Tbm tunnel comprising a plurality of precast structures under an active fault zone and method of construction

Abstract

The application discloses a kind of TBM tunnel comprising multiple prefabricated structures under active fracture zone and construction method, belong to tunnel engineering field, to solve the problem of poor damping effect, low construction efficiency and drainage difficulty when existing TBM tunnel passes through active fracture zone. The structure adopts "rigid skeleton + flexible damping + integrated drainage" composite design, mainly including primary support, reinforced concrete mouth piece, foam concrete damping layer and reinforced concrete secondary lining. The primary support forms a closed loop by "steel skeleton + shotcrete"; the prefabricated reinforced concrete mouth piece integrates support leg, longitudinal drainage ditch and rapid bearing layer; the foam concrete damping layer has a three-dimensional drainage network built in, which is connected with the mouth piece drainage ditch; the reinforced concrete secondary lining uses impermeable concrete and eliminates cavities by grouting. Through rigid-flexible collaborative damping, prefabricated component rapid construction and three-dimensional drainage system, the structure can effectively improve the seismic performance, construction efficiency and drainage capacity of the tunnel, and is suitable for water-rich active fracture zone tunnel engineering.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, specifically to a TBM tunnel containing multiple prefabricated structures under an active fault zone and its construction method. Background Technology

[0002] The mountainous terrain often necessitates tunneling through active fault zones. Open-face tunnel boring machines (TBMs) are commonly used in tunnel construction, but current technologies present significant challenges when TBMs traverse active fault zones.

[0003] (1) Insufficient damping capacity: The existing TBM tunnels do not have independent damping layers, and the secondary lining structure is easily damaged under seismic conditions;

[0004] (2) Low construction efficiency: After the initial support is constructed, it is necessary to wait for the backfilling of the invert arch or the construction of the trestle bridge, which results in a delay;

[0005] (3) Drainage difficulties: In a pure circular tunnel, the primary support and secondary lining are closely attached, and the installation of longitudinal drainage pipes requires weakening the structure, resulting in low drainage efficiency in water-rich fault sections.

[0006] Existing technologies are mostly designed for mining tunnels, such as bypassing through inclined shafts or strengthening support, but they have problems such as large environmental damage, high cost, and long construction period, and cannot meet the adaptability requirements of open TBM tunnels. Summary of the Invention

[0007] To address the problems of poor vibration reduction, low construction efficiency, and difficult drainage when existing TBM tunnels cross water-rich active fault zones, this invention provides a sandwich vibration reduction structure and construction method that integrates vibration reduction, rapid construction, and efficient drainage functions.

[0008] A TBM tunnel comprising multiple prefabricated structures beneath an active fault zone includes:

[0009] The initial support consists of shotcrete and a first steel ring embedded in the shotcrete.

[0010] The reinforced concrete opening component has legs and an integrated longitudinal drainage ditch. The bottom of the reinforced concrete opening component is filled with foamed concrete to form a foamed concrete filling layer. The legs are equipped with a second type of steel, which is connected to the first type of steel of the initial support to form a ring through a reserved steel plate.

[0011] The reinforced concrete secondary lining is connected to the bottom reinforced concrete opening through the secondary lining connection interface and closed into a ring;

[0012] The foamed concrete damping layer is located between the initial support and the reinforced concrete secondary lining, and has a thickness of not less than 20cm.

[0013] Furthermore, the reinforced concrete opening includes at least three longitudinal drainage ditches, which are interconnected, and drainage holes are provided in the longitudinal drainage ditches on both sides.

[0014] Furthermore, the density of the foamed concrete damping layer is not less than A11 grade, and longitudinal and circumferential drainage pipes are pre-embedded inside. The longitudinal and circumferential drainage pipes are connected to the drainage holes of the longitudinal drainage ditch of the reinforced concrete component through a tee pipe.

