Reinforcement effect of yielding bolts

According to the mechanical behaviors and deformation characteristics of yielding bolts, a coupling model is proposed to account for the interaction between the bolt and the rock mass. An analytical solution for the coupling model applied in a circular tunnel is achieved. The reinforcement mechanism of the yielding bolts is demonstrated through an illustrative case study and verified by numerical simulations. Based on the proposed model, the influences of different parameters, including stress condition of rock mass, strength of rock mass, density of bolts, length and installing time of bolts the, on reinforcement effect are estimated quantitatively. The parameter studies show that the performance of the yielding bolts is better in the case of large rock deformation. The yielding bolts can reduce the deformation of plastic zone significantly, while the control effect in the elastic zone is not very obvious. The influences of reinforcing time are studied by changing the artificial inner stress when the bolts are installed. The results may provide a necessary theoretical basis for the design and parameter optimization of yielding bolts.