Tunnel inverted arch thin layer rubber toughening structure construction method

Abstract

This invention discloses a construction method for a thin-layer rubber-reinforced structure for a tunnel invert arch, comprising the following steps: Step 1, spraying concrete onto the initial support of the invert arch and leveling it to form a cement mortar leveling layer; Step 2, laying multiple rings of rubber-reinforced layers sequentially along the tunnel direction from the end onto the cement mortar leveling layer to form a rubber-reinforced layer structure. Each ring of the rubber-reinforced layer includes multiple polyurethane foam boards connected sequentially in the ring direction. A rectangular hole is formed in the center of each polyurethane foam board, and a rubber vibration damping pad is nested within each rectangular hole; Step 3, laying a waterproof sheet on top of the rubber-reinforced layer structure from Step 2; Step 4, pouring invert arch concrete onto the waterproof sheet. This method utilizes a rubber-reinforced layer structure, integrating vibration damping and load-bearing functions, which can absorb a large amount of energy from seismic dynamic loads and reduce the risk of structural resonance.

Description

Technical Field

[0001] This invention belongs to the field of tunnel and underground engineering construction technology, specifically relating to a construction method for a thin-layer rubber toughened structure for tunnel invert arches. Background Technology

[0002] Currently, numerous railway mountain tunnels traverse active fault zones and high-intensity earthquake zones. The frequent occurrence of high-magnitude earthquakes and the widespread distribution of adverse geological structures pose significant challenges to tunnel construction, operation, and maintenance, and many related technical problems remain unresolved. Theoretical research suggests that tunnel structures, constrained by surrounding rock masses, experience smaller amplitude and fewer vibrations during earthquakes, thus exhibiting good seismic resistance. However, in engineering practice, the actual seismic damage to tunnels does not conform to theory; many tunnels traversing active fault zones suffer severe seismic damage, with significant structural failure.

[0003] According to existing research, setting up a toughening layer can control the deformation of the tunnel lining structure, improve the stress state of the tunnel lining, reduce the range of the plastic zone of the surrounding rock mass, and enable the support structure and the surrounding rock to work together to bear the load in the event of an earthquake, thereby reducing the degree of damage to the tunnel structure and improving the structural toughness.

[0004] Traditional rubber-reinforced layer structures are applied to the damaged area when tunnels are damaged and cracks appear, followed by a thin layer of reinforced concrete. The traditional rubber-reinforced layer structure and the already cracked tunnel share the surrounding rock load. Designed for seismic conditions, the thickness typically exceeds 10cm, and depending on the manufacturing process, the dimensions are generally between 1.5m and 2m. This results in significant weight, difficult construction, and challenges in securing the material. Based on field experience, each construction cycle requires approximately 10 workers and takes about 12 hours, leading to poor economic and social benefits. Summary of the Invention

[0005] The purpose of this invention is to provide a construction method for a thin-layer rubber-toughened structure for tunnel invert arches. The rubber-toughened layer structure integrates shock absorption and load-bearing functions, which can absorb a large amount of energy from seismic dynamic loads and reduce the risk of structural resonance.

[0006] This invention adopts the following technical solution: a construction method for a thin-layer rubber toughening structure for tunnel invert arches, comprising the following steps: Step 1: Shot concrete is sprayed onto the initial support of the invert arch and leveled to form a cement mortar leveling layer; Step 2: On the cement mortar leveling layer, starting from the end, lay multiple rings of rubber toughening layer body in sequence along the tunnel direction to form a rubber toughening layer structure. Each ring of the rubber toughening layer body includes multiple polyurethane foam boards connected in sequence in the ring direction. A rectangular hole is opened in the center of each polyurethane foam board, and a rubber vibration isolation pad is nested in each rectangular hole. Step 3: Lay a waterproof sheet on top of the rubber toughening layer structure in Step 2; Step 4: Pour the inverted arch concrete onto the waterproof sheet.

[0007] Furthermore, in step two, the laying of each ring of rubber toughening layer body is as follows: taking the centerline of the initial support of the inverted arch along the tunnel direction as the dividing line, multiple polyurethane foam boards are laid sequentially from the centerline toward the left and right side walls, and rubber vibration isolation pads are nested in the rectangular holes of each polyurethane foam board.

[0008] Furthermore, in step one, before spraying concrete on the initial support of the invert arch, the exposed material on the initial support base surface of the invert arch is removed.

[0009] Furthermore, in step two, the size of the rubber vibration isolation pad is 1 / 3 to 2 / 3 of the outer perimeter of the polyurethane foam board.

