A method for constructing a post-pouring belt of a submarine immersed tube tunnel

Abstract

The present application relates to the technical field of immersed tube tunnel construction, and particularly relates to a kind of submarine immersed tube tunnel post-pouring band construction method.The method comprises the following steps: structure installation before post-pouring band construction, secondary water stop of immersed tube tunnel post-pouring band, immersed tube tunnel post-pouring band through measurement, post-pouring band reinforcement binding, post-pouring band formwork erection, post-pouring band concrete pouring and post-pouring band waterproofing measure.The present application adopts a complete and detailed set of construction process of underwater jacking post-pouring to complete the construction of immersed tube tunnel post-pouring band.Through the post-pouring band structure system, the problems of traditional submarine immersed tube tunnel underwater butt joint, such as large operation amount, low efficiency, high risk, need for transportation and lifting operation, difficulty in controlling butt joint precision, etc., are optimized.Through the research on the construction process of immersed tube tunnel post-pouring band, the control difficulty of immersed tube tunnel butt joint installation is greatly simplified, and the quality control of post-pouring band structure concrete cast-in-place and construction efficiency are also greatly guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of immersed tube tunnel construction, in particular to a method for constructing a post-poured band of a submarine immersed tube tunnel. BACKGROUND

[0002] Currently, the main schemes for connecting the joints of the immersed tube tunnel are the water stop formwork method and the V-shaped block scheme. The water stop formwork method mainly involves first making and installing a flat weir plate on the end of the pipe section on both sides of the joint while the pipe section is being welded, and then, after the pipe section is completely immersed, installing a circular steel cofferdam plate on both sides of the flat weir plate in the water, and using a steel plate to separate the inside and outside of the tunnel to form the final underwater water stop formwork of the joint, and then pouring underwater concrete into the cofferdam to form the connection of the pipe section underwater. The V-shaped block scheme mainly involves setting an end closure wall in each adjacent pipe section on both sides of the joint, setting a double-wedge-shaped end face on both sides of the adjacent pipe section, and setting a contact surface and a rubber water stop belt on the two end faces, so that the final joint is double-wedge-shaped and forms a V shape, and the two sides of the V-shaped final joint block are also provided with a contact surface and a rubber water stop belt. After the adjacent pipe sections are installed, the pre-fabricated V-shaped final joint block is hoisted and immersed to press the water stop belt tightly against the two pipe sections, and the adjacent pipe sections and the V-shaped final joint block are connected by bolts.

[0003] The water stop formwork method requires a large amount of underwater welding to ensure the airtightness of the water stop formwork and meet the requirements of pouring structural concrete underwater. The construction time is greatly affected by hydrological conditions and underwater welding operations, and the operation time is uncontrollable. The welding connection of the formwork and the pouring of the concrete need to be done underwater, which is very dangerous. The V-shaped block scheme requires the two sides of the immersed tube and the V-shaped block of the final joint to be pre-fabricated into a wedge shape during construction, which is difficult to control in terms of installation precision. Moreover, four water stop belts are required, which makes the installation control more complex. In particular, during transportation and hoisting, the V-shaped block is small in weight, which makes it difficult to control and operate underwater. Moreover, since precise docking with the two pipe sections is required underwater, the structure and the water stop belt may be damaged, which poses a great risk to the already installed pipe sections on both sides. Both of the above methods have the problem of difficulty in controlling the docking precision of the final joint due to the difficulty in controlling the formwork erection and the pre-fabrication and hoisting precision during underwater docking and installation. SUMMARY

[0004] The present application aims to solve the above problems and provides a method for constructing a post-poured band of a submarine immersed tube tunnel.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows: a method for constructing a post-poured band of a submarine immersed tube tunnel, characterized in that:

