Abstract
Considering the ground-bolts interaction in the rational design of tunnel support using the New Austrian Tunnelling Method (NATM), the mechanical behavior of the grouted rock bolts and supporting effect on tunnel stability was analyzed. A new elasto-plastic analysis solution was obtained, in which the shear stress due to the cohesive action between the rock bolts and ground owing is modeled to the effect of the rock bolts, the strain softening and dilatancy behavior of the rock after it yielded was taken into consideration. By a detailed parametric study with the newly proposed analytical theory, a method for the optimum bolt length and support pattern was found which effectively controls the tunnel convergence and the size of the plastic zone arround the tunnel.