[0010] Furthermore, in step one, the cement mortar leveling layer satisfies the following: the depth-to-length ratio D / L ≤ 1 / 50, where D is the depression depth between two adjacent protrusions on the base surface of the cement mortar leveling layer, L is the distance between two adjacent protrusions on the base surface of the cement mortar leveling layer, and L ≤ 0.5m.

[0011] The present invention also discloses a thin-layer rubber toughening structure for tunnel invert arches, used in the above-mentioned construction method of a thin-layer rubber toughening structure for tunnel invert arches, comprising multiple adjacent rings of rubber toughening layer bodies, each ring of the rubber toughening layer body comprising multiple polyurethane foam boards connected sequentially in the ring direction, and a rectangular hole is provided in the center of each polyurethane foam board, and a rubber vibration isolation pad is nested in each rectangular hole.

[0012] Furthermore, the rubber toughening layer structure is either raised or arched rib type.

[0013] The beneficial effects of this invention are: 1. The rubber-reinforced layer structure integrates shock absorption and load-bearing functions, which can absorb a large amount of energy from seismic dynamic loads, rapidly attenuate the energy transmission of seismic waves, and reduce the risk of structural resonance. 2. The rubber-reinforced layer structure adopts a raised or arched rib design, which can increase its deformation capacity, disperse external dynamic loads, avoid stress concentration, and improve the load-bearing performance of the structure. 3. The rubber-reinforced layer structure has strong toughness and durability, reducing maintenance frequency and costs, extending the structural life, and providing good economic benefits. 4. Although the rubber-reinforced layer structure increases costs, its excellent seismic resistance can effectively reduce the degree of damage to tunnel structures when dealing with earthquake damage or high-energy dynamic load failure, reducing post-disaster maintenance costs, and providing a better overall cost-performance ratio. 5. It has strong adaptability to multiple scenarios. For tunnel projects that may be damaged by strong dynamic loads or accidental loads, such as active fault zones, the rubber toughening layer structure can reduce the high-energy damage to the tunnel structure caused by fault slippage or accidental dynamic loads. For heavy traffic tunnels, the energy absorption effect of the rubber toughening structure can reduce structural fatigue damage and extend the structural life in the face of external loads such as frequent vibrations (e.g., subways and heavy-duty vehicles on highways). Attached Figure Description

[0014] Figure 1 A schematic diagram of a thin-layer rubber toughening structure for a tunnel invert arch; The components include: 1. Initial support of the invert arch; 2. Cement mortar leveling layer; 3. Rubber vibration isolation pad; 4. Polyurethane foam board; 5. Waterproof board; 6. Invert arch concrete. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0016] This invention discloses a construction method for a thin-layer rubber-reinforced structure for tunnel inverts, applicable to composite lining tunnel projects in earthquake-prone areas, active fault zones, and those experiencing structural cracking due to dynamic overload on the invert. During tunnel construction, large machinery is used, and the invert backfill layer bears the dynamic loads of these machines, easily causing concrete damage in the invert area. During operation, high-speed trains exert high-frequency dynamic loads on the track bed and the invert concrete beneath it, leading to concrete cracking. Therefore, installing a rubber-reinforced seismic isolation layer in the tunnel invert not only reduces the dynamic load damage to the track bed or invert backfill concrete from high-speed trains and construction machinery but also effectively improves the vertical seismic performance of the tunnel structure and enhances its overall toughness.

[0017] This invention discloses a construction method for a thin-layer rubber toughening structure for tunnel invert arches, comprising the following steps: Step 1: Remove exposed anchor bolt heads and rebar heads, and other protrusions from the initial support base surface. The remaining length after cutting should not exceed 0.5cm to prevent puncturing the rubber toughening layer during vibration energy absorption. After completion, water is sprayed to soak the shotcrete surface of the initial support 1 of the invert arch, and leveling is performed to form a cement mortar leveling layer 2. Water is then sprayed on and the surface is covered for curing. After curing, the flatness of the base surface should meet the requirement that the depth-to-length ratio D / L ≤ 1 / 50, where D is the depth of the depression between two adjacent protrusions on the cement mortar leveling layer base surface, and L is the distance between two adjacent protrusions on the cement mortar leveling layer base surface, and L ≤ 0.5m.