[0006] Step 1: Structure installation before post-poured band construction

[0007] The successful jacking is realized by opening the valve at the top of the outer sleeve and connecting with seawater. The jacking segments are pushed out by 4 jacks at the bottom of the outer sleeve synchronously. The control accuracy of the jacking axis is high, and the axis deviation is controlled within 1.5 cm. The jacking force of each jacking jack is 300 t, the oil pressure is 350 Bar, the pullback force is 150 t, the oil pressure is 400 Bar, the jacking stroke is 1.7 m, and the weight of a single jack is 3 t. The end steel shell of the jacking segment is in contact with the GINA water stop at the tail end of the last pipe segment. The water inlet hole at the top of the outer sleeve has a diameter of 25 cm, a submergence depth of 14.221 m, and a water inlet capacity of 0.8 m³ / s, which can meet the maximum jacking speed of 145 mm / min. The manhole door at the south side of the concrete sealing door of the pipe segment is opened to enter the cavity of the jacking segment, and the jacking segment is measured to confirm that the jacking segment is correctly connected with the pipe segment before the next step is performed. When the jacking jacks push out the jacking segment, the remaining temporary thrust steel supports of the top and bottom plates are also taken out at the same time. 24 temporary thrust steel supports are installed in the outer sleeve, the connection steel support is 4.13 m long, the specific length is determined after the jacking of the jacking segment is completed, the weight is 1.3 t, the circular pipe diameter is 402 mm, and the flange diameter is 600 mm. The temporary thrust steel support is locked by 24 flat jacks to realize the force transmission between the temporary thrust steel support and the counterforce bracket II. The jacking force of the flat jack is 550 t, the oil pressure is 362 Bar, the stroke is 40 mm, the mechanical lock function is 600 t, and the weight of a single flat jack is 500 kg. During the jacking process, the diver assists in measurement, and the distance between the jacking segment and the last pipe segment before and after jacking is measured by measuring ruler and measuring line. During the jacking process, the diver is positioned at the side wall position of the support beam on both sides of the jacking segment, the distance between the side wall of the jacking segment and the side wall of the support beam is measured, and the segment deviation during the jacking process is monitored in real time. The measurement and control system includes three devices: measuring line displacement meter, camera displacement meter, and magnetic displacement sensor. Each device can independently complete high-precision positioning. The measurement and control system mainly uses the measuring line instrument, and the camera displacement meter and the magnetic displacement sensor are used as verification. The three-dimensional attitude of the jacking segment is displayed to ensure the installation accuracy. During the installation process, the deformation and stress of the concrete sealing door on both sides of the post-cast strip are monitored to ensure the safety of the installation structure.

[0008] Second step: secondary water stop of the immersed tunnel post-cast strip

[0009] When the outer sleeve water inlet valve is closed, the outer sleeve concrete sealing door pressure gauge value is 2.23 Bar, slowly open the outer sleeve concrete sealing door air inlet valve, the opening is 1 / 8 turn, the joint cavity water is discharged from the air inlet valve, the drainage capacity is about 0.066 m³, the pressure value in the joint cavity changes from 2.23 Bar to 0.73 Bar, at this time the joint cavity starts to intake air, the single force of the flat jack top plate is 244 t, the single force of the side wall is 204 t, and the average force of the bottom plate is 171 t; by grouting the groutable waterproof band, the secondary water stop of the post-poured band of the immersed tunnel is completed; the material of the groutable waterproof band is SBR, the density is 1.16±0.03 t / m³, the tensile strength is ≥16 MPa, the elongation at break is ≥400%, and the tear strength is ≥45 N.

[0010] Step 3: Post-poured band penetration measurement of immersed tunnel

[0011] After the jacking segment installation is completed, the manhole of the pipe gallery in the last segment of the immersed tube is opened, the initial attitude positioning deviation measurement of the immersed tunnel installation is performed, and the installation deviation of the immersed tunnel is determined; after the jacking segment and the manhole of the outer sleeve sealing door are opened, the full line penetration is completed.

[0012] Step 4: Post-poured band reinforcement binding

[0013] Enter the cavity of the jacking segment through the concrete sealing door manhole, and then perform the post-poured band reinforcement binding after the interface of the end face of the post-poured band is chiseled and treated. The longitudinal reinforcement of the post-poured band is mainly connected through the mechanical sleeves reserved in the two ends of the jacking segment and the outer sleeve, and the middle part is fixed by welding. The hoop reinforcement and stirrup are normally mechanically connected and bound and fixed. The maximum radius of the hoop reinforcement is 90 cm, 1920 longitudinal pre-buried mechanical sleeves are connected, and 960 longitudinal welds are connected.

