welding long welds by intermittently skipping several short weld segments first, and then welding other positions after the short weld segments have cooled down.

[0011] Among them, the space truss connection system refers to a structural form in which multiple sets of reinforcing ribs are welded along the axial and circumferential directions on the outer wall of the guide tube to form a multi-point rigid connection between the guide tube and the I-beam frame in three-dimensional space.

[0012] The guide tube is fitted with flanges at both ends and rubber sealing rings, and the outer side is secured with bolts to the steel plate cover.

[0013] The positive pressure protective gas is compressed air with a pressure of 0.05 MPa. The outward thrust formed by the internal and external pressure difference prevents concrete slurry from entering the pipe from the pipe end or the gap in the pipe wall.

[0014] The stress diffusion layer, 150mm thick, is formed by pouring C15 grade concrete to diffuse concentrated loads from the arch foot foundation and reduce stress concentration. The guide sleeve, 1.0m long, is welded to the I-beam frame; during drilling, the drill rod passes through the inner hole of the guide sleeve to constrain the initial drilling direction. The anchor bolt, 6m long and 4m deep into the rock, is connected to the I-beam frame using a single-sided lap weld. The thickness of each layer of the guide wall concrete is controlled to be within 300mm during layered pouring. The low-frequency vibrator operates at 25Hz to avoid the natural frequency of the guide pipe, which is the vibration frequency of the guide pipe as an elastic structure during free vibration. The position deviation control threshold is 9mm; if the position deviation of the guide pipe centerline exceeds the control threshold, pouring is immediately stopped and the position is corrected.

[0015] This invention solves the technical problem of controlling the positional accuracy of the guide tube during concrete pouring by employing a combined technical approach: establishing an I-beam spatial truss connection system, implementing welding line energy control, injecting positive pressure protective gas, and real-time monitoring and dynamic correction of positional deviations. The I-beam frame forms a stable reference skeleton through seven rigid connection units. The spatial truss connection system fixes the guide tube and the I-beam frame at multiple points in three-dimensional space, improving buoyancy resistance. Welding line energy control and anti-deformation pre-setting technology reduce initial positional deviations caused by welding thermal deformation from the source. The positive pressure protective gas uses the outward thrust generated by the internal and external pressure difference to resist the lateral pressure of the concrete slurry. The low-frequency vibrator avoids the natural frequency of the guide tube to prevent resonance amplification of displacement. The real-time monitoring system captures changes in positional deviation and immediately applies a reverse torque using jacks for correction when the deviation exceeds a threshold. In summary, this invention solves the technical problem of controlling the positional accuracy of the guide tube during concrete pouring, as mentioned in the background art. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method of the present invention.

[0017] Figure 2 Detailed construction drawings for the installation of I-beam steel frames.

[0018] Figure 3 Design drawing for the distribution of anchor bolts for arch foot foundation.

[0019] Figure 4 This is a detailed construction drawing showing the distribution of anchor bolts for the arch foot foundation.

[0020] Figure 5 This is a diagram showing the distribution of the guide tube position deviation.

[0021] Figure 6 This is a diagram showing the distribution of the axial deviation of the steel pipes in the pipe shed. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0023] like Figure 1 The diagram shows a flowchart of a method for laying guide pipes for tunnel pipe roofs provided by the present invention. This method includes the following steps:

[0024] S1. Mark the tunnel centerline and outer arch elevation on the slope surface according to the tunnel centerline control piles and elevation control points. Draw the outer arch arc according to the outline of the tunnel excavation to complete the establishment of the guide wall positioning benchmark.

[0025] S2. Install an I-beam frame inside the guide wall. The I-beam frame is divided into seven connection units. Each connection unit is rigidly connected by welding connection plates and bolts. The bottom of the I-beam frame is placed on stable bedrock and the height of the arch foot is 15-20cm lower than the upper excavation bottom line.

[0026] S3. Reserve the thickness of the concrete protective layer between the bottom of the I-beam frame and the top surface of the inner formwork of the guide wall. Use a segmented symmetrical welding process to weld the guide pipe onto the I-beam frame. Control the welding line energy within the designed welding line energy range. Use the skip welding method and perform reverse deformation pre-setting during the welding process.

[0027] S4. Weld reinforcing ribs to the outer wall of the guide tube to form a spatial truss connection system with the I-beam frame. Install flanges and rubber sealing rings at both ends of the guide tube. Secure the steel plate cover to the outside with bolts. Fill the tube with positive pressure protective gas.

[0028] S5. When constructing the arch foot foundation, a stress diffusion pad is set at the bottom of the foundation. A guide sleeve is used to constrain the drilling direction of the anchor bolts. The anchor bolts are 6m long and have a rock penetration depth of 4m. The anchor bolts are connected to the I-beam frame by single-sided lap welding.

[0029] S6. When pouring concrete for the guide wall in layers, the thickness of each layer should be controlled within the limit of the layer pouring thickness. Use a low-frequency vibrator to avoid the natural frequency of the guide pipe and monitor the position deviation of the guide pipe in real time.

[0030] S7. When the deviation of the center line of the guide pipe exceeds the position deviation control threshold, stop pouring immediately and use a jack to apply a reverse torque for position correction. After the correction is completed, continue pouring until the concrete initially sets.

[0031] S8. After the concrete has initially set, release the positive pressure protective gas inside the guide pipe, remove the steel plate cover, and use high-pressure gas to purge the residue inside the pipe to complete the guide pipe installation.

[0032] The concrete protective layer thickness is 21cm. This is achieved by maintaining a 21cm gap between the bottom of the I-beam frame and the top surface of the inner formwork of the guide wall to ensure adequate protection of the I-beam frame after concrete pouring. The concrete protective layer thickness was determined through a steel corrosion protection experiment. Ten groups of I-beam specimens were selected and subjected to protective layer thicknesses ranging from 10cm to 30cm. These specimens were immersed in a simulated groundwater environment for 180 days, with the rust depth on the steel surface and the carbonation depth of the concrete measured every 30 days. Experimental data showed that when the protective layer thickness was less than 18cm, the steel rust depth exceeded 0.5mm; when the protective layer thickness reached 21cm, the steel rust depth stabilized below 0.1mm. Considering both construction errors and long-term durability requirements, the concrete protective layer thickness was determined to be 21cm.

