ABSTRACT
A distinguishing feature of investigations for rock foundations is that it is particularly important to focus on the details of the structural geology. For example, the.orientation of one clay-filled discontinuity can make the difference between stability and instability, or a compressible seam may cause settlement of the structure. This condition means that it is usually necessary to carry out a drilling program to investigate sub-surface conditions, and in some cases drive exploration adits to examine
in situ conditions. Figure 4.1 shows a diamond drill on a platform on a steep cliff investigating the foundations for a bridge abutment. However, drilling may not be required in circumstances where the applied loads are significantly less than the bearing capacity of the rock, where there is no possibility of a sliding type failure, or where there are extensive outcrops and the sub-surface conditions can be confidently established by interpretation.
