Cross-sea shield construction method under long-distance and complex stratum

Abstract

The invention discloses a cross-sea shield construction method under a long-distance complex stratum. The cross-sea shield construction method comprises the steps of construction preparation and site arrangement, end reinforcement, shield machine type selection and debugging, trial tunneling, formal tunneling, muddy water system management, waterproof and reinforcement measures, shield arrival receiving and the like. According to the cross-sea shield construction method under the long-distance and complex stratum, all construction links are systematically optimized, safe and efficient construction of a cross-sea shield tunnel under the long-distance and complex stratum is achieved, and the cross-sea shield construction method can be widely applied to similar projects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel engineering, in particular to a long-distance, complex stratum-crossing sea shield construction method. BACKGROUND

[0002] With the rapid development of urban underground traffic and cross-water channel construction, long-distance cross-sea shield tunnel projects are increasing. Such projects face technical challenges such as complex stratum conditions (e.g., soft soil, silt, sand, hard rock, and alternating distribution of soft and hard composite strata), high water pressure, long excavation distance, and sensitive surrounding environment. Traditional shield construction methods are prone to risks such as excavation face instability, ground settlement exceeding limits, segment damage, and water and sand inflow, which seriously affect construction safety and project quality.

[0003] In the prior art, single reinforcement measures or fixed excavation parameters are often used for shield construction in complex strata, which cannot adapt to the dynamic changes in geological and hydrological conditions in the cross-sea section. The management precision of the slurry system is insufficient, which can easily lead to slurry performance degradation or pipeline blockage. The end reinforcement and receiving process lack reliability, and seepage can easily occur under high water pressure. The waterproof measures are not perfect, and there is a risk of seepage water during long-term operation.

[0004] Therefore, there is an urgent need for a construction method that can comprehensively solve the problems of long-distance, complex stratum-crossing sea shield construction. SUMMARY

[0005] To overcome the problems in the prior art, the present application provides a long-distance, complex stratum-crossing sea shield construction method, which optimizes end reinforcement, shield selection, parameter control, slurry management, waterproofing, and receiving process to achieve safe and efficient construction of cross-sea tunnels.

[0006] The technical solution of the present application is as follows:

[0007] A long-distance, complex stratum-crossing sea shield construction method, comprising the following steps:

[0008] S1, construction preparation and site arrangement: according to the construction range, combined with the needs of shield construction and station construction, the shield construction facilities are arranged;

[0009] S2, end reinforcement: a combination of full-closed steel sleeve, glass fiber reinforcement, and double-pipe jet grouting pile is used for reinforcement at the starting end and receiving end, with a reinforcement range of 3m longitudinally, 3m to the left and right of the shield tunnel structure contour line, and 3m vertically above and below to the moderately weathered rock surface or 2m;

[0010] S3, shield machine selection and debugging: a composite slurry balance shield machine is selected, and the main drive, propulsion system, and slurry circulation system parameters are debugged;

[0011] S4, trial excavation: a 120m trial excavation section is set before formal excavation, and the optimal excavation parameters of different strata are determined by adjusting the slurry tank pressure, slurry specific gravity, advancing speed, cutter head speed and synchronous grouting parameters;

[0012] S5, formal excavation: a dynamic parameter control strategy is adopted, and the excavation speed is controlled to be 20-50mm / min, 15-30mm / min and 10-25mm / min for soft soil layer, hard rock layer and upper soft and lower hard composite stratum respectively, the slurry tank pressure fluctuation is not more than ±0.1bar, and the deviation amount of each ring is less than or equal to 4mm;

[0013] S6, slurry system management: a slurry treatment equipment is adopted, which is composed of a primary sand removal system, a primary cyclone system and a secondary cyclone system, to realize slurry circulation, control the slurry specific gravity to be 1.05-1.35, the viscosity to be 20-35s, and the slurry discharge flow difference to be adjusted according to a 1.5 diffusion coefficient;

[0014] S7, waterproof and reinforcement measures: synchronous grouting adopts cement-fly ash-bentonite slurry, the grouting amount is 130-200% of the building gap, the grouting pressure is 0.3-0.5MPa, and the secondary double-liquid grouting is combined to fill the pipe piece backing gap;

[0015] S8, shield arrival receiving: the receiving end adopts a steel sleeve receiving process, the shield attitude is re-measured 50 rings in advance, and the shield body is supported by the supporting wheel set and grouted to block the hole door after entering the steel sleeve.

[0016] As a preferred scheme of the application, in step S2, after the end reinforcement, end reinforcement effect checking is performed, including drilling 2-3 inspection holes, the water inflow in the hole is ≤0.2L / min·m, the single-point water leakage amount is ≤10L / min, the soil permeability coefficient is <10 -6 cm / s, the unconfined compressive strength is >1MPa, and the horizontal exploration hole is not less than 9, and the depth is not less than 1 / 2 of the reinforcement depth.

