AUTOBORE HAS become the first UK contractor to offer dry-rock directional drilling following the purchase of a Powermole SE drilling system.
The PM903 dry-rock drilling machine, launched in the UK earlier this year, has already been successfully deployed on a series of contracts in South Wales and Oxfordshire.
While con-ventional rock directional drilling systems use mud motors with bentonite flush, the new system, developed by Power- mole's Italian partner SE Technology, is claimed to be the first capable of drilling through hard rock without bentonite.
Instead, the drilling system uses high-powered com-pressed air with a small amount of biodegradable additive as a lubricant, leaving no fluid residue.
The system comprises a drilling section fitted with a percussive head that engages when rock is hit. Powermole claims this simul- taneous drilling and percussion ensures consistent pene- tration through hard ground.
Progress of the head can be mon- itored with a detection unit housed in a specially developed shock absorber, which allows it to work during drilling.
The PM903 can drill up to 400mm diameter holes in shale and 250mm diameter holes in solid rock and uses flexible steel rods to allow rapid pullback and simultaneous back reaming.
AutoBore, the trenchless division of Walter Lawrence Civil & Mechanical, has used the machine on a range of contracts in South Wales for utility company Hyder.
Work includes crossings of a dual carriageway at Neath, Swansea and a river at Camarthen, as well as a cable duct through a mountain at Caerphilly for a mobile telephone transmitter, which at 140m is the company's longest run to date.