Investigate the effect of rock mass joint intensity on performance of support systems in the tunnel by using DFN-DEM numerical modeling (Case study: the access tunnel of Rudbar Lorestan Dam plant)

In this paper, DFN-DEM simulation using PFC3D software to evaluate the effect of joint intensity variation on tunnel support systems performance has been performed. Three dimensional distinct element software of PFC3D is considered for numerical modeling in this paper. This software has many advantages such as ability to create three-dimensional distinct joints with limited size and with different statistical characteristics, flexibility in different conditions and ability to monitoring a momentaril caving and falling during tunnel stability analysis. In this paper, at the first stage, by using of discrete fracture network (DFN) modeling and based on the surveyed data from access tunnel to the gallery of Rudbar Lorestan dam, fractures in this region have been simulated in the software and then is linked to the intact rock model. Finally, the performance of tunnel support systems of shotcrete and steel frame relative to change of the rock mass fracture intensity is investigated. The obtained results indicate more resistance of steel frame against fracture intensity variation compare with the shotcrete support system. Serious damage to shotcrete support system occurs by doubling the number of joints, while about the steel frame, serious damage occurs with four times the number of joints. Therefore, by increasing joint intensity which is caused by various factors such as explosions, earthquakes and etc, the steel frame support system has higher reliability.