Construction method for shield ground-to-ground butt joint in strong water-permeable sand stratum

Abstract

The present application belongs to the technical field of shield tunnel engineering, and particularly relates to a construction method for shield ground-to-ground butt joint in strong water-permeable sand stratum, comprising the following steps: first, stop the shield machine, keep pressure and grout the surrounding stratum for reinforcement, then, the trailing shield machine is grouted in advance for reinforcement, the posture of the trailing shield machine is adjusted, the butt joint position of the two shield machines is frozen and reinforced in the grouted and reinforced stratum, and the like. The construction method solves the problems that single method for stratum reinforcement in strong water-permeable sand stratum cannot meet the requirements of shield ground-to-ground butt joint and shield posture adjustment in strong water-permeable sand stratum, shortens the stratum reinforcement time, reduces the stratum frost heaving and thawing settlement effect, improves the shield butt joint construction efficiency, and reduces the longitudinal deformation of the formed tunnel.

Description

A method for underground docking of shield tunnels in highly permeable sandy strata Technical Field

[0001] This invention belongs to the field of shield tunnel engineering technology, specifically relating to a construction method for underground docking of shield tunnels in highly permeable sandy strata. Background Technology

[0002] In recent years, with the rapid development of the social economy and urbanization, shield tunneling technology has become an indispensable key technology in the construction of major transportation and other infrastructure projects in my country. Typically, when excavating a tunnel, a single shield tunneling machine starts from the launching shaft and tunnels to the receiving shaft. However, due to the increasing length of tunnels, the increasing complexity of geological conditions, and the need for shorter construction periods, a conventional single shield tunneling machine is insufficient to meet the demands of modern tunnel construction. Therefore, two shield tunneling machines are used, each starting from a different shaft and tunneling towards the other, connecting underground to complete the tunnel breakthrough. This significantly reduces the distance of each excavation, saves construction time, and meets the needs of modern tunnel construction.

[0003] Underground shield tunneling is a key technology in tunnel construction. There are two main methods for underground shield tunneling: mechanical docking and civil docking. Mechanical docking involves modifying the shield machines to allow for a continuous connection between the front shields of two machines. However, mechanical docking equipment is expensive and requires extremely high alignment precision. Civil docking involves reinforcing the soil and water near the docking point to stabilize the soil and cut off water flow for tunnel breakthrough. Civil docking generally increases costs and has lower precision requirements, making it more widely used than mechanical docking. Many large tunnels abroad have adopted underground shield tunneling docking technology, such as the Channel Tunnel, the Tokyo Bay Tunnel, and the Störbelt Tunnel in Denmark. In China, the Lion Ocean Tunnel and the Qiongzhou Strait Tunnel also employed underground docking technology.

[0004] Currently, tunnel boring machine (TBM) docking sections are mainly selected in locations with favorable geological and hydrological conditions. Document CN113775342A discloses a method for ground freezing reinforcement, and document CN113494295A discloses a method for underground docking construction using ground freezing. The paper "Current Status and Feasibility Analysis of Underground Docking Technology for Shield Tubes in Soft Soil Strata" summarizes several common ground reinforcement methods, such as grouting reinforcement and freezing, while pointing out that grouting reinforcement is more suitable for rock strata but less applicable to soft sandy soils. Unlike cohesive soft soil strata, sandy soils have poor self-stability and high permeability, reducing the stability of the excavation face at the docking section and increasing the difficulty of waterproofing construction.

[0005] The "Code for Geological Investigation of Water Conservancy and Hydropower Projects GB50487-2008" defines a permeability coefficient between 10 and 10 as a threshold. -2Soil with a permeability of 1 cm / s to 1 cm / s is defined as highly permeable soil. Highly permeable soil has a strong hydraulic connection with the environment and complex hydrological conditions. Despite extensive work by engineers and researchers, research and engineering applications of shield tunneling in highly permeable sandy strata are relatively limited, mainly due to the following engineering challenges:

