A pipe-roof method for box culvert jacking construction under airport runway

Abstract

The application relates to the field of pipe curtain jacking technology, in particular to a pipe curtain jacking construction method for a box culvert under an airport runway, which has the beneficial effects that: through the device with real-time precision adjustment and monitoring, strict precision control is realized on each process in the jacking process, problems are found and timely measures are taken for correction, each monitoring point in the jacking process communicates through a intercom, timely and effective construction is ensured, the construction precision in the jacking process is improved, deviation is avoided, and the protection of the soil layer is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of pipe jacking technology, specifically to a method for constructing a box culvert under an airport runway using the pipe jacking method. Background Technology

[0002] During tunnel construction, the most common method is to use the pipe jacking method for box culverts. During normal jacking, common measuring devices are used for position correction.

[0003] However, in the actual jacking process, because the jacking process of the pipe jacking method requires cutting the soil layer, there is a large interaction force at the jacking position. As a result, during the jacking process, the cutting head is very easy to deviate due to the interaction force. The existing equipment lacks a precision adjustment device, which causes the error to accumulate during the jacking process. Therefore, after the jacking, it is necessary to repair the direction and inner contour dimensions of the tunnel, which seriously affects the processing efficiency and prolongs the construction period. Summary of the Invention

[0004] The purpose of this invention is to provide a method for jacking a box culvert under an airport runway using the pipe jacking method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for jacking a box culvert under an airport runway using the pipe jacking method, the method comprising:

[0007] S1: Construction Preparation

[0008] According to the design plan, multiple sets of jacks are arranged on the bottom plate of the tunnel jacking method for tunneling under the main runway of the airport. They are symmetrically arranged on the left and right sides with the center of the frame as the axis, and a hydraulic transmission system is set up to match the jacks.

[0009] S2: Tunnel Start

[0010] After the precast main body of the tunnel is poured, the grid loader head is hoisted into the working shaft and installed and debugged in the working shaft. Then the initial demolition work is carried out. The retaining structure of the working shaft is a 120cm thick retaining pile. Before exiting the tunnel, the steel concrete on the tunnel section needs to be removed. A sample hole is opened at the starting tunnel entrance of the working shaft to observe the actual situation of soil reinforcement before the concrete removal work at the tunnel entrance is carried out. Before the tunnel starting tunnel entrance is removed, the grid loader head has been installed in the correct position in the working shaft. Then the starting tunnel entrance is removed.

[0011] S3: Water-stopping device installation. The water-stopping device at the tunnel entrance is installed on the pipe curtain ring beam. The pre-embedded steel plate of the water-stopping device is anchored to the pipe curtain ring beam with steel bars and fixed around the pipe curtain ring beam with bolts.

[0012] S4: Push the machine head into the tunnel entrance. After starting, use the hydraulic cylinder of the jack to push the machine head and the first tunnel section toward the starting tunnel entrance. The pushing speed can be appropriately increased to 10cm / min. At the same time, a laser theodolite is installed in the buried section. Every 50cm of advance, the left and right attitude of the tunnel is checked until the machine head is in close contact with the reinforced soil.

[0013] S5: Jacking process:

[0014] Test jacking: The test jacking work continues until the tunnel is jacked. The test jacking work involves operating all the jacks to push out together. When the jacking blocks touch the tunnel and overcome the starting resistance of the tunnel, the tunnel is jacked and the pressure drops rapidly. The highest pressure value read on the pressure gauge at this time is converted into the starting thrust of the tunnel. The first section of the tunnel is used as the test section. Information is fed back in a timely manner based on the monitoring data to select various construction parameters from theory and experience for subsequent jacking and crossing.

[0015] Jacking: This involves starting a high-pressure oil pump, which causes the jacks to be subjected to hydraulic pressure and generate jacking force, pushing the tunnel forward. After the tunnel advances one step, the piston of the jack returns to its original position, and C30 plain concrete blocks are placed in the gap. This cycle is repeated until the tunnel is in place.

[0016] Excavation and transportation: After the jacking begins, the excavator excavates, turns over and loads soil into the tunnel using the machine head. During the excavation, the machinery excavates 30cm-40cm of soil in front of the tunnel at a slope of 1:0.33. The main jacking pushes the tunnel forward, which is one jacking work cycle.

[0017] S6: Monitoring and adjustment, through technical personnel to conduct precision monitoring of the construction site, and the precision detection benchmark is calibrated at intervals by the detection components;

[0018] S7: Assisted propulsion. During tunnel advancement, mud or mud with added water-stopping agent is injected between the tunnel and the pipe curtain to fill the construction gap between the tunnel and the pipe curtain in a timely manner.

[0019] S8: Tunnel Reception and Slurry Solidification

[0020] When the tunnel boring machine (TBM) is 10m from the receiving shaft entrance, a survey is conducted along the entire tunnel to correct the advance axis. After the tunnel enters the reinforced area of ​​the receiving shaft entrance, the left and right attitude of the TBM is checked every 50cm to ensure that the TBM accurately enters the receiving shaft entrance. When the TBM head is 0.3m from the receiving shaft entrance, the advance speed is slowed down again, and the TBM slowly moves towards the outside of the receiving shaft retaining piles. At this time, grouting is carried out in the grouting holes throughout the tunnel to ensure the mud pressure around the tunnel. At the same time, the removal of the underground wall of the receiving shaft begins. After the concrete and steel bars inside the receiving shaft entrance are cleared, the TBM head cuts into the entrance at the fastest speed to complete the entry and reception.

[0021] After the slurry solidifies and the tunnel jacking is completed, the slurry between the tunnel and the pipe curtain needs to be replaced. The replacement slurry can be a mixture of cement and fly ash, forming a cement slurry sleeve around the tunnel to bear the upper load. There is a grouting section every 6 meters around the tunnel. The cement slurry still uses the same grouting hole. The surface deformation is controlled by the grouting pressure and injection volume. After the cement slurry solidifies, multiple sets of transverse support beams spaced 6 meters apart are formed.

