Tunnel pipe roof advanced pre-building primary support and lining structure and construction method

Abstract

The invention relates to the technical field of tunnel construction, in particular to a tunnel pipe roofing advance pre-building primary supporting and lining structure and a construction method.The tunnel pipe roofing advance pre-building primary supporting and lining structure comprises a circumferential pipe roofing, the circumferential pipe roofing comprises a plurality of pipe roofing steel pipes arranged in parallel, and pipe roofs are arranged above a top pipe roofing and a bottom pipe roofing in a driving mode; the pipe roofs are arranged above the pipe roofing steel pipes of the top pipe roofs and the bottom pipe roofs; all the pipe roofing steel pipes on the circumferential pipe roofing are cut and are connected in a welded mode at the cutting positions through steel plates, so that all the pipe roofing steel pipes form an annular pipe roofing inner cavity, and the pipe roofing inner cavity is filled with concrete in a poured mode. Through a pipe-roofing advanced pre-building construction method, a primary support and a lining are integrated to form a super-strong combined structure of a pipe roofing and steel plate concrete, and ground surface settlement is controlled to be smaller than 10 mm.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel construction. Specifically, it relates to a tunnel pipe roof advanced prefabricated primary support and lining structure and construction method. Background Technique

[0002] The construction of urban underground space faces various problems, especially in the crossing of multiple fields such as transportation, municipal engineering, and buildings. During the construction process, the crossing environment becomes a major problem. Especially when passing under in the urban environment, the control of deformation settlement becomes extremely difficult.

[0003] For crossings under special conditions, such as high-speed railway lines, historical and cultural relic protection areas, etc., the construction difficulty and risk increase exponentially. In addition, due to the narrow construction space, the construction methods adopted need to be innovative to ensure that the project can be completed efficiently and safely within the limited space.

[0004] During the construction of the tunnel, millimeter-level settlement control becomes the core goal of engineering design and construction. In order to avoid affecting facilities such as the upper rail transit, the settlement amount must be strictly controlled, usually required not to exceed 10 millimeters. Ensuring the integrity and safety of the structure and reducing the safety risks brought by settlement become key factors that must be emphasized during the construction process. Summary of the Invention

[0005] The purpose of the present application is to provide a tunnel pipe roof advanced prefabricated primary support and lining structure and construction method. Through the pipe roof advanced prefabricated construction method, the primary support and lining are integrated to form a super-strong combined structure of the pipe roof and steel plate concrete, and the ground settlement is controlled to be less than 10 mm.

[0006] To achieve the above purpose, in the first aspect, the present invention provides a tunnel pipe roof advanced prefabricated primary support and lining structure, including: a circumferential pipe roof arranged on the periphery of the tunnel, the circumferential pipe roof includes a top pipe roof and a bottom pipe roof located in the upper and lower layers, and a left pipe roof and a right pipe roof located on the left and right sides, forming a rectangular pipe roof structure; The circumferential pipe roof includes a plurality of pipe roof steel pipes arranged in parallel. Pipe sheds are driven above both the top pipe roof and the bottom pipe roof, and the pipe sheds are arranged above the pipe roof steel pipes of the top pipe roof and the bottom pipe roof; All the pipe roof steel pipes on the circumferential pipe roof are cut, and are welded and connected at the cutting parts through steel plates, so that all the pipe roof steel pipes form an annular pipe roof inner cavity, and concrete is poured and filled in the pipe roof inner cavity.

[0007] In the second aspect, the present invention provides a construction method for a tunnel pipe roof advanced prefabricated primary support and lining structure, which constructs the tunnel pipe roof advanced prefabricated primary support and lining structure described above, including the following steps: The axis of the pipe curtain steel pipe is calibrated through three-dimensional spatial positioning; Grouting pipe sheds are respectively installed above the pipe curtain steel pipes of the top pipe curtain and the bottom pipe curtain to form pre-support; The circumferential pipe curtain of the tunnel section is constructed by the skip hole method, and the settlement of a single pipe curtain steel pipe is controlled; After the pipe curtain steel pipes are in place, all pipe curtain steel pipes are cut and welded at the cut parts through steel plates to form a rigid ring of the circumferential pipe curtain, and the closed space of the rigid ring constitutes an annular pipe curtain inner cavity; The inner cavity of the pipe curtain of the rigid ring is filled with self-compacting concrete to form a composite load-bearing structure; The construction of the tunnel pipe roof's pre-built primary support and lining structure is completed, and the soil excavation is carried out in layers and zones after the stiffness meets the standard.

[0008] In an optional implementation, during the construction of the circumferential pipe curtain, the bottom pipe curtain is first pushed forward by double-tube jacking, the excavation volume of a single pipe is controlled at 95%-105% of the theoretical value, and a temporary steel support is set up every 1.5m of advancement; The top pipe curtain is installed 48 hours later than the bottom pipe curtain; During the double-tube jacking process, single-tube excavation and synchronous grouting were coordinated and controlled. The excavation chamber pressure was stabilized at 0.18-0.22MPa, and the grouting pressure was increased in stages between 0.5-1.8MPa, forming a composite reinforcement ring with a thickness of 3.2m. The left and right pipe curtains are constructed in longitudinal sections and H-shaped steel temporary reinforcement ribs are erected immediately after each 6m pipe section is completed.

[0009] In an optional embodiment, after the circumferential pipe curtain is penetrated, temporary supports are set up on both sides of the cutting area, and single-side cutting is implemented by cutting equipment. The incision is deflected 15° along the longitudinal circumference of the pipe curtain steel pipe to form a guide groove, and then the annular connecting plate is positioned. When welding, the longitudinal weld is first welded, and then the annular weld is welded by alternating double-sided welding. Prestressed support is applied immediately after each 3m weld is completed, and finally a fully closed steel structure bearing ring is formed.

