Drilling is one of the most expensive stages of open pit mining and has more complexity. In drilling process many parameters influence simultaneously, where studying each parameter requires recognition of the effects of the characteristics of the rock mass and its material.
In this paper, the main aim was directed to investigate the joints dipping among the structural parameters of the rock mass. In the course of study, geometrical condition of penetration and transition of drill bit from joint surface were analyzed and different conditions of dips considered mathematically. This was followed by physical modeling of each of the geometrical conditions and penetration rate of cross bit measured by using rotary drilling system. Based on the numerical results obtained from experiments, mathematical equation between angles of joint dip with respect to drilling prolongation and penetration rates was presented. Furthermore, in conformity with the presented equation, by decreasing relative angle of joints dip, penetration rate of drill bit in jointed rock masses decreases linearly.