[0022] Preferably, in step one, the jacks are fixed on the support and symmetrical to the vertical line of the center of the force transmission column. The point of application of their resultant force should be on the vertical line of the center of the force transmission column. The oil circuits of the jacks should be connected in parallel. Each jack has an oil inlet and outlet control system. The hydraulic transmission system includes a power mechanism, a high-pressure oil pump, an oil tank and its auxiliary devices.

[0023] Preferably, during the jacking process, the excavation in front of the tunnel frame leaves 10cm above the bottom slab to ensure the tunnel continues to advance at a level slope. Timely monitoring and observation are conducted, with leveling observation points set at the four corners of each frame. A central observation scale is set at the centerline of the front and rear ends of the tunnel roof slab, with the scale suspended on the roof to ensure that surveyors can simultaneously observe two scales at the rear end (both the total station and level are mounted on a sliding plate). The axis and elevation are observed after each jacking stroke of the tunnel frame, and any deviations are corrected promptly. Deviations in the centerline can be addressed by adjusting the torque of the jacks on the tunnel centerline. The horizontal elevation deviation of the tunnel frame is controlled by the jacking excavation.

[0024] Preferably, in step two, scaffolding is erected in front of the tunnel boring machine. The concrete at the tunnel entrance must be removed in layers and blocks, from top to bottom and from middle to edge, in an orderly manner. Since the retaining piles are reinforced concrete, the surface concrete layer is removed first to expose the inner reinforcing bars, which are then cut. Subsequently, a concrete layer of about 50-60cm thickness is removed, and the concrete is removed in blocks down to the outer reinforcing bars, while retaining the outer reinforcing bars. Before cutting the connected reinforcing bars, each block of concrete must be firmly supported with wooden supports, and lifting points must be chiseled out and the lifting jacks must be attached. The lifting of concrete blocks at the entrance should follow the order of "top to bottom and from middle to edge". Before the welder cuts the connecting reinforcing bars, the crane operator fixes the wire rope to the lifting points. After the reinforcing bars are cut, the concrete blocks fall off naturally and are then lifted away from the working shaft by the crane. The entrance after the concrete of the ground wall is removed must be cleaned, and the remaining reinforcing bars at the entrance must be cut off.

[0025] Preferably, the following should be done during the test top:

[0026] ① There are designated personnel at each relevant location and observation point to monitor changes at all times;

[0027] ②After starting the pump, the pump must be stopped and observed whenever the oil pressure rises by 5-10MPa. If any abnormality is found, it should be dealt with promptly.

[0028] ③When the jack piston begins to extend and the jack block is pressed down, stop jacking immediately. After checking the condition of each part, if there are no abnormalities, the pump can be restarted until the tunnel starts.

[0029] ④ After the trial jacking is completed, a comprehensive inspection should be carried out. If all conditions are good, the formal jacking operation can be carried out.

[0030] Preferably, in step five, the force-transmitting concrete blocks need to be replaced or replenished as needed according to the jacking length. The placement of the concrete blocks must be consistent with the jacking axis and perpendicular to the crossbeam. During jacking, the centerline and horizontal level are observed and recorded after each jacking operation. At the same time, the construction supervisor and technicians make specific adjustments as needed to prevent head-up, head-down, or tilting. In particular, the direction is strictly controlled during the empty jacking period to prevent deviation from the centerline. The direction is adjusted by adding or removing jacks to ensure that there is no deviation in direction when the front end of the main body enters the soil.

[0031] Preferably, the excavation slope of the jacking excavation shall not be steeper than the cutting edge slope, the advance step shall not exceed 0.5m each time, the excavation shall be carried out from top to bottom, and the reverse slope excavation shall be strictly prohibited. The slope surface shall be kept smooth, and the jacking shall be carried out while excavating. The soil on both sides of the cutting edge shall be excavated to the center of the side wall, and the soil at the bottom shall be excavated to 400mm on the bottom surface of the bottom plate. Each pick shall ensure that the box body and the soil layer are compacted without gaps.

[0032] Preferably, the monitoring content in step six mainly includes: measurement and prediction of the jacking direction of the box body; monitoring of the jacking force, sliding plate and back of the box body during the jacking process; monitoring of the soil quality at the jacking front; directing the excavation team to excavate; directing the jacking jack team to start and stop the jacking equipment; providing instructions according to the proposed plan; measuring during the jacking process; and analyzing the operating trend of the box body based on the recorded data.

[0033] Preferably, in step seven, during tunnel advancement, two independent grouting systems are established: synchronous grouting (A grout) and supplementary grouting (B grout). Different grout ratios, grouting equipment, and grouting controls are used. The synchronous grouting (A grout) provides support grouting for the pipe curtain, while the supplementary grouting (B grout) provides lubrication grouting for the pipe curtain.

[0034] The synchronous grouting (A-grout) system is controlled together with the grid tool head;

[0035] The supplementary grouting system (B grout) is equipped with a supplementary grouting control console. The start and grouting position of the supplementary grouting are jointly controlled based on the thrust magnitude, the mud pressure box pre-embedded at the top of the tunnel, settlement monitoring, and other factors.