[0006] 1. Grouting and other ground reinforcement methods are difficult to achieve ideal water-stopping effects in highly permeable sandy strata. Due to the influence of water flow in the strata, freezing methods often require several months to complete the freezing reinforcement, and the frost heave and thawing settlement cause longitudinal deformation of the formed tunnel. Therefore, a single method for ground reinforcement is insufficient to meet the requirements for underground docking of shield tunnels;

[0007] 2. Underground docking places high demands on the alignment posture of the tunnel boring machine (TBM), but adjusting the TBM's posture in highly permeable sandy strata is difficult, making precise docking hard to achieve;

[0008] 3. Waterproofing at the shield tail is difficult to guarantee during prolonged shutdowns;

[0009] 4. The connecting section between the first and second tunnels is constructed using cast-in-place reinforced concrete, which requires the installation of reinforcing bars on the precast concrete segments at both ends. This construction is difficult and can easily damage the precast concrete segments.

[0010] Therefore, it is essential to properly address key technical issues such as construction safety and difficulties in the underground docking of shield tunnels in highly permeable sandy strata. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the present invention aims to provide a construction method for underground docking of shield tunnels in highly permeable sandy strata. This method solves the problems of difficulty in achieving underground docking of shield tunnels in highly permeable sandy strata with a single construction method for strata reinforcement, as well as the difficulties in adjusting the attitude of shield tunnels in highly permeable sandy strata. Furthermore, it shortens the strata reinforcement time, reduces the frost heave and thaw settlement effect of the strata, improves the efficiency of shield docking construction, and reduces the longitudinal deformation of the formed tunnel.

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] A method for underground docking of a shield tunnel in highly permeable sandy strata includes the following steps:

[0014] S1. After the lead tunnel boring machine reaches the designated position, the segments are reinforced, the machine is stopped under pressure, and grouting is performed to reinforce the stratum, reducing the displacement of the lead tunnel boring machine in the stratum and facilitating precise docking of the follow-up tunnel boring machine.

[0015] S2. When the distance between the rear tunnel boring machine and the cutterhead of the leading tunnel boring machine is 40-50m, the rear tunnel boring machine shall carry out the first advance grouting.

[0016] S3. The rear-mounted tunnel boring machine excavates in the reinforced strata while taking measurements, and adjusts its attitude and controls the excavation parameters based on the measurement results.

[0017] S4. When the distance between the rear tunnel boring machine and the cutterhead of the leading tunnel boring machine is 20-30m, the rear tunnel boring machine shall carry out a second advance grouting.

[0018] S5. The tunnel boring machine advances through the reinforced strata while taking measurements and adjusting its attitude and controlling the tunneling parameters based on the measurement results.

[0019] S6. When the distance between the rear tunnel boring machine and the cutterhead of the leading tunnel boring machine is 5-8m, the rear tunnel boring machine shall carry out the third advance grouting.

[0020] S7. The tunnel boring machine advances through the reinforced strata while taking measurements and adjusting its attitude and controlling the tunneling parameters based on the measurement results.

[0021] S8. When the cutterhead of the rear tunnel boring machine (TBM) contacts the cutterhead of the lead TBM, the rear TBM stops to maintain pressure and performs segment reinforcement and pre-grouting to reduce the impact on the lead TBM and minimize disturbance to the connecting soil layer.

[0022] S9. Apply freezing treatment to the grout-reinforced soil layer at the docking point of the two tunnel boring machines to stabilize the docking soil layer and prevent water from entering.

[0023] S10. Disassemble the tunnel boring machine (TBM) and the tunnel boring machine (TBM) inside the tunnel. After the cutterhead is disassembled, weld sealing steel plates along the cut of the TBM to the exposed parts that are connected to the frozen ground, so that the shield shells of the TBM and the TBM are connected to form a closed space.

[0024] S11. Conduct the butt lining and waterproofing construction in an enclosed space. The construction is completed after the concrete reaches the design strength.

[0025] Preferably, the shutdown pressure holding step S1 includes the following steps:

[0026] S11. Inject mortar into the mud and water chamber. The height of the first injection of mortar should be 1 meter higher than the front chamber door. Cure for 24 hours.

[0027] S12. When injecting mortar for the second time, keep the pressure at the working face stable. Stop grouting when the mortar injection pressure exceeds 1MPa and cure for 24 hours.