[0015] Furthermore, the first type of steel in the initial support is welded to the second type of steel in the arch, side wall and bottom reinforced concrete support leg to form a closed ring. The first type of steel is welded with a limiting steel bar embedded part, which is exposed externally. The spacing of the limiting steel bar embedded parts is no more than 50cm×50cm. Then, steel mesh is installed on the limiting steel bar embedded parts, with a steel mesh spacing of 20cm×20cm.

[0016] Furthermore, the reinforced concrete secondary lining has a concrete grade of not less than C35, and a conical grouting hole is pre-embedded at the top. The conical grouting hole is used for subsequent secondary grouting to reduce the number of holes in the arch crown.

[0017] A construction method for a TBM tunnel containing multiple prefabricated structures under an active fault zone as described above includes the following steps:

[0018] After the TBM is excavated, the arch system anchor bolts are installed, and reinforced concrete joints with outriggers are laid.

[0019] Precast foamed concrete particles are filled into the bottom of the reinforced concrete opening, and flowing foamed concrete is poured in to form a foamed concrete filling layer, so that the reinforced concrete opening can quickly reach the bearing capacity conditions of the construction access road.

[0020] C25 concrete is sprayed onto the sidewalls and arches to form shotcrete. At the same time, the first type of steel is embedded in the shotcrete to form initial support, so that the arch and sidewall steel and the second type of steel of the support legs of the reinforced concrete joint are closed into a ring. The limiting steel bar embedded parts are welded on the first type of steel, and then the steel mesh is installed on the limiting steel bar embedded parts.

[0021] Install steel formwork on the steel mesh and pour foamed concrete damping layer in layers with a thickness of not less than 20cm. Remove the steel formwork after the strength meets the standard.

[0022] The secondary lining reinforcement is tied and connected to the reserved steel plates at both ends of the reinforced concrete joint of the joint. The secondary lining concrete is poured to form a reinforced concrete secondary lining. The foamed concrete damping layer is located between the initial support and the reinforced concrete secondary lining.

[0023] Furthermore, the density of the flowing foamed concrete is not less than A11 grade, and the precast foamed concrete particles are ensured to be densely filled before pouring.

[0024] Furthermore, the installation of steel formwork also includes the application of steel mesh. The steel formwork is installed in layers on the steel mesh. The pre-embedded limiting reinforcing bars on the steel mesh are welded to the pre-embedded limiting reinforcing bars on the first type of steel. The distance between the steel mesh and the initial support is equal to the thickness of the foamed concrete damping layer.

[0025] Furthermore, a release coating is applied to the steel formwork before installation, and the foamed concrete is poured in layers until a ring is formed.

[0026] Furthermore, during the pouring of the secondary lining concrete, it is supported by a formwork trolley, and a conical grouting hole is pre-embedded at the top for secondary grouting.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) Improved damping performance: The 20cm thick foamed concrete damping layer absorbs seismic energy through plastic deformation, reducing damage to the secondary lining structure;

[0029] (2) Improved construction efficiency: Precast opening components and foamed concrete particles can be quickly backfilled without waiting for the concrete to solidify, saving the construction time of the invert arch and improving the tunneling efficiency;

[0030] (3) Enhanced drainage capacity: The longitudinal and circumferential drainage pipes and drainage ditches in the sandwich layer form a three-dimensional drainage system, which effectively reduces the water pressure outside the water-rich fault and can adapt to high-pressure water-rich strata.

[0031] (4) Structural integration: The joints integrate the construction platform, drainage and structural connection functions, reducing the overlap of processes and simplifying the construction process. Attached Figure Description

[0032] Figure 1 This is a schematic cross-sectional view of a TBM tunnel containing multiple prefabricated structures under an active fault zone, according to an embodiment of the present invention.

[0033] Figure 2 for Figure 1 Sectional view of AA;

[0034] Figure 3 This is a structural schematic diagram of the reinforced concrete joint component of the present invention;

[0035] Figure 4 This is a schematic diagram of a structure in which foamed concrete is filled into the support leg of a reinforced concrete joint according to an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the structure of pre-embedded longitudinal drainage pipes and circumferential drainage pipes in the foamed concrete damping layer according to an embodiment of the present invention.

