Study on the shear Resistance Behaviour of Bolted Rock Joints

The Grouted rock bolts have a wide application in the geomechanical engineering. Besides the advantages such as simplicity of construction, low cost, durability and reliability of anchorage, this type of adhesive rock bolts effectively enhances the tension and shear resistance on weak plane in rock masses with developed joints, and hence improves the strength of jointed rock masses.On the basis of laboratory simulation tests, theoretical research has conducted, the emphasis of which has been laid upon the influence cf bolts on the shear resistance behaviour of bolted joints,the mechanism of the bolts' "dowel"effect to prevent the joints from dislocating, and an improved formula derived for evaluating the shear strength of bolted rock joints.The tests have shown that the shear strength of bolted rock joints is closely related to shear displacements. Both experimental and theoretical analyses have indicated that the "dowel" effect of the bolts is fully developed even in the presence of very small shear displacements. The influence of the bolt inclination on the shear resistance behaviour of the joints is evidently reflected in the testing results. In this paper, analysis models and theoretical analysis methods for description of bolted rock joints are presented, and thereby a formula for calculating the optimum bolt inclination is derived, the value of which obtained with this formula is entirely conformable to the test results. Therefore it seems that this formula will play a positive role in guiding the design of the layout for bolts. Also, shortcomings in the models of bolt elements commonly used in the current FEM analysis are discussed and the opinion for the further improvement is suggested.