[0017] As a preferred scheme of the application, in step S3, the cutter head of the composite slurry balance shield machine adopts a 6-spoke and 6-panel structure, is configured with 18-inch heavy-duty cutters and scrapers, the cutter head outer diameter is 6450mm, the excavation diameter is 6500mm, the opening rate is 30-34%, the main drive rated torque is 6680kNm, the maximum torque is 8100kNm, the pushing system rated thrust is 3161kN, the maximum thrust is 4255kN, the slurry circulation system slurry inlet pipe diameter is DN300, the slurry outlet pipe diameter is DN300, the slurry inlet flow is 900m 3 / h, and the slurry outlet flow is 1000m 3 / h.

[0018] As a preferred scheme of the present application, in step S4, the trial tunneling parameters include slurry tank pressure 2-2.2 bar, total thrust 5000-10000 kN, cutter head speed 1.4-1.6 r / min, 0.8-1.2 r / min when cutting the tunnel face for 5 rings before exiting the hole, and synchronous grouting amount 6.5-9.0 m 3 / ring, shield tail sealing grease 70 Kg / ring.

[0019] As a preferred scheme of the present application, in step S5, the formal tunneling parameters include slurry tank pressure 2-3.2 bar, total thrust 8000-20000 kN, soft soil layer grouting specific gravity 1.05-1.1, hard rock layer, upper soft and lower hard composite stratum grouting specific gravity 1.1-1.2, soft soil layer and hard rock layer grouting viscosity 15-25 s, upper soft and lower hard composite stratum grouting viscosity 20-30 s, cutter head speed 1.4-1.6 r / min, torque < 3000 kNm, synchronous grouting amount 6.5-9.0 m 3 / ring, shield tail sealing grease 70 Kg / ring.

[0020] As a preferred scheme of the present application, in step S6, the slurry treatment system is continuously circulated for 3-5 minutes when stopped, the amount of soil discharged is monitored by an electromagnetic flowmeter and a gamma ray density instrument, the amount of dry sand is calculated according to the density difference of the slurry sent and discharged, and the deviation of the amount of soil discharged per ring from the theoretical value is controlled within ± 5%.

[0021] As a preferred scheme of the present application, in step S7, the synchronous grouting slurry is mixed in a ratio of cement 216-200 kg, fly ash 385-350 kg, bentonite 60-45 kg, sand 782-450 kg, and water 517-480 kg, the gelation time is 3-10 h, and the 28-day consolidation strength is ≥ 2.0 MPa; the secondary grouting is injected through the segment grouting holes after the synchronous grouting, and 300 Kg of cement is injected per hole at a pressure of 0.3-0.5 MPa.

[0022] As a preferred scheme of the present application, in step S7, the secondary double-liquid grouting cement slurry is mixed in a ratio of water glass = 1:1.

[0023] As a preferred scheme of the present application, step S8 specifically includes the following sub-steps:

[0024] S81, receiving preparation: re-measuring the shield posture 50 rings in advance, controlling the axis deviation ± 10 mm, installing a steel sleeve, backfilling coarse sand in the sleeve and testing under pressure;

[0025] S82, receiving process: after the shield enters the steel sleeve, supporting the shield body by 12 groups of supporting wheels, timely jacking the supporting wheels after the cutter head passes, and preventing the shield body from tilting; after the shield body completely enters, injecting the consolidation material through the grease injection hole to block the gap, and removing the steel sleeve after testing that there is no water gushing;

[0026] S83, hole closure: the last 3 ring segments of the receiving section are injected with double slurry to form a water stop plug.

[0027] As a preferred scheme of the present application, in step S81, the central axis of the steel sleeve is consistent with the design axis of the tunnel during installation, the horizontal axis is perpendicular to the direction with an angle deviation of <±2‰ from the steel support, and the pressure of the pressure test is greater than the theoretical water and soil pressure by 0.2 bar.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] 1. The full-closed steel sleeve, glass fiber bar and double-pipe jet grouting pile combined reinforcement system improves the stability and impermeability of the end soil under high water pressure, and reduces the risk of water and sand gushing;

[0030] 2. The optimal parameters of different strata are determined by trial excavation, and the dynamic control strategy is combined to realize the precise matching of the excavation parameters under complex strata, effectively controlling the ground settlement and segment deformation;

[0031] 3. The mud system adopts three-stage treatment and real-time monitoring, ensuring stable mud performance and accurate control of the earth discharge, avoiding pipeline blockage and excavation face instability;

[0032] 4. The combination of simultaneous grouting and secondary grouting with multiple waterproof measures for segment joints significantly improves the waterproof performance of the tunnel, meeting the long-term operation requirements in a cross-sea environment;

[0033] 5. The steel sleeve receiving process ensures the safety of long-distance cross-sea segment receiving. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 The flow chart of a long-distance, complex stratum cross-sea shield construction method in an embodiment of the present application;

[0036] Figure 2 The specific flow chart of the step of receiving the shield in an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in conjunction with the drawings and examples. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings. It is hereby declared that the following described examples are only for explaining the present application and not for limiting the present application.

