Super-large-diameter dual-mode TBM starting counter-force system and design and construction method thereof

Abstract

The invention relates to the technical field of TBM tunnel starting, and provides an ultra-large-diameter dual-mode TBM starting counter-force system and a design and construction method thereof.The system comprises a counter-force frame, a pre-buried steel plate, a temporary lining structure and a pre-stressed anchor cable, the front end face of the counter-force frame abuts against a TBM oil cylinder and is connected with the pre-buried steel plate through an inclined strut, and the pre-stressed anchor cable is connected with the temporary lining structure; and the thrust is transmitted to the temporary lining structure and the pre-stressed anchor cable through the pre-embedded steel plate, so that an integrally stressed counter-force supporting system is formed. The reaction frame adopts a modular annular frame structure, so that sectional installation and positioning leveling are facilitated; the temporary lining structure is integrally poured by reinforced concrete and is reliable in stress. According to the design method, scientific and reliable structural design is achieved through working condition and counter-force sharing determination, stress checking calculation and numerical simulation checking of the temporary lining structure and the pre-stressed anchor cable; the construction method comprises the steps of temporary lining structure pouring, embedded part and pre-stressed anchor cable installation, counter-force frame installation and leveling and TBM starting trial tunneling, and construction controllability is guaranteed. The structure is reasonable, construction is convenient, and applicability is high.

Description

Technical Field

[0001] This invention relates to the field of TBM tunnel initiation technology, and in particular to an ultra-large diameter dual-mode TBM initiation reaction system and its design and construction method. Background Technology

[0002] The launch of a tunnel boring machine (TBM) is a crucial step in tunnel construction, relying on a stable and reliable reaction support system. In recent years, direct TBM launch from within the main tunnel has become a common and efficient construction method. Since the main tunnel structure is typically a permanent cross-section, with dimensions and structural form determined during the design phase, the reaction system must adapt to its spatial and stress conditions without damaging the existing structure. In traditional methods, the reaction frame often relies on the frictional resistance between the completed secondary lining and the surrounding rock to provide support. However, when the TBM launch point is far from the tunnel entrance, waiting for the secondary lining to extend inward from the entrance to the launch point not only affects the overall construction rhythm but also causes significant delays in long-distance tunnels with large cross-sections.

[0003] For the aforementioned problems, the "cast-in-place lining + anchor bolt (cable)" combined reaction system is a targeted solution. Taking into account the actual geological conditions and main tunnel structure of the project, a stable reaction frame is formed by constructing a temporary secondary lining in the initial stage and installing high-strength prestressed anchor cables, meeting the large thrust reaction force requirements of the TBM during the initial stage. This method ensures that...

[0004] The safety and reliability of TBMs under the huge thrust effectively solve the bottleneck of construction period when starting in the case of no lining structure in the tunnel using traditional methods.

[0005] However, current literature lacks systematic design and coordinated construction strategies for the initial reaction force system in TBM tunnels without internal lining structures, especially for ultra-large diameter TBM tunnels, where effective coordination of construction design and schedule is difficult. In the future, tunnel engineering will develop towards larger diameters, deeper burials, and more complex geological conditions. How to construct an efficient, safe, and adaptable initial reaction force system is a key concern and problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide an ultra-large diameter dual-mode TBM initiation reaction system and its design and construction method, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In the first aspect, this application provides an ultra-large diameter dual-mode TBM initiation reaction system, including: a temporary lining structure cast into the wall of the tunnel, a plurality of prestressed anchor cables with one end placed in the temporary lining structure and the other end inserted into the tunnel wall, a pre-embedded steel plate embedded in the temporary lining structure, and a reaction frame fixedly connected to the pre-embedded steel plate, wherein the front end face of the reaction frame abuts against the TBM cylinder.

[0009] The reaction frame is a modular ring frame structure, which includes: multiple segmented and detachably connected arc-shaped frame units, multiple radial embedded parts located on the outside of the arc-shaped frame units, and multiple diagonal braces located on the rear end face of the arc-shaped frame units; a column is provided between the arc-shaped frame units and the radial embedded parts; the end of the diagonal brace is connected to the embedded steel plate.

[0010] The thrust of the TBM cylinder is transmitted to the temporary lining structure and prestressed anchor cable through the reaction frame and embedded steel plate, forming an overall reaction support.

[0011] Preferably, the arc-shaped frame units are connected by segmented bolting, and the connecting end faces of the arc-shaped frame units are provided with end plates, the end plates are provided with a plurality of bolt holes, and the inner side of the arc-shaped frame unit is provided with an installation port near the end plate.

[0012] Preferably, the distance from the connection point between the end of the diagonal brace and the embedded steel plate to the rear end face of the arc-shaped frame unit is 1.21 to 1.56 m.

[0013] Preferably, the size of the embedded steel plate is slightly larger than the size of the end of the diagonal brace; the minimum spacing between adjacent embedded steel plates is 1210mm, and the embedded steel plates are anchored to the temporary lining structure.

[0014] Preferably, the temporary lining structure is a reinforced concrete structure, which includes: reinforcing bars in the inner and outer circumferential layers, supporting bars arranged longitudinally along the tunnel, and concrete.

[0015] Preferably, the prestressed anchor cables are arranged in a rectangular array, with an external insertion angle of 45°, a rock penetration depth of not less than 4.5m, and are anchored within the temporary lining structure with an anchorage length of not less than 1.1m.

[0016] Secondly, this application provides a design method for the aforementioned ultra-large diameter dual-mode TBM initiation reaction system, comprising the following steps:

[0017] S1. Determine the working conditions and reaction force sharing. Based on the combination of operation / maintenance / completion working conditions, determine the design working conditions, confirm the TBM initial thrust, and determine the reaction force sharing ratio between temporary lining structure-surrounding rock friction and prestressed anchor cable-surrounding rock anchoring.

