Experimental and numerical investigations of stresses in a fully grouted rock bolts

Rock bolts are widely used for rock reinforcement in hard-rock mining and civil engineering since a long time. However the use of fully grouted rock bolts and cable bolts is limited in coal mines. In order to improve performance of the rock bolts as a supplementary roof support system for any type of roof condition in coal measured formations, it is necessary to have a good understanding of the behavior of the bolt-grout and grout-rock interactions as well as the mechanism of load transfer in rock bolts. As the performance of grouted bolts depends on bond strength, extensive laboratory pullout as well as pushout tests were conducted in the present investigations with the variations in the bolt diameters, length and cement-water mixing ratios of grout. The load-displacement curves were developed and were verified with the numerical results obtained from finite element analysis using ALGOR software. Numerical models were validated for pushout tests and a det ailed analysis was carried out to know the displacement, stress, strain distribution along the bolt. © Springer 2005.