[0038] Referring to Figure 1 The present embodiment provides a long-distance, complex stratum-crossing sea shield construction method, comprising the following steps:

[0039] S1, construction preparation and site arrangement

[0040] According to the construction range, in combination with the shield construction needs and station construction conditions, the shield construction facilities are arranged, and the installation of supporting facilities and equipment mainly includes gantry crane track beam, mud equipment foundation, slag pool, office area and site pavement, gantry crane, synchronous grouting mortar mixing station, power system, on-site material storage, etc., and emergency passages and monitoring points are reserved to ensure that the site function zoning is reasonable and meets the construction and emergency needs.

[0041] S2, end reinforcement

[0042] Under the conditions of high water pressure and complex stratum (including silt, medium-coarse sand, weathered rock stratum, etc.) at the starting and receiving ends of the crossing sea shield, a combined reinforcement system of full-closed steel sleeve, glass fiber reinforced plastic and double-pipe jet grouting pile is used for the starting and receiving ends to form a triple protection of water stop curtain + structural reinforcement + rigid support, and the reinforcement range is 3m longitudinally, 3m to the left and right of the shield tunnel structure contour line, 3m above and below vertically to the weathered rock surface or 2m, and the end reinforcement effect is detected by exploratory hole to ensure that the soil strength and impermeability meet the standards.

[0043] Specifically, the end reinforcement effect inspection includes: after all the grouting holes are completed, 2-3 inspection holes are drilled for inspection, and the core is taken to observe the grout filling condition, the water inflow in the hole is ≤0.2L / min·m, and the single-point water leakage is ≤10L / min, the soil permeability coefficient should be <10 -6 cm / s, and the unconfined compressive strength is >1MPa; horizontal detection adopts horizontal exploratory hole, and the number of horizontal exploratory holes is not less than 9 (evenly distributed at the top, bottom, left and right waist and four corners), and the depth is not less than 1 / 2 of the reinforcement depth.

[0044] The full-closed steel sleeve is made of Q355B steel plate and is divided into upper half, lower half and transition ring. The thickness of the sleeve is 20-25 mm and the inner diameter is 240 mm larger than the outer diameter of the shield machine (the outer diameter of the shield machine is 6500 mm and the inner diameter of the steel sleeve is 6740 mm), so as to ensure sufficient operation space for the shield machine. The transition ring is welded with the pre-buried steel ring of the portal, and the height of the weld is greater than or equal to 10 mm, so as to ensure the sealing performance.

[0045] The arrangement range of the glass fiber bar is:

[0046] The glass fiber bar mesh is arranged inside the double-tube rotary jet grouting pile reinforced area (i.e. close to the tunnel structure contour line) to replace the traditional steel bar and avoid the collision and wear of the shield cutter when cutting; the glass fiber bar is arranged along the longitudinal direction and the circumferential direction of the tunnel, the longitudinal spacing is 300 mm, and the circumferential spacing is 250 mm, so as to form a reinforcing structure with a grid size of 300 mm x 250 mm.

[0047] The reinforced range of the double-tube rotary jet grouting pile is defined as:

[0048] 1) Planar range: the length along the direction of shield tunnel excavation (longitudinal direction) is 3 m; the transverse width is 3 m on both sides of the shield tunnel structure contour line, i.e. 3 m on both sides of the outer diameter of the tunnel;

[0049] 2) Vertical range: at the starting end, 3 m above the shield tunnel structure contour line and 2 m below, covering the full section of the tunnel top to the bottom and the soil body within a certain range around the tunnel; at the receiving end, 3 m above the shield tunnel structure contour line and to the moderately weathered rock surface below, so as to ensure that the bottom of the reinforced body is embedded in the stable rock layer and avoid disturbance of the lower permeable layer;

[0050] 3) The rotary jet grouting pile is arranged in a plum blossom shape, the pile diameter is Φ600 mm, the pile spacing is 450 mm, and the pile body lap joint length is greater than or equal to 150 mm, so as to form a continuous waterproof curtain.

