Vahid Hosseini Toudeshki - Department of Civil Engineering, Zanjan Branch, Islamic Azad University, Zanjan, Iran
Mohammad Hossein noori Gheidari - Department of Civil Engineering, Zanjan Branch, Islamic Azad University, Zanjan, Iran
Hadi Kalantari Azad - Master of Geotechnics, Zanjan Branch, Islamic Azad University, Zanjan, Iran

This paper presents numerical analysis the effect of seismic loading on the axial force of rock bolts in tunnels by means of elasto-plastic finite element method. The circular tunnels are modeled in the shale rocks and they are supported by end anchored rock bolts. The seismic loading is done for different earthquakes and horizontal and vertical acceleration coefficients are calculated for different depths. The axial force of rock bolts are measured for each of the acceleration coefficients of earthquakes. The results of the evaluations show that the axial force of rock bolts is greater when the direction of the vertical seismic coefficient (Kv) is in the same direction as the gravitational force. Furthermore, with increasing earthquake magnitude, the changes of rock bolt axial force have greatly increased and in the small tunnels, the horizontal seismic coefficient (Kh) plays a decisive role to increase the changes of rock bolt axial forces.

Quasi-static analysis; Circular tunnels; Axial Force; Rock bolt