boring tunnels in a soft rock conditions rock header is used. It will be
problematic to use road header in hard rocks or mixed ground conditions.
The advantage of using road header is that it can both excavate and
clear the tunnel simultaneously. This is achieved by ground support
installed behind the road header and consists of bolts shotcrete and
steel sets depending on the ground conditions.
Road header machine consists of a crawler similar to a mini-excavator
with an articulated boom with one or more rotating drums on the end.
These drums have replaceable teeth's which dig and fractures earth or
rock as the drums spin. Other devices like jack-hammer, a slicer head,
simple jaw-like buckets etc adds versatility to the road headers. The
excavated materials are conveyed to the bins by the conveyor belt.
Road header is applied in soft rocks conditions for the construction of
tunnels for the purpose of :
- Laying cables
- Laying pipes
- Other municipal purposes