The wet shotcrete machine is needed early in tunnel construction, typically during the initial support phase after excavation.
Here's when and why you need it:
Key Phases for Wet Shotcrete Application in Tunnel Construction:
Initial Ground Support (Immediately After Excavation)
Wet shotcrete is applied right after excavation to stabilize the exposed rock or soil.
It prevents loose material from falling and controls deformations in weak rock formations.
Often used with rock bolts, wire mesh, or steel ribs for added support.
Primary Lining
In tunnels using the New Austrian Tunneling Method (NATM), wet shotcrete forms the primary support.
It works well in soft ground, fractured rock, or areas with water seepage.
Final Lining (If Needed)
In some cases, wet shotcrete may be used as a final lining instead of cast-in-place concrete, especially in temporary tunnels or mining operations.
Factors Affecting Shotcrete Timing:
Geological Conditions: Weak or unstable ground may require immediate shotcrete application.
Excavation Method: TBM-driven tunnels might need shotcrete later compared to drill-and-blast or roadheader methods.
Tunnel Design: Some tunnels rely more on precast segments, reducing the need for early wet shotcrete.
Summary
You'll need a wet shotcrete machine right after starting excavation, particularly for ground stabilization and initial support. It plays a crucial role in ensuring safety and tunnel integrity.