[0014] Step 5: Post-poured band formwork erection

[0015] Disclosed is a construction method for a post-poured strip template of a immersed tunnel. The post-poured strip template of the immersed tunnel is supported by a disc buckle scaffold as a post-poured strip scaffold force support and operation system. A fastener scaffold is combined with the disc buckle scaffold in conflict positions with a steel support. The disc buckle scaffold is of a φ48.3mm type, a horizontal rod standard step is 1.5m, a vertical rod spacing is 0.912m*0.912m, and a diagonal rod is full of steel supports and manhole door positions. A frame body is used as a support force system in the post-poured strip range, a support frame front is combined with an operation platform to adapt to post-poured strip operation space. A top plate needs to be pumped and pumped with steel support avoidance, a template overall force and a pre-embedded pump pipe connection and fixing, fully considering the convenience and operability of the operating personnel, a group scattered combination piece type steel template system is applied, a template main beam is placed on a scaffold top support in a top support spacing along a mileage direction by using double-pinned groove steel, a secondary beam is also evenly arranged in three rows along the structure width direction by using double-pinned groove steel to ensure the force of the template middle and both sides of the joint; the secondary beam and the combined piece steel panel are fixed by fasteners.

[0016] Step 6: Post-poured strip concrete pouring

[0017] The post-poured strip concrete pouring is layered pouring, the bottom plate and the wall are poured once to the top plate and the corner, the formwork reinforcement system full-frame support is also used as the operation platform for concrete pouring; the secondary concrete pouring is top plate concrete; the temporary thrust steel support cannot be removed before the post-poured strip concrete curing reaches the design strength; the post-poured strip concrete has the following proportions:

[0018] Water-cement ratio 0.34

[0019] Sand ratio 41%

[0020] Cement 335 kg / m 3

[0021] Sand 701 kg / m 3

[0022] Stone 1009 kg / m 3

[0023] Water consumption 170 kg / m 3

[0024] Fly ash 75 kg / m 3

[0025] Mineral powder 50 kg / m 3

[0026] Water reducing agent 8.5 kg / m 3

[0027] Air entraining agent 1.56 kg / m 3

[0028] Expanding agent 40kg / m 3 ;

[0029] The working performance of reaching self-compensating shrinkage includes C50 final strength, p10 impermeability grade, df80 frost resistance grade, the mixture ratio is suitable for post-poured concrete pouring, does not need to be vibrated, has good working performance such as concrete fluidity and cohesiveness, and has fast strength growth, and is suitable for post-poured support stress requirements;

[0030] A 125mm top-punching concrete pump pipe is pre-embedded on the formwork at the middle position of the structure, the nozzle is 40cm away from the top plate in comprehensive consideration of the influencing factors of concrete pumping, an exhaust pipe is embedded between the two pump pipes to ensure that the gas in the post-poured belt operation cavity is discharged and a channel is left for subsequent grouting and densification; a one-way valve is arranged on the concrete pump pipe at a position 50cm away from the bottom formwork, and a ball valve is arranged on the exhaust pipe at a position 30cm away from the bottom formwork;

[0031] Seventh step: waterproof measure of post-poured belt

[0032] Water-swelling waterproof glue and pre-embedded grouting pipe are arranged at the joint between the new and old concrete of the post-poured belt as the last waterproof measure; the water-swelling waterproof glue needs to keep the base surface dry after the chiseling and cement-based brushing are completed; the thickness of the water-swelling waterproof glue is uniform and continuous and reaches 10mm, and the distance from the structure edge and the grouting pipe is controlled to be 15cm; two post-grouting pipes are reserved on the top plate of the post-poured belt, grouting and filling and densification are performed after the concrete of the top plate is poured to ensure that the whole structure is dense; grouting liquid is poured into the grouting pipe from the low end of the pre-embedded grouting pipe, and the grouting liquid is extruded upward by using a hand pressure equipment; in order to ensure the grouting effect, the grouting liquid is slowly advanced at low pressure; after the grouting liquid is discharged from the other end of the pipe, the grouting pipe is closed, and the pressure is increased to 0.8MPa; when the pressure is kept for 5 minutes without obvious decrease, the grouting is completed.

[0033] The axial deviation of the post-poured belt after pouring is 1cm.

