Load distribution and redistribution in discontinua

Abstract

Deformation in a blocky (jointed) material is, in many cases, dependent on the mechanisms of slip and rotation. Once slip occurs it is shown using photoelastic blocky models, that the load redistributes in what appears to be a regular and repetitive pattern. The contact area between particles, be they rotund or blocky, appears to determine whether moment transfer has a marked effect on the load transmitting characteristics between the particles. This is the basic difference between the load transmitting characteristics of a rotund granular material (sand) and a blocky material (rock). Moment transfer between blocks readily induces stress gradients within the intact material making up the blocks with a consequent development of tensile stresses. This readily creates an environment where the appropriate blocks may rupture. Whether this rupture, which causes a redistribution of interblock loads, will continue appears to be a function of the energetics related to the joint sets and failure characteristics of the intact material. Besides particle fracture there is the problem of overall stability of the deforming discontinuous body. That is, a stage is reached where, after a number of slips and particle failures, the blocky mass as a whole will collapse. This aspect is considered in terms of a discontinuous structure such as a voussoir arch.