What is a Temporary Support for a Tunnel?  A temporary support for a tunnel is a provisional structural system installed immediately after or during excavation to stabilize the tunnel’s walls, roof, and floor until a permanent lining or support system can be put in place. In essence, it prevents collapse and controls deformation during construction.These supports are critical in maintaining tunnel integrity under geological stresses and dynamic construction loads.

　　Depending on the ground conditions and excavation method, temporary supports can take various forms—for example, steel sets (movable frameworks that hold the tunnel open until concrete cures), shotcrete (sprayed concrete applied quickly to the tunnel face), rock bolts, forepoles, or even tunnelling shields. Once the permanent lining (such as cast-in-place or precast concrete segments) is installed, these temporary supports are either removed or become redundant.

　　Key Functions

　　1. Stability Assurance: Counteracts ground pressure and redistributes stresses to mitigate deformation or collapse risks.

　　2. Safety Protection: Shields workers and equipment from falling debris or sudden ground movements.

　　3. Workface Stabilization: Maintains excavation stability during sequential construction phases.

　　Common Types and Materials

　　- Steel Arch Supports: Prefabricated steel ribs or lattice girders installed at intervals to bear radial loads. Often combined with shotcrete for composite rigidity.

　　- Rock Bolts and Mesh: Reinforce unstable rock masses using tensioned bolts and welded wire mesh to create a cohesive load-bearing layer.

　　- Shotcrete (Sprayed Concrete): Rapidly applied concrete layers that provide immediate surface support and integrate with steel arches.

　　- Timber or Hydraulic Props: Temporary struts used in soft-ground tunnels to support excavation faces or specific weak zones.