[0028] S13. Inject cement grout from the upper grouting pipe until the mud and water chamber is completely filled, then stop grouting.

[0029] Preferably, the measurements in steps S3, S5, and S7 include the following steps:

[0030] S31. Set up measurement and control networks at the starting points of the first and subsequent shield tunnels respectively;

[0031] S32. Perform joint measurements on the two measurement control networks mentioned above to increase accuracy;

[0032] S33. Based on the measurement and control network of the starting point of the tunnel boring machine, conduct connection measurement and traverse control measurement inside the tunnel of the tunnel boring machine, and measure the real-time attitude of the tunnel boring machine.

[0033] S34. Based on the measurement and control network of the starting point of the rear tunnel boring machine, conduct connection measurement and traverse control measurement inside the tunnel of the rear tunnel boring machine, and connect and measure the real-time attitude of the rear tunnel boring machine.

[0034] Preferably, the attitude adjustment in steps S3, S5 and S7 includes lateral deviation, vertical deviation, pitch angle, azimuth angle, roll angle and cut-off mileage; the tunneling parameters include thrust, torque, cutterhead speed, tunneling speed, cut-off water pressure, synchronous grouting filling rate, synchronous grouting pressure, mud specific gravity and mud consistency.

[0035] Preferably, in step S8, the subsequent tunnel boring machine (TBM) advances at a speed of less than 10 mm / min and contacts the cutterhead of the preceding TBM. After contact, it stops immediately and performs shutdown and pressure maintenance on the subsequent TBM according to the shutdown and pressure maintenance steps described in step S1.

[0036] Preferably, in step S9, freezing is performed using two rows of radial freezing tubes combined with three-ring attached freezing tubes.

[0037] Preferably, the dismantling of the tunnel boring machine inside the tunnel in step S10 includes the following steps:

[0038] S101, removal of the rear supporting trolley;

[0039] S102, segment assembly machine and H-beam dismantling;

[0040] S103, Remove the hydraulic cylinder;

[0041] S104, Dismantle the drive unit cylinder and push ring;

[0042] S105, the drive unit is pulled out and removed after being flipped over;

[0043] S106. The remaining part of the front shield and the cutter head are cut into small pieces from top to bottom and transported out.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The construction method for underground docking of shield tunneling machines in highly permeable sandy strata provided by the present invention reduces the settlement and head-down deformation of the shield tunneling machine in the sandy strata by reinforcing the soil around the shield tunneling machine in highly permeable sandy strata, which is conducive to the accurate docking of the subsequent shield tunneling machine.

[0046] (2) The construction method for underground docking of shield tunneling machines in highly permeable sandy strata provided by the present invention adopts advanced reinforcement when the rear shield tunneling machine approaches the front shield tunneling machine, which improves the soil strength on the tunneling line of the rear shield tunneling machine, which is conducive to the attitude adjustment of the rear shield tunneling machine and realizes precise docking with the front shield tunneling machine.

[0047] (3) The construction method for shield tunneling in the ground in highly permeable sandy strata provided by the present invention cuts off the hydraulic connection with the outside world after the soil around the docking part is reinforced, which can improve the freezing effect and shorten the freezing time. At the same time, the porosity of the soil around the docking part is greatly reduced after reinforcement, which reduces the effect of soil layer frost heave and thaw settlement and reduces the longitudinal deformation of the formed tunnel. Attached Figure Description

[0048] Figure 1 is a schematic diagram of the preliminary shield tunneling machine and grouting pipe structure of the present invention;

[0049] Figure 2 is a schematic diagram of the two tunnel boring machines of the present invention when the distance between them is 25m;

[0050] Figure 3 is a schematic diagram of the docking of two tunnel boring machines according to the present invention;

[0051] Figure 4 is a schematic diagram of the mortar filling and reinforcement in the slurry chamber of the tunnel boring machine according to the present invention.

[0052] Figure 5 is a schematic diagram of the segment reinforcement of the present invention;

[0053] Figure 6 is a schematic diagram of the outer surface structure of the tunnel boring machine after docking.