[0051] In step S2, the double-tube rotary jet grouting pile forms a continuous waterproof curtain through high-pressure grouting, the pile body is tightly lapped, and cooperates with the steel sleeve joint waterproof strip, so as to effectively block the infiltration of groundwater and seawater, and the permeability coefficient is controlled to be less than or equal to 10 -6cm / s, the water inflow is far below the limit, and the risk of water and sand inflow at the end under the condition of high water pressure in the cross-sea section is solved. The double-pipe jet grouting pile and the glass fiber mesh form a composite reinforcement, and the unconfined compressive strength is improved to more than 1 MPa, and the integrity of the soil body is significantly improved; the steel sleeve provides rigid restraint and can withstand the water and soil pressure and the thrusting reaction force during the initiation / reception of the shield, avoiding deformation or collapse of the end soil body, and providing a solid foundation for the safe entry and exit of the shield machine; the glass fiber reinforcement is used instead of the traditional steel reinforcement, avoiding the risk of cutter collision during shield cutter cutting, reducing cutter wear and tear and the number of cutter replacement; through the double detection means of inspection hole + horizontal probe hole, the integrity, impermeability and strength of the reinforcement body can be comprehensively evaluated, and the unqualified area is treated by grouting in time to ensure that the reinforcement effect is 100% up to standard, laying a reliable safety guarantee for subsequent shield tunneling.

[0052] S3, selection and debugging of shield machine

[0053] Based on long-distance cross-sea, complex strata (including cohesive soil, silt cohesive soil, medium-coarse sand, fully / strongly / mediumly weathered mixed granite, and upper-soft-lower-hard composite strata) and high water pressure conditions, a composite slurry balance shield machine is selected, and the main drive, propulsion system and slurry circulation system parameters are debugged to ensure that the equipment meets the needs of hard rock and composite strata tunneling.

[0054] Specifically, the cutter head of the composite slurry balance shield machine adopts a 6-spoke, 6-panel structure, is configured with 18-inch heavy-duty cutters and scrapers, has an outer diameter of 6450 mm, an excavation diameter of 6500 mm, an opening rate of 30-34%, a main drive rated torque of 6680 kNm, a maximum torque of 8100 kNm, a propulsion system rated thrust of 3161 kN, a maximum thrust of 4255 kN, a slurry circulation system inlet pipe diameter of DN300, an outlet pipe diameter of DN300, an inlet flow of 900 m 3 / h, and an outlet flow of 1000 m 3 / h. Among them, the opening rate of the central area is larger than that of the edge area, and increasing the opening rate of the central area can reduce the accumulation of hard rock segment in the center of the cutter head, and reducing the opening rate of the edge area can enhance the structural rigidity.

[0055] The composite slurry balance shield machine with the above settings has a 6-spoke, 6-panel structure cutter head, strong impact resistance, good cutter protection, and hard rock tunneling capacity; 18-inch heavy-duty cutters are selected, which have good rock breaking capacity; tunneling is controlled with high speed and low torque, which can solve the construction problem of long-distance shield tunneling in hard rock strata; the main drive maximum torque of 8100 kNm can cope with the high resistance of hard rock section, and the propulsion system maximum thrust of 4255 kN ensures the continuous advancement of the shield; a large flow of slurry circulation (inlet flow of 900 m 3 / h, outlet flow of 1000 m 3 / h) to ensure that the excavation face does not collapse or leak under high water pressure in the cross-sea section, providing a stable working environment for continuous tunneling.

[0056] S4, Trial Excavation

[0057] Before formal tunneling, a 120m test tunneling section is set up. By adjusting the slurry chamber pressure, slurry specific gravity, propulsion speed, cutterhead rotation speed and synchronous grouting parameters, the optimal tunneling parameters for different strata are determined, providing a quantitative basis for formal tunneling and reducing the risks caused by blindly adjusting parameters.

[0058] Specifically, the trial tunneling parameters included a slurry chamber pressure of 2-2.2 bar, a total thrust of 5000-10000 kN, a cutterhead rotation speed of 1.4-1.6 r / min, a cutting speed of 0.8-1.2 r / min during the first 5 rings of cutting at the tunnel face after exiting the tunnel, and a simultaneous grouting volume of 6.5-9.0 m³. 3 / ring, shield tail sealing grease 70Kg / ring.

[0059] After the trial tunneling is completed, the following conditions must be met: ① All systems of the tunnel boring machine are operating normally without any major faults; ② Ground settlement is controlled within +10mm to -30mm; ③ Segment misalignment is ≤5mm (circumferential) and ≤6mm (longitudinal); ④ The strength of the grouting solidified body after 24 hours is ≥0.2MPa; ⑤ A "Trial Tunneling Parameter Optimization Report" is prepared, which clarifies the range of formal tunneling parameters.

[0060] S5, Formal Tunneling

[0061] A dynamic parameter control strategy was adopted to control the tunneling speed at 20-50 mm / min, 15-30 mm / min, and 10-25 mm / min for soft soil, hard rock, and composite strata with soft upper and hard lower layers, respectively. The pressure fluctuation of the slurry chamber did not exceed ±0.1 bar, and the correction amount per ring was ≤4 mm.