[0018] S2. Structural design of the temporary lining structure: Based on the design load combination, calculate the internal forces of the temporary lining structure; based on the calculation results, design the geometric dimensions of the temporary lining structure and the arrangement of reinforcing bars and stirrups; finally, verify the bearing capacity of the completed design scheme, including local bearing pressure calculation of key stress areas; the local bearing pressure calculation satisfies the following formula:

[0019] KF t ≤ωβ t f c A t ;

[0020]

[0021] In the formula, K is the bearing capacity safety factor; F t ω is the design value of the local load or pressure acting on the locally compressed surface; β is the influence coefficient of the load distribution; t It is the strength enhancement factor under localized compression; f c It is the design value of the material's axial compressive strength; A t It is the localized area under pressure; A b This is the calculated base area of ​​the concrete when it is under localized compression.

[0022] S3. Design of embedded steel plate and reaction frame layout: Design the reaction frame size according to the TBM cylinder layout; Design the reaction frame columns and diagonal braces according to the reaction limit conditions and reaction frame size; Design the embedded steel plate size and position according to the short diagonal brace position of the reaction frame.

[0023] S4. Prestressed anchor design: Based on reaction force distribution, geological conditions, and structural requirements, the design tension, material specifications, and rock anchorage length of a single prestressed anchor bundle are initially selected, thereby calculating the total number of prestressed anchor bundles and the grid spacing required; then, the pull-out resistance of the prestressed anchor bundles is verified to meet the following requirements:

[0024]

[0025] N d ≤f′ ms ·n·π·d·L a ·ξ;

[0026] In the formula, N d L is the design value of the axial tensile force of the prestressed anchor cable or unit prestressed anchor cable; a f is the length of the anchorage section (m); mg f' is the standard value of the ultimate bond strength between the grouting body in the anchorage section and the stratum; msξ is the design value of the bond strength between the grout and the reinforcement in the anchorage section; D is the borehole diameter of the prestressed anchor cable anchorage section; d is the diameter of the reinforcing bar or steel strand; K is the safety factor for the pull-out resistance of the bond between the grout and the stratum in the prestressed anchor cable section; ξ is the coefficient for reducing the interface bond strength; ψ is the coefficient for the influence of the anchorage section length on the ultimate bond strength; n is the number of reinforcing bars or steel strands.

[0027] S5. Numerical simulation verification: Verify whether the temporary lining structure and prestressed anchor cable obtained from the above theoretical calculations meet the bearing capacity requirements through numerical simulation.

[0028] Preferably, the calculated load combination for the temporary lining structure of the tunnel section considers permanent loads, general loads, and grouting pressure S. Q21 Combination; the permanent load is the structural self-weight S G1 Surrounding rock pressure S G2 The general load mentioned is the internal water pressure S. Q11 External water pressure S Q12 Dynamic water pressure S Q13 .

[0029] Thirdly, this application provides a construction method based on the above-mentioned ultra-large diameter dual-mode TBM initiation reaction system, including the following steps:

[0030] Step 1: Temporary lining structure pouring. Based on the laser guidance system, the inner contour line of the temporary lining structure is accurately laid out. The excavated rock surface is leveled with shotcrete. Then, the prestressed anchor cables are installed. Holes are drilled and prestressed anchor cables are laid out according to the design requirements. After the prestressed anchor cables are installed, steel bars are laid out according to the design results to prepare for subsequent concrete pouring. Concrete pouring is carried out by continuous pumping in two sections, and layered compaction is achieved with an immersion vibrator. After demolding, curing is carried out. After curing, a hydraulic jack is used to push the bearing plate for pre-compression test.

[0031] Step 2, Installation of the reaction frame:

[0032] Step 2.1: Installation of embedded steel plates. According to the structural design drawings, before the reaction support is installed, embedded steel plates and radial embedded parts need to be installed in the temporary lining structure of the tunnel. The position of the embedded steel plates is determined according to the position of the reaction frame diagonal brace, and the position of the radial embedded parts is determined according to the position of the arc frame unit. The embedded steel plates and radial embedded parts are anchored to the temporary lining structure.

[0033] Step 2.2, Reaction frame positioning measurement;

[0034] Step 2.3: Connect the segmented arc-shaped frame units by bolting and hoisting them to construct a ring frame, and install and fix the columns and short diagonal braces;

[0035] Step 2.4: Leveling the reaction frame. Before assembling the first ring segment, first grind the welds and burrs on the end face of the reaction frame to make it smooth. Take 25 points evenly distributed along the circumference on the end face and measure the distance from each point to the starting axis. Based on the measurement results, fit the relationship between the reaction frame end face and the designed ring end face, as well as the flatness of the reaction frame end face, and determine the distance that needs to be adjusted at each point.

[0036] For points larger than 5mm, use steel plates of appropriate thickness for leveling; for points smaller than 5mm, use nitrile cork rubber pads of appropriate thickness for leveling.

[0037] Step 3: TBM Launch. After all the above work is completed, the TBM will be launched. After the first ring of segments is assembled, a demonstration test tunneling will be carried out to determine the tunneling parameters.

[0038] Preferably, the reaction frame positioning measurement includes the following steps:

[0039] 1) Positioning: Perform preliminary layout and installation of the base of the reaction frame in three dimensions and elevation at the preset position;

[0040] 2) Initial attitude measurement: After the reaction frame is initially fixed, a measuring instrument is used to obtain the three-dimensional coordinate data of multiple preset measuring points on its reaction surface;

[0041] 3) Attitude deviation calculation: Based on the three-dimensional coordinate data of the multiple preset measurement points, the actual spatial plane of the reaction surface is fitted and generated, and its actual normal vector is determined; the actual normal vector is compared with the preset tunnel design axis vector to calculate the attitude deviation of the reaction frame in pitch and azimuth angles.

[0042] 4) Attitude adjustment: Based on the calculated attitude deviation, the attitude of the reaction frame is adjusted by an adjustment mechanism;

[0043] 5) Closed-loop detection: Repeat the initial attitude measurement, attitude deviation calculation and attitude adjustment until the attitude deviation is less than the preset accuracy tolerance value.