[0033] The designed welding heat input range was 15–20 kJ / cm, determined through welding heat deformation control experiments. The experiment involved selecting 12 sets of welding specimens of I-beams and guide tubes, with welding heat inputs set to 10 kJ / cm, 12 kJ / cm, 15 kJ / cm, 17 kJ / cm, 20 kJ / cm, 23 kJ / cm, and 25 kJ / cm, respectively. Three specimens were prepared for each welding heat input. After welding, the centerline offset of the guide tube and the deformation of the I-beam frame were measured. Experimental data showed that when the welding heat input was less than 15 kJ / cm, the weld penetration was insufficient, resulting in a weld strength of only 65% ​​of the design strength. When the welding heat input exceeded 20 kJ / cm, the centerline offset of the guide tube exceeded 12 mm, and the I-beam frame exhibited wavy deformation. When the welding heat input was controlled within the range of 15–20 kJ / cm, the weld strength reached more than 95% of the design strength, and the centerline offset of the guide tube was controlled within 5 mm. Therefore, the designed welding heat input range was determined to be 15–20 kJ / cm.

[0034] Anti-deformation presetting refers to a technical method in which the expected deformation value is calculated based on the welding shrinkage before welding, and a deviation value opposite to the welding shrinkage direction is pre-set on the I-beam frame or guide tube. This ensures that the cooling shrinkage after welding exactly cancels out the pre-set deviation, thereby achieving the designed positional accuracy. The anti-deformation presetting amount is obtained through welding shrinkage measurement experiments. The experiment involved welding 20 sets of I-beam and guide tube welding test pieces. Before welding, a baseline was marked on the guide tube. After welding and cooling, the displacement of the baseline was measured. The experimental data showed that the welding shrinkage was between 2.5 mm and 3.8 mm, with an average welding shrinkage of 3.2 mm. Based on the experimental data, the centerline position of the guide tube was pre-offset by 3.2 mm in the opposite direction of welding shrinkage before welding. After welding, the deviation of the centerline position of the guide tube was controlled within 1 mm.

[0035] The skip welding method refers to welding long seams in a non-continuous manner, using an intermittent skip welding approach. Several short, dispersed weld segments are welded first, and other positions are welded after the short weld segments have cooled down. This disperses the heat input and avoids the accumulation of thermal deformation caused by excessively high local temperatures.

[0036] The spatial truss connection system refers to a structural form in which multiple sets of reinforcing ribs are welded axially and circumferentially to the outer wall of the guide tube, forming a multi-point rigid connection between the guide tube and the I-beam frame in three-dimensional space. This spatial truss connection system improves the guide tube's resistance to buoyancy and lateral forces through the principle of triangular stability. The arrangement of the reinforcing ribs was determined through an anti-buoyancy test experiment. The experiment involved fabricating eight sets of welded specimens of the guide tube and the I-beam frame, with the number of reinforcing ribs set to 2, 4, 6, 8, 10, 12, 14, and 16 sets respectively. Each set of specimens was immersed in simulated concrete fluid to apply different buoyancy loads, and the displacement of the guide tube was measured. Experimental data showed that when the number of reinforcing ribs was less than 6 sets, the displacement of the guide tube under buoyancy exceeded 15 mm. When the number of reinforcing ribs reached 8 sets, the displacement of the guide tube decreased to below 3 mm. Further increasing the number of reinforcing ribs did not significantly improve the displacement control effect but increased the welding workload. Therefore, the number of reinforcing ribs was determined to be 8 sets.

[0037] The positive pressure protective gas is compressed air with a pressure of 0.05 MPa. By filling the sealed guide pipe with compressed air at a pressure higher than the external atmospheric pressure, the outward thrust formed by the pressure difference between the inside and outside is used to prevent concrete slurry from entering the pipe from the pipe end or the gap in the pipe wall. The positive pressure protective gas pressure value was determined through a grout intrusion protection experiment. The experiment involved preparing 10 sets of sealed guide tube specimens, filling them with compressed air at pressures of 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.05 MPa, 0.07 MPa, 0.10 MPa, 0.12 MPa, and 0.15 MPa, respectively. Simulated concrete grout pressure was applied externally, and the grout intrusion was observed over 24 hours. The experimental data showed that when the gas pressure inside the tube was below 0.03 MPa, grout intruded through the gaps at the tube ends, reducing the cleanliness of the tube to 85%. When the gas pressure inside the tube reached 0.05 MPa, grout could not intrude at all, and the cleanliness of the tube remained above 98%. When the gas pressure inside the tube exceeded 0.10 MPa, the sealing rubber ring was at risk of deformation. Considering both the protective effect and the sealing safety, the positive pressure protective gas pressure was determined to be 0.05 MPa.

[0038] The stress diffusion cushion layer, with a thickness of 150 mm, is formed by pouring C15 grade concrete. It is used to diffuse the concentrated load transmitted from the arch foot foundation at the contact surface with the rock mass, reducing stress concentration. The thickness of the stress diffusion cushion layer was determined through rock mass stress distribution experiments. The experiment involved placing concrete cushion layers with thicknesses of 50 mm, 100 mm, 150 mm, 200 mm, and 250 mm on rock mass specimens, respectively. A concentrated load of 300 kN was applied on top, and stress distribution within the rock mass was measured using embedded stress sensors. Experimental data showed that without the cushion layer, the maximum stress at the contact surface reached 8.5 MPa, exceeding the rock mass compressive strength. With a cushion layer thickness of 100 mm, the maximum stress at the contact surface decreased to 6.2 MPa, and with a cushion layer thickness of 150 mm, the maximum stress at the contact surface decreased to 4.8 MPa, below the rock mass compressive strength. Further increasing the cushion layer thickness did not significantly improve the stress diffusion effect; therefore, a thickness of 150 mm was determined for the stress diffusion cushion layer.

[0039] A guide sleeve is a steel pipe that is pre-embedded at the predetermined anchor position in the arch foot foundation. The guide sleeve is 1.0m long and is welded and fixed to the I-beam frame. During drilling, the drill rod constrains the initial drilling direction through the inner hole of the guide sleeve, thereby reducing the drilling deviation rate by limiting the lateral displacement of the initial section of the drill rod. The length of the guide sleeve was determined through a borehole deviation control experiment. The experiment involved drilling anchor bolt holes in a simulated rock mass. The guide sleeve lengths were set to 0.3m, 0.5m, 0.8m, 1.0m, 1.2m, and 1.5m, with 12 holes drilled for each length. The drilling depth was 6m, and the deviation distance at the bottom of the hole was measured using an inclinometer. The experimental data showed that the borehole deviation rate reached 4.5% without the guide sleeve. When the guide sleeve length was 0.5m, the borehole deviation rate decreased to 2.8%. When the guide sleeve length was 1.0m, the borehole deviation rate decreased to 1.3%, meeting the design requirements. The improvement effect on the deviation rate was not significant when the guide sleeve length exceeded 1.0m. Therefore, the guide sleeve length was determined to be 1.0m.