[0036] Preferably, the detection component in step six includes a push plate. One side of the push plate is fixedly connected to the excavator's outer shell by four sets of telescopic rods arranged in a circumferential array. The excavator is equipped with a drive component, which includes a motor-driven shaft and an excavator head fixed on the shaft. An inner tube is provided in the middle of the push plate, and an outer tube is provided on the outside of the inner tube. A stepped inner cavity is provided between the inner and outer tubes. The inner diameter of the inner tube is smaller than the inner diameter of the outer tube. Multiple sets of first telescopic detection rods and second telescopic detection rods are arranged in a circumferential array on the arc-shaped outer walls of the push plate and the outer tube, respectively. An outer sleeve is provided on the outer wall of the drive component and fitted onto the shaft. The outer sleeve faces the port of the stepped inner cavity. An annular sleeve with an outer diameter larger than the second telescopic detection rod is provided on the outer wall of the excavator. A limit cap is provided at the outer end of the second telescopic detection rod. A pointed cone is provided on the outer end face of the limit cap. A stepped rod is provided in the middle section of the shaft. The stepped rod is located in the gap between the outer tube and the outer sleeve.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] This invention employs a device with real-time precision adjustment and monitoring to strictly control the precision of each process during jacking, promptly taking corrective measures when problems are detected. During the jacking process, each monitoring point communicates via walkie-talkie to ensure timely and effective construction, thereby improving the construction precision during jacking, avoiding deviation, and effectively improving the protection of the soil layer.

[0039] At the same time, the detection components are used to correct the reference of the precision measurement equipment in real time, avoiding the reduction in detection accuracy caused by the overall offset of the device, thereby further improving the detection of construction accuracy. Attached Figure Description

[0040] Figure 1 This is a flowchart of the construction accuracy testing process of the present invention;

[0041] Figure 2 This is a three-dimensional structural diagram of the detection device of the present invention;

[0042] Figure 3 This is a schematic diagram of the pusher plate structure in the detection device of the present invention;

[0043] Figure 4 This is a schematic diagram of the connection structure between the push plate and the rotating shaft in the detection device of the present invention;

[0044] Figure 5 This is a flowchart illustrating the construction process of the present invention.

[0045] In the diagram: 1. Push plate; 2. Telescopic rod; 3. First telescopic detection rod; 4. Inner tube; 5. Outer tube; 6. Through the inner cavity of the stepped structure; 7. Second telescopic detection rod; 8. Circular sleeve; 9. Outer sleeve; 10. Rotating shaft; 11. Limiting cover; 12. Pointed cone; 13. Stepped rod. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Please see Figures 1 to 5 The present invention provides a technical solution:

[0048] A method for jacking a box culvert under an airport runway using the pipe jacking method, the method includes:

[0049] 1. Construction Preparation

[0050] The preparatory work before tunnel jacking should comply with the following regulations:

[0051] ① A comprehensive inspection and acceptance should be carried out on the bridge structure and its backing, and the concrete strength of the main tunnel should meet the design requirements.

[0052] ②After the jacking equipment and site lighting are installed, the jacking hydraulic system should meet the requirements after trial operation.

[0053] ③ After the observation instruments, observation points, and scales are installed and calibrated, they should be aligned with the reference point and the initial readings should be taken.

[0054] ④ An on-site command structure should be established, a list of on-site personnel should be compiled, and their division of labor and responsibilities should be clearly defined, with responsibilities assigned to specific individuals.

[0055] ⑤ Excavation machinery, access roads, and soil stockpiling sites should be arranged and ready, and all personnel should be on duty and conduct technical briefings before the jacking operation.

[0056] ⑥ Accurately measure the axis and elevation of the box body, prepare lighting, complete the tunnel waterproofing layer and test roof work, and hoist the top iron, force transmission plain concrete blocks and rear pad steel plates and other facilities to the site.

[0057] Jacking equipment and layout

[0058] According to the design plan, a total of 90 250T jacks were selected. The jacks were arranged symmetrically on both sides of the base plate of the tunnel jacking method for tunneling under the main runway of the airport, with the center of the frame as the axis. The jacks should be fixed on the support and symmetrical with the vertical line of the center of the force transmission column. The point of application of their resultant force should be on the vertical line of the center of the force transmission column. The hydraulic circuits of the jacks should be connected in parallel, and each jack should have a control system for oil inlet and outlet.

[0059] The tunnel's advancement is achieved using C35 plain concrete force-transfer blocks. The specific size of the concrete force-transfer blocks can be adjusted by the construction unit according to the site conditions, but it must be ensured that the tunnel is subjected to uniform stress. The jacking structure is made of four 43# rails with welded steel plates at both ends, with lengths of 1m, 2m, and 4m. The arrangement of the power mechanism, high-pressure oil pump, oil tank, and auxiliary devices of the hydraulic transmission system, the use of oil pumps and jacks should be compatible, and the installation of hydraulic system oil pipes should meet the following requirements:

[0060] ① The inner diameter of the oil pipe should be determined according to the flow rate, but the inner diameter of the main oil pipe in the return oil line should not be less than 10mm, and the inner diameter of the branch oil pipe should not be less than 6mm. Grease should be filtered, the oil pipes should be clean, the oil circuit should be reasonably arranged, the seals should be good, and adjustments and controls should be convenient without affecting construction work.

[0061] ② Each component of the hydraulic system should undergo individual testing. Only after passing the test can it be installed. After all components are installed, a trial run must be conducted. The oil circuit, jacks, and control box must be thoroughly inspected to ensure they meet the requirements before use.

[0062] ③ During the jacking process, if the hydraulic system malfunctions, it is strictly forbidden to make adjustments or controls while the system is in operation, in order to prevent injury.

[0063] Jacking direction and elevation control

[0064] During jacking, the soil in front of the tunnel frame is excavated to leave 10cm above the bottom slab to maintain the tunnel's continuous horizontal slope and ensure timely monitoring. Leveling observation points are set at the four corners of each frame, and a central observation scale is set at the centerline of the front and rear ends of the tunnel roof slab. The scale is suspended from the roof slab to ensure that surveyors can simultaneously observe two scales at the rear end (the total station and level are both mounted on sliding plates). The axis and elevation are observed after each jacking stroke of the tunnel frame. Deviations are corrected promptly, with a gradual correction principle. Deviations in the centerline can be addressed by adjusting the torque of the jacks on the tunnel centerline. The horizontal elevation deviation of the tunnel frame is controlled by the jacking excavation, specifically: excavate more if too high, and less if too low. Excavation advance is controlled in 0.5-meter increments. During excavation, the excavator is under the direct supervision and protection of a designated person. Excavation beyond the permitted distance is strictly prohibited. The height and rotation angle of the excavator boom are strictly controlled to ensure jacking safety.