[0044] The present invention discloses an ultra-large diameter dual-mode TBM initiation reaction system and its design and construction method, which has the following beneficial effects.

[0045] This invention's system constructs a stable and robust reaction frame by installing a temporary secondary lining (temporary lining structure) in the initial stage, along with high-strength prestressed anchor cables. This fully meets the reaction force requirements of the TBM under the enormous thrust during the initial launch phase. This combined reaction system effectively ensures the structural safety and operational reliability of the TBM under immense thrust, significantly reducing potential risks during the initial launch phase.

[0046] Furthermore, this invention provides a mature and feasible set of supporting design and construction methods for the proposed initial reaction force system, ensuring that the initial reaction force system can be implemented accurately, safely, and effectively. This invention can ensure the safe and reliable completion of the initial launch task under the huge thrust of the TBM, and effectively solves the bottleneck of construction period when using traditional methods for TBM initial launch in the case of no lining structure inside the tunnel.

[0047] Specifically, the system consists of a reaction frame, embedded steel plates, a temporary lining structure, and prestressed anchor cables. The reaction frame abuts against the TBM cylinder at its front end and is connected to the embedded steel plates via diagonal braces. The thrust is transferred through the embedded steel plates to the temporary lining structure and prestressed anchor cables, forming a unified reaction support system. The reaction frame adopts a modular ring frame structure, facilitating segmented installation and positioning leveling. The prestressed anchor cables are rationally arranged to ensure sufficient anchoring force. The temporary lining structure is integrally cast reinforced concrete, ensuring reliable stress distribution. The design method achieves a scientific and reliable structural design through determination of working conditions and reaction force sharing, stress verification of the temporary lining structure and prestressed anchor cables, and numerical simulation verification. The construction method includes the casting of the temporary lining structure, installation of embedded parts and prestressed anchor cables, installation and leveling of the reaction frame, and TBM launch and trial excavation, ensuring the overall performance and construction controllability of the system. This invention can effectively meet the reaction force requirements of ultra-large diameter TBM launches and has the advantages of reasonable structure, convenient construction, and strong applicability. Attached Figure Description

[0048] Figure 1 A cross-sectional view of an ultra-large diameter dual-mode TBM initiation reaction system provided by the present invention;

[0049] Figure 2 This is a schematic diagram of the reaction frame model of the reaction system provided by the present invention;

[0050] Figure 3 A schematic diagram of the bottom arc-shaped frame unit of the reaction frame provided by the present invention;

[0051] Figure 4 A plan view of the reaction frame and temporary lining structure provided by the present invention;

[0052] Figure 5 This is a plan view of the ultra-large diameter dual-mode TBM initiation reaction system provided by the present invention.

[0053] Figure 6 A schematic diagram of the calculation model of the temporary lining structure provided by the present invention;

[0054] Figure 7 The finite element analysis simulation cloud diagram of the temporary lining structure and prestressed anchor cable stress provided by the present invention.

[0055] In the figure, 1-reaction frame, 101-ring frame, 102-radial embedded part, 103-diagonal brace, 1011-arc frame unit, 1012-end plate, 1013-bolt hole, 1014-bottom plate; 2-embedded steel plate; 3-temporary lining structure; 4-prestressed anchor cable; 5-TBM, 501-TBM cylinder, 502-TBM segment. Detailed Implementation

[0056] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0057] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0058] Example 1

[0059] A dual-mode TBM initiation reaction system with an ultra-large diameter, such as Figure 1 The diagram shows a cross-sectional view of a dual-mode TBM initiation reaction system for a large diameter TBM provided by the present invention, comprising: a temporary lining structure 3 cast into the tunnel wall; multiple prestressed anchor cables 4, one end of which is placed inside the temporary lining structure 3 and the other end inserted into the tunnel wall; a pre-embedded steel plate 2 embedded in the temporary lining structure 3; and a reaction frame 1 fixedly connected to the pre-embedded steel plate 2, wherein the front end face of the reaction frame 1 abuts against the TBM cylinder 501.

[0060] The reaction frame 1 is a modular ring frame 101 structure, which includes: multiple segmented and detachably connected arc-shaped frame units 1011, multiple radial embedded parts 102 located on the outside of the arc-shaped frame units 1011, and multiple diagonal braces 103 located on the rear end face of the arc-shaped frame units 1011; a column is provided between the arc-shaped frame units 1011 and the radial embedded parts 102; the ends of the diagonal braces 103 are connected to the embedded steel plates 2;

[0061] The thrust of TBM cylinder 501 is transmitted through reaction frame 1 and embedded steel plate 2 to temporary lining structure 3 and prestressed anchor cable 4, forming an overall reaction support.

[0062] It should be noted that during the initial launch of TBM5, the TBM cylinder 501 first comes into direct contact with the reaction frame 1. The axial thrust generated by the TBM cylinder 501 is transmitted to the temporary lining structure 3 and the prestressed anchor cable 4 through the radial embedded part 102 and the diagonal brace 103 set on the annular frame 101 of the reaction frame 1. The initial reaction force is provided by the frictional resistance between the temporary lining structure 3 and the surrounding rock and the anchoring force between the prestressed anchor cable 4 and the surrounding rock. TBM5 advances forward, and then the TBM segment 502 is installed. The TBM cylinder 501 then acts on the TBM segment 502, and the thrust is then transmitted to the reaction frame until the TBM segment 502 can withstand the TBM5's counter-thrust.

[0063] like Figure 2 , 3 As shown, a schematic diagram of the reaction frame 1 model of the ultra-large diameter dual-mode TBM initiation reaction system provided by the present invention is given. Preferably, in this embodiment, the arc-shaped frame units 1011 are connected by segmented bolting. An end plate 1012 is provided on the connecting end face between the arc-shaped frame units 1011. The end plate 1012 is provided with a plurality of bolt holes 1013. An installation port is provided on the inner side of the arc-shaped frame unit 1011 near the end plate 1012.