[0040] Single-sided lap welding refers to a welding method in which the end of the anchor rod is lapped to the surface of the I-beam at a certain angle, and welding is performed only on one side of the contact surface. Compared with double-sided welding, it requires less construction space and has higher welding efficiency.

[0041] The maximum thickness for each layer of concrete pouring was 300 mm, determined through an experiment on the effect of concrete vibration. The experiment involved pouring concrete in layers in a simulated guide tube environment. Each layer was set to thicknesses of 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, and 450 mm, with each thickness poured six times. During pouring, the displacement of the guide tube and the uniformity of vibration were monitored. Experimental data showed that when the layer thickness was less than 250 mm, excessive vibration caused the cumulative displacement of the guide tube to exceed 8 mm. When the layer thickness was 300 mm, vibration was sufficient and the displacement of the guide tube was controlled within 4 mm. When the layer thickness exceeded 350 mm, an area of ​​insufficient compaction appeared at the bottom of the concrete. Therefore, the maximum thickness for each layer of concrete pouring was determined to be 300 mm.

[0042] The natural frequency of the guide tube refers to the vibration frequency value of the guide tube as an elastic structure during free vibration. The natural frequency is determined by the material properties, geometric dimensions, and boundary constraints of the guide tube. When the external excitation frequency approaches the natural frequency of the guide tube, resonance occurs, leading to displacement amplification. The natural frequency of the guide tube was determined through modal analysis experiments. The experiment involved hammering 10 seamless steel guide tubes with a diameter of 140mm, a wall thickness of 6mm, and a length of 2.0m. Vibration response signals were collected using accelerometers and spectral analysis was performed. The experimental data showed that the natural frequency of the guide tube was concentrated in the range of 45Hz to 52Hz, with an average natural frequency of 48Hz. Therefore, a low-frequency vibrator with an operating frequency of 25Hz was selected during concrete compaction to avoid the natural frequency of the guide tube.

[0043] The position deviation control threshold is 9mm. When the position deviation of the guide tube centerline exceeds the position deviation control threshold, position correction is required. The position deviation control threshold was determined through a drilling construction adaptability experiment. The experiment involved pre-embedding guide tubes with different position deviations (3mm, 6mm, 9mm, 12mm, 15mm, and 18mm) into concrete test blocks. Five guide tubes were pre-embedded for each deviation. Subsequent drilling was carried out through the guide tubes, and the deviation between the drilling axis and the design axis was measured. Experimental data showed that when the guide tube position deviation was less than 9mm, the drilling axis deviation was controlled within 15mm, meeting the requirements for pipe roof construction. When the guide tube position deviation exceeded 12mm, the drilling axis deviation exceeded 25mm, affecting the quality of the pipe roof. Therefore, the position deviation control threshold was determined to be 9mm.

[0044] The specific implementation methods of the above steps are described in detail below.

[0045] The specific implementation of step S1 includes: Step 101, obtaining the coordinates of the tunnel centerline control piles and the elevation data of the elevation control points according to the design drawings, and establishing a spatial coordinate system by conducting multi-point measurements on the slope using a total station; Step 102, transforming the tunnel centerline coordinates in the design coordinate system to the on-site spatial coordinate system using a coordinate transformation algorithm, and fitting the actual terrain surface equation of the slope using the least squares method; Step 103, calculating the radius and center position of the outer arch based on the design parameters of the tunnel excavation outline, marking the tunnel centerline projection points on the slope and extending the outer arch outline to both sides; Step 104, verifying the elevation error of each marked point using a level, and readjusting the marked positions until the accuracy requirements are met when the elevation error exceeds 5mm. In this step S1, spatial coordinate transformation and surface fitting are used, and the design parameters are accurately mapped to the actual construction surface through mathematical modeling, resulting in improved positioning benchmark accuracy and accurate position control of subsequent processes.

[0046] The specific implementation of step S2 includes: Step 201, pre-assembling the seven connecting units of the I-beam frame according to the designed curvature on a flat site, and checking the flatness and curvature continuity of the interfaces of each connecting unit; Step 202, welding connecting plates to the ends of each connecting unit, the connecting plates being 200mm×150mm×10mm in size, and grinding the weld surface after welding to ensure flatness; Step 203, connecting adjacent connecting units with bolts through the connecting plates, using 6 sets of bolts and nuts at each interface, the bolts being M20, and the tightening torque controlled at 180 N·m; 204. Hoist the assembled I-beam frame to the predetermined position inside the guide wall, and use a laser positioning instrument to check the coincidence of the center line of the I-beam frame with the center line of the tunnel; Step 205. Excavate the arch foot foundation pit on the bedrock surface, controlling the depth so that the position of the arch foot of the I-beam frame is 15-20cm lower than the upper excavation bottom line. If the bedrock surface is uneven, lay a 20mm thick cement mortar leveling layer; Step 206. Use an adjustable support frame to temporarily fix the position of the I-beam frame, and measure the lateral elevation and verticality using a level and plumb line. If the deviation exceeds the allowable range, adjust the height and angle of the support frame. In this step S2, modular assembly and multi-point measurement and verification were adopted. Through segmented combination and precision positioning technology, high-precision installation of the large-span steel structure was achieved, resulting in the technical effect of ensuring the overall structural rigidity and meeting the design requirements for positional accuracy.

[0047] The specific implementation of step S3 includes: Step 301, marking a position line 21cm away from the top surface of the inner mold at the bottom of the I-beam frame as the positioning reference for welding the guide tube; Step 302, marking the welding position of the guide tube on the I-beam frame according to the designed spacing. The circumferential spacing of the guide tube is determined according to the design density of the pipe shed, usually 0.3-0.5m; Step 303, processing the end of the guide tube into an arc-shaped cut that fits against the surface of the I-beam frame. The cut angle is calculated and determined according to the inclination angle of the guide tube and the curvature of the I-beam frame; Step 304, pre-setting a 3.2mm anti-deformation pre-set amount at the contact position between the guide tube and the I-beam frame. The pre-set direction is opposite to the expected welding shrinkage direction; Step 305, using a segmented symmetrical welding process. Welding begins with welding 50mm sections at each end of the guide tube. After cooling, the middle section is welded, and then the welding continues, alternating between the end and middle sections. The welding current is controlled at 180–220A, and the welding speed at 8–12mm / s, maintaining the welding heat input within the range of 15–20kJ / cm. Step 306: Immediately after welding, the weld is forcibly cooled with compressed air for at least 2 minutes. Then, a jack is used to apply a corrective force of 500–800N to the end of the guide tube, opposite to the direction of welding deformation. Step 307: A laser rangefinder is used to measure the deviation of the guide tube's centerline. If the deviation exceeds 5mm, the correction process is repeated until the requirements are met. In step S3, a combination of heat input control and deformation compensation is used. Precise control of welding parameters and anti-deformation technology enable active deformation management during the welding process, resulting in significantly improved guide tube positioning accuracy and stable, reliable welding quality.

