DEFORMATIONAL RESPONSE IN DISCONTINUA

Deformation in a discontinuum, be it rotund or blocky, is related not only to material deformation but also mechanisms such as slip and rotation. Because of this, deformation is inextricably related to the frictional characteristics of the surfaces of slip. In turn, this slip has a profound influence on the load transmitting characteristics of the slip surfaces. These load transmitting characteristics effect the stress distribution within the intact material and therefore control the subsequent deformational response and modes of failure. In the first part of this paper, the minimum energy concepts, as applied to a granular material, are shown to be applicable to a blocky material representing a rock. From this it is shown, as for granular material, that there is a relationship between the principal stresses given in terms of the joint friction angle. The magnitude of this angle is however not only dependent on the smooth joint friction angle and roughness but also on the rotation of the blocks brought about by slip. This rotational effect on load transmission in a granular material (sand) is minor while in a blocky material (rock) the effect on load transmission is most important. It is shown that in a jointed material it is not possible to define conclusively the mass deformational response when inhomogeneous stresses are induced by joint slip and or block rotation. Therefore the use of any continuum analysis using conventionally determined design parameters is suspect. © 1979.