[0064] Specifically, in this embodiment, the main structure of the reaction frame 1 adopts a ring frame 101, which is composed of multiple arc-shaped frame units 1011 connected by segmented bolting to meet the requirements of hoisting weight and installation space. In this embodiment, there are 8 arc-shaped frame units 1011, and bolt holes 1013 are reserved at the end plates 1012 at both ends of the arc-shaped frame units 1011. The reaction frame 1 has 25 radial embedded parts 102 distributed along the circumference, and 25 columns are provided to transmit radial pressure. At the same time, there are 25 corresponding diagonal braces 103, of which the bottom diagonal braces 103 are connected to the arc-shaped frame units 1011 through the bottom plate 1014 to enhance the structural stability.

[0065] like Figure 4 As shown, the reaction frame 1 is placed on the temporary lining structure 3 through the radial embedded part 102 and the diagonal brace 103. The diagonal brace 103 acts on the embedded steel plate 2 in the temporary lining structure 3. The spacing between the diagonal brace 103 and the radial support is 1.21 to 1.56 m, that is, the distance from the end of the diagonal brace 103 to the connection point of the embedded steel plate 2 to the rear end face of the arc frame unit 1011 is 1.21 to 1.56 m.

[0066] Preferably, in this embodiment, the size of the embedded steel plate 2 is slightly larger than the size of the end of the diagonal brace 103; the minimum spacing between adjacent embedded steel plates 2 is 1210mm, and the embedded steel plate 2 is anchored to the temporary lining structure 3.

[0067] Specifically, in this embodiment, the embedded steel plate 2 is a rectangular plate structure, and the position of the embedded steel plate 2 is determined according to the position of the diagonal brace 103 of the reaction frame 1.

[0068] Preferably, in this embodiment, the temporary lining structure 3 is a reinforced concrete structure, which includes: reinforcing bars in the inner and outer circumferential layers, support bars arranged longitudinally along the tunnel, and concrete.

[0069] Preferably, in this embodiment, the prestressed anchor cables 4 are arranged in a rectangular array, the external insertion angle of the prestressed anchor cables 4 is 45°, the rock penetration depth is not less than 4.5m, and they are anchored in the temporary lining structure 3 with an anchorage length of not less than 1.1m.

[0070] Specifically, in this embodiment, such as Figure 5 As shown, the reaction system consists of four main structures: reaction frame 1, embedded steel plate 2, temporary lining structure 3, and prestressed anchor cable 4. In the reaction system, the initial reaction force is transmitted from the radial embedded part 102 and the diagonal brace 103 of the reaction frame 1 to the temporary lining structure 3 and the prestressed anchor cable 4, and is jointly borne by the frictional resistance between the temporary lining structure 3 and the surrounding rock and the anchoring force between the prestressed anchor cable 4 and the surrounding rock.

[0071] The external angle is the included angle of the TBM5 tunneling direction.

[0072] Example 2

[0073] Based on Example 1, this example provides a design method for the above-described ultra-large diameter dual-mode TBM initiation reaction system, including the following steps:

[0074] S1. Determine the working conditions and reaction force sharing. Based on the combination of operation / maintenance / completion working conditions, determine the design working conditions, confirm the initial thrust of TBM5, and determine the reaction force sharing ratio of temporary lining structure 3—surrounding rock friction and prestressed anchor cable 4—surrounding rock anchoring.

[0075] In this embodiment, for safety reasons, the calculations consider that the friction between the cast-in-place temporary lining structure 3 and the surrounding rock bears approximately 50% of the force, and the prestressed anchor cable 4 bears 50% of the shear force under the thrust. The estimated maximum initial thrust of TBM5 is approximately 3000t. Considering the unevenness of the thrust, and for safety reasons, this embodiment calculates based on the following possible maximum thrust of 3944t (39440KN), with the prestressed anchor cable 4 bearing 50% of the force.

[0076] S2. Structural design of temporary lining structure 3: Based on the design load combination, calculate the internal forces of temporary lining structure 3; based on the calculation results, design the geometric dimensions, reinforcement, and stirrup arrangement of temporary lining structure 3; finally, verify the load-bearing capacity of the completed design scheme, including local bearing capacity verification of key stress areas; the local bearing capacity verification satisfies the following formula:

[0077] KF t ≤ωβ t f c A t ;

[0078]

[0079] In the formula, K is the bearing capacity safety factor; F t ω is the design value of the local load or pressure acting on the locally compressed surface; β is the influence coefficient of the load distribution; t It is the strength enhancement factor under localized compression; f c It is the design value of the material's axial compressive strength; A t It is the localized area under pressure; A b This is the calculated base area of ​​the concrete when it is under localized compression.

[0080] Specifically, in this embodiment, such as Figure 6 As shown, the calculation load combination for the temporary lining structure 3 in the tunnel section considers the permanent load (structure self-weight S). G1 Surrounding rock pressure S G2 ) and general loads (internal water pressure S) Q11 External water pressure S Q12 Dynamic water pressure S Q13 ) and grouting pressure S Q21 The load combinations and operating conditions are shown in Table 1.

[0081] Table 1. Calculation Load Combinations for Temporary Lining Structures in Tunnel Sections

[0082]

[0083]

[0084]

[0085] Based on the design load combination, the internal forces of the temporary lining structure 3 are calculated; based on the internal force calculation results and construction requirements, the geometric dimensions, reinforcement and support reinforcement arrangement of the temporary lining structure 3 are designed.

[0086] In this embodiment, the required reinforcing bars and stirrups area is obtained by calculating the internal forces of the temporary lining structure 3, and then the reinforcing bars and stirrups are arranged according to the structural requirements.

[0087] The thickness of the temporary lining structure 3 can be estimated by referring to 1 / 15 to 1 / 25 of the tunnel outer diameter. C20 to C30 concrete is preferred. C25 concrete can be used in conventional projects, while C30 concrete is recommended for cases with high surrounding rock pressure and strict deformation control requirements.

