Reinforcement mechanics of passive bolts in conventional tunnelling

According to the conventional pullout tests for passive bolts, a spring–slider model is adopted in this paper to account for the interaction relationship between the bolt and the rock mass. Based on the incremental theory of plasticity and the plane strain axial symmetry assumption, an elasto-plastic ground and bolt responses analyses method is proposed. In addition, the validity of the proposed method is verified by numerical simulations. The reinforcement mechanics of passive bolts in conventional tunnelling is clearly demonstrated via an illustrative case study. Through parameter studies, the influence of the bolt properties on the reinforcement effect is highlighted. The proposed method provides a framework to the elasto-plastic ground response analyses with passive bolts reinforcement. It also permits incorporating other features about the bolt–rock interaction model or other failure criterion of the rock mass in further analyses.