[0065] 2. Tunnel Start

[0066] After the precast main tunnel structure is completed, the grid demolition machine head is hoisted into the working shaft and installed and debugged there before the initial demolition work begins. The working shaft retaining structure consists of 120cm thick retaining piles. Before exiting the tunnel, the reinforced concrete on the tunnel cross-section needs to be removed. Before removing the tunnel portal, the relevant reinforcement test report should be checked. The reinforced soil must meet the design requirements for unconfined compressive strength, permeability coefficient, self-supporting capacity, and other technical indicators. Then, a sample hole is opened at the starting tunnel portal in the working shaft to observe the actual situation of the soil reinforcement before proceeding with the concrete removal work at the portal. Before removing the tunnel portal, the grid demolition machine head is already correctly installed and positioned inside the working shaft.

[0067] Scaffolding is erected in front of the tunnel boring machine. The concrete at the tunnel entrance must be removed in layers and sections, from top to bottom and from the middle to the edges, in an orderly manner. Since the retaining piles are reinforced concrete, the surface concrete layer is removed first to expose the inner reinforcing bars, which are then cut off. Subsequently, approximately 50-60cm of concrete is removed, and the process is repeated in sections down to the outer reinforcing bars, while retaining the outermost reinforcing bars. During the removal of the tunnel entrance, to ensure the stability of the soil at the entrance and the safety of personnel working near the entrance, the soil properties must be monitored, and water seepage must be observed.

[0068] Finally, before cutting the connecting reinforcing bars, each concrete block must be firmly supported with wooden supports, and lifting points must be chiseled out and hoisting jacks attached. When lifting concrete blocks from the opening, the order should be "top to bottom, middle to edges." Before the welder cuts the connecting reinforcing bars, the crane operator must secure the wire rope to the lifting points. After the reinforcing bars are cut, the concrete block will fall naturally and then be lifted away from the working shaft by a crane. The opening after the concrete wall has been chiseled out must be cleaned, and any remaining reinforcing bars at the opening must be cut off.

[0069] Water-stopping device installation

[0070] The tunnel portal water-stopping device is installed on the pipe jack ring beam. The pre-embedded steel plate of the water-stopping device is anchored to the pipe jack ring beam with steel bars and fixed around the circumference of the pipe jack ring beam with bolts. Considering the large grouting pressure between the tunnel and the pipe jack, a curtain rubber plate is used for the tunnel portal water-stopping device to achieve a good water-stopping effect. Before the box culvert starts, the portal dimensions are checked and measured again to ensure that they meet the necessary space for the box culvert to start. After confirming that there are no foreign objects at the starting portal and that the water-stopping device is functioning properly, the machine head and the first tunnel section are advanced towards the starting portal by the hydraulic cylinder of the jack. The advancing speed can be appropriately increased, up to 10cm / min. At the same time, a laser theodolite is installed in the buried section. Every 50cm of advancement, the left and right posture of the tunnel is checked to ensure that the tunnel machine head quickly and accurately cuts into the portal until the machine head is in close contact with the reinforced soil.

[0071] The first box culvert section's initial vertical orientation

[0072] During the advancement of the box culvert, the propulsion force acts on the bottom slab of the box culvert, creating an upward lifting moment on the main body of the box culvert and the machine head. Therefore, the machine head may "lift up." In addition, the machine head and the main body of the box culvert are quite heavy, and when advancing to the undisturbed soil, the box culvert may "drag down."

[0073] With the lower pipe jacking serving as a constraint, the likelihood of the excavator head "diving" is low. Furthermore, the excavator head has a significant weight, resulting in a large "diving" moment, and subsequent box culvert advancement will not result in any "head-up" phenomenon.

[0074] Test jacking: Test jacking continues until the tunnel is jacked up. This involves operating all jacks simultaneously to push the tunnel forward until the jacking blocks touch the ground. Once the tunnel's starting resistance is overcome, the tunnel is jacked up, and the pressure drops rapidly. The highest pressure value read on the pressure gauge at this point, after conversion, represents the starting thrust of the tunnel. The first tunnel section serves as the test section. Information is promptly fed back based on monitoring data to inform subsequent jacking operations. Various construction parameters are selected theoretically and empirically. During test jacking, the following should be observed:

[0075] ① There are designated personnel at each relevant location and observation point to monitor changes at all times;

[0076] ②After starting the pump, the pump must be stopped and observed whenever the oil pressure rises by 5-10MPa. If any abnormality is found, it should be dealt with promptly.

[0077] ③When the jack piston begins to extend and the jack block is pressed down, stop jacking immediately. After checking the condition of each part, if there are no abnormalities, the pump can be restarted until the tunnel starts.

[0078] ④ After the trial jacking is completed, a comprehensive inspection should be carried out. If all conditions are good, the formal jacking operation can be carried out.

[0079] Jacking: Before jacking, the following conditions must be met before construction can begin: the main structure concrete and the back beam concrete must reach 100% strength. The jacking equipment must be in good working order. Jacking involves starting the high-pressure oil pump, causing the jacks to generate jacking force under hydraulic pressure, propelling the tunnel forward. After the tunnel advances one section, the piston of the jack returns to its original position, and C30 plain concrete blocks are placed in the gap. This cycle is repeated until the tunnel is in place. When the tunnel is jacked on the working pit slide, special attention should be paid to the tunnel's axial direction. Tunnel jacking should be carried out in three shifts continuously to keep the tunnel advancing. The force-transmitting concrete blocks should be replaced or replenished as needed according to the jacking length. The concrete blocks must be placed in line with the jacking axis and perpendicular to the crossbeam. During the jacking process, the tunnel axis and elevation should be observed and recorded in detail after each jacking stroke. If any deviation is found, the jacking commander should be notified immediately to take corrective measures.

