The general objective of a site investigation is to assess the suitability of a site for the proposed purpose. As such, it involves exploring the ground conditions at and below the surface (Anon, 1999). It is a prerequisite for the successful and economic design of engineering structures and earthworks. Accordingly, a site investigation also should attempt to foresee and provide against difficulties that may arise during construction because of ground and/or other local conditions. Indeed, investigation should not cease once construction begins. It is essential that the prediction of ground conditions that constitute the basic design assumption be checked as construction proceeds and designs modified accordingly if conditions are revealed to be different from those predicted. The investigation of a site for an important structure requires exploration and sampling of strata likely to be significantly affected by the structural load. Data appertaining to groundwater conditions, extent of weathering, and discontinuity pattern in rock masses are also important. In some areas there are special problems that need investigating, for example, potential subsidence in areas of shallow abandoned mine workings and contaminated ground. What is more, as Culshaw (2005) pointed out, the rapid development of information technology and the digitization of increasing amounts of geological data now means that it often is possible to produce three-dimensional (3D) special models of the shallow subsurface.

The complexity of a site investigation depends upon the nature of the ground conditions and the type of engineering structure. More complicated ground conditions and sensitive large engineering structures...