Kayvan Ghorbani - Department of Civil Engineering, Faculty of Engineering, Razi University, Kermanshah, Iran
Mohsen Zahedi - Department of Civil Engineering, Faculty of Engineering, Razi University, Kermanshah, Iran
Ahmad Asaadi - Department of Civil Engineering, Faculty of Engineering, Razi University, Kermanshah, Iran

The rock masses in a construction site of underground cavern are generally not continuous, due to the presence of discontinuities, such as bedding, joints, faults, and fractures. The performance of an underground cavern is principally ruled by the mechanical behaviors of the discontinuities in the vicinity of the cavern. During underground excavation, many surrounding rock failures have close relationship with joints. The stability study on tunnel in jointed rock mass is of importance to rock engineering, especially tunneling and underground space development. In this study, using the probability density distribution functions of negative exponential, log-normal and normal, we investigated the effect of joint trace length on the stability parameters such as stress and displacement of tunnel constructed in rock mass using UDEC (Universal Distinct Element Code). It was obtained that normal distribution function of joint trace length is more critical on the stability of tunnel, and exponential distribution function has less effect on the tunnel stability compared to the two other distribution functions.

joint trace length, statistical distribution functions, tunnel stability, UDEC