[0080] Excavation and soil transportation: During the jacking process, two 1m3 excavators are used for soil excavation and transfer in each hole. After the jacking begins, the excavators use their tool heads to excavate, turn over, and load soil into trucks inside the tunnel. Local corners are cleaned manually.

[0081] During tunneling, the machinery excavates 30-40cm of soil in front of the tunnel at a strict slope of 1:0.33. One tunneling cycle is achieved by the main jacking pushing the tunnel forward. The excavation depth and slope are strictly determined based on the soil conditions, and over-excavation should be avoided.

[0082] Excavators are stationed inside the tunnel to excavate. The excavator operation at the tunnel front, the excavation face, and the excavation elevation are all directed by designated personnel; excavation is prohibited without supervision. When excavating inside the tunnel, large-amplitude movements are strictly prohibited to avoid contact with the overhead excavator head or the tunnel roof. To shorten the jacking period, workers operate on an 8-hour, 3-shift system, with machinery operating continuously 24 hours a day, ensuring continuous operation even when personnel stop.

[0083] Precautions:

[0084] ① Before jacking, a detailed construction plan should be developed based on the actual situation to ensure operational safety, construction safety, personal safety, jacking progress, and quality control during the jacking process.

[0085] ② When jacking up the soil, the excavation slope should not be steeper than the cutting edge slope. Each advance should not exceed 0.5m. Dig frequently and jack up quickly.

[0086] ③ The central aspect of on-site jacking work is jacking. A comprehensive inspection of the equipment is conducted before each jacking operation. During jacking, the excavation, jacking, and jacking cessation are all under the unified command of the construction supervisor, and orders must be strictly followed.

[0087] ④ During the jacking process, the centerline and level are observed and recorded after each jacking operation. Simultaneously, the construction supervisor and technicians make specific adjustments as needed to prevent issues such as head-up, head-down, or skewing. In particular, the direction is strictly controlled during the unjacking phase to prevent deviation from the centerline. The direction is adjusted by adding or removing jacks to ensure that the front end of the main structure enters the soil without deviation.

[0088] ⑤ Excavation inside the tunnel shall be carried out under the unified command of the construction supervisor. Each excavation shall be carried out after a comprehensive inspection by the construction supervisor. The slope of the excavation shall be determined by the technicians and the site supervisor according to the soil conditions. During excavation, it is strictly forbidden to over-excavate or under-excavate at will, and it is strictly forbidden to remove soil from the bottom. Excavation shall be carried out from top to bottom, and it is strictly forbidden to excavate against the slope. The slope shall be kept smooth, and the top shall be lifted as the excavation is carried out.

[0089] ⑥ Over-excavation is strictly prohibited. Excavate the soil on both sides of the cutting edge to the center of the side wall, and excavate the soil at the bottom to 400mm above the bottom surface of the base plate. Ensure that the box body and the soil layer are tightly squeezed together without gaps with each pick.

[0090] Monitoring and control measures for the jacking process are implemented by technical personnel conducting precision monitoring of the construction site, with precision testing benchmarks being calibrated at intervals using testing components.

[0091] As the core team of the frontline construction, the construction technicians are responsible for monitoring the entire construction process. Their duties mainly include: measuring and predicting the direction of the jacking of the box girder; monitoring the jacking force, sliding plate, and backrest during the jacking process; monitoring the soil conditions at the jacking front; directing the excavation team; directing the operation of the jacking jacks; and providing instructions according to the planned scheme. During the jacking process, measurements are taken continuously, and the recorded data is analyzed to determine the box girder's operational trend. Problems are identified and corrective measures are taken promptly. Communication between monitoring points is maintained via walkie-talkies to ensure timely and effective construction.

[0092] Box jacking attitude control

[0093] (1) Measures to ensure direction

[0094] ① Guide blocks are installed every 1.6m on both sides of the sliding plate to horizontally tighten the box body during jacking and limit lateral displacement;

[0095] ② During the jacking process, try to maintain balanced jacking. If a large deviation is found on the left or right, adjust by increasing or decreasing the jacking force on one side or by digging soil.

[0096] (2) Measures to ensure elevation

[0097] ① An 8.3m foundation reinforcement section (2m thick C20 plain concrete) is set at the front end of the jacking, and the bottom pipe curtain is equipped with reinforced concrete beams. The bottom pipe curtain steel pipe (filled with concrete inside) has high overall rigidity to ensure that the tunnel will not "head-slam" during jacking.

[0098] ② Ensuring the construction accuracy of the bottom pipe curtain steel pipe can effectively guarantee that the jacking frame slides on the bottom pipe curtain, so that the jacking tunnel can advance according to the design elevation.

[0099] ③ When jacking the tunnel, pay attention to preserving the soil between the top of the tunnel and the top layer of the pipe curtain. When installing the grid tool head, raise it 1cm higher than the top elevation of the frame to ensure that the frame will not "raise its head" during jacking.

[0100] ④ If the elevation is found to be too high during the jacking process, it can be gradually adjusted by over-excavating slightly below the bottom plate at the front end of the bottom plate.

[0101] (3) Method for adjusting the left and right deviation of the box

[0102] ① Adjust the jacking force on one side by opening or closing the valve on one side of the jack to increase or decrease the jacking force. If the jack deflects to the left, close the valve on the right side to reduce the jacking force; if it deflects to the right, do the opposite.

[0103] ② Start both high-pressure oil pumps to adjust; if it deviates to the left, start the left high-pressure oil pump, and if it deviates to the right, start the right high-pressure oil pump.

[0104] ③ Adjustment of the back support blocks (columns): When adding or replacing back support blocks, depending on the magnitude of the deviation, wed one side of the back support block tightly and the other side loosely or leave a gap of about 10cm. If the tunnel front end deviates to the right, leave a gap in the left side of the back support block. After starting the pump, the right side will be pushed forward first, while the left side remains stationary. During adjustment, the regularity should be explored and mastered, and attention should be paid to the changes caused by uneven stress on the tunnel.