[0037] The reference numerals in the figure are described below:

[0038] 1-Initial support, 2-Foamed concrete damping layer, 3-Reinforced concrete secondary lining, 4-Reinforced concrete joint fittings, 5-Arch system anchor bolts; 11-Shotcrete, 12-First steel section, 21-Reinforcing mesh, 22-Limiting steel embedded parts, 41-Outrigger, 42-Longitudinal drainage ditch, 43-Second steel section, 44-Reserved steel plate, 45-Secondary lining connection interface, 46-Drainage hole, 47-Foamed concrete filling layer. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] This embodiment provides a TBM tunnel with multiple prefabricated structures under an active fault zone. Through a composite design of "rigid frame + flexible damping + integrated drainage", the tunnel achieves seismic resistance, rapid construction and efficient drainage functions.

[0041] The TBM tunnel under the active fault zone includes various prefabricated structures, including initial support 1, reinforced concrete joint components 4, reinforced concrete secondary lining 3, and foamed concrete damping layer 2. The following is a combination of... Figure 1-5 The implementation methods for each key component are explained below:

[0042] (1) Initial support 1, which is composed of shotcrete 11 and a first steel section 12 embedded in the shotcrete 11 forming a ring, and its specific construction process is as follows:

[0043] The structure employs a combination of steel frame and shotcrete: C25 concrete (25cm thick) is shotcreted onto the arch and sidewalls to form shotcrete 11. Simultaneously, HW150×150 type first steel profile 12 (circumferential spacing 1m) is pre-embedded, and welded to the second steel profile 43 embedded in the legs 41 of the bottom reinforced concrete opening component 4 via ∠100×8 angle steel to form a closed ring. Φ22 limiting steel reinforcement pre-embedded parts 22 (50cm×50cm spacing) are welded onto the first steel profile 12, and the exposed portion is fitted with 20cm×20cm spacing steel mesh 21, forming the reference frame for the vibration damping layer construction. Figure 2 ).

[0044] (2) Reinforced concrete joint 4

[0045] Precast reinforced concrete joint components 4 with legs 41 (each section 2m long), with Φ20 steel bar interfaces reserved on both sides of the top, and three interconnected longitudinal drainage ditches 42 (cross-sectional dimensions 30cm×40cm, such as...) at the bottom. Figure 3As shown), Φ100 drainage holes 46 are opened on the side walls of the drainage ditches on both sides. The support legs 41 have a second type of steel 43 built in them, and the bottom is filled with precast foamed concrete particles with a particle size of 5-10mm (bulk density 600kg / m³), and then A11 grade flowing foamed concrete (dry density 800kg / m³) is poured in to form a foamed concrete filling layer 47. The bearing capacity can reach 80% of the design value within 2 hours. Figure 3 , 4 ).

[0046] (3) Foamed concrete damping layer 2, located between the initial support 1 and the reinforced concrete secondary lining 3, with a thickness of not less than 20cm, is constructed as follows:

[0047] A 20cm thick closed circumferential damping layer is formed between the reinforcing mesh 21 and the initial support 1. A layered pouring process (each layer 1.5m high) is adopted, using 700kg / m³ dry density foamed concrete. Φ150 longitudinal drainage pipes 23 (5m spacing) and Φ100 circumferential drainage pipes 24 (3m spacing) are pre-embedded inside, connecting to the drainage holes 46 of the drainage ditch 42 via tee pipes, forming a three-dimensional drainage network. A 12mm thick steel mold is used, with a release agent applied to the inside. After curing for 3 days until the strength reaches 5MPa, the mold is removed.

[0048] (4) The reinforced concrete secondary lining 3 is connected to the bottom reinforced concrete opening 4 through the secondary lining connection interface 45 and closed into a ring.