[0034] The complete and detailed whole underwater jacking post-poured construction process is adopted to complete the butt joint construction of the immersed tunnel, the post-poured belt structure system of the immersed tunnel is adopted, the traditional underwater operation of the immersed tunnel is optimized, the operation amount is large, the efficiency is low, the risk is large, and transportation and hoisting operations are needed, the post-poured belt operation cavity is formed by jacking and pushing the segments, the problems of pouring concrete and underwater hoisting and placing the joint V-shaped block by standing the formwork for underwater operation are avoided, the operation of the post-poured belt is completed in only 20 days of operation time to form the final through connection of the immersed tunnel, and there is no large operation risk during the operation. During the operation process and after the pouring of the post-poured belt concrete is completed, basically no water leaks. The axial deviation of the post-poured belt after pouring is 1cm, and the problem of difficult control of the butt joint precision is solved. Through the research on the construction process of the post-poured belt of the immersed tunnel, the control difficulty of the butt joint installation of the immersed tunnel is greatly simplified, and the quality control of the post-poured belt structure concrete cast in place is also greatly guaranteed. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the longitudinal section of the post-cast strip structure of the immersed tunnel of the present invention.

[0036] Figure 2 This is a schematic cross-sectional view of the post-cast strip structure of the immersed tunnel according to the present invention.

[0037] Figure 3 This is a schematic diagram of the waterproofing structure of the post-cast strip in the immersed tunnel according to the present invention.

[0038] Figure 4 This is a schematic diagram illustrating the construction process of the post-cast strip in the immersed tunnel according to the present invention.

[0039] In the diagram: 1. External sleeve; 2. Jacking segment; 3. Post-cast strip structure; 4. Reaction bracket one; 5. Reaction bracket two; 6. Concrete sealing gate; 7. Manhole door; 8. Connecting steel support; 9. Expandable waterstop; 10. Groutable waterstop; 11. Post-grouting pipe; 12. Bottom post-grouting pipe; 13. Temporary thrust steel support; 14. Roughening and cement base; 15. Water-swellable sealing adhesive; 16. Pre-embedded grouting. 17. Grouting conduit, 18. Grouting pipe sealing box, 19. Jack, 20. Reserved mechanical sleeve, 21. Sleeve connector, 22. Post-cast strip bottom slab reinforcement, 23. Post-cast strip scaffolding support and working system, 24. Modular loose-fitting steel formwork and embedded grouting pump pipe system, 25. Post-cast strip top slab reinforcement, 26. GINA waterstop, I. Jacking segment cavity, II. Post-cast inner cavity of jacking segment. The last immersed tunnel segment. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Example

[0041] like Figures 1-4 As shown, the post-cast strip structure 3 of the immersed tunnel is located between the jacking segment and the outer sleeve of the immersed tunnel. It is a full-section concrete structure. After the jacking segment 2 is jacked and connected with the last immersed tunnel segment, the steel reinforcement binding, concrete pouring and other engineering work will be carried out.

[0042] Step 1: Structural installation before post-pouring strip construction

[0043] The successful jacking is realized by opening the valve at the top of the outer sleeve 1 to communicate with seawater. The jacking segment 2 is pushed out by the 4 jacks 19 at the bottom of the outer sleeve synchronously, and the control accuracy of the jacking axis is high. The jacking force of each jacking jack is 300t, the oil pressure is 350Bar, the pullback force is 150t, the oil pressure is 400Bar, the jacking stroke is 1.7m, and the weight of a single jack is 3t. The end steel shell of the jacking segment contacts the GINA sealing band 26 at the tail end of the last pipe segment. The water inlet hole at the top of the outer sleeve has a diameter of 25cm, a submergence depth of 14.221m, and a water inlet capacity of 0.8m³ / s, which can meet the maximum jacking speed of 145mm / min. The manhole door 7 of the concrete sealing door 6 at the south side of the pipe segment is opened to enter the cavity of the jacking segment, and the jacking segment is measured to confirm that the jacking segment is correctly connected with the pipe segment before the next step. When the jacking segment is pushed out by the jacking jack, the remaining temporary thrust steel support 8 of the top and bottom plates is also taken out at the same time. 24 temporary thrust steel supports 13 are installed in the outer sleeve, the connection steel support is 4.13m long and weighs 1.3t, the circular pipe diameter is 402mm, and the flange diameter is 600mm. The temporary thrust steel support is locked by 24 flat jacks to realize the force transmission between the temporary thrust steel support and the counterforce bracket 1 and 2, the jacking force of the flat jack is 550t, the oil pressure is 362Bar, the stroke is 40mm, the mechanical lock function is 600t, and the weight of a single flat jack is 500kg. During the jacking process, the diver assists in measurement, and the distance between the jacking segment and the last pipe segment is measured by measuring ruler and measuring line before and after the jacking segment is jacked. During the jacking process, the diver is positioned at the position of the support beam side wall on both sides of the jacking segment, the distance between the jacking segment side wall and the support beam side wall is measured, and the segment deviation is monitored in real time during the jacking process. The measurement and control system includes three devices: measuring line displacement meter, camera displacement meter and magnetic displacement sensor, each of which can independently complete high-precision positioning. The measurement and control system mainly uses the measuring line instrument, and the camera displacement meter and the magnetic displacement sensor are used as verification to display the three-dimensional attitude of the jacking segment to ensure the installation accuracy. During the installation process, the deformation and stress of the concrete sealing door on both sides of the post-cast strip are monitored to ensure the safety of the installation structure.