[0105] Thixotropic mud drag reduction: During tunnel advancement, mud or mud with added water-stopping agent is injected between the tunnel and the pipe curtain to fill the construction gap between the tunnel and the pipe curtain in a timely manner, maintain the support, lubrication and water-stopping of the tunnel and the pipe curtain, control the surface deformation caused by tunnel advancement, and effectively reduce the jacking resistance.

[0106] During tunnel construction, it is planned to establish two independent grouting systems: synchronous grouting (A grout) and supplementary grouting (B grout), employing different grout ratios, grouting equipment, and grouting control methods. Synchronous grouting (A grout) will primarily focus on providing good pipe curtain support and water retention, while supplementary grouting (B grout) will primarily focus on lubrication and friction reduction.

[0107] The synchronous grouting (A-grout) system is controlled together with the grid grouting head. The grout used is a thick grout with a high bentonite content, relatively poor fluidity, and good water retention and support. The grouting control is adjusted according to the actual grout mix ratio and the results of on-site commissioning.

[0108] The supplementary grouting system (B grout) is equipped with a separate control console, operated by a designated person. The initiation and injection location of the supplementary grouting are jointly controlled based on the thrust magnitude, the pre-embedded mud pressure box at the tunnel top, and settlement monitoring. The supplementary grouting system uses a low-bentonite content grout, which has relatively good fluidity but poor water retention and support. Grouting control is based on the actual grout mix ratio and on-site adjustment of control parameters.

[0109] Tunnel reception and mud solidification

[0110] (1) Tunnel boring machine receiving

[0111] When the tunnel boring machine is 10m away from the receiving shaft, the entire tunnel is surveyed and oriented to correct the advance axis, providing a theoretical basis for accurately entering the receiving shaft.

[0112] After the tunnel enters the reinforced area of ​​the receiving shaft entrance, the tunnel boring machine's (TBM) left and right posture is checked every 50cm to ensure precise entry into the receiving shaft entrance. When the TBM head is 0.3m away from the receiving shaft entrance, the advancing speed is slowed down again, and it slowly moves towards the outside of the receiving shaft retaining piles. At this time, grouting is carried out in the grouting holes throughout the tunnel to ensure mud pressure around the tunnel perimeter; simultaneously, the removal of the underground wall of the receiving shaft begins. After the concrete and steel bars inside the receiving shaft entrance are cleared, the TBM head cuts into the entrance at the fastest speed, completing the entry and receiving process.

[0113] (2) Slurry solidification

[0114] After the tunnel jacking is completed, the slurry between the tunnel and the pipe curtain needs to be replaced. The replacement slurry can be a mixture of cement and fly ash.

[0115] A cement grout sleeve is formed around the tunnel to bear the load from the upper part. There is a grouting section every 6 meters around the tunnel. The cement grout is still injected through the same grouting holes. The surface deformation is controlled by the grouting pressure and injection volume. After the cement grout solidifies, it is equivalent to forming a transverse support beam every 6 meters. Even if some mud between the beams has not solidified, the load can be transferred to the tunnel due to the pipe curtain effect, so as not to cause a large post-construction settlement.

[0116] In step six, the detection component includes a push plate 1. One side of the push plate 1 is fixedly connected to the excavator's outer shell by four sets of telescopic rods 2 arranged in a circumferential array. The excavator is equipped with a drive component, which includes a motor-driven rotating shaft 10 and an excavator head fixed on the rotating shaft 10. An inner tube 4 is arranged in the middle of the push plate 1, and an outer tube 5 is arranged on the outside of the inner tube 4. A through-step inner cavity 6 is arranged in the inner cavity between the inner tube 4 and the outer tube 5. The inner diameter of the inner tube 4 is smaller than the inner diameter of the outer tube 5. Multiple sets of first telescopic detection rods 3 and second telescopic detection rods 7 are arranged in a circumferential array on the arc-shaped outer walls of the push plate 2 and the outer tube 5, respectively. An outer sleeve 9 is sleeved on the rotating shaft 10 on the outer wall of the drive component. The outer sleeve 9 is directly opposite the port of the through-step inner cavity 6. A ring sleeve 8 with an outer diameter larger than the second telescopic detection rod 7 is arranged on the outer wall of the excavator.

[0117] By setting up the cooperation between the second telescopic detection rod 7 and the circular sleeve 8, the installation accuracy of the outer sleeve 9 is tested when the excavator is used as the detection reference.

[0118] The outer end of the second telescopic detection rod 7 is provided with a limit cover 11, and a pointed cone 12 is provided on the outer end face of the limit cover 11. A stepped rod 13 is provided in the middle section of the rotating shaft 10, and the stepped rod 13 is located in the gap between the outer tube 5 and the outer sleeve tube 9.

[0119] By setting a limit cover 11, the second telescopic detection rod 7 is protected when it is retracted, and the pollutants generated by the excavator are prevented from affecting the second telescopic detection rod 7. By setting a pointed cone 12, it is made to abut against the inner wall of the ring sleeve 8, thereby achieving the purpose of accuracy detection.

[0120] During the jacking process, before each accuracy test, the push plate 1 is driven forward by the telescopic rod 2, so that the through-step inner cavity 6 is sleeved on the rotating shaft 10. The first telescopic detection rod 3 extends and abuts against the inner wall of the excavated tunnel to detect the center position of the rotating shaft 10 relative to the inner contour of the tunnel. Then, the push plate 2 is driven back by the telescopic rod 2. Due to the step rod 13, the through-step inner cavity 6 is sleeved on the outer sleeve 9. The front end of the through-step inner cavity 6 is separated from the outer wall of the rotating shaft 10 and is gapped on the outside of the step rod 13. At this time, the second telescopic detection rod 7 is driven to extend to detect the position of the drive component relative to the excavator shell.

