ABSTRACT
Despite variety of lockless rock bolt’s designs, they are characterized (except screw-threaded bolts) by a number of the general principles of force interaction with blast-hole walls:
– bolt fastening is basically carried out by means of friction and cohesion (adhesion) forces. So, the main role of tubular rock bolt’s fastening belongs to friction forces; ferro-concrete, polymeric and ferropolymeric bolts have cohesion forces; and a tubular bolt with a fastening layer has friction and cohesion forces, when extending mixture is applied;
– bearing element (a rod, a cylinder, etc.) of a rock bolt perceives the basic tensile load, directly or through the fastening layer, contacting with blast-hole walls. On these contacts the tangential stresses are operated due to friction and cohesion forces, or their combination;
– lockless rock bolt’s interaction with a rock is characterized not only by a direct, but also by a reverse connection of normal tensile stresses in the bearing element with tangential stresses, operating along contact surface of the bearing element with blast-hole walls or the fastening layer, and also fastening layer with blast-hole walls. It is explained that during the deformation process of mine working’s bolted mass the bearing element of a bolt is loaded by axial tensile stresses through the rock contact. It leads to changing of the existing stress field of the “boltrock” system.
