ABSTRACT
The effective utilisation of geological data by an engineer depends upon that engineer's ability to comprehend the data, to digest them and to incorporate them into his design. The communication between geologists and engineers is particular ly important when the stability of the rock mass surrounding an underground excavation is likely to be controlled by through-going structural features such as faults or well developed joints. In such cases, the three-dimensional geometrical relationship between structural features and the roof and walls of the excavation is very important since this relationship will control the freedom of blocks to fall or s1ide.