[0010] In an optional embodiment, during the concrete filling stage, the height section of the tunnel is divided into three bins: lower, middle, and upper, and the pouring interval between each bin is 72 hours; When pouring C50 self-compacting concrete into the lower bin, the pouring rate is controlled to be ≤0.6m / h, and the hydraulic fracturing monitoring system is started simultaneously; 8% expansion agent is added to the middle layer to compensate for shrinkage and deformation; Low-temperature concrete is used in the upper warehouse to suppress temperature stress.

[0011] Thirdly, the present invention provides a method for checking and calculating the advanced precast primary support and lining structure of a tunnel pipe roof, including the calculation of the bearing load, structural stiffness, load intensity check, and ground settlement volume; In the calculation of the bearing load of the advanced precast primary support and lining structure of the tunnel pipe roof, the bearing load includes load combinations, and the load combinations include dead load, live load, and environmental load; The calculation of the structural stiffness of the advanced precast primary support and lining structure of the tunnel pipe roof includes a structural stiffness calculation model; In the check of the load intensity of the advanced precast primary support and lining structure of the tunnel pipe roof, it includes ultimate limit state combinations and safety checks; In the calculation of the ground settlement volume of the advanced precast primary support and lining structure of the tunnel pipe roof, it includes the calculation of the maximum settlement volume and the secondary correction of the settlement by the welded joints.

[0012] In an optional embodiment, in the calculation of the bearing load, the dead load includes the self-weight of the structure, overburden pressure, and groundwater buoyancy, the live load includes the static load of the train and the live load of the train, and the environmental load includes the lateral earth pressure and water pressure.

[0013] In an optional embodiment, in the calculation of the structural stiffness, the structural stiffness calculation model includes considering the circumferential pipe roof and the filled concrete as a composite structure and establishing an equivalent flexural stiffness model: ; where EI eq is the stiffness of the composite structure, E 钢 represents the elastic modulus of the pipe roof steel pipe, E 混凝土 represents the elastic modulus of the concrete, I 钢 represents the moment of inertia of the pipe roof steel pipe, I 混凝土 represents the moment of inertia of the concrete; Parameters of the pipe roof steel pipe: ; where D represents the outer diameter of the pipe roof steel pipe, and t represents the wall thickness of the pipe roof steel pipe; Parameters of the concrete: ; where D_inner represents the inner diameter of the pipe roof steel pipe; Introduce a stiffness correction coefficient and take the reference stiffness, then: ; where EI_reference represents the reference stiffness; In the calculation of the structural stiffness, it also includes the stiffness correction of the contribution of the welded joint stiffness. Consider the pipe roof steel pipe and the welded steel plate of the circumferential pipe roof as an integral frame, and use the beam, column, and joint domain composite model to calculate the stiffness: ; Circumferential pipe roof stiffness: ; Among them, L represents the overall span of the circumferential pipe roof; Welded joint stiffness: ; Based on the rotational stiffness correction of the welded joint, the semi-rigid effect of the welded joint introduces the rotational spring coefficient k; ; Among them, t w represents the thickness of the gusset plate, with the unit of m, h w represents the effective height of the joint, with the unit of m; d b represents the bolt spacing, with the unit of m. For the welded joint, when taking it as a rigid connection, d b →0, and the denominator term is ignored after simplification; ν represents the Poisson's ratio, taking 0.3 for steel, and l e represents the effective length of the joint; The calculation of the corrected equivalent stiffness includes the calculation of the single-span steel frame stiffness and the equivalent flexural stiffness of the overall structure; The calculation of the single-span steel frame stiffness includes: Taking the transverse steel frame with a typical span of 18.5m: ; The correction coefficient is: ; The calculation of the equivalent flexural stiffness of the overall structure considers the action of continuous steel frames within the full cross-section range: .

[0014] In an alternative implementation, the load intensity check includes the check of load combinations and structural strength; The ultimate limit state combinations include: ; In the safety check, it includes the structural anti-floating safety factor: ; Used to determine whether it meets the code requirements; Taking a single-span simply supported beam for the roof slab moment check: ; Allowable stress of the steel plate: ; Allowable compressive stress of the concrete: ; The actual stress should be less than the allowable stress specified in the code.

[0015] In an alternative embodiment, in the calculation of the ground settlement amount, the calculation of the maximum settlement amount includes: ; where S max represents the maximum settlement amount, q 面 represents the surface load, and the calculation formula includes: ; ; where B represents the bearing width, and k s represents the bedding coefficient, taking 1×10 4 kN / m³; After the calculation of the maximum settlement amount, it includes the secondary correction of the settlement by the welded joint. The secondary correction of the settlement by the welded joint includes the update of the stiffness correction coefficient: , and the calculation formula represents the calculation of the stiffness correction coefficient; represents the equivalent flexural stiffness; the equivalent flexural stiffness of the overall structure; the corrected settlement amount: .

[0016] In the tunnel pipe roof advanced precast primary support and lining structure and construction method of the present invention, millimeter-level settlement control of large-span structures can be achieved, and through the checking calculations of the load-bearing capacity, stiffness, and settlement amount, it can be characterized that the strength of the tunnel pipe roof advanced precast primary support and lining structure meets various requirements, and at the same time, it verifies that the actual settlement amount is within the millimeter-level settlement control range.