[0088] In this embodiment, a 60cm thick cast-in-place C30 concrete temporary lining structure 3 is used, with an inner diameter of 10.4m and an outer diameter of 11.6m.

[0089] The arrangement of reinforcing bars needs to be considered, as well as the stress calculation of temporary lining structure 3 under loads such as self-weight, surrounding rock pressure, external water pressure, internal water pressure, and grouting pressure. The arrangement of the stirrups also needs to be considered.

[0090] The force exerted by the TBM5 starting cylinder thrust on the temporary lining structure 3.

[0091] The reinforcement bars are mainly considered for the compression calculation of the temporary lining structure 3 within the influence range of a single set of hydraulic cylinders, and are considered as eccentrically compressed columns, without considering second-order effects. TBM hydraulic cylinder 501 acts on the reaction frame 1, which has 25 radially embedded parts 102 distributed circumferentially to transmit radial pressure. Simultaneously, 25 corresponding diagonal braces 103 are provided, supporting the embedded steel plates 2. Considering the bending moment generated on the surface by the diagonal braces 103, and appropriately reducing it (reduction coefficient can be taken as 0.5), and considering the eccentricity of the hydraulic cylinder to the edge of the concrete lining, according to the calculation assumption of short columns, the reinforcement of the main reinforcement and the reinforcement bars is structural reinforcement, using the minimum reinforcement ratio. In the bearing capacity verification formula for the temporary lining structure 3, K is the bearing capacity safety factor, considered as a plain concrete member, with a coefficient of 1.45; F t The design value (N) of the local load or local pressure acting on the locally compressed surface is calculated according to regulations; A t The localized area under pressure (mm²) 2 ); β t f is the strength enhancement factor for concrete under localized compression; c It is the design value of the material's axial compressive strength; A b Calculated base area (mm²) of concrete under localized compression 2 The value of ω can be determined based on the principle that the local pressure area and the calculated bottom area are concentric and symmetrical; ω is the influence coefficient of load distribution. When the load in the local pressure area is uniformly distributed, ω = 1; when the local load is non-uniformly distributed (such as the end support surface of beams and lintels), ω = 0.75.

[0092] S3. Arrangement design of reaction frame 1 and embedded steel plate 2: The dimensions of reaction frame 1 are designed according to the arrangement of TBM cylinder 501. The columns and diagonal braces 103 of reaction frame 1 are designed according to the reaction force limit and the dimensions of reaction frame 1. The diagonal brace 103 is preferably inclined at a 45° angle, and its minimum cross-sectional area should meet A. min =F max / [σ];The dimensions and position of the pre-embedded steel plate 2 are designed according to the position of the short diagonal brace 103 of the reaction frame 1.

[0093] In this embodiment, the reaction frame 1 is constructed from Q235B steel plates, with a height of 12.53m and a width of 3m (preferably 1.5 to 2 times the segment ring width). The steel has a yield strength of 235MPa, tensile, compressive, and bending strengths of 215MPa, and an allowable shear stress of 125MPa. The number of columns and diagonal braces 103 is designed according to the TBM cylinder 501 and should correspond to the number and position of the thrust cylinders. The reaction frame 1 frame consists of 25 sets of columns and diagonal braces 103 welded to the embedded steel plates 2 and radial embedded parts 102 in the temporary lining, dividing the entire ring into 8 arc-shaped frame units 1011. The circumferential connection is made of high-strength bolts, using M24 8.8 grade high-strength bolts with a guaranteed stress of 600MPa, a tensile strength design value of 400MPa, and a shear strength design value of 320MPa.

[0094] S4, the design of prestressed anchor cable 4: Based on the reaction force distribution, stratum conditions, and structural requirements, the design tension, material specifications, and rock anchorage length of a single prestressed anchor cable 4 are initially selected, thereby calculating the total number of prestressed anchor cables 4 and the grid spacing required; then, the pull-out resistance of prestressed anchor cable 4 is verified to meet the following requirements:

[0095]

[0096] N d ≤f′ ms ·n·π·d·L a ·ξ;

[0097] In the formula, N d L is the design value of the axial tensile force of prestressed anchor cable 4 or unit prestressed anchor cable 4; a f is the length of the anchorage section (m); mg f' is the standard value of the ultimate bond strength between the grouting body in the anchorage section and the stratum; ms ξ is the design value of the bond strength between the grout and the reinforcement in the anchorage section; D is the borehole diameter of the 4th anchorage section of the prestressed anchor cable; d is the diameter of the reinforcing bar or steel strand; K is the safety factor for the pull-out resistance of the bond between the grout and the stratum in the 4th section of the prestressed anchor cable; ξ is the coefficient for reducing the interface bond strength; ψ is the coefficient for the influence of the anchorage section length on the ultimate bond strength; n is the number of reinforcing bars or steel strands.

[0098] Specifically, in this embodiment, the HRB400 system mortar prestressed anchor cable 4 is used in the design. For safety, the calculations consider that the friction between the cast-in-place temporary lining structure 3 and the surrounding rock bears approximately 50% of the force, and that the system prestressed anchor cable 4 bears 50% of the shear force under the thrust. Since the prestressed anchor cable 4 has a 45° outward insertion angle, it exhibits a mixed tensile-shear action under the initial thrust; therefore, a mixed tensile-shear action calculation is performed. The estimated maximum initial thrust of the TBM is approximately 3000t. Considering the unevenness of the thrust, and for safety, this embodiment calculates based on the following possible maximum thrust of 3944t (39440KN), with the prestressed anchor cable 4 bearing 50% of the force.