[0062] Specifically, the formal tunneling parameters include: slurry chamber pressure 2-3.2 bar, total thrust 8000-20000 kN; slurry specific gravity for soft soil layers 1.05-1.1; slurry specific gravity for hard rock layers and composite strata (soft upper layer, hard lower layer) 1.1-1.2; slurry viscosity for soft soil and hard rock layers 15-25 s; slurry viscosity for composite strata (soft upper layer, hard lower layer) 20-30 s; cutterhead rotation speed 1.4-1.6 r / min; torque <3000 kNm; and simultaneous grouting volume 6.5-9.0 m³. 3 / ring, shield tail sealing grease 70Kg / ring.

[0063] In step S5, based on the dynamic parameter control strategy of trial excavation results, precise adaptation to different strata is achieved: low specific gravity mud (1.05-1.1) and higher advance speed (20-50 mm / min) are used in soft soil layer to reduce disturbance; hard rock layer is ensured by increasing mud water tank pressure (2-3.2 bar) and total thrust (8000-20000 kN); for soft upper and hard lower strata, the balance between excavation face stability and tunneling efficiency is achieved by adjusting the slurry viscosity (20-30 s) and controlling the advance speed (10-25 mm / min), effectively solving the technical problem that a single parameter cannot adapt to composite strata. By strictly limiting the mud water tank pressure fluctuation (≤±0.1 bar), the balance of water and soil pressure on the excavation face is ensured, effectively preventing the risks of water and sand inrush and collapse; at the same time, strict control of cutter head torque (<3000 kNm) and per ring correction amount (≤4 mm) reduces additional disturbance to the stratum, ensuring the integrity of the soil structure around the tunnel, especially suitable for construction safety in high-risk areas such as cross-segment. The synchronous grouting amount (6.5-9.0 m 3 / ring) is controlled according to 130%-200% of the construction gap, combined with continuous injection of shield tail sealing grease (70 Kg / ring), effectively filling the gap between the segment and the stratum, reducing the risk of segment settlement and joint error. Under the control of dynamic parameters, the tunnel axis deviation can be controlled within the design allowable range, and the segment assembly quality (such as circumferential / longitudinal joint error, ovality) is guaranteed, laying a foundation for long-term stability of the tunnel structure.

[0064] S6, mud water system management

[0065] Mud water treatment equipment is used, which is composed of primary sand removal system, primary cyclone system and secondary cyclone system to realize mud water circulation.

[0066] Specifically, the slurry specific gravity is controlled to 1.05-1.35, the viscosity is controlled to 20-35 s, the discharge flow difference is controlled according to the 1.5 diffusion coefficient, so that the mud can form effective pressure support for the excavation face and has good sludge carrying capacity; when the mud water treatment system is stopped, it is continuously circulated for 3-5 minutes, which can timely transport the residual high-concentration sludge or easily precipitated particles in the pipeline to the ground for treatment, preventing the mud from settling and forming blockage in the pipeline; the soil discharge amount is monitored by electromagnetic flowmeter and gamma ray density instrument, the dry sand amount is calculated according to the density difference of the mud water, the overbreak is increased by increasing the grouting amount, and the overbreak or underbreak problem can be found in time by controlling the overbreak or underbreak amount within ±5% of the theoretical value.

[0067] In step S6, the slurry discharged by the shield is purified by a primary desanding system, a primary cyclone system and a secondary cyclone system of the slurry treatment device, the primary desanding system (coarse screen) removes large-diameter muck (≥45 mm) first, the medium-diameter sand particles (20-45 mm) are separated in the primary cyclone separation, and the secondary cyclone further removes fine particles (≤20 mm), so that the sand content of the circulating slurry is controlled within a reasonable range; the purified slurry can meet the tunneling requirements again, reduce the preparation amount of new slurry, reduce material consumption, avoid pipeline blockage and cutter head wear caused by excessive impurities, and ensure the continuous and stable operation of the slurry circulation system.

[0068] S7, waterproofing and reinforcement measures

[0069] The synchronous grouting adopts cement-fly ash-bentonite slurry, combined with secondary double-liquid grouting to fill the gap of the segment backing, and the segment joint is provided with three waterproof structures of sponge rubber strip, elastic sealing pad and embedded joint, and the segment joint is provided with three waterproof measures of sponge rubber strip, elastic sealing pad and embedded joint, and the elastic sealing pad is mainly used as the waterproof measure to ensure the waterproof performance.