[0017] Other features and advantages of the present application will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0019] Figure 1 FIG. is a schematic diagram of the overall structure of the tunnel pipe roof advanced precast primary support and lining structure; Figure 2 FIG. is a schematic flow chart of the construction method of the tunnel pipe roof advanced precast primary support and lining structure; Figure 3It is a process flow chart of the construction method for the advanced prefabricated primary support and lining structure of the tunnel pipe roof.

[0020] Icon: 1 - Circumferential pipe roof; 11 - Top pipe roof; 12 - Bottom pipe roof; 13 - Pipe roof steel pipe; 2 - Pipe shed; 3 - Steel plate; 4 - Concrete. Specific implementation manners

[0021] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Usually, the components of the embodiments of the present application described and illustrated herein can be arranged and designed in various different configurations.

[0022] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of this application is usually placed during use. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. In addition, terms such as "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present application, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0024] The advanced prefabricated primary support and lining structure and construction method of the tunnel pipe roof in the present application are applied to the excavation of extra-large cross-section tunnels. Through the pipe roof advanced prefabrication method, the primary support and lining are integrally formed into a super-strong combined structure of pipe roof and steel plate concrete, and the ground settlement is controlled to be less than 10 mm. The overall structure schematic diagram of the combined structure is as Figure 1 shown, and the flow schematic diagram of the construction method is as Figure 2 shown, and the process flow chart of the construction method is as Figure 3 shown.

[0025] See Figure 1, in the advanced pre - constructed primary support and lining structure of the tunnel pipe curtain in this application, the main structure includes a circumferential pipe curtain 1 arranged around the tunnel. The circumferential pipe curtain 1 includes a top pipe curtain 11 and a bottom pipe curtain 12 located in the upper and lower layers, as well as a left - hand pipe curtain and a right - hand pipe curtain located on the left and right sides, forming a rectangular pipe curtain structure; The circumferential pipe curtain 1 includes multiple parallel pipe - curtain steel pipes 13. Pipe sheds 2 are driven above both the top pipe curtain 11 and the bottom pipe curtain 12, and the pipe sheds 2 are arranged above the pipe - curtain steel pipes 13 of the top pipe curtain 11 and the bottom pipe curtain 12; All the pipe - curtain steel pipes 13 on the circumferential pipe curtain 1 are cut, and are welded and connected at the cutting parts through steel plates 3, so that all the pipe - curtain steel pipes 13 form an annular pipe - curtain inner cavity, and the pipe - curtain inner cavity is filled with concrete 4.

[0026] Combined with Figure 2 , in the construction process of the advanced pre - constructed primary support and lining structure of the tunnel pipe curtain, it mainly includes the following steps: Calibrate the axis of the pipe - curtain steel pipes 13 through three - dimensional space positioning; Drive grouting pipe sheds 2 above the pipe - curtain steel pipes 13 of the top pipe curtain 11 and the bottom pipe curtain 12 respectively to form pre - support; Construct the circumferential pipe curtain 1 of the tunnel section by the skip - hole method and control the settlement of a single pipe - curtain steel pipe 13; After the pipe - curtain steel pipes 13 are in place, cut all the pipe - curtain steel pipes 13 and weld them at the cutting parts through steel plates 3 to form a rigid ring of the circumferential pipe curtain 1, and make the enclosed space of the rigid ring form an annular pipe - curtain inner cavity; Pour and fill self - compacting concrete 4 in the pipe - curtain inner cavity of the rigid ring to form a composite load - bearing structure; Complete the construction of the advanced pre - constructed primary support and lining structure of the tunnel pipe curtain, and conduct soil excavation in layers and zones after the stiffness meets the standard.

[0027] Specifically, first, carry out positioning and lofting. Drive small pipe sheds 2 in the upper and lower layers of the positioning pipe curtain. The purpose is to control the surface settlement generated during the excavation of each pipe curtain and reduce the superposition effect. It is not necessary to drive pipe sheds 2 on both sides because both the upper and lower sides of the pipe curtain need to be welded with steel plates 3, and the effect on the left and right sides is verified by numerical simulation to be very small, so it is not necessary to drive. Then, drive the pipe curtain. After all the pipe curtain construction is completed, cut the pipe curtain and weld it with steel plates 3 so that adjacent pipe curtains are welded to each other to form an overall large - span structure, and fill concrete 4 inside the structure to complete the construction of the final structure.

[0028] Combined with Figure 3, in the construction method of the tunnel pipe roof advanced precast primary support and lining structure in the present invention, first, the pipe roof axis is accurately calibrated through three-dimensional space positioning technology. Subsequently, grouting pipe sheds 2 are driven above the pipe roof steel pipes 13 of the top pipe roof 11 and the bottom pipe roof 12 to form a pre-support system. Then, the circumferential pipe roof 1 of the entire tunnel section is constructed by the skip hole method, and the settlement of the pipe roof steel pipes 13 is controlled. After the pipe roof is in place, the ends are cut and the rigid rings of the circumferential pipe roof 1 are welded, and the closed space of the rigid rings forms an annular pipe roof inner cavity. Self-compacting concrete 4 is poured into the pipe roof inner cavity to form a composite load-bearing structure. Finally, after the stiffness meets the standard, the soil is excavated in layers and zones.

[0029] The entire process of the construction method in the present invention can achieve millimeter-level settlement control of large-span structures through the mechanical conversion of "first flexible then rigid".

[0030] Taking a specific embodiment as an example, for the 18.5m×10.5m large-section underground project in the present invention, first, a precise positioning system integrating multi-source data is adopted. A pipe roof space matrix is established through three-dimensional laser scanning and BIM reverse modeling. Seven Φ2.0×0.095m pipe roof steel pipes 13 in the upper and lower layers are arranged at equal intervals of 1.0m, and two vertical pipe roofs on the left and right sides form a closed ring frame. The setting-out accuracy of the total station reaches ±3mm.

