ABSTRACT
The extent of the subsurface or ground investigation is determined by the character and variability of the ground and groundwater, the type and scale of the project, and the amount, quality and availability of the existing information. Planning for an investigation — which should be completed before the roadworks are finally designed — should be flexible so that the work can be changed as necessary when fresh information is obtained. The ground investigation is a process of continuous exploration and interpretation, and its scope will need regular amendment as data are interpreted. (Detailed guidance regarding the planning of a site investigation, and a general work specification, are given in references 2 and 3, respectively.)
A measure of the importance of carrying out adequate ground investigations can be gathered from a report4 by the National Audit Office over a decade ago, in which it is pointed out that 210 premature failures during highway works cost some 260 million pounds sterling, and that geotechnical failures were a major cause for concern.
