Experimental and analytical investigation of the shear resistance of a rock joint held by a fully-grouted bolt and subject to large deformations

Abstract Failures of rock bolts installed in jointed rock masses due to shear movement along weak joints in bedding rock slopes or underground caverns are common. Existing models to design rock bolts often only consider a rock bolt’s shear behavior in the elastic stage and ignore their larger non-elastic deformations, which significantly underestimates the bolt’s contribution to the joint shear resistance. Therefore, developing an analytical model capable of reflecting the plastic strain‑hardening of rockbolts subjected to large deformation is very necessary for more effective numerical simulation models as well as rock support design. An experimental investigation was conducted on grouted bolts subjected to joint shear movement. The bolt installation angle with respect to the joint was varied in the tests. Pairs of strain gauges attached to the surface of the bolt shank near the joint measured the bolt deformation during the shear testing. The deformation characteristics of the bolt and grout in the elastic and the plastic stages were evaluated. Based on the experimental measurements, a new analytical model to predict the bolt’s ultimate contribution to the shear resistance of a joint was developed. This model considers large deformations. The analytical model includes the influences of the bolt angle, rock mass strength, joint dilation angle, and bolt tensile strain. A comparison of the model predictions with results from large-scale tests and other existing methods shows good agreement with the tests and an improvement over existing methods.