[0031] In the lock connection link, Φ159×12mm pipe sheds 2 are arranged in a circumferential layered manner with an outer inclination angle of 7°, and the longitudinal segments are spaced 1.2m apart. The adjacent pipe shed 2 units are synchronously pushed forward through the double-pipe jacking process, and the double-fluid grouting system compensates for the formation loss in real time. To explore in detail the effect of the concrete 4 filling layer and anchor grouting, calculations are carried out for the cases with and without filling respectively, and it can be seen that the concrete 4 is crucial for improving the stiffness of the overall structure.

[0032] To further analyze why the pipe shed 2 can only be constructed at the top of the upper and lower layers and not on both sides, a numerical simulation analysis of the pipe shed 2 on both sides is carried out. Through calculation, it can be known that the construction of the pipe shed 2 on both sides has a weak influence on the structural force and has not much impact. Moreover, in actual engineering construction, there are many inconveniences in cutting the pipe roof after driving the pipe shed 2. Therefore, the pipe shed 2 should not be driven on both sides.

[0033] The construction process strictly follows the principles of circumferential layering, longitudinal segmentation, bottom-up first, and interval construction: First, the bottom pipe roof 12 is pushed forward by double-pipe jacking. The bottom pipe roof 12 is preferably pushed forward by the double-pipe jacking system, and the single-pipe soil output is strictly controlled within 95%-105% of the theoretical value. Temporary steel supports are erected every 1.5m.

[0034] The top pipe curtain 11 was constructed 48 hours later than the lower layer. During the double-pipe jacking process, coordinated control of single-pipe excavation and synchronous grouting was implemented. The pressure in the excavation bin was stabilized at 0.18-0.22MPa, and the grouting pressure was increased in stages between 0.5-1.8MPa, forming a composite reinforcement ring with a thickness of 3.2m.

[0035] The left and right pipe curtains are constructed in longitudinal sections and H-shaped steel temporary reinforcement ribs are erected immediately after each 6m pipe section is completed.

[0036] The structural cutting and welding process includes temporary reinforcement, longitudinal first and then circumferential, unilateral cutting, timely support and closure into a ring: after the pipe curtain is connected, temporary supports of Φ609×16mm are set up on both sides of the cutting area, and the axial force is pre-applied to 1200kN. The single-side cutting is carried out by CNC plasma equipment, and the incision is deflected 15° along the longitudinal axis to form a guide groove, and then the circumferential connecting plate is positioned. The welding is carried out in the order of longitudinal seam first and then circumferential seam. The longitudinal weld adopts multi-layer and multi-pass welding (weld width ≤12mm), and the circumferential weld is welded alternately on both sides. After each 3m weld is completed, 200kN prestressed support is applied immediately, and finally a fully closed steel structure bearing ring is formed.

[0037] The concrete filling stage adopts the compartment skipping construction technology, dividing the 10.5m high section into three compartments: lower, middle and upper, with a pouring interval of 72 hours for each compartment. When pouring C50 self-compacting concrete in the lower compartment, the pouring rate is controlled to be ≤0.6m / h, and the hydraulic fracturing monitoring system is started simultaneously; 8% CSA expansion agent is added to the middle compartment to compensate for shrinkage deformation; low-temperature concrete (molding temperature ≤25℃) is used in the upper compartment to suppress temperature stress.

[0038] The deformation gradient of the structure was controlled within 0.03‰ / m by 32 sets of pre-buried fiber grating sensors throughout the whole process. The final monitoring data showed that the water seepage of the pipe curtain joints was ≤0.1L / (m²·d), the maximum surface settlement was 9.5mm, and the overall stiffness of the structure was 1.8 times the design value, which verified the reliability of this method in large-span water-rich strata.

[0039] Through the construction method of the present invention, the construction of the small pipe shed greatly reduces the surface settlement caused by the excavation of the pipe shed. The small pipe shed effectively controls the formation loss rate within 0.5%, and through grouting, it can share the formation pressure well. The addition of accelerators to the grouting material can also weaken the superposition effect during the construction of the pipe shed.

[0040] The pipe curtains are welded together in pairs, which greatly increases the structural stiffness of the support. Therefore, the stiffness correction method is used to calculate the overall stiffness of the large-span structure, especially for pouring concrete support in the pipe curtains. The structural stiffness of the initial support has met all requirements and no further support is required.

[0041] The present invention is applied to the excavation of extra-large cross-section tunnels. Through the method of advanced prefabrication of pipe curtains, the primary support and lining are integrated to form a super-strong combined structure of pipe curtains and steel plate concrete, controlling the ground settlement to be less than 10 mm.

[0042] In addition to the above construction method, the present invention also provides calculations for the load-bearing capacity, structural stiffness, load intensity verification, and ground settlement amount verification of the advanced prefabricated primary support and lining structure of the tunnel pipe curtain.

[0043] In the calculation of the load-bearing capacity of the advanced prefabricated primary support and lining structure of the tunnel pipe curtain, the load-bearing capacity includes load combinations, and the load combinations include dead loads, live loads, and environmental loads; The calculation of the structural stiffness of the advanced prefabricated primary support and lining structure of the tunnel pipe curtain includes a structural stiffness calculation model; In the load intensity verification of the advanced prefabricated primary support and lining structure of the tunnel pipe curtain, it includes ultimate limit state combinations and safety verification; In the calculation of the ground settlement amount of the advanced prefabricated primary support and lining structure of the tunnel pipe curtain, it includes the calculation of the maximum settlement amount and the secondary correction of the settlement by welding joints.

