Keller is using the new PRA-Sline rock augering system, provided by Stratum Drilling Solutions, to drill through hard sandstone to install piling to support the mining head gear at the £3.2 billion (US$3.9 billion) polyhalite mine development.

A new Hutte 207 rig is being used to install the six 750mm diameter cased and bored piles to 20m depth below the piling platform, all this working at 46m below ground level.

"We wouldn't have been able to carry out this job without these augers and the Hutte 207," said Shaun Davison, Keller's GM for Piling and Rail.

"The rock augering system is being used rather than down the hole hammer techniques and has allowed us to get the job done, along with a combination of good planning, plant, equipment and personnel.

"We knew the rock strata was quite hard due to previously working within the mine shaft and coupled with the fact that DTHH compressed air drilling wasn't allowed in the shaft, we knew our rock augering systems would struggle. Therefore, we needed to source an alternative. After months of researching the latest rock auguring technique the PRA-Sline stood out and the most efficient and reliable augers to use and this proved the case.

"Working with two drilling crews on 12hour shifts 24/7, drilling the bores took an average 20 hours to auger to depth. We were able to install all the piles to programme."

As well as working with Stratum, Keller has worked closely for the last six months with engineers Arup, main contractor Careys Civil Engineering and mine owners Sirius Minerals to come up with the solution.

Sirius is in the process of sinking production and service shafts down to the potash deposits, which are located 1.5km below the Earth's surface. The production shaft is one of the deepest in Europe at 1,530m.

Diaphragm walls have been installed at the service shaft to ensure the passages are stable and waterproof and Keller has installed the piling, which will be bolted to the mining head gear which must be constructed underground for environmental reasons.

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