[0048] The specific implementation of step S4 includes: Step 401, welding a set of reinforcing ribs every 250mm along the axial direction on the outer wall of the guide tube, each set including two circumferential reinforcing ribs and two diagonal reinforcing ribs, the reinforcing ribs using angle steel with specifications of L50×50×5; Step 402, welding one end of the circumferential reinforcing rib to the outer wall of the guide tube, and the other end to the web of the I-beam frame, the diagonal reinforcing ribs connecting the guide tube and the flange of the I-beam frame at a 45-degree angle to form a spatial triangular truss structure; Step 403, welding flanges at 50mm from the end face at both ends of the guide tube, the flanges having an outer diameter of 200mm, an inner diameter of 150mm, and a thickness of 15mm, the inner mounting section of the flange having dimensions of 10mm×1. 0mm nitrile rubber sealing ring; Step 404: Place an 8mm thick steel plate cover on the outside of the flange. A 10mm diameter air inlet hole is pre-drilled in the center of the steel plate cover. Secure the steel plate cover to the flange with 8 M12 bolts, controlling the tightening torque to 60 N·m; Step 405: Inflate the guide pipe with compressed air through the air inlet hole. During inflation, install a pressure gauge on the steel plate cover to monitor the air pressure inside the pipe in real time. When the air pressure reaches 0.05MPa, close the air inlet valve and seal the air inlet hole with a rubber plug; Step 406: Check the flange sealing effect. Apply soapy water to the cover surface and observe for bubbles. If leaks are found, tighten the corresponding bolts or replace the sealing ring. In this step S4, the principles of space truss mechanics and positive pressure isolation technology are adopted. A stable support system is constructed through multi-directional reinforced connections, and the air pressure difference is used to prevent slurry intrusion, resulting in a significant enhancement of the guide pipe's deformation resistance and effective guarantee of the pipe's cleanliness.

[0049] The specific implementation of step S5 includes: Step 501, excavating a foundation pit at the bottom of the arch foot foundation and cleaning loose rock layers, using high-pressure water to wash the bedrock surface to remove weathered layers and loose soil; Step 502, laying a 150mm thick C15 concrete cushion layer on the cleaned bedrock surface, smoothing the surface of the cushion layer and roughening it to increase roughness; Step 503, marking 10 anchor bolt drilling positions at the arch foot according to the design drawings, with the hole spacing evenly distributed within a 1m range of the arch foot width; Step 504, welding a 1.0m long guide sleeve to the corresponding anchor bolt position on the I-beam frame, the guide sleeve having an inner diameter of 110mm, ensuring that the axis of the guide sleeve coincides with the designed anchor bolt axis during welding; Step 505, drilling anchor bolts through the guide sleeve. The process involves drilling a 42mm diameter hole using a pilot drilling method to a depth of 2m, then replacing the drill bit with a reaming bit and continuing drilling to a total depth of 6m. Step 506: Every 0.5m of drilling, use an inclinometer to measure the borehole inclination angle. If the inclination angle deviation exceeds 1 degree, adjust the drilling rig angle or replace the drill bit to ensure the anchor rod penetrates the rock to a depth of 4m. Step 507: Insert a 6m long, 28mm diameter HRB400 steel rebar anchor rod into the borehole. The outer end of the anchor rod overlaps the web of the I-beam at a 30-degree angle, with an overlap length of 150mm, using single-sided welding with a weld height of 8mm. Step 508: Inject cement grout with a water-cement ratio of 0.45 into the anchor rod hole for anchoring. The grouting pressure is controlled between 0.3 and 0.5 MPa. Stop grouting when grout returns from the borehole opening. In step S5, the stress dispersion principle and guiding constraint technology are adopted. By expanding the bearing area through the concrete cushion layer and controlling the drilling direction through the guide sleeve, the technical effects of uniform distribution of foundation bearing capacity and significant improvement of anchoring effect are achieved.

[0050] The specific implementation methods for steps S6 and S7 include: Step 601: Apply a release agent to the inner wall of the guide wall template and check the stability and sealing of the template support system; Step 602: Start pouring C30 concrete in layers from the top surface of the arch foot foundation. The thickness of the first layer is controlled at 300mm. During the pouring process, use a chute or pump to slowly inject the concrete to avoid impact; Step 603: Use a low-frequency vibrator with a working frequency of 25Hz to compact the concrete. The insertion depth of the vibrator should not exceed two-thirds of the thickness of the concrete layer. During vibration, maintain a distance of more than 100mm from the guide pipe; Step 604: Install displacement sensors at key positions around the guide pipe. The sensor accuracy is 0.1mm. Automatically collect the centerline coordinate data of the guide pipe every 10 minutes; Step 605: When the displacement monitoring system shows that the deviation of the centerline position of the guide pipe exceeds... When the 9mm threshold is reached, the monitoring terminal issues an audible and visual alarm signal, and construction personnel immediately stop concrete pouring and vibration operations. Step 606: Apply corrective force in the opposite direction of the guide tube's deviation using hydraulic jacks. The jack support points are set on the I-beam frame. Torque is applied in stages, with each 50N load observed after which the displacement sensor data changes. Step 607: When the deviation of the guide tube's centerline position decreases to within 5mm, stop applying the corrective force and temporarily fix the guide tube's position using an adjustable support rod to prevent rebound. Step 608: After confirming the guide tube's position is stable, continue concrete pouring, repeating the above layered pouring and monitoring process until the guide wall concrete reaches the design elevation. Step 609: After the concrete pouring is completed, observe it statically. When the concrete surface loses its luster and leaves no obvious indentation when pressed with a finger, it is considered to have reached the initial setting state. This step employs a closed-loop management method combining real-time monitoring feedback and dynamic adjustment control. By continuously collecting displacement data through sensors and triggering corrective measures based on thresholds, it achieves enhanced controllability during construction and ensures the final positional accuracy of the guide tube.