[0044] Specifically, in the calculation of the load-bearing capacity of the advanced prefabricated primary support and lining structure of the tunnel pipe curtain, the load-bearing capacity includes load combinations, and the load combinations include dead loads, live loads, and environmental loads; Dead loads include the self-weight of the structure, overburden pressure, and groundwater buoyancy, live loads include train static loads and train live loads, and environmental loads include lateral earth pressure and water pressure.

[0045] In the specific calculation process, the calculation of dead loads includes: Self-weight of the structure: ; : Unit weight, : Volume; Overburden pressure: ; : Load, : Specific weight, : Overburden thickness; Groundwater buoyancy: ; Calculation of live loads with dynamic coefficient: ; : Track bearing area, : Dynamic coefficient, taking 1.4; : Considering full train stop, the calculation method is as follows: Total weight of a single car body: ; : Number of axles per carriage : Static load per single axle Total static load of single track: ; : Number of carriages stopping at each track Distribution width of track load transferred to roof slab: Diffusion width of wheel load (along track longitudinal direction): ; : Ballast diffusion angle : Wheelbase : Laying thickness of ballast bed in track structure, used to disperse wheel load to subgrade

[0046] Load acting area of single track: ; : Track length : Actual bearing width Uniform static load on roof slab: ; Total static load of whole platform: ; : Number of tracks ; Therefore: ; Lateral pressure:

[0047] ; where k a represents the friction angle, z represents the depth of water coverage; q 覆土 represents the overburden pressure, q 活 represents the live load

[0048] In the calculation process of the stiffness of the advanced precast primary support and lining structure of the tunnel pipe curtain, including the structural stiffness calculation model, regarding the circumferential pipe curtain and the filled concrete as a combined structure, an equivalent flexural stiffness model is established: ; where EI eq is the stiffness of the combined structure, E 钢 represents the elastic modulus of the pipe curtain steel pipe, E混凝土 Denotes the elastic modulus of concrete, I 钢 Denotes the moment of inertia of the pipe roof steel pipe, I 混凝土 Denotes the moment of inertia of concrete; Pipe roof steel pipe parameters: ; Among them, D denotes the outer diameter of the pipe roof steel pipe, and t denotes the wall thickness of the pipe roof steel pipe; Concrete parameters: ; Among them, D_inner denotes the inner diameter of the pipe roof steel pipe; Introduce a stiffness correction coefficient, take the reference stiffness, then: ; Among them, EI_reference denotes the reference stiffness; In the calculation of structural stiffness, it also includes the stiffness correction contributed by the welding joint stiffness. Regard the pipe roof steel pipe and the welded steel plate of the circumferential pipe roof as an integral frame, and use the composite model of beam, column and joint domain to calculate the stiffness: ; Circumferential pipe roof stiffness: ; Among them, L denotes the overall span of the circumferential pipe roof; Welding joint stiffness: ; Based on the welding joint, adopt the rotational stiffness correction, and introduce the rotational spring coefficient k for the semi-rigid effect of the welding joint; ; Among them, t w Denotes the thickness of the gusset plate, with the unit of m, h w Denotes the effective height of the joint, with the unit of m; d b Denotes the bolt spacing, with the unit of m. For the welded joint, take d b →0, and ignore the denominator term after simplification; ν denotes the Poisson's ratio, take 0.3 for steel, l e Denotes the effective length of the joint; The calculation of the corrected equivalent stiffness includes the calculation of the single-span steel frame stiffness and the equivalent flexural stiffness of the overall structure; The calculation of the single-span steel frame stiffness includes: Take the transverse steel frame with a typical span of 18.5m: ; The correction coefficient is: ; The calculation of the equivalent flexural stiffness of the overall structure takes into account the action of continuous steel frames within the entire cross-section range: 。

[0049] After calculating the loads and the structural stiffness, perform the checks of load combinations and structural strength, including ultimate limit state combinations and safety checks; Ultimate limit state combinations: ; In the safety check, it includes the structural anti-floating safety factor: ; Used to judge whether it meets the code requirements; Take a single-span simply supported beam to check the bending moment of the roof slab: ; Allowable stress of the steel plate: ; Allowable compressive stress of concrete: ; The actual stress should be less than the allowable stress specified in the code.

[0050] The final check includes the calculation of the ground surface settlement amount, including the calculation of the maximum settlement amount; The maximum settlement amount includes: ; Among them, S max represents the maximum settlement amount, q 面 represents the surface load, and the calculation formula includes: ; ; Among them, B represents the bearing width, k s represents the bedding coefficient, taking 1×10 4 kN / m³.

[0051] At the same time, after calculating the maximum settlement amount, it includes the secondary correction of the settlement by the welded joints: The secondary correction of the settlement by the welded joints includes the update of the stiffness correction coefficient: , and the calculation formula represents the calculation of the stiffness correction coefficient; represents the equivalent flexural stiffness; The equivalent flexural stiffness of the overall structure; The corrected settlement amount: 。

[0052] To fully illustrate the checking calculation process in this application, the following uses a specific structural case for actual checking calculation.