[0099] Among them, the pull-out resistance of prestressed anchor cable 4 must satisfy the following relationship, where N d L represents the design value (kN) of the axial tensile force of prestressed anchor cable 4 or unit prestressed anchor cable 4; a f is the length of the anchorage section (m); mg The standard value (MPa or kPa) of the ultimate bond strength between the grouting body and the formation in the anchoring section should be determined by testing; f' ms ξ is the design value of the bond strength between the grout and the reinforcing bar in the anchorage section (MPa); D is the borehole diameter of the 4th anchorage section of the prestressed anchor cable (mm); d is the diameter of the reinforcing bar or steel strand (mm); K is the safety factor for the bond pull-out resistance between the grout and the stratum in the 4th anchorage section of the prestressed anchor cable, taken according to the specification; when using 2 or more reinforcing bars or steel strands, the interface bond strength reduction coefficient is taken as 0.70 to 0.85; ψ is the influence coefficient of the anchorage section length on the ultimate bond strength, taken according to the specification; n is the number of reinforcing bars or steel strands.

[0100] It should be noted that for the design of prestressed anchor cable 4, parameters can be estimated based on experience according to the project conditions, and then verified. If the requirements are met, the estimated value is feasible; if not, the parameters should be optimized.

[0101] Typically, for hard, intact rocks (such as slightly weathered granite): L a We can first take 6 to 8 meters for verification. Since the temporary lining structure 3 is designed to be 9 meters long, according to the structural requirements, the spacing of the prestressed anchor cables 4 should not be less than 1.5 meters. Here, we take 1.5 meters, so there are a total of six rows.

[0102] Based on the calculation results and in accordance with the structural requirements, HRB400φ28@1.5m×1.5m (spaced between rows) was selected. a =6.0m, 6 rows of prestressed anchor cables 4 are laid out, totaling 145 prestressed anchor cables 4. The external insertion angle of the prestressed anchor cable 4 is 45° (the angle with the tunneling direction is 45°), the rock penetration depth of the prestressed anchor cable 4 is not less than 4.5m, and the anchoring depth into the temporary lining structure 3 is not less than 1.1m.

[0103] S5. Numerical simulation verification: Verify whether the temporary lining structure 3 and prestressed anchor cable 4 obtained from the above theoretical calculations meet the bearing capacity requirements through numerical simulation.

[0104] In this embodiment, as Figure 7 As shown, numerical simulation was used to verify whether the results obtained from the theoretical calculations met the requirements. The cloud map shows that under an ultimate thrust of 3944 tons, the maximum stress value in the local compression zone of the temporary lining structure 3 did not exceed the bearing capacity limit of the concrete, verifying the calculation results of the theoretical formula and meeting the design requirements. Simultaneously, the simulated maximum axial tensile force of the prestressed anchor cable 4 was also lower than its pull-out capacity design value, proving the reliability of the prestressed anchor cable 4 under the combined action of tension and shear. The displacement deformation of the entire structure was within a reasonable range, indicating that the designed temporary lining structure 3 and prestressed anchor cable 4 could effectively withstand the enormous thrust brought by the TBM's initiation, ensuring structural safety during construction.

[0105] Example 3

[0106] Based on Example 1, this example provides a construction method for the above-described ultra-large diameter dual-mode TBM initial reaction force system, including the following steps:

[0107] Step 1: Temporary lining structure 3 is poured. The inner contour line of the temporary lining structure 3 is accurately laid out according to the laser guidance system. The excavated rock surface is leveled with shotcrete. Then, the prestressed anchor cables 4 are installed. Holes are drilled and prestressed anchor cables 4 are laid out according to the design requirements. After the prestressed anchor cables 4 are installed, steel bars are laid out according to the design results to prepare for subsequent concrete pouring. Concrete pouring is carried out by continuous pumping in two sections, and layered compaction is achieved with an immersion vibrator. After demolding, curing is carried out. After curing, a hydraulic jack is used to push the bearing plate for pre-compression test.

[0108] Specifically, in this embodiment, the inner contour line of the temporary lining structure 3 is accurately laid out based on the laser guidance system. The excavated rock surface is leveled with shotcrete to ensure that the surface flatness deviation is ≤30mm. C35 concrete is continuously pumped in two sections, and the concrete is compacted in layers by an immersion vibrator. Curing is carried out immediately after demolding. After the curing strength reaches 90% of the design value, a hydraulic jack is used to push the bearing plate for pre-compression test (the load is 1.1 times the design reaction force) to verify the integrity of the structure and the uniformity of the interface contact. Finally, a circumferential force system with precise geometric positioning and high compressive strength is formed, providing a reliable reaction force foundation for the TBM launch.

[0109] Step 2, Installation of reaction frame 1:

[0110] Step 2.1 Installation of embedded steel plate 2: According to the structural design drawings, before the reaction support is installed, embedded steel plate 2 and radial embedded part 102 need to be installed in the temporary lining structure 3 of the step tunnel. The position of embedded steel plate 2 is determined according to the position of diagonal brace 103 of reaction frame 1, and the position of radial embedded part 102 is determined according to the position of arc frame unit 1011. Both embedded steel plate 2 and radial embedded part 102 are anchored to the lining structure 3.

[0111] Specifically, in this embodiment, the reaction frame 1 is arranged along the longitudinal width of the tunnel of 3m, and the top is reserved with prestressed anchor cables 4 as the installation lifting point of the reaction frame 1. The specific location and number of prestressed anchor cables 4 are determined according to the structural weight of the lifting component.

[0112] It should be noted that, due to the large weight of the arc-shaped frame unit 1011 of the reaction frame 1, hoisting requires special equipment. When constructing in the confined space of the tunnel, the special equipment cannot re-enter the construction site during the later stages of construction. Therefore, before the later work is carried out, the top arc-shaped frame unit 1011 of the reaction frame 1 is hoisted and connected to the prestressed anchor cable 4.

[0113] The reaction frame 1 adopts a ring structure. The supporting reaction force of the entire reaction frame 1 is transferred from the pre-embedded steel plate 2 of the tunnel to the lining structure 3 and the prestressed anchor cable 4.