[0049] C35P8 impermeable concrete is used, with Φ25 steel bars as the main reinforcement (20cm spacing) and Φ10 stirrups (15cm spacing). A 44mm (Φ20, 50cm long) steel plate is pre-installed at the top of the joint. Figure 3 As shown, a single-sided weld connection (weld length 10d) is adopted. A 12m long formwork trolley is used for support, and Φ50 conical grouting holes are pre-embedded in the arch crown (spaced 5m apart). After the concrete strength reaches 70%, a 1:1 water-cement ratio secondary grouting is carried out to eliminate voids in the arch crown.

[0050] This invention absorbs the impact energy generated by the activity of the fault zone through a flexible foamed concrete damping layer, while the rigid frame and secondary lining provide structural resistance, effectively reducing the risk of damage to the tunnel by seismic loads. The design of prefabricated opening components and rapid bearing layer enables "immediate bearing capacity upon laying," achieving 80% bearing capacity within 2 hours, solving the problem of construction delays caused by unstable strata in traditional construction. A three-dimensional drainage network collects seepage water through circumferential and longitudinal drainage pipes to the opening component drainage ditch, achieving "zonal drainage and rapid drainage," avoiding water accumulation in water-rich strata that affects construction safety. The secondary lining uses C35P8 impermeable concrete, combined with secondary grouting at the arch (1:1 water-cement ratio) to eliminate voids, improving the structure's impermeability and long-term stability, and adapting to water-rich and high-stress geological environments.

[0051] This invention also provides a construction method for a TBM tunnel containing multiple prefabricated structures under an active fault zone, comprising the following steps:

[0052] Step 1: TBM tunneling and installation of excavation components

[0053] After the TBM tunneling is completed, the arch system anchor bolts 5 (spacing 1.2m×1.2m) are first installed. Then, the precast reinforced concrete support member 4 (2m / section) with support leg 41 is hoisted. Φ20 steel bar interfaces are reserved on both sides of the top. The second steel section 43 (model HW150×150) is set at the bottom of the support leg for welding with the subsequent initial support steel section.

[0054] Step 2: Fill the bottom with foamed concrete

[0055] After the reinforced concrete joint 4 is installed, immediately fill the bottom with precast foamed concrete particles with a particle size of 5-10mm (bulk density 600kg / m³), and then pour in flowing foamed concrete (density 800kg / m³, conforming to A11 grade standard) to fill the gaps between the particles and form foamed concrete damping layer 2. It can reach 80% of the design bearing capacity within 2 hours.

[0056] Step 3: Initial support construction

[0057] C25 concrete (25cm thick) was sprayed onto the sidewalls and arch using a wet spraying process. Simultaneously, the first type of steel 12 (circumferential spacing 1m) was pre-embedded. The first type of steel 12 in the arch and sidewalls was welded to the second type of steel 43 of the reinforced concrete joint 4 using ∠100×8 angle steel to form a ring. Figure 2 As shown, a limiting steel bar embedded part 22 (Φ22, spacing 50cm×50cm) is welded on the first steel section 12, and then a steel mesh 21 (spacing 20cm×20cm) is installed on the limiting steel bar embedded part 22. The steel mesh 21 is 20cm away from the initial support 1 (i.e. the thickness of the foamed concrete damping layer 2).

[0058] Step 4: Pouring the foamed concrete damping layer

[0059] Install 12mm thick steel formwork (in 3 layers, each layer 1.5m high). The steel formwork is installed layer by layer on the steel mesh 21, and the inside of the formwork is coated with release agent. Pour foamed concrete (dry density 700kg / m³), and vibrate to compact each layer after pouring. After curing for 3 days until the strength reaches 5MPa, remove the formwork to form a fully enclosed foamed concrete damping layer 2.

[0060] Step 5: Pouring reinforced concrete secondary lining

[0061] The secondary lining reinforcement (main bars Φ25, spacing 20cm; stirrups Φ10, spacing 15cm) is tied and connected to the pre-reserved steel plate 44 (Φ20, length 50cm) at the top of the reinforced concrete joint 4 using single-sided welding (weld length 10d). A 12m long formwork trolley is used for support, and C35P8 impermeable concrete is poured. At the same time, Φ50 conical grouting holes (spaced 5m) are pre-embedded in the arch. After the secondary lining strength reaches 70% of the design value, secondary grouting (water-cement ratio 1:1) is carried out.