[0051] The specific implementation of step S8 includes: Step 801, after confirming that the concrete has reached the initial setting state, slowly open the vent valve on the steel plate cap at the end of the guide pipe to release the compressed air in the pipe, controlling the release rate so that the pressure in the pipe decreases by 0.01 MPa per minute; Step 802, when the pressure in the pipe drops to equal atmospheric pressure, loosen the 8 bolts fixing the steel plate cap in sequence, using a diagonal loosening order to avoid uneven stress and deformation of the cap; Step 803, remove the rubber sealing ring on the inside of the steel plate cap and flange, and check whether the surface of the sealing ring is damaged or aged; Step 804, use high-pressure gas at 0.6 MPa to purge the residue in the pipe through one end of the guide pipe, while purging at the other end. Step 805: Place a collection container to receive the blown-out impurities; Step 806: The blowing time should be no less than 3 minutes until no visible particles are found in the gas discharged from the other end of the guide tube; Step 807: Use an endoscope to check the cleanliness of the inner wall of the guide tube from one end. The diameter of the endoscope probe should not exceed 100mm. Move it along the axial direction of the tube to observe the condition of the inner wall throughout; Step 808: When the endoscope inspection finds that there are attached substances on the inner wall of the tube, use a long-handled brush with high-pressure gas for secondary cleaning. After cleaning, check again with an endoscope to confirm that the cleanliness meets the standard; Step 809: Install temporary protective covers at both ends of the guide tube to prevent debris from entering. The protective covers are made of perforated plates that can both ventilate and block solid particles. In this step S8, a combination of gradient pressure relief and mechanical cleaning is used. By controlling the pressure release rate to avoid impact on the internal structure of the tube and using high-pressure airflow to carry away the residue, the technical effect of ensuring that the cleanliness of the tube meets the requirements of subsequent construction and protecting the integrity of the guide tube structure is achieved.

[0052] The key technical ideas of this invention include: First, an active management technology for welding deformation with pre-set anti-deformation and precise control of heat input. Traditional welding methods rely solely on post-weld correction to passively eliminate deformation. This invention, by pre-calculating the welding shrinkage and setting a reverse deviation, combined with controlling the welding line energy within the range of 15-20 kJ / cm and using the skip welding method to disperse heat input, achieves predictive compensation for deformation during the welding process. This fundamentally reduces the generation of welding deformation rather than correcting it afterward, reducing the positional accuracy of the guide tube from 10-15 mm in traditional methods to within 5 mm, and avoiding material fatigue and construction efficiency loss caused by repeated correction. Secondly, the composite protection technology of spatial truss connection system and positive pressure gas isolation addresses the challenge of traditional methods that rely solely on end sealing or single-point fixing to simultaneously solve the problems of buoyancy resistance and grout intrusion prevention. This invention utilizes a triangular spatial truss structure formed by welding circumferential and diagonal reinforcing ribs to the outer wall of the guide tube, establishing multi-point rigid connections between the guide tube and the I-beam frame. Simultaneously, 0.05MPa compressed air is injected into the sealed tube to create an outward thrust. This dual effect of mechanical constraint and air pressure isolation enhances deformation resistance and prevents grout intrusion from ports or gaps, achieving simultaneous protection of structural stability and internal cleanliness. Thirdly, the real-time monitoring-triggered threshold response and dynamic correction closed-loop control technology addresses the issue of traditional construction relying on manual visual inspection or post-construction testing, which cannot promptly detect and correct deviations. This invention uses displacement sensors deployed at key locations to continuously collect guide tube coordinate data. When the deviation exceeds a 9mm threshold, an alarm is automatically triggered, and jack correction is immediately implemented, forming a closed-loop feedback system for monitoring, judgment, correction, and verification. This transforms passive quality control into proactive process intervention, ensuring controllable positional accuracy throughout the entire construction process. The synergistic effect of the above three key technical approaches is as follows: the anti-deformation pre-positioning technology reduces welding deformation from the source; the space truss connection system provides a stable structural foundation; and the real-time monitoring closed-loop control continuously corrects deviations during construction. The three form a full-process quality assurance chain of pre-construction prevention, in-process control, and post-construction verification. Compared with the single-link control of traditional methods, this invention establishes a multi-level and multi-dimensional precision maintenance mechanism, systematically solving the technical problems of difficulty in ensuring positional accuracy during guide pipe installation, easy blockage inside the pipe, and insufficient structural stability, thus achieving an overall leap in construction quality.

[0053] It should be noted that this invention also solves the following technical problems: In the construction of pipe roofs in tunnel culverts, the arch foot foundation anchoring system suffers from high borehole deviation and stress concentration in the rock mass. Traditional anchor drilling relies on operators visually controlling the drilling direction. During the initial drilling stage, the drill rod is prone to lateral deviation, causing the bottom of the hole to deviate from the design position. Simultaneously, the arch foot foundation directly transfers concentrated loads to the rock mass contact surface, causing local stress to exceed the rock mass's compressive strength, leading to foundation settlement. This invention, by pre-embedding a 1.0m long guide sleeve at the predetermined anchor position in the arch foot foundation, constrains the initial drilling direction of the drill rod. The guide sleeve's inner hole limits the lateral displacement of the drill rod, reducing the borehole deviation to within the design requirements. Simultaneously, a 150mm thick stress diffusion pad is installed at the bottom of the foundation. The deformation characteristics of the pad material diffuse the concentrated load across the rock mass contact surface, reducing the maximum stress at the contact surface to below the rock mass's compressive strength, thus solving the technical problems of high borehole deviation and stress concentration in the rock mass.

[0054] Specifically, the principle of this invention is as follows: The invention solves the problem of guide tube position accuracy control by constructing a multi-layered position control system. The first layer of control is the I-beam frame, which, by placing its bottom on stable bedrock and using rigid connections, forms a non-deformable positioning benchmark. The second layer of control is the spatial truss connection system, which, through the principle of triangular stability, forms a rigid whole between the guide tube and the I-beam frame, enhancing anti-buoyancy performance. The third layer of control is welding process control, which minimizes welding thermal deformation by limiting linear energy input and using anti-deformation pre-setting technology. The fourth layer of control is positive pressure protective gas, which balances the lateral pressure of the concrete slurry through the outward force generated by the pressure difference. The fifth layer of control is vibration frequency control, which prevents the accumulation and amplification of vibration energy in the guide tube structure by avoiding the natural frequency. The sixth layer of control is real-time monitoring and dynamic correction, which immediately applies a reverse torque to restore the guide tube to the designed position when the position deviation exceeds a threshold. The synergistic effect of these six control layers ensures that the position accuracy of the guide tube meets the requirements of pipe roof construction throughout the entire pouring process.

[0055] The following provides a specific embodiment 1 of the present invention. The specific implementation methods of steps S1, S2, S4, S5 and S8 in this embodiment 1 are the same as those described above, and will not be repeated in detail here. The specific implementation methods of other steps are described in detail below.

[0056] The specific implementation of step S3 involves controlling the connection quality between the guide tube and the I-beam frame based on welding parameters, and the welding heat input. The calculation formula is expressed as follows:

[0057] ;

[0058] In the formula, Welding line energy, unit: ; This refers to the welding voltage, in units of... ; Welding current, unit: ; Welding speed, unit: The 1000 in the denominator is a unit conversion factor, used to convert... Convert to .

