ABSTRACT
Layered rocks above underground openings are often modeled using elementary beam equations. Composite beam equations provide a more realistic method of predicting deflections and stresses in layered rock systems.
Results using published equations show the variation of interlaminar shear stress and deflection as a function of position along the beam and as a function of the stiffness of shear connectors (rockbolts). Such results are useful in understanding rockbolt reinforcement mechanisms, and show that considerable shear reinforcement is obtained even with moderately soft shear connectors.
The maximum interlaminar shear in a composite beam with clamped ends is not located at the ends, as predicted by elementary beam theory, but away from the ends toward the inflection point of the beam. This finding may help explain why roof-rock shear failures in many coal mines are commonly observed to be located away from the ribline.