[0070] Specifically, the grouting amount of synchronous grouting is 130-200% of the construction gap, the grouting pressure is 0.3-0.5 MPa, the synchronous grouting slurry ratio is cement 216-200 kg, fly ash 385-350 kg, bentonite 60-45 kg, sand 782-450 kg, and water 517-480 kg, the gel time is 3-10 h, and the 28-day consolidation strength is ≥2.0 MPa. During synchronous grouting, the grouting amount is controlled at 130-200% of the construction gap, which far exceeds the theoretical filling requirement and can fully fill the annular gap formed between the segment and the stratum during the shield advancing process; combined with the grouting pressure of 0.3-0.5 MPa, it is ensured that the slurry can penetrate into the gap of the surrounding soil, effectively preventing the stratum from collapsing or settling due to the gap, especially in soft soil, silt soil and other easily deformed strata, which can significantly reduce the ground settlement and control the settlement within the design range of +10 mm to-30 mm. The cement-fly ash-bentonite slurry with a specific ratio has a gel time (3-10 h) that can be adjusted according to the stratum conditions and the advancing speed. In water-rich strata or areas requiring rapid and stable conditions, a setting accelerator can be added to shorten the gel time to avoid slurry loss; in soft soil strata, the gel time is extended to ensure sufficient filling of the slurry. The 28-day consolidation strength is ≥2.0 MPa, which can provide long-term stable support for the segment to prevent post-settlement or deformation of the segment and ensure the long-term stability of the tunnel structure. The addition of bentonite in the slurry improves the fluidity and water retention, avoids segregation or pipe blockage during grouting, and ensures continuous and smooth grouting.

[0071] Specifically, the secondary grouting is injected through the segment grouting hole after the synchronous grouting, 300 Kg of cement is injected per hole, the pressure is 0.3-0.5 MPa, and the cement slurry of the secondary double-liquid grouting is water glass = 1:1. Since the synchronous grouting slurry will generate a volume shrinkage of about 1.4% during the solidification process, the secondary grouting process with the above specific parameters can fill the gap formed by the shrinkage in time and eliminate the potential space of stratum deformation; for the area where the synchronous grouting is not full and there are cavities (such as the top and side of the segment where filling defects are prone to occur), the secondary grouting can achieve precise filling through pressure grouting, thereby improving the filling density of the backing; the double-liquid slurry has a fast solidification speed (a few seconds to a few minutes), and in the water-rich stratum or the segment joint leakage position, a water-stopping curtain can be quickly formed to effectively control the infiltration of underground water and reduce the risk of tunnel leakage water. The secondary grouting pressure of 0.3-0.5 MPa can make the slurry closely combine with the segment backing and the surrounding stratum, thereby enhancing the cooperative stress capacity of the segment and the stratum, reducing the deformation or dislocation of the segment under the action of water and soil pressure, and improving the integrity and anti-deformation capacity of the tunnel structure.

[0072] Specifically, in the waterproofing of the segment joint, the elastic sealing gasket is made of ethylene propylene diene rubber, has a high compression and rebound performance through special section design, closely adheres under the action of the segment assembly pressure, blocks the water infiltration path, and adapts to the slight deformation of the segment joint; the inside of the joint is treated by caulking, and the caulking material is polymer cement or polysulfide sealant; the outside of the joint is pasted with chloroprene sponge rubber to block the mud, grease and other substances from entering the joint.

[0073] S8, shield arrives at the receiving end

[0074] The receiving end adopts a steel sleeve receiving process, the shield attitude is re-measured 50 rings in advance, the shield body is supported by the supporting wheel set and grouting is performed after entering the steel sleeve to block the hole, and safety receiving is ensured.

[0075] Please refer to Figure 2 , specifically, the following sub-steps are included:

[0076] S81, preparation before receiving: the shield attitude is re-measured 50 rings in advance, the axis deviation is controlled to be ±10 mm, the shield machine is ensured to approach the receiving end along the optimal path, the collision between the shield body and the steel sleeve or the hole structure caused by the large attitude deviation is avoided, the foundation for the subsequent smooth entry into the steel sleeve is laid, the steel sleeve is installed, the center axis is consistent with the tunnel design axis, and the horizontal axis is perpendicular to the angle deviation of the steel support is <±2‰, the steel sleeve is ensured to be completely matched with the receiving track of the shield machine, the sleeve is backfilled with coarse sand and pressure test is performed, the pressure of the pressure test is greater than the theoretical water and soil pressure by 0.2 bar, on the one hand, uniform support of the shield body is achieved through sand backfilling, on the other hand, the sealing performance and structural strength of the steel sleeve are verified through the overpressure test, the steel sleeve is ensured not to leak and deform under high water pressure, a rigid protection space is provided for the shield receiving,

[0077] S82, receiving process: after the shield enters the steel sleeve, the shield body is supported by 12 groups of supporting wheel sets, the cutter head is timely jacked up after passing through, which can effectively resist the sinking trend of the shield body due to self weight or stratum pressure after long distance tunneling, and prevent the shield body from being planted; after the shield body completely enters the steel sleeve, the gap between the shield body and the sleeve is blocked by injecting solidified material through the grease injection hole to form a water stop barrier, combined with the sealing structure of the steel sleeve, the double waterproof effect of active blocking and passive protection is realized, the safety risk of water and sand inrush during the receiving stage is significantly reduced, and the steel sleeve is removed after testing no water inrush.

