Restricted Access Investigation: London

RSA Geotechnics were requested to drill four boreholes at a location where access was restricted, adjacent to a recently completed student accommodation building in central London.

The boreholes were required within an approximately 3m wide pathway at basement level between the new building and a retaining wall. There were four permanent drainage pipes across the void above the pathway and the only access was via steps at one end.

Use of a standard sized cable percussion rig to drill the boreholes was considered, however, a crane would have been required to lift the rig into position, the working space would have been very limited and the locations of the boreholes would have been constrained by the overhead drainage pipes.

Following discussions with the client, RSA Geotechnics mobilised a demountable rig to the site. It was transported to site on a trailer and broken down into sections which were manhandled down the stairs. The rig components were then assembled at the location of the first borehole and drilling commenced.

By using the demountable rig RSA Geotechnics was able to mobilise quickly, avoid the restrictions and practical difficulties of using a standard sized rig and significantly reduce costs.