[0114] According to the structural design drawings, before the reaction support is installed, it is necessary to install embedded steel plate 2 and radial embedded part 102 in the temporary lining structure 3 of the tunnel. The position of embedded steel plate 2 is determined according to the position of diagonal brace 103 of reaction frame 1, and the position of radial embedded part 102 is determined according to the position of arc frame unit 1011. Both embedded steel plate 2 and radial embedded part 102 are anchored to the lining. Embedded steel plate 2 is made of 18mm thick ordinary steel plate with a size of 850mm×850mm and radial embedded size of 850mm×1000mm.

[0115] Step 2.2, Positioning and measurement of reaction frame 1;

[0116] Preferably, in this embodiment, the positioning measurement of the reaction frame 1 includes the following steps:

[0117] 1) Positioning: Perform preliminary layout and installation of the three-dimensional coordinates and elevation of the base of the reaction frame 1 at the preset position;

[0118] 2) Initial attitude measurement: After the reaction frame 1 is initially fixed, the three-dimensional coordinate data of multiple preset measurement points on its reaction surface are obtained by measuring instruments;

[0119] 3) Attitude deviation calculation: Based on the three-dimensional coordinate data of multiple preset measurement points, the actual spatial plane of the reaction surface is generated by fitting and the actual normal vector is determined; the actual normal vector is compared with the preset tunnel design axis vector to calculate the attitude deviation of the reaction frame 1 in pitch and azimuth angles.

[0120] 4) Attitude adjustment: Based on the calculated attitude deviation, the attitude of the reaction frame 1 is adjusted through the adjustment mechanism;

[0121] 5) Closed-loop detection: Repeat the initial attitude measurement, attitude deviation calculation and attitude adjustment until the attitude deviation is less than the preset accuracy tolerance value.

[0122] It should be noted that the positioning measurement of reaction frame 1 includes the planar position positioning, elevation positioning, and flatness and verticality measurement of the reaction surface of reaction frame 1. The attitude of reaction frame 1 is determined by the starting attitude of the TBM after it is in place on the starting guide.

[0123] Step 2.3: Segmentally bolt the arc-shaped frame unit 1011 and hoist it to construct the ring frame 101, and install and fix the columns and short diagonal braces 103;

[0124] Step 2.4: Leveling of Reaction Frame 1. Before assembling the first ring segment, first grind the welds and burrs on the end face of Reaction Frame 1 to make it smooth. Take 25 points evenly along the circumference on the end face and measure the distance from each point to the starting axis. Based on the measurement results, fit the relationship between the end face of Reaction Frame 1 and the designed ring end face and the flatness of the end face of Reaction Frame 1, and determine the distance that needs to be adjusted at each point.

[0125] For points larger than 5mm, use steel plates of appropriate thickness for leveling; for points smaller than 5mm, use nitrile cork rubber pads of appropriate thickness for leveling.

[0126] Step 3: TBM Launch. After all the above work is completed, the TBM will be launched. After the first ring of segments is assembled, a demonstration test tunneling will be carried out to determine the tunneling parameters.

[0127] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Substitutions may include replacements for some structures, devices, or method steps, or may be complete technical solutions. Equivalent substitutions or modifications made to the technical solutions and inventive concepts of the present invention should all be covered within the scope of protection of the present invention.

Claims

1. A dual-mode TBM initiation reaction system with an ultra-large diameter, characterized in that, include: The temporary lining structure is cast into the tunnel wall, and a number of prestressed anchor cables are placed in the temporary lining structure at one end and inserted into the tunnel wall at the other end. An embedded steel plate is embedded in the temporary lining structure and a reaction frame is fixedly connected to the embedded steel plate. The front end face of the reaction frame abuts against the TBM cylinder. The reaction frame is a modular ring frame structure, which includes: multiple segmented and detachably connected arc-shaped frame units, multiple radial embedded parts located on the outside of the arc-shaped frame units, and multiple diagonal braces located on the rear end face of the arc-shaped frame units; a column is provided between the arc-shaped frame units and the radial embedded parts; the end of the diagonal brace is connected to the embedded steel plate. The thrust of the TBM cylinder is transmitted to the temporary lining structure and prestressed anchor cable through the reaction frame and embedded steel plate, forming an overall reaction support.

2. The ultra-large diameter dual-mode TBM initiation reaction system according to claim 1, characterized in that, The arc-shaped frame units are connected by segmented bolting. The connecting end faces of the arc-shaped frame units are provided with end plates, and the end plates are provided with several bolt holes. The inner side of the arc-shaped frame unit is provided with an installation port near the end plate.

3. The ultra-large diameter dual-mode TBM initiation reaction system according to claim 1, characterized in that, The distance from the connection point between the end of the diagonal brace and the embedded steel plate to the rear end face of the arc-shaped frame unit is 1.21 to 1.56 m.

4. The ultra-large diameter dual-mode TBM initiation reaction system according to claim 1, characterized in that, The size of the embedded steel plate is slightly larger than the size of the end of the diagonal brace; the minimum spacing between adjacent embedded steel plates is 1210mm, and the embedded steel plates are anchored to the temporary lining structure.

5. The ultra-large diameter dual-mode TBM initiation reaction system according to claim 1, characterized in that, The temporary lining structure is a reinforced concrete structure, which includes: reinforcing bars in the inner and outer circumferential layers, supporting bars arranged longitudinally along the tunnel, and concrete.

6. The ultra-large diameter dual-mode TBM initiation reaction system according to claim 1, characterized in that, The prestressed anchor cables are arranged in a rectangular array, with an external insertion angle of 45°, a rock penetration depth of not less than 4.5m, and are anchored within the temporary lining structure with an anchorage length of not less than 1.1m.

