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).