Tunnel construction is governed by the ground and hence site investigation

is vital to obtain ground characteristics and geotechnical parameters.

Knowledge of the ground conditions plays a key role in the choice of

construction technique, and hence the success of a tunnel project. It is

important to realize that the ability to influence the project outcome (in terms

of cost and schedule) is easier earlier on in the project programme and much

more difficult at a later stage, and the site investigation results can be a key

influence on the early decisions. In many respects the site investigation for

tunnelling projects is similar to other civil engineering projects and thus

general textbooks and standards should be consulted (for example SISG

1993a, b and c, Attewell 1995, Clayton et al. 1995, BSI 1999, Simons et al.

2002, BSI 2007). However, more specific information related to tunnelling

can be found in Dumpleton and West (1976) and BTS/ICE (2005). The new

ICE Specification for Site Investigation to be published imminently will have

a Tunnelling Addendum (current reference SISG 1993c).