[0044] Second step: secondary water stop of the immersed tunnel post-cast strip

[0045] When the outer sleeve water inlet valve is closed, the outer sleeve concrete sealing door pressure gauge value is 2.23 Bar, slowly open the outer sleeve concrete sealing door air inlet valve, the opening is 1 / 8 turn, the joint cavity water is discharged from the air inlet valve, the drainage capacity is 0.066 m³, the pressure value in the joint cavity changes from 2.23 Bar to 0.73 Bar, at this time the joint cavity starts to intake air, the single force of the flat jack top plate is 244 t, the single force of the side wall is 204 t, and the average force of the bottom plate is 171 t; the grouting of the stretchable water stop belt 9 and the grouting of the stretchable water stop belt 10 through the rear grouting pipe 11 are completed, and the secondary water stop of the immersed tunnel post-poured belt is completed; the stretchable water stop belt material is SBR, the density is 1.16±0.03 t / m³, the tensile strength is ≥16 MPa, the elongation at break is ≥400%, and the tear strength is ≥45 N.

[0046] Step 3: Post-poured belt through measurement of immersed tunnel

[0047] After the jacking segment installation is completed, the last section of the immersed tube gallery manhole is opened, the initial attitude positioning deviation measurement of the immersed tunnel installation is performed, and the installation deviation of the immersed tunnel is determined; after the jacking segment and the outer sleeve sealing door manhole are opened, the full-line through measurement is completed, and accurate structure is provided for subsequent post-poured belt construction;

[0048] Step 4: Post-poured belt reinforcement binding

[0049] Enter the jacking segment cavity through the concrete sealing door manhole door, perform interface chiseling treatment on the end face of the post-poured belt, and then perform post-poured belt reinforcement binding, including post-poured belt bottom plate reinforcement 22, post-poured belt top plate reinforcement 25, post-poured belt longitudinal reinforcement mainly connected through two end jacking segments and outer sleeve reserved mechanical sleeves 20 and sleeve connectors 21, and intermediate welding fixed, ring reinforcement and stirrup normally mechanically connected and bound fixed; the maximum radius of the ring reinforcement is 90 cm, 1920 longitudinal pre-buried mechanical sleeves are connected, and 960 longitudinal weld seams are connected;

[0050] Step 5: Post-poured belt formwork erection

[0051] The post-pouring belt formwork support of the immersed tunnel adopts a disc buckle type scaffold as a post-pouring belt scaffold force support and operation system 23, and a fastener type scaffold is combined with the disc buckle type scaffold in the local conflict position with the steel support; the disc buckle type scaffold adopts a φ48.3mm type, the standard step distance of the horizontal rod is 1.5m, the vertical rod spacing adopts 0.912m*0.912m, and the inclined pull rod is fully distributed except for the steel support and manhole door positions; the frame body is used as a support force system in the post-pouring belt range, the support frame front is combined with the operation platform to adapt to the post-pouring belt operation space; the top plate needs to be pumped with the top concrete and the steel support to avoid, the template overall force and the connection and fixation of the embedded pump pipe, fully considering the convenience and operability of the operating personnel, the application of the grouped scattered assembly type scattered assembly steel template and the embedded grouting pump pipe system 24, the main beam of the template adopts double-pinned groove steel and is placed on the scaffold jacks in the direction of the top support according to the jacking distance, the secondary beam also adopts double-pinned groove steel and is evenly arranged in three rows in the direction of the structure width to ensure the force of the template across the joint and the two sides; the secondary beam and the combined sheet steel panel are fixed by fasteners;

