The Calculation of Strata Movement

Abstract

The mathematical effort required to calculate movement in strata affected by underlying workings can be kept at a justifiable level only if certain simplifying assumptions are made concerning the structure, the deformation behaviour, and the extent of the rock mass (Fig. 57). Thus in many procedures the rock mass is regarded as a continuum, the separate constituents of which, such as granular particles, rock beds, or theoretically assumed geometric forms, are held together by cohesive forces in such a way that the rock mass deforms as a single whole and has, like some homogeneous material, identical properties throughout. The deformation behaviour of this rock mass can be regarded as either elastic or plastic. It can be isotropic — i.e., homogeneous, or uniform — in all directions or, like a shaly rock, it can be subject to differing degrees of deformation at right angles and parallel to the stratification — in other words, anisotropic. For example, a stratified rock mass corresponds to a continuum with vertical inhomogeneity and horizontal isotropy, if fault and slip planes are ignored.