[0018] Step 2: On the cement mortar leveling layer in Step 1, a multi-ring rubber toughening layer body is laid sequentially along the tunnel direction starting from the end to form a rubber toughening layer structure. Each ring of the rubber toughening layer body includes multiple polyurethane foam boards 4 connected sequentially in the ring direction. A rectangular hole is opened in the center of each polyurethane foam board 4, and a rubber vibration isolation pad 3 is nested in each rectangular hole. The size of the rubber vibration isolation pad (3) is 1 / 3 to 2 / 3 of the outer size of the polyurethane foam board 4. For unfavorable conditions such as poor surrounding rock quality, large deformation, and large tonnage of on-site mechanical equipment, the size of the rubber vibration isolation pad should be larger, and vice versa.

[0019] Evenly distribute the polyurethane foam boards 4 on the cement mortar leveling layer and fix the four corners with a nail gun. The installation gap between two adjacent polyurethane foam boards 4 should be ≤10mm, and the misalignment between two adjacent boards should be ≤5mm. Embed each rubber vibration damping pad 3 into the corresponding rectangular hole of the polyurethane foam board 4.

[0020] In a specific embodiment, the dimensions of the rubber vibration isolation pad 3 are as follows: length × width × height 30 cm × 50 cm × 2 cm; the dimensions of the polyurethane foam board 4 are as follows: length × width × height 100 cm × 60 cm × 2 cm; the rectangular hole size should be designed with a 5mm gap on all four sides, so the dimensions of the rectangular hole are as follows: length × width × height 51 cm × 31 cm × 2 cm. During the seismic energy absorption process, the rubber vibration isolation pad 3 is the main load-bearing structure, while the polyurethane foam board 4 provides lateral constraint and fixation for the embedded rubber vibration isolation pad, ensuring that it does not shift and avoiding load-bearing failure.

[0021] For the invert arch cycle where the rubber-reinforced layer structure is to be laid, polyurethane boards 4 are laid ring by ring, starting from the side adjacent to the previous cycle's invert arch. The laying sequence for each ring proceeds sequentially from the center of the invert arch towards both side walls, fixing each board one by one. Immediately after laying each complete ring of polyurethane foam boards 4, the rubber vibration isolation pads 3 for that entire ring are installed. Installing rubber vibration isolation pads in skipped or alternate rings is prohibited. The reason for this construction sequence is that the curved slope within the invert arch makes it unstable for construction workers to stand; stepping on the already installed rubber vibration isolation pads 3 could easily cause them to shift.

[0022] During installation, debris such as gravel, concrete blocks, wire, rebar ends, or small tools should be avoided from entering the bottom surface of the rubber isolation layer to prevent reducing the structure's toughness and load-bearing capacity.

[0023] Step 3: For cases where the invert arch design includes a waterproof membrane, lay the waterproof membrane 5 on top of the rubber toughening layer structure from Step 2, such as... Figure 1 As shown.

[0024] During the construction of the waterproof membrane, its fixing points should be set at the corners of the polyurethane foam board. Four polyurethane foam boards 4 adjacent to the corners can be fixed at the same time. In addition, the waterproof membrane and the rubber toughening layer should be checked for foreign objects to avoid uneven stress.

[0025] Step 4: Pour the inverted arch concrete 6 onto the waterproof board 5; During the construction of the secondary lining reinforcement of the invert arch, the anchoring points of the erected reinforcement should be set at the joints of the rubber toughening layer structure to prevent puncture of the rubber toughening layer structure. In cases without a waterproof liner, if welding is performed, care should be taken to avoid burning or damaging the toughening layer structure with welded joints or overheated reinforcement ends. After the lower layer of reinforcement welding is completed, the toughening layer structure should be promptly inspected for misalignment or folding, and any issues should be addressed immediately.

[0026] Before pouring concrete, check the surface of the toughening layer for debris and clean it promptly. During the pouring of the invert concrete, vibrate carefully near the rubber toughening structure to prevent displacement or misalignment. If manual grouting is required, proceed with caution to avoid damaging the toughening layer surface with shovels or other tools.