[0052] Step 6: Post-pouring belt concrete pouring

[0053] The post-pouring belt concrete pouring adopts layered pouring, the bottom plate and the wall are poured once to the top plate and the corner, and the formwork reinforcement system full-frame support simultaneously serves as the operation platform for concrete pouring; the secondary concrete pouring is the top plate concrete; before the post-pouring belt concrete curing reaches the design strength, the temporary thrust steel support shall not be removed; the post-pouring belt concrete adopts the following proportions:

[0054] Water-cement ratio 0.34

[0055] Sand ratio 41%

[0056] Cement 335 kg / m 3

[0057] Sand 701 kg / m 3

[0058] Stone 1009 kg / m 3

[0059] Water consumption 170 kg / m 3

[0060] Fly ash 75 kg / m 3

[0061] Mineral powder 50 kg / m 3

[0062] Water reducing agent 8.5 kg / m 3

[0063] Air entraining agent 1.56 kg / m 3

[0064] Expanding agent 40kg / m 3 ;

[0065] The working performance of reaching self-compensating shrinkage includes C50 final strength, p10 impermeability grade, df80 frost resistance grade, the mixture ratio is suitable for post-pouring belt concrete pouring, no need for vibrating, good working performance such as concrete fluidity and cohesiveness, and fast strength growth, and is suitable for post-pouring belt support stress requirement;

[0066] A 125mm impact top concrete pump pipe is pre-embedded on the formwork at the middle position of the structure, the nozzle is 40cm away from the top plate considering the influence factors of concrete pumping, an exhaust pipe is embedded between the two pump pipes to ensure that the gas in the post-pouring belt operation cavity is discharged and a channel is left for subsequent grouting and densification; a cut-off check valve is arranged on the concrete pump pipe 50cm away from the bottom formwork, and a ball valve check is arranged on the exhaust pipe 30cm away from the bottom formwork;

[0067] Seventh step: waterproof measure of post-pouring belt

[0068] Water-swelling waterproofing adhesive 15 and pre-embedded grouting pipe 16 are arranged at the joint between new and old concrete of the post-pouring belt as the last waterproof measure; the water-swelling waterproofing adhesive needs to keep the base surface dry after the chiseling and cement-based 14 brushing are completed; the thickness is uniform and continuous to reach 10mm, and the distance from the structure edge and the grouting pipe is controlled to be 15cm; two post-grouting pipes are reserved on the top of the post-pouring belt top plate, and grouting and filling densification are carried out after the top plate concrete is poured to ensure the densification of the overall structure; grouting liquid is poured from the grouting guide pipe 17 at the low end of the pre-embedded grouting pipe, and the grouting liquid is extruded upward by using a hand pressure equipment to ensure the grouting effect and make the grouting liquid low-pressure and slow; after the grouting liquid is discharged from the other end of the guide pipe, the grouting guide pipe is closed, and the pressure is increased to 0.8MPa; when the pressure remains stable for 5 minutes without obvious decrease, the grouting is ended. The grouting pipe sealing box 18 is used to seal the grouting pipe to prevent mortar from entering during construction, and grouting and filling densification are carried out after the top plate concrete is poured to ensure the densification of the overall structure. The bottom of the post-pouring belt is grouted and densified by the bottom post-grouting pipe 12.

[0069] The application adopts the structure form of underwater jacking post-pouring to complete the construction of the seabed immersed tube tunnel, after the last pipe section is sunk and placed, the underwater cleaning and inspection of the immersed tube tunnel butt joint area is completed, the jacking section is pushed out through the reserved jacking device, the initial compression is carried out, then the water in the pipe joint cavity is discharged to complete the hydraulic compression, the locking structure is installed, the cavity of the jacking section is sealed and drained, the steel bar is bound and connected at the gap post-pouring belt part in the cavity of the jacking section, the formwork is erected, the waterproof construction is carried out and the concrete is poured. The construction of the post-pouring belt of the seabed immersed tube tunnel can provide the operation space for the normal jacking of the jacking section of the seabed immersed tube tunnel, ensure the smooth butt joint with the last immersed tube pipe section, ensure the accurate and stable posture of the jacking section of the immersed tube tunnel and the immersed tube, adjust the elevation of the jacking section and the external sleeve, ensure the overall elevation of the immersed tube tunnel structure after the construction is completed, reduce the settlement difference and ensure the construction quality.

