Key points for effective corner spraying are:
1. Equipment requirements
Robotic arm with multi-joint (double-curved or Z-type boom) to reach arch foot, sidewall–invert junction, and corner blind zones
360° rotating spray nozzle for precise angle adjustment
Stable concrete pump + accelerator dosing system to ensure uniform setting in corners
2. Spraying technique for tunnel corners
Spray angle: keep the nozzle 70–90° perpendicular to the corner surface to reduce rebound
Spray distance: usually 0.8–1.2 m from the rock surface
Spraying sequence:
First spray the corner root (arch foot / wall–invert junction)
Then move upward to the sidewall and arch
Layered spraying: apply in multiple thin layers (5–7 cm each) to avoid sagging and hollow areas
3. Quality control advantages
Better adhesion and compactness in corner areas
Lower rebound rate compared with dry spraying
Uniform thickness, reducing risks of voids and peeling at tunnel corners
4. Typical applications
Drill-and-blast tunnels
Hydropower and railway tunnels
Soft rock or fractured surrounding rock where corner support is critical
If you want,we can help you select a suitable wet shotcrete machine (arm length, pump capacity, single or double nozzle) specifically for tunnel corner construction.