[0054] Among them, 1. Rear segment of the advance shield machine; 2. Radial grouting pipe; 3. Advance grouting pipe; 4. Cutterhead; 5. Steel shield shell of the shield machine; 51. Shield shell of the advance shield machine; 52. Shield shell of the rear shield machine; 6. Sealing steel plate; 7. Frozen reinforced soil; 8. Grouting reinforced body; 9. Slurry chamber of the shield machine; 10. Front door of the slurry chamber; 11. Location of the first mortar injection; 12. Support steel plate for sealing the shield shells of the advance and rear shield machines. Detailed Implementation

[0055] 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.

[0056] Example 1

[0057] The following explanation will be based on a specific engineering project.

[0058] The tunnel boring machine (TBM) has a 27m thick overburden layer at each stage, with the bottom of the tunnel 27m below the water surface. The stratum where the TBM is located is layer 4-5, a medium-coarse sandy stratum with a permeability coefficient of 0.04 cm / s, which is a highly permeable stratum.

[0059] A measurement control network was set up at the starting sites of the first and subsequent tunnel boring machines (TBMs). A gyro total station was used to connect the two control networks to increase their accuracy. Based on the measurement control network, traverse surveys and tunnel traverse surveys were conducted, and the real-time attitude of the first TBM was measured. Based on the measurement control network at the starting site of the subsequent TBM, connection surveys and tunnel traverse control surveys were conducted, and the real-time attitude of the subsequent TBM was measured.

[0060] A method for underground docking of a shield tunnel in highly permeable sandy strata includes the following steps:

[0061] S1. As shown in Figures 1 and 5, after the tunnel boring machine (TBM) reaches the designated position, in order to ensure that the assembled segments do not experience stress relaxation, the segments are reinforced, the machine is stopped under pressure, and the stratum where the TBM is located is reinforced by grouting using radial grouting pipes and advanced grouting pipes to reduce the displacement of the TBM in the stratum and facilitate the precise docking of the subsequent TBM.

[0062] As shown in Figure 4, the shutdown pressure holding process includes the following steps:

[0063] S11. First, mortar is injected into the mud and water chamber through the lower flushing pipe to fill the lower part of the mud and water chamber. The initial filling height is 1 meter higher than the front door.

[0064] S12. After 24 hours, mortar is injected again through the middle flushing pipeline. The upper mud is discharged through the connecting pipe to keep the working face pressure at 6 bar. When the mortar flows out of the upper slurry discharge pipeline, the slurry discharge valve is closed. Grouting is stopped when the mortar injection pressure exceeds 1 MPa.

[0065] S13. After 24 hours, inject cement grout from the upper grouting pipeline until the mud and water chamber is completely filled and then stop grouting.

[0066] After the tunnel boring machine stops, attitude feature points are redeployed to monitor the attitude of the tunnel boring machine in real time.

[0067] S2. When the distance between the rear tunnel boring machine and the leading tunnel boring machine is 45m, the rear tunnel boring machine shall carry out advance grouting reinforcement to reinforce the soil layer in the direction of the rear tunnel boring machine's advance.

[0068] S3. The tunnel boring machine (TBM) then advances through the reinforced strata, adjusting its attitude and controlling the tunneling parameters. During this process, the TBM's tunneling parameters are as follows: cutterhead rotation speed 1.0~1.15 r / min, tunneling speed 18~30 mm / min, cutterhead water pressure 6~6.6 bar, synchronous grouting filling rate 130-140%, synchronous grouting pressure 9~10 bar, and mud specific gravity 1.15~1.20 g / cm³. 3 Mud consistency 18~25 seconds;

[0069] S4. As shown in Figure 2, when the distance between the rear tunnel boring machine and the leading tunnel boring machine is 25m, the rear tunnel boring machine will carry out advance grouting reinforcement to reinforce the soil layer in the direction of the rear tunnel boring machine's advance.