Claims

1. A method for constructing a post-cast band of a submarine immersed tube tunnel, characterized in that: Specifically comprising the following steps: First step: structure installation before construction of post-cast strip Confirm that the valve at the top of the external sleeve is open and in communication with seawater to ensure smooth jacking. Inside the external sleeve, the jacking segment is pushed out synchronously by 4 jacks at the bottom. The control requirements for the jacking axis are high in precision, and the axis deviation is controlled within 1.5 cm. The jacking force of each jacking jack is 300 t, the oil pressure is 350 Bar, the back tension is 150 t, the oil pressure is 400 Bar, the jacking stroke is 1.7 m, and the weight of a single jack is 3 t. The end steel shell of the jacking segment is in contact with the GINA water stop at the tail end of the last prefabricated immersed tube. The water inlet hole at the top of the external sleeve is 25 cm in diameter, the submergence depth is 14.221 m, the water inlet capacity is 0.8 m³ / s, and it can meet the maximum jacking speed of 145 mm / min. Open the manhole door of the concrete door at the southernmost side of the immersed tube segment to enter the cavity of the jacking segment, measure the jacking segment, and confirm that the jacking segment is correctly connected to the immersed tube segment before the next step. When the jacking jacks push out the jacking segment, the remaining temporary thrust steel supports of the top and bottom plates are also taken out at the same time. Install 24 temporary thrust steel supports in the external sleeve. The connecting steel support is 4.13 m long, weighs 1.3 t, the circular tube diameter is 402 mm, and the flange diameter is 600 mm. Lock the temporary thrust steel support through 24 flat jacks to realize the force transmission between the temporary thrust steel support and the counterforce bracket II. The flat jack jacking force is 550 t, the pressure is 362 Bar, the stroke is 40 mm, it has a mechanical lock function of 600 t, and the weight of a single flat jack is 500 kg. During the jacking process, divers assist in measurement, and before and after jacking the jacking segment, the measuring ruler and the measuring line are used to measure the distance between the jacking segment and the last immersed tube segment and the misalignment of the jacking segment. During the jacking process, divers are in place at the support beam side wall position on both sides of the jacking segment, measure the distance between the jacking segment side wall and the support beam side wall, and monitor the segment deviation in real time during the jacking process. The measurement and control system includes three types of equipment: tension meter, camera displacement meter, and magnetic displacement sensor. Each type of equipment can independently complete high-precision positioning. The measurement and control system mainly uses the tension meter, and the camera displacement meter and the magnetic displacement sensor are used as verification to display the three-dimensional attitude of the jacking segment to ensure installation accuracy. During installation, deformation and stress monitoring of the concrete doors on both sides of the post-cast strip is performed to ensure the safety of the installed structure. Second step: secondary water stop of immersed tunnel post-cast strip When the external sleeve water inlet valve is closed, the external sleeve concrete door pressure gauge value is 2.23 Bar. Slowly open the air inlet valve at the external sleeve concrete door, the opening degree is 1 / 8 turn, the joint cavity water is discharged from the air inlet valve, the drainage capacity is 0.066 m³, the joint cavity pressure value changes from 2.23 Bar to 0.73 Bar, at this time the joint cavity starts to intake air, the single flat jack top plate stress is 244 t, the single flat jack side wall stress is 204 t, and the average bottom plate stress is 171 t. Grouting of the groutable water stop is performed to complete the secondary water stop of the immersed tunnel post-cast strip. The material of the groutable water stop is SBR, the density is 1.16±0.03 t / m³, the tensile strength is ≥16 MPa, the elongation at break is ≥400%, and the tear strength is ≥45 N. Third step: Immersed tube tunnel post-cast strip through measurement After the last segment of the jacking segment installation is completed, the manhole of the immersed tube tunnel is opened, and the initial attitude positioning deviation measurement of the immersed tube tunnel installation is carried out to determine the installation deviation of the immersed tube tunnel. After the jacking segment and the external sleeve door manhole are opened, the full line through measurement is completed to provide accurate structure for the subsequent post-cast strip construction. Fourth step: Post-cast strip reinforcement binding Through the concrete door manhole door into the jacking segment cavity, the end face of the post-cast strip is treated by interface chiseling before the post-cast strip reinforcement binding. The longitudinal reinforcement of the post-cast strip is mainly connected through the mechanical sleeves reserved in the two ends of the