The Elusive Load Transference of Stratified Rock Roof

A roof of an underground opening composed of horizontally bedded competent rock is commonly encountered in mining and civil engineering. The mechanical behavior of such roof resembles a stack of elastic beams rigidly or compliantly confined at the abutments and sagging under their own weight. The clamping action of a bolting system will forestall slip between strata. When the strata vary in thickness, it has been largely assumed that considering friction and suspension effects, the average force per unit area exerted by the bolt system should include an elusively defined transferred load Δq. The purpose of this research is to analytically and numerically calculate this transferred load, taking into consideration all related parameters. A stress function solution of a gravity beam is proposed to account for the load transference, i.e. the vertical stress component sgr;_yy. A two-member stratified roof with strata of varying thickness is then modeled with a finite differences code and the results are used to verify the assumptions. Limits of applicability of load transference are prescribed for the specific cases that are analyzed.