[0027] To verify the role of the rubber toughening structure and the traditional damping layer in the tunnel invert arch, both were applied to a tunnel construction project, and the data are shown in Table 1 below: Table 1. Data Analysis of the Application of this Application and Rubber-Reinforced Structures in Tunnel Construction This invention discloses a construction method for a thin-layer rubber-reinforced structure for tunnel invert arches. During the construction of the tunnel invert arch, a rubber-reinforced structure is applied. This structure is approximately 2 cm thick, employing a thin-layer design with a single piece weighing only 6.9 kg. This makes construction convenient and efficient, with each cycle taking only 2 hours. The number of workers required is reduced from 10 to 5 compared to traditional toughening structure construction. The work efficiency is fast, with each cycle taking only 2 hours. The cost per linear meter of toughening structure is reduced by more than 50%, resulting in significant overall economic benefits. Using this rubber-reinforced structure improves the impact resistance of the lining structure, enabling coordinated deformation of the surrounding rock and support. It quickly absorbs and disperses the impact energy of high-energy external dynamic loads (earthquakes or large machinery dynamic loads), preventing structural defects such as lining cracking and misalignment. According to on-site monitoring data, the addition of the rubber-reinforced layer increases the load-bearing capacity of the structure by more than 50%, improving the structural stress state and preventing seismic damage to the tunnel structure during later operation. In addition, the rubber-reinforced structure improved the tunnel's seismic performance and structural quality, preventing cracking of the lining concrete and corrosion of the material by acidic or alkaline environments in groundwater. After construction, the invert arch remained crack-free, enhancing its load-bearing capacity against heavy machinery.

[0028] This invention also discloses a thin-layer rubber toughening structure for tunnel invert arches, used in the aforementioned construction method for a thin-layer rubber toughening structure for tunnel invert arches. It includes multiple adjacent rings of rubber toughening layer bodies. Each ring of the rubber toughening layer body includes multiple polyurethane foam boards 4 connected sequentially in the ring direction. A rectangular hole is formed at the center of each polyurethane foam board 4, and a rubber vibration isolation pad 3 is nested within each rectangular hole. The rubber toughening layer structure is either raised or arched, specifically, the rubber vibration isolation pad 3 and the polyurethane foam board 4 are raised or arched, which increases their deformation capacity, disperses external dynamic loads, avoids stress concentration, and improves the load-bearing capacity of the structure.

Claims

1. A construction method for a thin-layer rubber-reinforced structure for a tunnel invert arch, characterized in that, Includes the following steps: Step 1: Shot concrete on the initial support of the invert arch (1) and level it to form a cement mortar leveling layer (2). Step 2: On the cement mortar leveling layer (2) in Step 1, a multi-ring rubber toughening layer body is laid sequentially from the end along the tunnel direction to form a rubber toughening layer structure. Each ring of the rubber toughening layer body includes multiple polyurethane foam boards (4) connected sequentially in the ring direction. A rectangular hole is opened in the center of each polyurethane foam board (4), and a rubber vibration isolation pad (3) is nested in each rectangular hole. Step 3: Lay a waterproof sheet (5) on top of the rubber toughening layer structure in Step 2. Step 4: Pour the inverted arch concrete (6) onto the waterproof board (5).

2. The construction method of a thin-layer rubber toughening structure for a tunnel invert arch as described in claim 1, characterized in that, In step two, the laying of each ring of rubber toughening layer body is as follows: taking the center line of the initial support of the inverted arch along the tunnel direction as the dividing line, multiple polyurethane foam boards (4) are laid sequentially from the center line towards the left and right side walls, and rubber vibration isolation pads (3) are nested in the rectangular holes of each polyurethane foam board (4).

3. The construction method of a thin-layer rubber toughening structure for a tunnel invert arch as described in claim 2, characterized in that, In step one, before the initial support (1) of the invert arch is shotcreted, the exposed material on the initial support base surface of the invert arch is removed.

4. The construction method of a thin-layer rubber toughening structure for a tunnel invert arch as described in claim 3, characterized in that, In step two, the size of the rubber vibration isolation pad (3) is 1 / 3 to 2 / 3 of the outer dimensions of the polyurethane foam board (4).

5. The construction method of a thin-layer rubber toughening structure for a tunnel invert arch as described in claim 4, characterized in that, In step one, the cement mortar leveling layer (2) satisfies the following: the depth-to-length ratio D / L≤1 / 50, where D is the depression depth between two adjacent protrusions on the base surface of the cement mortar leveling layer, L is the distance between two adjacent protrusions on the base surface of the cement mortar leveling layer, and L≤0.5m.

6. A thin-layer rubber toughening structure for tunnel invert arches, used in the construction method of the thin-layer rubber toughening structure for tunnel invert arches as described in claim 5, characterized in that, The rubber toughening layer body includes multiple adjacent rings. Each ring of the rubber toughening layer body includes multiple polyurethane foam boards (4) connected sequentially in the ring direction. A rectangular hole is opened in the center of each polyurethane foam board (4), and a rubber vibration isolation pad (3) is nested in each rectangular hole.

7. The thin-layer rubber toughening structure for tunnel invert arch as described in claim 6, characterized in that, The rubber toughening layer has a raised or arched rib structure.

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