7. A design method for an ultra-large diameter dual-mode TBM initiation reaction system according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Determine the working conditions and reaction force sharing. Based on the combination of operation / maintenance / completion working conditions, determine the design working conditions, confirm the TBM initial thrust, and determine the reaction force sharing ratio between temporary lining structure-surrounding rock friction and prestressed anchor cable-surrounding rock anchoring. S2. Structural design of the temporary lining structure: Based on the design load combination, calculate the internal forces of the temporary lining structure; based on the calculation results, design the geometric dimensions of the temporary lining structure and the arrangement of reinforcing bars and stirrups; finally, verify the bearing capacity of the completed design scheme, including local bearing pressure calculation of key stress areas; the local bearing pressure calculation satisfies the following formula: KF t ≤ωβ t f c A t ; In the formula, K is the bearing capacity safety factor; F t ω is the design value of the local load or pressure acting on the locally compressed surface; β is the influence coefficient of the load distribution; t It is the strength enhancement factor under localized compression; f c It is the design value of the material's axial compressive strength; A t It is the localized area under pressure; A b This is the calculated base area of ​​the concrete when it is under localized compression. S3. Design of embedded steel plate and reaction frame layout: Design the reaction frame size according to the TBM cylinder layout, and design the reaction frame columns and diagonal braces according to the reaction limit and reaction frame size. The dimensions and location of the embedded steel plate are designed according to the position of the short diagonal brace of the reaction frame; S4. Prestressed anchor design: Based on reaction force distribution, geological conditions, and structural requirements, the design tension, material specifications, and rock anchorage length of a single prestressed anchor bundle are initially selected, thereby calculating the total number of prestressed anchor bundles and the grid spacing required; then, the pull-out resistance of the prestressed anchor bundles is verified to meet the following requirements: N d ≤f′ ms ·n·π·d·L a ·ξ; In the formula, N d L is the design value of the axial tensile force of the prestressed anchor cable or unit prestressed anchor cable; a f is the length of the anchorage section (m); mg f′ represents the standard value of the ultimate bond strength between the grouting body in the anchorage section and the stratum. ms ξ is the design value of the bond strength between the grout and the reinforcement in the anchorage section; D is the borehole diameter of the prestressed anchor cable anchorage section; d is the diameter of the reinforcing bar or steel strand; K is the safety factor for the pull-out resistance of the bond between the grout and the stratum in the prestressed anchor cable section; ξ is the coefficient for reducing the interface bond strength; ψ is the coefficient for the influence of the anchorage section length on the ultimate bond strength; n is the number of reinforcing bars or steel strands. S5. Numerical simulation verification: Verify whether the temporary lining structure and prestressed anchor cable obtained from the above theoretical calculations meet the bearing capacity requirements through numerical simulation.

8. The design method for the ultra-large diameter dual-mode TBM initiation reaction system according to claim 7, characterized in that, The calculation load combination for the temporary lining structure of the tunnel section considers permanent loads, general loads, and grouting pressure S. Q21 Combination; the permanent load is the structural self-weight S G1 Surrounding rock pressure S G2 The general load mentioned is the internal water pressure S. Q11 External water pressure S Q12 Dynamic water pressure S Q13 .

9. A construction method for an ultra-large diameter dual-mode TBM initial reaction system according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Temporary lining structure pouring. Based on the laser guidance system, the inner contour line of the temporary lining structure is accurately laid out. The excavated rock surface is leveled with shotcrete. Then, the prestressed anchor cables are installed. Holes are drilled and prestressed anchor cables are laid out according to the design requirements. After the prestressed anchor cables are installed, steel bars are laid out according to the design results to prepare for subsequent concrete pouring. Concrete pouring is carried out by continuous pumping in two sections, and layered compaction is achieved with an immersion vibrator. After demolding, curing is carried out. After curing, a hydraulic jack is used to push the bearing plate for pre-compression test. Step 2, Installation of the reaction frame: Step 2.1: Installation of embedded steel plates. According to the structural design drawings, before the reaction support is installed, embedded steel plates and radial embedded parts need to be installed in the temporary lining structure of the tunnel. The position of the embedded steel plates is determined according to the position of the reaction frame diagonal brace, and the position of the radial embedded parts is determined according to the position of the arc frame unit. The embedded steel plates and radial embedded parts are anchored to the temporary lining structure. Step 2.2, Reaction frame positioning measurement; Step 2.3: Connect the segmented arc-shaped frame units by bolting and hoisting them to construct a ring frame, and install and fix the columns and short diagonal braces; Step 2.4: Leveling the reaction frame. Before assembling the first ring segment, first grind the welds and burrs on the end face of the reaction frame to make it smooth. Take 25 points evenly distributed along the circumference on the end face and measure the distance from each point to the starting axis. Based on the measurement results, fit the relationship between the reaction frame end face and the designed ring end face, as well as the flatness of the reaction frame end face, and determine the distance that needs to be adjusted at each point. For points larger than 5mm, use steel plates of appropriate thickness for leveling; for points smaller than 5mm, use nitrile cork rubber pads of appropriate thickness for leveling. Step 3: TBM Launch. After all the above work is completed, the TBM will be launched. After the first ring of segments is assembled, a demonstration test tunneling will be carried out to determine the tunneling parameters.

10. The construction method of the ultra-large diameter dual-mode TBM initiation reaction system according to claim 9, characterized in that, The reaction frame positioning measurement includes the following steps: 1) Positioning: Perform preliminary layout and installation of the base of the reaction frame in three dimensions and elevation at the preset position; 2) Initial attitude measurement: After the reaction frame is initially fixed, a measuring instrument is used to obtain the three-dimensional coordinate data of multiple preset measuring points on its reaction surface; 3) Attitude deviation calculation: Based on the three-dimensional coordinate data of the multiple preset measurement points, the actual spatial plane of the reaction surface is fitted and generated, and its actual normal vector is determined; the actual normal vector is compared with the preset tunnel design axis vector to calculate the attitude deviation of the reaction frame in pitch and azimuth angles. 4) Attitude adjustment: Based on the calculated attitude deviation, the attitude of the reaction frame is adjusted by an adjustment mechanism; 5) Closed-loop detection: Repeat the initial attitude measurement, attitude deviation calculation and attitude adjustment until the attitude deviation is less than the preset accuracy tolerance value.

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