[0121] When the error of the second telescopic detection rod 7 is too large, it indicates that the excavator head has shifted relative to the excavator's outer shell. When the detection error of the first telescopic detection rod 3 is too large, it indicates that the excavator has shifted relative to the tunnel, that is, the excavator's direction has shifted.

[0122] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for jacking a box culvert under an airport runway using the pipe jacking method, characterized in that: The construction method includes: S1: Construction Preparation According to the design plan, multiple sets of jacks are arranged on the bottom plate of the tunnel jacking method for tunneling under the main runway of the airport. They are symmetrically arranged on the left and right sides with the center of the frame as the axis, and a hydraulic transmission system is set up to match the jacks. S2: Tunnel Start After the precast main body of the tunnel is poured, the grid loader head is hoisted into the working shaft and installed and debugged in the working shaft. Then the initial demolition work is carried out. The retaining structure of the working shaft is a 120cm thick retaining pile. Before exiting the tunnel, the steel concrete on the tunnel section needs to be removed. A sample hole is opened at the starting tunnel entrance of the working shaft to observe the actual situation of soil reinforcement before the concrete removal work at the tunnel entrance is carried out. Before the tunnel starting tunnel entrance is removed, the grid loader head has been installed in the correct position in the working shaft. Then the starting tunnel entrance is removed. S3: Water-stopping device installation. The water-stopping device at the tunnel entrance is installed on the pipe curtain ring beam. The pre-embedded steel plate of the water-stopping device is anchored to the pipe curtain ring beam with steel bars and fixed around the pipe curtain ring beam with bolts. S4: Push the machine head into the tunnel entrance. After starting, use the hydraulic cylinder of the jack to push the machine head and the first tunnel section toward the starting tunnel entrance. The pushing speed can be appropriately increased to 10cm / min. At the same time, a laser theodolite is installed in the buried section. Every 50cm of advance, the left and right attitude of the tunnel is checked until the machine head is in close contact with the reinforced soil. S5: Jacking process: Test jacking: The test jacking work continues until the tunnel is jacked. The test jacking work involves operating all the jacks to push out together. When the jacking blocks touch the tunnel and overcome the starting resistance of the tunnel, the tunnel is jacked and the pressure drops rapidly. The highest pressure value read on the pressure gauge at this time is converted into the starting thrust of the tunnel. The first section of the tunnel is used as the test section. Information is fed back in a timely manner based on the monitoring data to select various construction parameters from theory and experience for subsequent jacking and crossing. Jacking: Start the high-pressure oil pump to make the jacks generate jacking force under hydraulic pressure, which pushes the tunnel forward. After the tunnel advances one step, the piston of the jack returns to its original position. C30 plain concrete blocks are filled in the gap. This cycle is repeated until the tunnel is in place. Excavation and transportation: After the jacking begins, the excavator excavates, turns over and loads soil into the tunnel using the machine head. During the excavation, the machinery excavates 30cm-40cm of soil in front of the tunnel at a slope of 1:0.

33. The main jacking pushes the tunnel forward, which is one jacking work cycle. S6: Monitoring and adjustment, through technical personnel to conduct precision monitoring of the construction site, and the precision detection benchmark is calibrated at intervals by the detection components; S7: Assisted propulsion. During tunnel advancement, slurry with added water-stopping agent is injected between the tunnel and the pipe curtain to fill the gap between the tunnel and the pipe curtain in a timely manner. S8: Tunnel Reception and Slurry Solidification When the tunnel boring machine (TBM) is 10m from the receiving shaft entrance, a survey is conducted along the entire tunnel to correct the advance axis. After the tunnel enters the reinforced area of ​​the receiving shaft entrance, the left and right attitude of the TBM is checked every 50cm to ensure that the TBM accurately enters the receiving shaft entrance. When the TBM head is 0.3m from the receiving shaft entrance, the advance speed is slowed down again, and the TBM slowly moves towards the outside of the receiving shaft retaining piles. At this time, grouting is carried out in the grouting holes throughout the tunnel to ensure the mud pressure around the tunnel. At the same time, the removal of the underground wall of the receiving shaft begins. After the concrete and steel bars inside the receiving shaft entrance are cleared, the TBM head cuts into the entrance at the fastest speed to complete the entry and reception. After the slurry solidifies and the tunnel jacking is completed, the slurry between the tunnel and the pipe curtain needs to be replaced. The replacement slurry can be a mixture of cement and fly ash, forming a cement slurry sleeve around the tunnel to bear the upper load. There is a grouting section every 6 meters around the tunnel. The cement slurry still uses the same grouting hole. The surface deformation is controlled by the grouting pressure and injection volume. After the cement slurry solidifies, multiple sets of transverse support beams spaced 6 meters apart are formed.

2. The method for jacking a box culvert under an airport runway using the pipe jacking method according to claim 1, characterized in that: In S1, the jacks are fixed on the support and are symmetrical to the vertical line of the center of the force transmission column. The point of application of their resultant force should be on the vertical line of the center of the force transmission column. The oil circuits of the jacks should be connected in parallel. Each jack has an oil inlet and outlet control system. The hydraulic transmission system includes a power mechanism, a high-pressure oil pump, an oil tank and its auxiliary devices.

3. The method for jacking a box culvert under an airport runway using the pipe jacking method according to claim 1, characterized in that: During the jacking process, the soil in front of the tunnel frame is excavated to leave 10cm above the bottom slab, ensuring the tunnel continues to advance at a level slope. Timely monitoring and observation are conducted, with leveling observation points set at the four corners of each frame. A central observation scale is set at the centerline of the front and rear ends of the tunnel roof slab, suspended from the roof to ensure that surveyors can simultaneously observe two scales at the rear end. The axis and elevation are observed after each jacking stroke of the tunnel frame, and any deviations are corrected promptly. Deviations in the centerline can be addressed by adjusting the torque of the jacks on the tunnel centerline. Horizontal elevation deviations of the tunnel frame are controlled by the jacking excavation.

