Mechanical model for a jointed rock mass

When a rock mass weakened by a system of parallel horizontal joints is loaded at the surface, some settlement, comprised of the displacement due to deformation of the weathered material and the result of drawing together of joint edges, may take place. For such a system, the simplest model consists of a composite specimen subjected to one-dimensional compression. The advantage of such a procedure lies in the transformation of the three-dimensional stress state, reflecting actual stress conditions in the reek, into a simple one-dimensional system. The physicaI phenomena which take place in the specimens may be mathematically represented, very conveniently, in the onedimensional case. Subsequently, resulu obtained by such a treatment could be extended to a three-dimensiona l system with the help of well known methods. Figure 1 presents the stress-strain relationships obtained by M. Pancini [1] on composite gypsum-coal specimens subjected to one-dimensional compression. The number of joints simulated during the tests was less than the number of blocks by one. It is obvious that the total deformation Ah may be determined from the equation