Typical construction sequence
Excavation (drill & blast or mechanical excavation)
Initial scaling and cleaning of loose rock
Erection of steel arch frame
Installation of temporary fixing (foot-lock bolts or braces if needed)
Wet shotcrete spraying
First layer: embed and fix the steel arch
Subsequent layers: reach designed thickness
Rock bolt and mesh installation (if not already done)
Secondary shotcrete layer (if required by design)
Key points to note
Spray from arch feet to crown, ensuring full encapsulation.
Avoid voids behind the steel arch.
Apply shotcrete as soon as possible after arch erection to achieve early strength.
If you want, we can also explain how shotcrete thickness and spraying volume are determined for different surrounding rock grades, or how a wet shotcrete machine is selected for arch-supported tunnels.
