Geological contributions to engineering investigation of rock mass

Abstract

Rock masses comprise densely packed blocks bounded by joints and other discontinuous geological structures. The strength of a rock mass is controlled by the geometry of the blocks and by the frictional properties of the block surfaces. Empirical engineering methods combine structural geology features into design parameters. There are numerous aspects where geological information and methodology can contribute to advancing engineering investigations of rock mass. Three of these aspects are 1) explicit analysis of the anisotropy of fracture systems, 2) structural analysis of anastomose fracture patterns and 3) application of hydrothermal alteration studies to engineering assessment of joint coatings. Investigations of rock mass anisotropy can be enhanced by recording the orientation of fractures relative to a system of reference axes. Anastomose patterns of fractures can be detected in borehole data by recording the relationship between spacing and dihedral angle of adjacent fractures. The systematic definition of mineral assemblages in hydrothermal alteration studies forms a useful framework for characterising the mechanical properties of joint surfaces.