[0053] The structural parameters of the advanced precast primary support and lining structure of the tunnel pipe roof include: Cross-sectional dimensions: 18.5 m (width) × 10.5 m (height); Pipe roof arrangement: 7 steel pipe roofs of Φ2.0×0.095 m each on the upper and lower sides, 2 on each of the left and right sides, and the total length of the tunnel is 210.1 m; Overburden thickness: 5 m (miscellaneous fill, γ = 18 kN / m³); Groundwater level: buried at a depth of 10 m (the bottom of the structure is 15.5 m underground); The train parameters include: Axle load: 25 t (single axle 250 kN); Axle spacing: 3 m, wheelbase 1.5 m; Number of tracks: 10 (platform area); Full stop state: 10 carriages are parked on each track (total weight 1000 t / track); Dead load calculation: Self-weight of the structure: ; ; ; Overburden pressure: ; ; Buoyancy of water: ; ; Live load calculation (including dynamic coefficient); Static load: ; Dynamic load (dynamic coefficient 1.4): ; ; Lateral pressure: Lateral pressure of miscellaneous fill (Ka = 0.406): ; ; Lateral pressure of new loess (Ka = 0.333): ; ; In the load calculation model, the following verification processes are included: Vertical load distribution: Uniform load at the top: ; Buoyancy force of water at the bottom: ; Lateral load distribution: Miscellaneous fill layer (0 - 5m): Linear distribution of 50.8 kN / m 2 -87.3 kN / m 2 ; New loess layer (5 - 15.5m): Linear distribution of 41.7 kN / m 2 -107.6 kN / m 2 ; Water pressure (10 - 15.5m): Triangular distribution of 0 - 55 kN / m 2 ; Check of load combination and structural strength: Ultimate limit state combination: ; Structural stiffness calculation model: Regarding the pipe curtain and the filled concrete as a composite structure, an equivalent flexural stiffness model is established: ; Steel pipe parameters: ; Concrete parameters: ; Equivalent stiffness: ; Introduce a stiffness correction coefficient and take the reference stiffness, then: ; Among them, EI_reference represents the reference stiffness; ; In the calculation of structural stiffness, it also includes the stiffness correction contributed by the welded joint stiffness. Regarding the pipe curtain steel pipe and the welded steel plate of the circumferential pipe curtain as an integral frame, a beam, column, and joint domain composite model is used to calculate the stiffness: ; Stiffness of the pipe curtain element (steel pipe + concrete composite section): ; Among them, L represents the overall span of the circumferential pipe curtain; Welded joint stiffness:

[0054] Wherein: t w = 20 mm, h w = 1.81 m, d b = 0.3 m, ν represents the Poisson's ratio, and for steel it is taken as 0.3; The semi-rigid effect of the welded joint introduces the rotational spring coefficient k; ; ; ; Calculation of the modified equivalent stiffness: Calculation of the stiffness of a single-span rigid frame: Take the lateral steel frame with a typical span of 18.5 m:

[0055] Original equivalent stiffness: ; Joint rotational stiffness: ; Correction factor: ; Modified stiffness: ; Equivalent flexural stiffness of the overall structure, considering the effect of continuous rigid frames within a 210.1 m full cross-section: .

[0056] In the calculation process of the ground settlement amount, a settlement calculation theoretical model is adopted, and specifically, the maximum settlement amount of the roof is calculated by the elastic foundation beam method: The maximum settlement amount includes: ; Wherein, S max represents the maximum settlement amount; q_surface represents the surface load, and the calculation formula includes: ; ; ; The secondary correction of the welded joint to the settlement includes the update of the stiffness correction factor: ; Modified settlement amount: , meeting the requirements of micro-settlement control.

[0057] In the advanced pre - construction of the initial support and lining structure of the tunnel pipe roof in this application, the main improvement points lie in the calculation of surface settlement of large - span structures considering stiffness correction, the construction technology of large - span structures from flexible to rigid, and the train load combination.

[0058] In the calculation of surface settlement of large - span structures considering stiffness correction: 1) Composite stiffness calculation: Using the conversion section method, the concrete section is converted into an equivalent steel section according to the elastic modulus ratio, and the total moment of inertia after the combination of steel pipes and concrete is calculated. Considering the semi - rigid characteristics of welded joints, the local stiffness is corrected through the thickness of the gusset plate, the size of the steel pipe, and the Poisson's ratio, and finally the overall equivalent flexural stiffness EI of the structure is obtained. eq It is assumed that the material is in the elastic stage, ignoring concrete cracking and steel plastic deformation.

[0059] 2) Load analysis: Dead load: It includes the self - weight of the structure (steel and concrete), overburden pressure, and buoyancy force. The overburden pressure is linearly superimposed according to the soil unit weight and thickness, and the buoyancy force is calculated according to the depth of the groundwater level.

[0060] Live load: The train load is converted into an equivalent uniform load by multiplying the static load by the dynamic coefficient (1.4).

[0061] Lateral earth pressure: Based on the active earth pressure theory, the lateral pressure distribution is calculated in combination with the overburden and live load.

[0062] 3) Settlement calculation method: Elastic foundation beam method: The structure is regarded as a beam on an elastic foundation, and based on the equivalent bedding coefficient and composite stiffness, the elastic deformation curve under the action of the load is calculated.

[0063] 4) Key assumptions and limitations: All materials are ideal elastic, without creep and shrinkage effects; Welded joints are simplified to be completely rigid, ignoring bolt connection slip; The ground loss rate is based on empirical values, without considering dynamic construction disturbances; The elastic foundation beam method assumes that the bedding coefficient is uniformly distributed along the depth.

[0064] Through composite stiffness correction, load layered calculation and settlement prediction model, combined with theoretical formulas and finite - element verification, the final controlled settlement is 2.15 mm, meeting the design requirements (≤10 mm). The core lies in accurately quantifying the stiffness contribution and the interaction with the stratum, providing a standardized calculation process for similar projects.