[0070] S5. The tunnel boring machine (TBM) then advances through the reinforced strata, adjusting its attitude and controlling the tunneling parameters. During this process, the TBM's tunneling parameters are as follows: cutterhead rotation speed 0.8~1.0 r / min, tunneling speed 10~15 mm / min, cutterhead water pressure 6.2~6.6 bar, synchronous grouting filling rate 130-140%, synchronous grouting pressure 9~10 bar, and mud specific gravity 1.18~1.20 g / cm³. 3 Mud consistency 18~25 seconds;

[0071] S6. When the rear tunnel boring machine is 5m away from the leading tunnel boring machine, the rear tunnel boring machine shall carry out advance grouting reinforcement to reinforce the soil layer in the direction of the rear tunnel boring machine's advance.

[0072] S7. The tunnel boring machine (TBM) then advances through the reinforced strata, adjusting its attitude and controlling the tunneling parameters. During this process, the TBM's tunneling parameters are as follows: cutterhead rotation speed 0.8~1.0 r / min, tunneling speed 5~10 mm / min, cutterhead water pressure 6.2~6.7 bar, synchronous grouting filling rate 130-140%, synchronous grouting pressure 9~10 bar, and mud specific gravity 1.18~1.20 g / cm³. 3 Mud consistency 18~25 seconds;

[0073] S8. As shown in Figure 3, when the rear tunnel boring machine (TBM) contacts the cutterhead of the leading TBM, the power to the rear TBM is cut off, and the segments behind the rear TBM are reinforced. The TBM is reinforced in advance, and the soil around the joint is reinforced.

[0074] S9. Apply freezing treatment to the grout-reinforced soil layer at the docking point of the two tunnel boring machines (TBMs); utilize the existing 18 circumferential grouting pipes of the TBMs to inject double-liquid grout (or single-liquid grout) to form a circumferential water-stop curtain in the docking area; lay two rows of freezing pipes, 50 pipes per row, with a longitudinal spacing of 1m and a circumferential stagger of 1m; the freezing method is brine freezing; freezing temperature: designed brine temperature -28℃~-30℃; brine flow rate: 5~7m³ / h per freezing hole. 3 / h; Frozen wall thickness: not less than 3m, 25~28mm / d; After freezing is completed, subsequent work can be carried out after passing the inspection; otherwise, freezing construction will continue.

[0075] S10. After the freezing and solidification of the docking area is safe and stable, dismantle the tunnel boring machines (TBMs) inside the tunnel, including the first and second TBMs. First, dismantle the edges from top to bottom, and then use steel plates to connect the front shields of the two TBMs, as shown in Figure 6. Weld as you dismantle until a closed ring is formed connecting the shield shells of the first and second TBMs, achieving support and sealing.

[0076] The tunnel boring machine dismantling operation inside the tunnel includes the following steps:

[0077] S101, removal of the rear supporting trolley;

[0078] S102, segment assembly machine and H-beam dismantling;

[0079] S103, Remove the hydraulic cylinder;

[0080] S104, Dismantle the drive unit cylinder and push ring;

[0081] S105, the drive unit is pulled out and removed after being flipped over;

[0082] S106. The remaining part of the front shield and the cutter head are cut into small pieces from top to bottom and transported out.

[0083] S11. After the cutterhead is removed, the tunnel is completed and a closed space is formed under the support of two shield shells and steel plates. Cast-in-place reinforced concrete lining and waterproofing are carried out in this closed space. When the cast-in-place lining reaches the design strength, freezing is stopped and the construction is completed.