[0062] This invention solves the problems of poor vibration reduction, long construction period, and poor drainage in traditional TBM tunnels in water-rich active fault zones through modular prefabrication, rapid filling, and the synergistic design of rigid steel constraints and flexible damping materials. Engineering verification shows that this structure can improve the seismic resistance of tunnels by more than 40% and shorten the construction period by 30%. It is suitable for tunnel projects in water-rich active fault zones with a burial depth ≤500m and a water pressure ≤2MPa.

[0063] The technical specifications of the main items in this embodiment are shown in Table 1:

[0064] Table 1

[0065]

[0066] This invention has the following characteristics:

[0067] 1. Significantly improves shock absorption performance

[0068] Foamed concrete damping layers absorb the energy of earthquakes or fault activity through their own plastic deformation, and, in conjunction with the rigid constraints of steel rings, effectively reduce the vibration response of TBM tunnels in water-rich active fault zones.

[0069] 2. Achieve efficient drainage and siltation prevention

[0070] The multi-channel longitudinal drainage ditch and the pre-embedded drainage pipe in the shock-absorbing layer work together to improve the drainage capacity by more than 30% compared with the traditional structure, avoiding the floating of the pipe segments or structural instability caused by water accumulation in water-rich strata.

[0071] 3. Significantly shorten the construction period

[0072] The bottom foamed concrete filling layer can reach the design bearing capacity within 24 hours, saving more than 50% of the curing time compared with conventional concrete pouring process, and achieving seamless connection of the "tunneling-support-drainage" process.

[0073] 4. Enhance the long-term durability of the structure

[0074] The steel ring forming and secondary grouting technology reduces the risk of structural cracks. The C35 and above grade secondary lining concrete has a permeability grade of P8, which can meet the long-term use requirements of water-rich and high water pressure environments.

[0075] 5. Reduce construction costs and risks

[0076] Integrated design reduces the consumption of temporary support materials, and the factory production of precast foamed concrete particles reduces the intensity of on-site operations. At the same time, rapid construction reduces the exposure time of the working face, thereby reducing the risk of water and mud inrush.

[0077] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A construction method for a TBM tunnel comprising multiple prefabricated structures under an active fault zone, wherein the TBM tunnel comprising multiple prefabricated structures under an active fault zone includes: The initial support (1) is formed by shotcrete (11) and a first steel section (12) embedded in the shotcrete (11) in a ring; the reinforced concrete opening member (4) is equipped with a support leg (41) and an integrated longitudinal drainage ditch (42); the bottom of the reinforced concrete opening member (4) is filled with foamed concrete to form a foamed concrete filling layer (47); a second steel section (43) is provided in the support leg (41); the second steel section (43) is connected to the first steel section (12) of the initial support (1) in a ring through a reserved steel plate (44); the reinforced concrete secondary lining (3) is connected to the bottom reinforced concrete opening member (4) through the secondary lining connection interface (45) and closed in a ring; the foamed concrete damping layer (2) is located between the initial support (1) and the reinforced concrete secondary lining (3) and has a thickness of not less than 20cm; the construction method is characterized by the following steps: TBM tunneling and installation of joint components: After the TBM tunneling, the arch system anchor bolts (5) are installed, and the reinforced concrete joint components (4) with outriggers (41) are installed. Bottom foam concrete filling: precast foam concrete particles are filled into the bottom of the reinforced concrete opening (4), and flowing foam concrete is poured to form a foam concrete filling layer (47), so that the reinforced concrete opening (4) can quickly reach the bearing capacity condition of the construction access road. Initial support construction: C25 concrete is sprayed on the side walls and arch to form shotcrete (11), and first steel (12) is pre-embedded in the shotcrete (11) to form initial support (1), so that the arch, side wall steel and the second steel (43) of the support leg (41) of the reinforced concrete opening (4) are closed into a ring; the limiting steel reinforcement pre-embedded part (22) is welded on the first steel (12), and then the steel mesh (21) is installed on the limiting steel reinforcement pre-embedded part (22); Foamed concrete damping layer pouring: Install steel formwork on steel mesh (21) and pour foamed concrete damping layer (2) in layers with a thickness of not less than 20cm. Remove steel formwork after the strength reaches the standard. Reinforced concrete secondary lining pouring: tie the secondary lining reinforcement and connect it with the reserved steel plates (44) at both ends of the reinforced concrete opening member (4). The secondary lining concrete is poured through the formwork trolley to form the reinforced concrete secondary lining (3), so that the foamed concrete damping layer (2) is located between the initial support (1) and the reinforced concrete secondary lining (3).