[0078] S83, hole sealing: the last 3 rings of segments are pressure injected with double liquid slurry to form a water stop plug, the fast setting speed and high early strength of the double liquid slurry (cement slurry: water glass = 1:1) are used to build a rigid water stop barrier between the tunnel and the receiving well, the water stop plug can block the longitudinal water seepage channel of the tunnel, prevent underground water at the receiving end from seeping into the inside of the tunnel along the outside of the segment or the joint, at the same time, the segment is formed secondary reinforcement, the integrity and deformation resistance of the segment in the hole area are enhanced, and the long-term stability of the hole structure is ensured.

[0079] In summary, the cross-sea shield construction method of the application realizes safe and efficient construction of cross-sea shield tunnel in long distance and complex stratum by systematically optimizing each link of construction, and can be widely applied to similar projects; the full-closed steel sleeve, glass fiber reinforcement and double-pipe rotary jet pile combined reinforcement system are used to improve the stability and impermeability of the end soil under high water pressure and reduce the risk of water and sand inrush; the optimal parameters of different strata are determined through trial tunneling, combined with dynamic control strategy, the precise matching of tunneling parameters in complex stratum is realized, and the ground settlement and segment deformation are effectively controlled; the three-stage treatment and real-time monitoring of the slurry system ensure the stability of the slurry performance and the precise control of the earth discharge, and avoid pipeline blockage and excavation face instability; the combination of synchronous grouting and secondary grouting, together with multiple waterproof measures for segment joints, significantly improves the waterproof performance of the tunnel and meets the long-term operation demand in cross-sea environment; the steel sleeve receiving process is adopted to ensure the safety of the cross-sea section shield receiving.

[0080] It should be noted that the terms "include" and "have" in the specification and claims of the application, as well as any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product or device.

[0081] Furthermore, although the operations of the method of the present application are described in a particular, sequential order, this order is not meant to be a limitation and is not intended to imply that there is an absolute requirement that the operations be performed in the order described. On the contrary, many of the operations can be performed in any order, added to, or omitted from the operations described. Also, in some implementations, aspects of two or more of the operations can be combined into a single operation, and / or a single operation can be separated into two or more operations.

[0082] It is to be understood that all such modifications and variations that can be made by those of ordinary skill in the art are intended to be encompassed by the present application.

[0083] The above description of the present application has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

Claims

1. A method for constructing a cross-sea shield tunnel over long distances and in complex geological formations, characterized in that, Includes the following steps: S1. Construction preparation and site layout: Based on the construction scope, the needs of shield tunneling and the station construction situation, the shield tunneling facilities will be arranged. S2. End reinforcement: The starting end and receiving end adopt a combination reinforcement system of fully enclosed steel sleeve, glass fiber reinforcement and double pipe jet grouting pile. The reinforcement range is 3m longitudinally and 3m to the left and right of the shield tunnel structure outline, and 3m above and 2m below the moderately weathered rock surface. S3. Tunnel Boring Machine Selection and Commissioning: A composite slurry balance tunnel boring machine was selected, and the parameters of the main drive, propulsion system and slurry circulation system were commissioned. S4. Trial Excavation: A 120m trial excavation section is set up before formal excavation. The optimal excavation parameters for different strata are determined by adjusting the slurry chamber pressure, slurry specific gravity, propulsion speed, cutterhead speed and synchronous grouting parameters. S5. Formal Tunneling: A dynamic parameter control strategy is adopted to control the tunneling speed at 20-50 mm / min, 15-30 mm / min, and 10-25 mm / min for soft soil, hard rock, and composite strata with soft upper and hard lower layers, respectively. The pressure fluctuation of the slurry chamber shall not exceed ±0.1 bar, and the correction amount per ring shall be ≤4 mm. S6. Slurry system management: Slurry treatment equipment is adopted, which consists of a primary sand removal system, a primary cyclone system, and a secondary cyclone system to realize slurry circulation, control the feed slurry specific gravity to 1.05-1.35, viscosity to 20-35s, and adjust the discharge flow rate difference according to a diffusion coefficient of 1.

5. S7. Waterproofing and reinforcement measures: Simultaneous grouting uses cement-fly ash-bentonite grout, with a grouting volume of 130-200% of the building voids and a grouting pressure of 0.3-0.5MPa, combined with secondary double-liquid grouting to fill the voids in the pipe segment backing; S8. Shield arrival and reception: The receiving end adopts the steel sleeve receiving process. The shield attitude is re-measured 50 rings in advance. After the shield enters the steel sleeve, it is supported by the roller group and the tunnel entrance is sealed by grouting.