4. The method for jacking a box culvert under an airport runway using the pipe jacking method according to claim 1, characterized in that: Scaffolding is erected in front of the tunnel boring machine in S2. The concrete at the tunnel entrance must be removed in layers and blocks, from top to bottom and from middle to edge, in an orderly manner. Since the retaining piles are reinforced concrete, the surface concrete layer is removed first to expose the inner reinforcing bars, which are then cut. Subsequently, 50-60cm thick concrete layers are removed, and the concrete is removed in blocks down to the outer reinforcing bars, while retaining the outer reinforcing bars. Before cutting the connecting reinforcing bars, each block of concrete must be firmly supported with wooden supports, and lifting points must be chiseled out and the lifting jacks must be attached. The lifting of concrete blocks at the entrance should follow the order of "top to bottom and from middle to edge". Before the welder cuts the connecting reinforcing bars, the crane operator fixes the wire rope to the lifting points. After the reinforcing bars are cut, the concrete blocks fall off naturally and are then lifted away from the working shaft by the crane. The entrance after the concrete of the ground wall is removed must be cleaned, and any remaining reinforcing bars at the entrance must be cut off.

5. The method for jacking a box culvert under an airport runway using the pipe jacking method according to claim 1, characterized in that: During the test top, the following should be done: ① There are designated personnel at each relevant location and observation point to monitor changes at all times; ②After starting the pump, the pump must be stopped and observed whenever the oil pressure rises by 5-10MPa. If any abnormality is found, it should be dealt with promptly. ③When the jack piston begins to extend and the jack block is pressed down, stop jacking immediately. After checking the condition of each part, if there are no abnormalities, the pump can be restarted until the tunnel is started. ④ After the trial jacking is completed, a comprehensive inspection should be carried out. If all conditions are good, the formal jacking operation can be carried out.

6. The method for jacking a box culvert under an airport runway using the pipe jacking method according to claim 1, characterized in that: In S5, the force-transmitting concrete blocks need to be replaced or replenished as needed according to the jacking length. The placement of the concrete blocks must be consistent with the jacking axis and perpendicular to the crossbeam. During jacking, the centerline and horizontal level must be observed and recorded after each jacking. At the same time, the construction supervisor and technicians will make specific adjustments as needed to prevent head-up, head-down, or tilting. In particular, the direction must be strictly controlled during the empty jacking period to prevent deviation from the centerline. The direction can be adjusted by adding or removing jacks to ensure that there is no deviation in direction when the front end of the main body enters the soil.

7. The method for jacking a box culvert under an airport runway using the pipe jacking method according to claim 1, characterized in that: The excavation slope of the jacking excavation shall not be steeper than the cutting edge slope. Each advance shall not exceed 0.5m. Excavation shall be carried out from top to bottom. Upward excavation is strictly prohibited. The slope surface shall be kept smooth. During excavation, the soil on both sides of the cutting edge shall be excavated to the center of the side wall. The soil at the bottom shall be excavated to 400mm above the bottom surface of the base plate. Each pick shall ensure that the box body is tightly sealed with the soil layer without gaps.

8. The method for jacking a box culvert under an airport runway using the pipe jacking method according to claim 1, characterized in that: The monitoring content in S6 mainly includes: measurement and prediction of the jacking direction of the box body; monitoring of the jacking force, sliding plate and back side during the jacking process; monitoring of the soil quality at the jacking front; directing the excavation team to excavate; directing the jacking jack team to start and stop the jacking equipment; providing instructions according to the proposed plan; measuring during the jacking process; and analyzing the operating trend of the box body based on the recorded data.

9. The method for jacking a box culvert under an airport runway using the pipe jacking method according to claim 1, characterized in that: During the advancement of the S7 tunnel, two independent grouting systems were established: synchronous grouting (A grout) and supplementary grouting (B grout). Different grout ratios, grouting equipment, and grouting control were used. Synchronous grouting (A grout) was used to support the pipe curtain, while supplementary grouting (B grout) was used to lubricate the pipe curtain. The synchronous grouting (A-grout) system is controlled together with the grid tool head; The supplementary grouting system (B grout) is equipped with a supplementary grouting control console. The start and grouting position of the supplementary grouting are jointly controlled based on the thrust magnitude, the mud pressure box pre-embedded at the top of the tunnel, and settlement monitoring.

10. The method for jacking a box culvert under an airport runway using the pipe jacking method according to claim 1, characterized in that: The detection component in S6 includes a push plate (1). One side of the push plate (1) is fixedly connected to the excavator's outer shell by four sets of telescopic rods (2) arranged in a circumferential array. The excavator is equipped with a drive assembly, which includes a motor-driven shaft (10) and an excavator head fixed on the shaft (10). An inner tube (4) is provided in the middle of the push plate (1), and an outer tube (5) is provided on the outside of the inner tube (4). A through-step inner cavity (6) is provided in the inner cavity between the inner tube (4) and the outer tube (5). The inner diameter of the inner tube (4) is smaller than the inner diameter of the outer tube (5). Circumferential arrays are respectively provided on the arc-shaped outer walls of the push plate (1) and the outer tube (5). Multiple sets of first telescopic detection rods (3) and second telescopic detection rods (7) are distributed. An outer sleeve (9) is provided on the outer wall of the drive assembly and is fitted onto the rotating shaft (10). The outer sleeve (9) is directly opposite the port that penetrates the stepped inner cavity (6). A ring sleeve (8) with an outer diameter larger than the second telescopic detection rod (7) is provided on the outer wall of the excavator. A limit cover (11) is provided at the outer end of the second telescopic detection rod (7). A pointed cone (12) is provided on the outer end face of the limit cover (11). A stepped rod (13) is provided in the middle section of the rotating shaft (10). The stepped rod (13) is located in the gap between the outer tube (5) and the outer sleeve (9).

Images