[0059] The parameter acquisition method is as follows: The value range is 15 to 20. This range was determined through welding heat deformation control experiments. The experimental procedure involved selecting 12 groups of H-beams and guide tubes for welding, with the welding heat input energy set to 10... 12 15 17 20 ,twenty three 25 Three specimens were fabricated for each welding heat input. After welding, the offset of the guide tube centerline and the deformation of the I-beam frame were measured. Experimental data showed that when the welding heat input was less than 15... Insufficient weld penetration resulted in weld strength reaching only 65% ​​of the design strength. This occurred when the welding heat input exceeded 20... When the centerline offset of the guide tube exceeds 12mm and the I-beam frame exhibits wavy deformation, the welding heat input should be controlled between 15 and 20. Within the specified range, the welding strength reaches more than 95% of the design strength and the offset of the guide tube centerline is controlled within 5mm. The value is obtained from the output voltage measurement of the welding equipment, and is usually taken as 24 to 32. . The value is obtained by measuring the output current of the welding equipment, and is usually taken as 180-250. . The welding torch movement speed is measured during the welding operation, and is typically taken as 0.3 to 0.5. .

[0060] Anti-deformation preset amount The calculation formula is expressed as follows:

[0061] ;

[0062] In the formula, This is the pre-set amount of anti-deformation, in units of... ; This is the welding shrinkage coefficient, in units of... The experience value is 3.2 ; The length of the weld is expressed in units of 1 / 200 mm. ; For reference weld length, the unit is... The experience value is 2.0. .

[0063] The parameter acquisition method is as follows: The shrinkage was determined by a welding shrinkage measurement experiment. The experiment involved welding 20 sets of I-beams and guide tubes. Before welding, a baseline was marked on the guide tube. After welding and cooling, the displacement of the baseline was measured. The experimental data showed that the welding shrinkage ranged from 2.5 mm to 3.8 mm, with an average welding shrinkage of 3.2 mm. The value is obtained by measuring the contact length between the guide tube and the I-beam frame, and is typically taken as 1.5 to 2.5. . The standardized reference length is used to normalize the shrinkage under different weld length conditions.

[0064] The specific implementation of step S6 is to control the positional stability of the guide pipe during the concrete pouring process, and the deviation of the guide pipe position. The monitoring calculation formula is expressed as follows:

[0065] ;

[0066] In the formula, This refers to the deviation in the guide tube position, in units of... ; The deviation of the guide tube centerline in the horizontal direction, in units of ; The deviation of the guide tube centerline in the horizontal longitudinal direction, in units of ; The vertical deviation of the guide tube centerline, in units of .

[0067] The parameter acquisition method is as follows: , , The difference between the centerline coordinates of the guide pipe and the design coordinates was obtained in real time by measuring the difference using a total station or laser rangefinder. The measurement interval was once after each layer of concrete was poured.

[0068] The criteria for selecting the vibration frequency are stated as follows:

[0069] ;

[0070] In the formula, The operating frequency of the vibrator, in units of ; The natural frequency of the guide tube, in units of ; The safety frequency interval coefficient is dimensionless and has an empirical value of 0.4.

[0071] The parameter acquisition method is as follows: The value is determined based on the technical parameters of the vibrating equipment, and is usually taken as 25. . The average value was obtained through calculation using the formula described later or through experimental determination, and was 48. .when At that time, the frequency avoidance requirements are met.

[0072] The specific implementation of step S7 is to perform correction when the guide tube position deviation exceeds the control threshold, and the correction torque is... The calculation formula is expressed as follows:

[0073] ;

[0074] In the formula, For the correction torque, the unit is . ; The corrective force applied to the jack, in units of ; The vertical distance from the point of application of the jack to the center line of the guide tube, in units of... .

[0075] The parameter acquisition method is as follows: The value is calculated based on the jack's output pressure and piston area, and is typically between 5000 and 15000. . The value is obtained by measuring the geometric relationship between the jack's installation position and the guide tube, and is typically taken as 0.3 to 0.8. The positional deviation control threshold is 9mm. This threshold was determined through a drilling construction adaptability experiment. The experiment involved pre-embedding guide tubes with different positional deviations in concrete test blocks. The positional deviations were 3mm, 6mm, 9mm, 12mm, 15mm, and 18mm, with 5 guide tubes pre-embedded for each deviation. Subsequent drilling was carried out through the guide tubes, and the deviation between the drilling axis and the design axis was measured. The experimental data showed that when the positional deviation of the guide tube was less than 9mm, the drilling axis deviation was controlled within 15mm, which met the requirements for pipe roof construction. When the positional deviation of the guide tube exceeded 12mm, the drilling axis deviation exceeded 25mm, affecting the quality of the pipe roof.

[0076] The concrete protective layer thickness was 21cm, which was obtained through a steel corrosion protection experiment. The experiment involved selecting 10 groups of I-beam specimens with different protective layer thicknesses ranging from 10cm to 30cm and immersing them in a simulated groundwater environment for 180 days. The rust depth on the steel surface and the carbonation depth of the concrete were measured every 30 days. The experimental data showed that when the protective layer thickness was less than 18cm, the steel rust depth exceeded 0.5mm. When the protective layer thickness reached 21cm, the steel rust depth stabilized below 0.1mm. Taking into account construction errors and long-term durability requirements, the concrete protective layer thickness was determined to be 21cm.

[0077] Guide tube natural frequency The calculation formula is expressed as follows:

[0078] ;

[0079] In the formula, The natural frequency of the guide tube, in units of ; The frequency coefficient is dimensionless. The length of the guide tube, in units of ; This refers to the elastic modulus of steel, in units of... ; The moment of inertia of the guide tube section is expressed in units of . ; The mass per unit length of the guide tube, in units of .

[0080] The parameter acquisition method is as follows: The empirical value for fixed boundary conditions at both ends is 4.73. The value is determined based on the design length of the guide tube, and is usually taken as 2.0. . The elastic modulus of steel is, empirically, denoted as . . The moment of inertia of the guide tube section is calculated based on the diameter and wall thickness of the guide tube. The calculation formula is expressed as follows:

[0081] ;

[0082] In the formula, The moment of inertia of the guide tube section is expressed in units of . ; The outer diameter of the guide tube is given in units of... ; The inner diameter of the guide tube is given in units of... .

[0083] The parameter acquisition method is as follows: The value is determined based on the outer diameter of the guide tube design, and is usually taken as 0.14. . according to Calculated, where The thickness of the guide tube wall is expressed in units of... The value is usually 0.006. ,therefore For a guide tube with a diameter of 140mm and a wall thickness of 6mm, the empirical value is... . The mass per unit length of the guide tube is calculated based on the material density and cross-sectional area of ​​the guide tube. The calculation formula is expressed as follows:

[0084] ;

[0085] In the formula, The mass per unit length of the guide tube, in units of ; This refers to the density of steel, in units of... The experience value is 7850. ; The cross-sectional area of ​​the guide tube is expressed in units of... .

