ABSTRACT
A laboratory investigation is presented of bolt reinforcement in bedded mine roofs. Included is the sequential progression from multiple initially continuous beams to ultimate collapse of the arch(es) formed after the beams fracture. Bolts allow the formation of a single high-rise arch as compared to the multiple shallow arches that develop in the unbolted models. The ultimate failure mode of the bolted sets is of the shear type, with dominant shear zones developing near the ribs. The collapse of the unbolted set progresses upwards by the sequential downward rotation of blocks exposed in the shallow arches formed within individual layers. The unbolted sets are brittle, the bolted models ductile. Collapse of each individual arch within the unbolted set, as well as initial beam fracture, coincides with a load and strength drop. In the bolted models considerable load transfer takes place, resulting in a prolonged maintaining of a high strength.
