Tunnel support encompasses a series of measures implemented to ensure the safety and stability of tunnels during construction and use. It is essential for ensuring the safety of workers and maintaining the structural integrity of the tunnel.
I. Purpose of Tunnel Support
During the excavation of a tunnel, the original geological equilibrium is disrupted, leading to a redistribution of stress in the surrounding rock mass. The primary purpose of tunnel support is to control the deformation of the surrounding rock, prevent collapses, ensure the safety of workers and equipment, and maintain the tunnel's functionality in a stable manner over time.
II. Types of Tunnel Support
1. Initial Support
- Shotcrete : High-pressure air is used to spray concrete onto the tunnel walls, forming a rapidly hardening protective layer that seals the surrounding rock and prevents weathering and loosening.
- Rock Bolting : Rock bolts are inserted into the surrounding rock to enhance its stability through their anchoring force. Rock bolts can be categorized into different types, such as regular rock bolts and prestressed rock bolts.
- Steel Arch Supports : Arch-shaped structures made of steel are installed against the tunnel walls, working in conjunction with shotcrete and rock bolts to provide significant support.
2. Secondary Lining
- Formed Concrete Lining : After the initial support is completed, concrete is poured using forms to create a permanent lining structure. The secondary lining enhances the tunnel's waterproofing and structural strength.
- Reinforced Concrete Lining : Steel reinforcement is added to the concrete to increase the load-bearing capacity of the lining.
III. Design Principles for Tunnel Support
1. Safety Principle : The support structure must withstand the pressure of the surrounding rock and other external loads to ensure the tunnel's safety.
2. Adaptability Principle : The selection of appropriate support types and parameters must be based on varying geological conditions, tunnel cross-section shapes, and construction methods.
3. Economic Principle : Support costs should be minimized while ensuring safety, thereby enhancing the project's economic efficiency.
IV. Key Points in Tunnel Support Construction
1. A thorough geological survey must be conducted before construction to develop a reasonable support plan.
2. Construction must strictly follow design requirements to ensure the quality of the support structure.
3. Monitoring and control during construction should be strengthened to timely adjust support parameters and ensure the safety and stability of the tunnel.
In conclusion, tunnel support is a critical aspect of tunnel engineering, directly impacting the safety and lifespan of the tunnel. Various factors must be carefully considered during the design and construction processes to select appropriate support methods, ensuring the stability and safety of the tunnel.