[0086] cross-sectional area of ​​guide tube The calculation formula is expressed as follows:

[0087] ;

[0088] In the formula, The cross-sectional area of ​​the guide tube is expressed in units of... ; The outer diameter of the guide tube is given in units of... The value is usually 0.14. ; The inner diameter of the guide tube is given in units of... The value is usually 0.128. .

[0089] Experience value: 15.6 The natural frequency of the guide tube was determined by modal analysis. The experiment involved hammering 10 seamless steel guide tubes with a diameter of 140 mm, a wall thickness of 6 mm, and a length of 2.0 m. Vibration response signals were collected by an accelerometer and the spectrum was analyzed. The experimental data showed that the natural frequency of the guide tube was concentrated in the range of 45 Hz to 52 Hz, with an average natural frequency of 48 Hz. Therefore, a low-frequency vibrator with a working frequency of 25 Hz was selected to avoid the natural frequency of the guide tube when vibrating concrete.

[0090] It should be noted that the variables involved in this embodiment are explained in detail in Table 1.

[0091] Table 1. Variable Explanation Table

[0092]

[0093] To better understand and implement this invention, a specific application scenario, Example 2, is provided below: Under these geological conditions, the traditional guide pipe installation method generally results in a positional deviation exceeding 15mm, causing the subsequent pipe roof drilling axis to deviate from the designed position and affecting the support effect. The technical team decided to adopt the guide pipe installation method of this invention to solve the positional accuracy control problem.

[0094] During the construction preparation phase, the technical team marked the tunnel centerline on the slope surface based on the tunnel centerline control stake K5+238 and elevation control point BM12. The actual elevation of the slope surface was measured to be 742.6m. According to the design drawings, the elevation of the outer arch was determined to be 751.8m. A total station was used to set an elevation control point every 0.4m on the slope surface, and the outer arch arc was marked with an ink line to complete the establishment of the guide wall positioning benchmark. The guide wall is designed to be 2.1m thick and 11.5m high. Twenty-nine seamless steel pipe guide tubes with a diameter of 140mm, a wall thickness of 6mm, and a length of 2.0m need to be embedded inside. The guide tubes are evenly distributed along the arch, with an adjacent guide tube spacing of 0.6m.

[0095] During the I-beam frame installation phase, the technical team selected I22a I-beams and fabricated them into seven connection units. The lengths of each unit were 3.2m, 3.0m, 2.8m, 2.8m, 2.8m, 3.0m, and 3.2m, respectively. 14mm thick steel plates were used as welded connection plates between the units, and each connection point was rigidly connected using 10 M22 high-strength bolts. Figure 2 As shown, the bottom of the I-beam frame was placed on fresh bedrock after the surface weathered rock was removed by blasting. The height of the arch foot was 17cm lower than the upper excavation bottom line. The overall span of the I-beam frame was 16.4m, and the arch height was 11.8m. A 21cm gap was set between the bottom of the I-beam frame and the top surface of the inner formwork of the guide wall by welding support rods to ensure that the I-beam frame was adequately protected after the concrete was poured.

[0096] During the guide tube welding stage, the technical team employed a segmented symmetrical welding process to weld 29 guide tubes onto the I-beam frame. A ZX7-500 inverter DC welding machine was used, with a welding current set to 185A, a welding voltage set to 27V, and a welding speed controlled at 14cm / min. The calculated welding heat input was 17.9kJ / cm. Before welding, based on experimental data from welding shrinkage measurements, the centerline position of each guide tube was pre-offset by 3.2mm in the opposite direction of welding shrinkage for reverse deformation pre-setting. The welding process used a skip welding method, dividing the contact line between each guide tube and the I-beam frame into 6 segments. Segments 1, 3, and 5 were welded first, and after these segments cooled for 35 minutes, segments 2, 4, and 6 were welded. This dispersed heat input prevented localized overheating. After welding, the deviation of the centerline position of the 29 guide tubes was measured, with a maximum deviation of 0.9mm, meeting the design requirements.

[0097] During the construction phase of the space truss connection system, the technical team welded eight sets of reinforcing ribs along the axial and circumferential directions on the outer wall of each guide tube. These ribs, made of 55mm × 7mm flat steel and 0.65m in length, were welded at intervals of 0.4m along the guide tube's axial direction. Each set contained four reinforcing ribs arranged in a cross shape. One end of each rib was welded to the outer wall of the guide tube, and the other end to the web of the I-beam frame, forming a triangular stable structure. DN140 flanges were installed at both ends of each guide tube, with the flanges fully welded to the guide tube. An 8mm thick rubber sealing ring was installed on the flange, and the outer side was secured with a 10mm thick steel plate cap using eight M16 bolts. Compressed air at a pressure of 0.05MPa was injected into the guide tube using an air compressor, and the gas pressure inside the tube was monitored in real time using a pressure gauge to ensure it remained stable within the range of 0.048 to 0.052MPa.

[0098] During the arch foot foundation construction phase, the technical team excavated foundation pits at the arch foot locations on both sides of the I-beam frame. The pits were 2.8m long, 2.0m wide, and 1.3m deep. After removing loose rock from the pits, a 150mm thick C15 strength concrete stress diffusion layer was poured at the bottom of the foundation. Figure 3 As shown, 14 anchor bolts are installed on each side of the arch foot foundation. The anchor bolts are 25mm in diameter and 6m in length, arranged in a quincunx pattern on the plane, with a spacing of 0.55m between them. Figure 4 As shown, 14 guide sleeves are pre-embedded at the predetermined anchor positions in the arch foot foundation. The guide sleeves are made of seamless steel pipe with an inner diameter of 32mm and a wall thickness of 4mm, and are 1.0m long. The guide sleeves are welded to the I-beam frame. A GK-250 engineering drilling rig with a 28mm drill bit is used for drilling. The drill rod is constrained in the initial drilling direction through the inner hole of the guide sleeve. The drilling depth is 6m, and the anchor rod penetration depth is 4m. The end of the anchor rod overlaps the surface of the I-beam frame at a 15-degree angle, using a single-sided lap weld connection with a weld length of 85mm.

