Useful for almost all site investigation projects, Cable Percussion Boreholes are a pivotal method of Site Investigation in order to gather information on overburden strata down to bedrock level.
OCB Geotechnical operate a fleet of two Cable Percussion Drilling Rigs currently; a Dando 2000 rig and a Pilcon rig.
Cable Percussion drilling (also known as shell and auger drilling) uses a drop tool type drilling method using steel casing to prevent borehole collapse. The rig is comprised of a large towable tripod, which is used to lift and drop cutting tools into the base of the borehole. Disturbed and undisturbed samples are collected from the boreholes to be logged by a qualified Geotechnical Engineer and can also be sent for testing in a laboratory. In-Situ testing techniques including Standard Penetration testing (SPT), Permeability Testing, Vane Testing and Piston Sampling can all be carried out in the borehole and provide information for input into geotechnical design.
OCB Geotechnical’s rigs are capable of using casing from 150mm up to 250mm diameter to a maximum depth of 50m depending on ground conditions and casing diameter used.  Where an obstruction is encountered, such as a large boulder or bedrock, chiselling is employed to either continue past the obstruction or prove the obstruction is bedrock.
Where bedrock is encountered, Rotary Drilling is required to prove bedrock level, extent, lithology, nature etc.
All fieldwork carried out in accordance with the relevant British Standards: BS 5930