2. The construction method for a TBM tunnel comprising multiple prefabricated structures under an active fault zone according to claim 1, characterized in that, The density of the flowing foamed concrete is not less than A11 grade, and the precast foamed concrete particles are ensured to be densely filled before pouring.

3. The construction method for a TBM tunnel comprising multiple prefabricated structures under an active fault zone according to claim 1, characterized in that, The installation of steel formwork also includes the construction of steel mesh (21). The steel formwork is installed in layers on the steel mesh (21). The pre-embedded limit steel bars (22) on the steel mesh (21) are welded to the pre-embedded limit steel bars (22) on the first steel (12). The distance between the steel mesh (21) and the initial support (1) is equal to the thickness of the foamed concrete damping layer (2).

4. The construction method for a TBM tunnel comprising multiple prefabricated structures under an active fault zone according to claim 1, characterized in that, Before installation, the steel formwork is coated with a release coating, and the foamed concrete is poured in layers until a ring is formed.

5. The construction method for a TBM tunnel comprising multiple prefabricated structures under an active fault zone according to claim 1, characterized in that, When the secondary lining concrete is poured, a conical grouting hole is pre-embedded at the top, and secondary grouting is carried out after the secondary lining strength reaches 70% of the design value.

6. The construction method for a TBM tunnel comprising multiple prefabricated structures under an active fault zone according to claim 1, characterized in that, The reinforced concrete opening (4) includes at least three longitudinal drainage ditches (42), each longitudinal drainage ditch (42) is interconnected, and the longitudinal drainage ditches (42) on both sides are provided with drainage holes (46).

7. The construction method for a TBM tunnel comprising multiple prefabricated structures under an active fault zone according to claim 6, characterized in that, The density of the foamed concrete damping layer (2) is not less than A11 grade, and a longitudinal drainage pipe (23) and a circumferential drainage pipe (24) are pre-embedded inside. The longitudinal drainage pipe (23) and the circumferential drainage pipe (24) are connected to the drainage hole (46) of the longitudinal drainage ditch (42) of the reinforced concrete fitting (4) through a tee pipe.

8. The construction method for a TBM tunnel comprising multiple prefabricated structures under an active fault zone according to claim 1, characterized in that, The first steel section (12) of the initial support (1) is welded to the second steel section (43) of the arch, side wall and bottom reinforced concrete opening (4) to form a closed ring. The first steel section (12) is welded with the limiting steel reinforcement embedded part (22), the limiting steel reinforcement embedded part (22) is exposed, the spacing of the limiting steel reinforcement embedded part (22) is no more than 50cm×50cm, and then the steel mesh (21) is installed on the limiting steel reinforcement embedded part (22), the spacing of the steel mesh (21) is 20cm×20cm.

9. The construction method for a TBM tunnel comprising multiple prefabricated structures under an active fault zone according to claim 1, characterized in that, The concrete grade of the reinforced concrete secondary lining (3) is not lower than C35, and a conical grouting hole is pre-embedded at the top. The conical grouting hole is used for subsequent secondary grouting to reduce the number of holes in the arch.

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