[0084] 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 construction method for underground docking of a shield tunnel in highly permeable sandy strata, characterized in that, Includes the following steps: S1. After the lead tunnel boring machine (TBM) reaches the designated position, the segments are reinforced, the machine is stopped for pressure maintenance, and grouting is performed to reinforce the strata. S2. When the follow-up TBM is 40-50m away from the cutterhead of the lead TBM, the follow-up TBM performs its first pre-grouting. S3. The follow-up TBM tunnels through the reinforced strata, while simultaneously conducting measurements and adjusting its attitude and controlling tunneling parameters based on the measurement results. S4. When the follow-up TBM is 20-30m away from the cutterhead of the lead TBM, the follow-up TBM performs its second pre-grouting. S5. The follow-up TBM... During tunneling in reinforced strata, measurements are taken simultaneously, and attitude adjustments and tunneling parameter control are implemented based on the measurement results; S6, when the distance between the rear tunnel boring machine (TBM) and the cutterhead of the lead TBM is 5-8m, the rear TBM performs its third advance grouting; S7, the rear TBM tunnels in the reinforced strata, measurements are taken simultaneously, and attitude adjustments and tunneling parameter control are implemented based on the measurement results; S8, when the cutterhead of the rear TBM contacts the cutterhead of the lead TBM, the rear TBM stops to maintain pressure, and segment reinforcement and advance grouting are performed; S9. Freeze the grout-reinforced soil layer at the docking point of the two tunnel boring machines (TBMs); S10. Disassemble the tunnel boring machines (TBMs) inside the tunnel. After the cutterheads are disassembled, weld sealing steel plates along the cut of the TBM to the exposed parts that are connected to the frozen strata, so that the shield shells of the TBMs are connected to the shield shells of the TBMs to form a closed space; S11. Carry out docking lining and waterproofing construction in the closed space. After the concrete reaches the design strength, the construction is completed.

2. The construction method for underground docking of a shield tunnel in a highly permeable sandy stratum according to claim 1, characterized in that, The shutdown and pressure maintenance described in step S1 includes the following steps: S11, inject mortar into the mud and water chamber. The height of the first injection of mortar is 1 meter higher than the front chamber door, and it is cured for 24 hours; S12, when injecting mortar for the second time, keep the working face pressure stable. Stop grouting after the mortar injection pressure exceeds 1 MPa, and cure for 24 hours; S13, inject cement grout from the upper grouting pipe until the mud and water chamber is completely filled, and then stop grouting.

3. The construction method for underground docking of a shield tunnel in a highly permeable sandy stratum according to claim 1, characterized in that, The measurements described in steps S3, S5, and S7 include the following steps: setting up measurement control networks at the starting points of the first and subsequent shield tunnels; connecting the two measurement control networks to increase accuracy; based on the measurement control network at the starting point of the first shield tunnel, performing connection measurements and traverse control measurements inside the tunnel of the first tunnel, and measuring the real-time attitude of the first shield machine; based on the measurement control network at the starting point of the subsequent shield tunnel, performing connection measurements and traverse control measurements inside the tunnel of the subsequent tunnel, and connecting the real-time attitude of the subsequent shield machine.

4. The construction method for underground docking of a shield tunnel in a highly permeable sandy stratum according to claim 1, characterized in that, The attitude adjustment mentioned in steps S3, S5 and S7 includes lateral deviation, vertical deviation, pitch angle, azimuth angle, roll angle and cut-off mileage; the tunneling parameters include thrust, torque, cutterhead speed, tunneling speed, cut-off water pressure, synchronous grouting filling rate, synchronous grouting pressure, mud specific gravity and mud consistency.

5. A construction method for underground docking of a shield tunnel in a highly permeable sandy stratum according to any one of claims 1-4, characterized in that, In step S8, the subsequent tunnel boring machine (TBM) advances at a speed of less than 10 mm / min and contacts the cutterhead of the preceding TBM. After contact, it stops immediately and performs shutdown and pressure maintenance on the subsequent TBM according to the shutdown and pressure maintenance steps described in step S1.

6. A construction method for underground docking of a shield tunnel in a highly permeable sandy stratum according to any one of claims 1-4, characterized in that, In step S9, freezing is performed using two rows of radial freezing tubes combined with three-ring attached freezing tubes.

7. A construction method for underground docking of a shield tunnel in a highly permeable sandy stratum according to any one of claims 1-4, characterized in that, The tunnel boring machine dismantling in step S10 includes the following steps: S101, dismantling of the rear supporting trolley; S102, dismantling of the segment assembly machine and H-beam; S103, dismantling of the propulsion cylinder; S104, dismantling of the drive unit cylinder and push ring; S105, pulling out the drive unit and dismantling it after flipping it over; S106, cutting the remaining part of the front shield and the cutterhead into small pieces from top to bottom and transporting them out.

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