Managing ground risk for major rail electrification projects

The United Kingdom has embarked on a series of major rail electrification projects, for example the Great Western, Midland Mainline, Transpennine and the North West. The schemes require the installation of thousands (over twenty thousand on Great Western alone) of new deep foundations to support the overhead line equipment (OLE) foundations, which are primarily laterally loaded cantilever structures. This paper discusses geotechnical aspects of such proposals and is based upon the difficulties of obtaining quality geotechnical information within the confines of an operational railway corridor to inform design and construction risks. The paper details the necessary desk study sources of information that are available on such schemes (that are not necessarily initially appreciated), the recommended strategy of ground investigation with respect to types and spacings. Also detailed are specific recommendations in reducing risks in areas of very poor deposits with respect to the standard method of ‘allocating’ foundations in accordance with the electrification system design requirements.