Bakhtiary dam and hydropower plant is the largest ongoing dam project in Iran. This project with height of 325 m would be the highest double-curve concrete dam in the word. This dam with the capacity 1500MW is constructing on Bakhtiary River, a branch of Dez River, with average flow rate of 144.6 m 3 /sec. Bakhtiary dam is located in North West part of Zagross folded zone that consist of limestone of sarvac formation, from geological view point this formation is divided to 7 different zone, that powerhouse and transformator caverns are located in Sv4 and Sv5 zone. The dimensions of these two caverns are 46 m height, 23 m width, 160 m length and 13 m height, 13 m width and 182 m length respectively. In this thesis, at first detailed joint study performed and main joint sets are characterized. Then according to these joint sets and stress conditions of the region, optimum direction for excavations is selected. In the next step, excavation of powerhouse and transformator caverns are modeled using Discrete Element Method, 3DEC, in 11 and 3 step, respectively. Using analytical relations and numerical method and changing of distance between two caverns from 25 m to 100 m, for boath Sv4 and Sv5 zones, optimum distance are determined 35 m and 25 m respectively. Finlay according to result of numerical modeling, suitable support system suggested. The suggested system include of tandons and monobars with 2×2 m network. According to plastic zone formed around two caverns, length of tandons and monobars at different part of each one determined. In Sv4 zone, for main cavern length of tandons selected, 10 m for roof, 20 m for right side wall and 15 m for left side wall and for transformator cavern roof tandons with length of 6 m and for its side walls monobars with length of 6 m have been chosen. In Sv5 zone for main cavern length of tandon selected, 10 m for roof, 15 m for right side wall and 12 m for left side wall and for transformator cavern roof and side walls are supported using monobars with length of 6 m.