[0065] In the construction technology of large - span structures from flexible to rigid: 1) Flexible construction of the pre - support system: Based on the concept of formation adaptability, a stepped pipe curtain support system is established: Staggered pipe curtain layout: A double-layer pipe curtain structure is adopted, with a 0.8m interval between the upper and lower layers arranged in a honeycomb pattern. Combined with high-pressure grouting, a continuous support layer is formed. The construction disturbance range of a single pipe is reduced from the traditional 3m to 1.2m; Quick-setting slurry control technology: Composite early-strength materials are added to the grouting material, and the slurry initializes within 20 minutes through multiphase reactions, quickly filling the pores of loose soil and inhibiting the accumulation of formation deformation.

[0066] 2) Progressive rigid conversion of the structural system: The stiffness gradient is increased through "step-by-step welding + dynamic monitoring": High-precision node forming: The low-temperature cutting process is used to groove the end of the pipe curtain, and an intelligent welding device is used to complete the circumferential weld, eliminating the displacement gap of traditional bolted joints. The bending resistance of the node is increased by more than 8 times; Stiffness threshold linkage control: Combining fiber optic sensing technology to monitor the evolution of structural stiffness in real time, setting the stiffness threshold (EI eq≥5×104 MN·pm2) as the process conversion node to ensure the safe and controllable rigid-flexible transition.

[0067] 3) Rigid strengthening of the composite bearing system: The final structure is formed by using "high-performance materials + stress compensation": Fiber-reinforced concrete technology: Nano-scale composite fiber materials are incorporated into C50 concrete, increasing the bond strength between the pipe and concrete by 35% and avoiding the risk of debonding; Stress compensation grouting process: Combining the structural deformation monitoring data, micro-expansion slurry is injected synchronously in key areas to compensate for the release of formation stress and control the rebound deformation ≤1mm.

[0068] 4) Comprehensive benefits of process innovation: Precision control: Integrating BIM reverse modeling and dynamic positioning technology, the axis positioning error ≤5mm, and the precision is improved by 80% compared with the traditional process; Settlement inhibition: Through the three-stage coordination of "flexible support - stiffness jump - stress balance", the surface settlement is reduced from the theoretical value of 17.4mm to the measured value of 1.0mm; Engineering efficiency: The skip-hole construction and intelligent decision-making system reduce redundant processes, shorten the construction period by 25%, and reduce the material loss rate by 18%.

[0069] Through the dynamic balance mechanism of "flexible control of disturbance, rigid protection of bearing capacity", the limitations of traditional rigid support are broken through. In the early stage, a low-intervention flexible system stabilizes the formation. In the middle stage, the stiffness jump is achieved through high-precision welding. Finally, the structural performance is strengthened relying on material modification, forming a full-chain control of "disturbance inhibition - stiffness evolution - bearing optimization".

[0070] In the calculation of train load combinations: Establish three combined working conditions of strength, deformation, and accident: Strength working condition: Integrate dead load, dynamic train load, and buoyancy force for the design of the ultimate bearing capacity of the structure.

[0071] It should be noted that, without conflict, the features in the embodiments of this application can be combined with each other.

[0072] The above are only the preferred embodiments of this application and are not used to limit this application. For those skilled in the art, this application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A pre-constructed primary support and lining structure for a tunnel pipe roof in advance, characterized in that, Comprising: A circumferential pipe curtain arranged around the tunnel. The circumferential pipe curtain includes a top pipe curtain and a bottom pipe curtain located in the upper and lower layers, and a left pipe curtain and a right pipe curtain located on the left and right sides, forming a rectangular pipe curtain structure; The circumferential pipe curtain includes multiple parallel pipe curtain steel pipes. Pipe roofs are driven above both the top pipe curtain and the bottom pipe curtain, and the pipe roofs are arranged above the pipe curtain steel pipes of the top pipe curtain and the bottom pipe curtain; All the pipe curtain steel pipes on the circumferential pipe curtain are cut, and welded at the cutting parts through steel plates, so that all the pipe curtain steel pipes form an annular pipe curtain inner cavity, and the pipe curtain inner cavity is filled with concrete.

2. A construction method for the advanced prefabricated primary support and lining structure of a tunnel pipe roof, which is used to construct the advanced prefabricated primary support and lining structure of the tunnel pipe roof described in claim 1, characterized in that, Including the following steps: Calibrate the axis of the pipe curtain steel pipe through three-dimensional space positioning; Drive grouting pipe roofs above the pipe curtain steel pipes of the top pipe curtain and the bottom pipe curtain respectively to form pre-support; Construct the circumferential pipe curtain of the tunnel section by the skip hole method and control the settlement of a single pipe curtain steel pipe; After the pipe curtain steel pipes are in place, cut all the pipe curtain steel pipes and weld them at the cutting parts through steel plates to form a rigid ring of the circumferential pipe curtain, and make the closed space of the rigid ring form an annular pipe curtain inner cavity; Pour and fill self-compacting concrete in the pipe curtain inner cavity of the rigid ring to form a composite bearing structure; Complete the construction of the advanced prefabricated primary support and lining structure of the tunnel pipe curtain, and conduct soil excavation in layers and zones after the stiffness meets the standard.

3. The construction method according to claim 2, characterized in that, During the construction of the circumferential pipe curtain, first use double-pipe jacking to push the bottom pipe curtain, control the single-pipe soil output within 95%-105% of the theoretical value, and erect temporary steel supports every 1.5 m of advancement; The top pipe curtain is constructed 48 hours after the bottom pipe curtain; During the double-pipe jacking process, implement coordinated control of single-pipe soil output and synchronous grouting. The pressure in the soil chamber is stabilized at 0.18-0.22 MPa, and the grouting pressure is gradually increased between 0.5-1.8 MPa to form a composite reinforcement ring with a thickness of 3.2 m; The left pipe curtain and the right pipe curtain are constructed at longitudinal segmented intervals, and immediately erect H-shaped steel temporary stiffeners every 6 m of pipe section completed.