[0099] During the concrete pouring stage, the technical team used C30 concrete to pour the guide wall, with a concrete mix ratio of 455 kg / m³ cement. , sand 675kg / 1160kg of crushed stone 188kg of water 8.5 kg of admixtures The pouring process adopted a layered pouring method, with each layer controlled at a thickness of 290mm, rising symmetrically from the arch foot to the arch crown. The vibratory equipment used was a ZN-50 low-frequency vibrator, operating at 25Hz with a power of 1.5kW. The vibrator was inserted to a depth of 50mm, with a vibration time of 25 to 35 seconds per point and a spacing of 380mm between vibration points. During the pouring process, a total station was set up outside the guide wall. After each layer of concrete was poured, the centerline coordinates of the 29 guide pipes were measured, and the positional deviation was monitored in real time, as shown in Table 2. When the 7th layer was poured, the positional deviation of the centerline of guide pipe No. 12 reached 9.4mm, exceeding the positional deviation control threshold of 9mm. The technical team immediately stopped pouring and placed two 20-ton jacks on both sides of guide pipe No. 12, applying a reverse torque to the guide pipe through steel plate force transmission. The positional deviation was measured after each force application. After five adjustments, the positional deviation was corrected to 1.1mm, and concrete pouring continued. The entire pouring process was completed in 16 layers, with a total pouring height of 4.64m and a pouring time of 11 hours. After the concrete initially set, the vent valve on the steel plate cap at the end of the guide pipe was opened to release the positive pressure protective gas inside the pipe. The bolts and steel plate cap were then removed, and high-pressure gas at 0.6MPa was used to blow away any residue inside the pipe from one end to the other to ensure the inside of the guide pipe was clean. Figure 5 As shown, the distribution of positional deviations of the 29 guide pipes after pouring is as follows: the maximum deviation is 5.2 mm and the average deviation is 2.6 mm.

[0100] Table 2. Monitoring data on positional deviations during the casting process of some guide pipes.

[0101]

[0102] During the pipe roof drilling phase, the technical team used a guide pipe for drilling. A GD-180 geological drilling rig with a 108mm drill bit was used, and the drilling depth was 20m. The drill rod entered the rock mass through the inner hole of the guide pipe, which provided precise guidance for the initial 2.0m section. The borehole inclination was measured every 3m during drilling. The maximum deviation distance at the bottom of the hole was 0.24m, and the deviation rate was 1.2%, meeting the requirements for pipe roof construction. After drilling, a 20m long, 108mm diameter, 6mm thick steel pipe for the pipe roof was installed. Cement mortar was injected between the steel pipe and the rock mass at a grouting pressure of 1.6MPa and a single-hole grouting volume of 0.95... After all 29 steel pipes for the pipe roof were installed, a closed support system was formed, providing reliable support for subsequent excavation of the tunnel. Figure 6 As shown, the deviations between the steel pipe axis of the pipe shed and the design axis are distributed. The deviations of the steel pipe axis of all 29 pipe sheds are controlled within the allowable range of the design.

[0103] The technological advancement of this invention compared to traditional guide pipe installation methods lies in the fundamental change in the position control mechanism. Traditional methods passively resist the effects of concrete buoyancy and vibration by increasing binding points or improving support stiffness, but these measures cannot eliminate initial positional deviations caused by welding thermal deformation, nor can they respond in real-time to positional changes during the pouring process. This invention establishes a stable positioning benchmark through a rigid I-beam frame connection system, ensuring accurate guide pipe installation from the source. Welding thermal deformation is minimized through welding line energy control and anti-deformation pre-setting technology. A spatial truss connection system forms a rigid whole between the guide pipe and the I-beam frame, enhancing anti-buoyancy performance. Positive pressure protective gas balances the side pressure of the concrete slurry using pressure difference. Avoiding natural frequencies prevents the accumulation and amplification of vibration energy. Real-time monitoring and dynamic correction immediately apply a reverse torque to restore the designed position when the positional deviation exceeds a threshold. These six control levels work synergistically to construct an active position control system, forming a complete technical chain from position benchmark establishment, deformation source control, structural stiffness enhancement, pressure balancing, vibration isolation to dynamic correction, ensuring that the guide pipe's positional accuracy meets the requirements of pipe roof construction throughout the entire pouring process.

[0104] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for laying guide pipes for tunnel pipe roofs, characterized in that, The process includes establishing a guide wall positioning benchmark by marking the tunnel centerline and outer arch elevation on the slope surface based on the tunnel centerline control piles and elevation control points; installing an I-beam frame inside the guide wall and placing the bottom of the I-beam frame on stable bedrock; welding the guide pipe to the I-beam frame using a segmented symmetrical welding process; welding reinforcing ribs to the outer wall of the guide pipe to form a spatial truss connection system with the I-beam frame; filling the guide pipe with positive pressure protective gas; setting a stress diffusion pad at the bottom of the foundation and using a guide sleeve to constrain the drilling direction of the anchor bolts during the construction of the arch foot foundation; using a low-frequency vibrator when pouring the guide wall concrete in layers; monitoring the position deviation of the guide pipe in real time and immediately stopping the pouring when it exceeds the position deviation control threshold; applying a reverse torque with a jack to correct the position; and releasing the positive pressure protective gas in the guide pipe after the concrete has initially set to complete the guide pipe installation.

2. The method according to claim 1, characterized in that, The I-beam frame is divided into seven connection units, and each connection unit is rigidly connected by welded connecting plates and bolts.

3. The method according to claim 2, characterized in that, The height of the arch foot at the bottom of the I-beam frame is 15 to 20 cm lower than the bottom line of the upper excavation.

4. The method according to claim 3, characterized in that, A 21cm thick concrete protective layer is reserved between the bottom of the I-beam frame and the top surface of the inner formwork of the guide wall.

5. The method according to claim 4, characterized in that, The welding heat input is controlled within the range of 15 to 20 kJ / cm. The welding process adopts the skip welding method and performs reverse deformation pre-setting.

6. The method according to claim 5, characterized in that, Anti-deformation presetting refers to calculating the expected deformation value based on the welding shrinkage amount before welding and setting a deviation value opposite to the welding shrinkage direction on the I-beam frame or guide tube in advance.

7. The method according to claim 6, characterized in that, The skip welding method refers to welding long welds by intermittently skipping sections, welding several short, dispersed sections first, and then welding other sections after the short sections have cooled down.

8. The method according to claim 7, characterized in that, The space truss connection system refers to a structural form in which multiple sets of reinforcing ribs are welded along the axial and circumferential directions on the outer wall of the guide tube to form a multi-point rigid connection between the guide tube and the I-beam frame in three-dimensional space.

9. The method according to claim 8, characterized in that, Flanges and rubber sealing rings are installed at both ends of the guide tube, and the outer side is secured with bolts to the steel plate cover.

10. The method according to claim 9, characterized in that, The positive pressure protective gas is compressed air with a pressure of 0.05 MPa. The outward thrust formed by the internal and external pressure difference prevents concrete slurry from entering the pipe from the pipe end or the gap in the pipe wall.

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