2. The method for cross-sea shield tunneling under long distances and complex geological conditions according to claim 1, characterized in that, In step S2, after the end is reinforced, the reinforcement effect is checked, including drilling 2-3 test holes. The water inflow in the holes should be ≤0.2L / min·m, and the single-point leakage should be ≤10L / min. The soil permeability coefficient should be <10. -6 cm / s, unconfined compressive strength > 1MPa, no less than 9 horizontal boreholes, with a depth not less than 1 / 2 of the reinforcement depth.

3. The method for cross-sea shield tunneling under long distances and complex geological conditions according to claim 1, characterized in that, In step S3, the cutterhead of the composite slurry balance shield machine adopts a 6-spoke, 6-panel structure, equipped with 18-inch heavy-duty roller cutters and scrapers. The cutterhead outer diameter is 6450mm, the excavation diameter is 6500mm, the opening ratio is 30-34%, the main drive rated torque is 6680kNm, the maximum torque is 8100kNm, the propulsion system rated thrust is 3161kN, the maximum thrust is 4255kN, the slurry circulation system has a slurry inlet pipe diameter of DN300, a slurry outlet pipe diameter of DN300, and a slurry flow rate of 900m³ / h. 3 / h, slurry flow rate 1000m³ 3 / h.

4. The method for cross-sea shield tunneling under long distances and complex geological conditions according to claim 1, characterized in that, In step S4, the trial tunneling parameters include a slurry chamber pressure of 2-2.2 bar, a total thrust of 5000-10000 kN, a cutterhead rotation speed of 1.4-1.6 r / min, a cutting speed of 0.8-1.2 r / min during the first 5 rings of cutting at the tunnel face before exiting the tunnel, and a synchronous grouting volume of 6.5-9.0 m³. 3 / ring, shield tail sealing grease 70Kg / ring.

5. The method for cross-sea shield tunneling under long distances and complex geological conditions according to claim 1, characterized in that, In step S5, the formal tunneling parameters include: slurry chamber pressure 2-3.2 bar, total thrust 8000-20000 kN, slurry specific gravity for soft soil layers 1.05-1.1, slurry specific gravity for hard rock layers and composite strata (soft upper layer, hard lower layer) 1.1-1.2, slurry viscosity for soft soil layers and hard rock layers 15-25 s, slurry viscosity for composite strata (soft upper layer, hard lower layer) 20-30 s, cutterhead rotation speed 1.4-1.6 r / min, torque <3000 kNm, and synchronous grouting volume 6.5-9.0 m³. 3 / ring, shield tail sealing grease 70Kg / ring.

6. The method for cross-sea shield tunneling under long distances and complex geological conditions according to claim 1, characterized in that, In step S6, the mud and water treatment system continues to circulate for 3-5 minutes when it stops. The amount of soil discharged is monitored by an electromagnetic flow meter and a gamma linear density meter. The amount of dry sand is calculated based on the density difference between the delivered and discharged mud and water. The deviation between the amount of soil discharged per ring and the theoretical value is controlled within ±5%.

7. The method for cross-sea shield tunneling under long distances and complex geological conditions according to claim 1, characterized in that, In step S7, the synchronous grouting slurry mix ratio is 216-200 kg of cement, 385-350 kg of fly ash, 60-45 kg of bentonite, 782-450 kg of sand, and 517-480 kg of water, with a cementing time of 3-10 hours and a 28-day consolidation strength ≥2.0 MPa. The secondary grouting is injected through the grouting holes of the segments after the synchronous grouting, with 300 kg of cement injected into each hole at a pressure of 0.3-0.5 MPa.

8. The method for long-distance, complex geological tunneling under sea conditions according to claim 1, characterized in that, In step S7, the ratio of cement grout to water glass in the secondary double-liquid grouting is 1:

1.

9. The method for long-distance, complex geological tunneling under sea conditions according to claim 1, characterized in that, Step S8 specifically includes the following sub-steps: S81. Preparations before receiving: Re-measure the shield attitude 50 rings in advance, control the axis deviation ±10mm, install the steel sleeve, backfill the sleeve with coarse sand and test the pressure. S82. Receiving process: After the shield enters the steel sleeve, the shield body is supported by 12 sets of rollers. After the cutterhead passes, the rollers are lifted in time to prevent the shield body from tilting. After the shield body is fully in, the solidification material is injected through the grease injection hole to seal the gap. After testing that there is no water inflow, the steel sleeve is removed. S83. Tunnel portal sealing: Double-liquid grout is injected into the last three rings of segments of the receiving section to form a water-stopping plug.

10. The method for constructing a cross-sea shield tunnel under long distances and complex geological formations according to claim 9, characterized in that, In step S81, the central axis of the steel sleeve is aligned with the tunnel design axis during installation, the deviation of the angle between the horizontal axis and the steel support is less than ±2‰, and the pressure of the pressure test is greater than the theoretical soil and water pressure by 0.2 bar.

Images