4. The construction method according to claim 2, characterized in that, After the circumferential pipe curtain penetrates, erect temporary supports on both sides of the cutting area, perform unilateral cutting through cutting equipment, deflect the cutting edge 15° along the longitudinal circumference of the pipe curtain steel pipe to form a guiding bevel groove, then position the circumferential connecting plate. When welding, first weld the longitudinal welds, and then weld the circumferential welds through double-sided alternating welding. Apply prestressed jacking immediately every 3 m of weld completed, and finally form a fully enclosed steel structure load-bearing ring.

5. The construction method according to claim 2, characterized in that, During the concrete filling stage, divide the height section of the tunnel into three bins: lower, middle, and upper. The pouring interval for each bin is 72 hours; When pouring C50 self-compacting concrete in the lower bin, control the pouring rate ≤0.6 m / h and start the hydraulic fracturing monitoring system synchronously; Add 8% expansion agent to the middle bin to compensate for shrinkage deformation; Use low-temperature concrete in the upper bin to inhibit temperature stress.

6. A checking calculation method for the advanced pre-construction primary support and lining structure of a tunnel pipe roof, characterized in that, Including the calculation of bearing load, structural stiffness, load strength check, and ground settlement; In the calculation of the bearing load of the advanced prefabricated primary support and lining structure of the tunnel pipe curtain, the bearing load includes load combinations, and the load combinations include dead load, live load, and environmental load; The calculation of the stiffness of the advanced prefabricated primary support and lining structure of the tunnel pipe curtain includes a structural stiffness calculation model; In the load intensity check calculation of the advanced precast primary support and lining structure of the tunnel pipe roof, it includes the ultimate state combination and safety check calculation; In the calculation of the ground settlement amount of the advanced precast primary support and lining structure of the tunnel pipe roof, it includes the calculation of the maximum settlement amount and the secondary correction of the settlement by the welding joints.

7. The checking method according to claim 6, characterized in that In the calculation of the load-bearing, the dead load includes the self-weight of the structure, the overburden pressure and the groundwater buoyancy, the live load includes the train static load and the train live load, and the environmental load includes the soil lateral pressure and the water pressure.

8. The checking method according to claim 6, characterized in that In the calculation of the structural stiffness, the structural stiffness calculation model includes considering the circumferential pipe roof and the filled concrete as a composite structure and establishing an equivalent flexural stiffness model: ； Among them, EI eq is the stiffness of the composite structure, E 钢 represents the elastic modulus of the pipe roof steel pipe, E 混凝土 represents the elastic modulus of concrete, I 钢 represents the moment of inertia of the pipe roof steel pipe, I 混凝土 represents the moment of inertia of concrete; Pipe roof steel pipe parameters: ； Among them, D represents the outer diameter of the pipe roof steel pipe, and t represents the wall thickness of the pipe roof steel pipe; Concrete parameters: ； Among them, D 内 represents the inner diameter of the pipe roof steel pipe; Introduce the stiffness correction coefficient and take the reference stiffness, then: ； Among them, EI reference represents the reference stiffness; In the calculation of the structural stiffness, it also includes the stiffness correction of the stiffness contribution of the welding joints. Consider the pipe roof steel pipe and the welding steel plate of the circumferential pipe roof as an integral frame and use the composite model of beam, column and joint domain to calculate the stiffness: ； Circumferential pipe roof stiffness: ； Among them, L represents the overall span of the circumferential pipe roof; Welding joint stiffness: ； Based on the welding joint, the rotational stiffness is corrected, and the semi-rigid effect of the welding joint introduces the rotational spring coefficient k; ； Among them, t w represents the thickness of the gusset plate, with the unit of m. h w Indicates the effective height of the node, with the unit of m; d b Indicates the bolt spacing, in m. For welded joints, d is taken according to rigid connections b →0, the denominator term is ignored after simplification; ν represents the Poisson's ratio, which is taken as 0.3 for steel, and l e represents the effective length of the node; The calculation of the corrected equivalent stiffness includes the calculation of the single-span steel frame stiffness and the equivalent flexural stiffness of the overall structure; The calculation of the single-span steel frame stiffness includes: Take the transverse steel frame with a typical span of 18.5m: ； The correction coefficient is: ； The calculation of the equivalent flexural stiffness of the overall structure considers the continuous steel frame action within the full cross-section range: 。 9. The checking method according to claim 6, wherein The load intensity check calculation includes the check calculation of the load combination and the structural strength; The ultimate state combination includes: ； In the safety check calculation, it includes the structural anti-floating safety factor: ； It is used to judge whether it meets the specification requirements; Take a single-span simply supported beam for the roof slab bending moment check calculation: ； Allowable stress of steel plate: ; Allowable compressive stress of concrete: ; The actual stress should be less than the allowable stress specified in the specification.

10. The verification method according to claim 6, characterized in that, In the calculation of the ground settlement amount, the calculation of the maximum settlement amount includes: ； Among them, S max represents the maximum settlement, and q 面 represents the surface load. The calculation formula includes: ； ； Among them, B represents the bearing width, and k s represents the subgrade reaction coefficient, taking 1×10 4 kN / m³; After the calculation of the maximum settlement amount, it includes the secondary correction of the settlement by the welding joints. The secondary correction of the settlement by the welding joints includes the update of the stiffness correction coefficient: , the calculation formula represents the calculation of the stiffness correction coefficient; Denotes the equivalent flexural rigidity; Equivalent flexural rigidity of the overall structure; The corrected settlement amount: 。

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