Analytical simulation of passive and pre-tensioned grouted rockbolts performances in bedding rock slopes

Rockbolts are one the best systems to stabilize plane failure of rock slopes. The passive bolts are loaded and activated when rock block slides while pre-tensioned types are initially loaded prior to any rock sliding. The pre-tensioned rock bolts make the rock layers pressed together and the friction between them is activated before slipping, and probably no displacement between the layers is occured. If a slippage occurs after the installation of a pre-tensioned rock-bolt, an excessive load is applied. In this paper, the bolt contribution generated by the pre-tensioned and passive rock-bolt in discontinuity is analytically simulated, and the effect of roughness angle, inclination of the bolt to the joint plane, pre-tensioned force, and strength of the rock are evaluated. For modeling, it is assumed the sliding imposes a bending moment to the rockbolt, which leads two plastic hinges to be created. The part of bolt between two hinges (located in either sides of the joint) is considered a beam with two cantilever supports, which is loaded by a uniform distribution generated by surrounding grout/ rock.The results show the pre-tensioned rock-bolts are effective when the resistance of the rock or grout around the bolt is high.