jacking segment and the external sleeve. The middle part is fixed by welding. The hoop reinforcement and stirrup are normally mechanically connected and bound and fixed. The maximum radius of the hoop reinforcement is 90 cm. There are 1920 longitudinal pre-buried mechanical sleeves and 960 longitudinal welded seams. Fifth step: Post-cast strip formwork erection The post-cast strip formwork erection of the immersed tube tunnel adopts disc buckle scaffolding as the post-cast strip scaffolding force support and operation system. The local conflict part with the steel support adopts the combined mode of the disc buckle scaffolding and the fastener type scaffolding. The disc buckle scaffolding adopts φ48.3mm type, the standard step distance of the horizontal rod is 1.5m, the vertical rod spacing adopts 0.912m*0.912m, and the diagonal bracing is full of the steel support and manhole door positions. In the post-cast strip range, the frame body is used as the support force system. The front of the support frame is combined with the operation platform to adapt to the post-cast strip operation space. The top plate needs to be pumped with the top concrete and to avoid the steel support. The whole formwork force and the connection and fixation of the pre-buried pump pipe are considered. The application of the grouped scattered combined sheet steel formwork system is fully considered for the convenience and operability of the operating personnel. The main beam of the formwork adopts double-pitched groove steel which is placed on the scaffold jacking according to the jacking interval in the direction of the mileage. The secondary beam also adopts double-pitched groove steel which is evenly distributed in three directions along the structure width direction to ensure the force of the formwork across the middle and both sides of the joint. The secondary beam and the combined sheet steel panel are fixed by fasteners. Sixth step: Post-cast strip concrete pouring The post-cast strip concrete pouring adopts layered pouring. The bottom plate and the wall are poured once to the top plate and the corner. The formwork reinforcement system full-frame support simultaneously serves as the operation platform for concrete pouring. The second concrete pouring is the top plate concrete. Before the post-cast strip concrete curing reaches the design strength, the temporary thrust steel support shall not be removed. The post-cast strip concrete adopts the following proportioning: Water-cement ratio 0.34 Sand ratio 41% Cement 335 kg / m 3 Sand 701 kg / m 3 Stone 1009 kg / m 3 Water consumption 170 kg / m 3 Fly ash 75 kg / m 3 Blast furnace slag 50 kg / m 3 Water reducing agent 8.5 kg / m 3 Air entraining agent 1.56 kg / m 3 Expanding agent 40 kg / m 3 ; The working performance of self-compensating shrinkage: C50 final strength, p10 impermeability grade, df80 frost resistance grade. This proportioning is suitable for post-cast strip concrete pouring. It does not need to be vibrated, has good fluidity and cohesiveness, and has fast strength growth, which is suitable for post-cast strip support force requirements. A 125mm top concrete pump pipe is pre-buried on the formwork in the middle of the structure. Considering the influence factors of concrete pumping, the pipe opening is 40cm away from the top plate. An exhaust pipe is buried between the two pump pipes to ensure that the gas in the post-cast strip operation cavity is discharged and to leave a channel for subsequent grouting. A one-way valve is set 50cm away from the bottom formwork on the concrete pump pipe. A ball valve is set 30cm away from the bottom formwork on the exhaust pipe. Step 7: Waterproofing measures for post-pouring belt Water-swelling waterproofing glue and pre-embedded grouting pipe are used as the last waterproofing measures at the joint between new and old concrete of the post-pouring belt; the water-swelling waterproofing glue needs to be applied after the chiseling and cement-based brushing are completed, and the base surface needs to be kept dry; the thickness of the water-swelling waterproofing glue needs to be uniform and continuous, reaching 10 mm, and the distance from the structure edge and the grouting pipe needs to be controlled within 15 cm; two post-grouting pipes are reserved on the top of the post-pouring belt, and grouting is carried out after the top plate concrete is poured to fill and compact the overall structure; grouting is carried out by pouring grouting liquid from the grouting guide pipe at the bottom end of the pre-embedded grouting pipe, and the grouting liquid is extruded upward by using a hand pressure equipment; in order to ensure the grouting effect, the grouting liquid is slowly advanced at low pressure; After the grouting liquid is discharged from the other end of the guide pipe, the grouting guide pipe is closed, and the pressure is increased to 0.8 MPa; when the pressure is kept for 5 minutes without obvious decrease, the grouting is completed.

2. The method for constructing a post-cast strip of a submarine immersed tunnel according to claim 1, characterized in that: The construction method can ensure that the post-pouring belt has an axis deviation of 1 cm after pouring.

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