Optimum horizontal distance between large scale caverns in alternation of weak and hard rocks

Due to the sensitivity and special use of these spaces, stability analysis and ensuring the safety of carven is very important.Nowadays, using the surface storage tanks is very costly; Therefore, the use of underground cavernsin large volumeseven in weak rock mass, is more economical than surface reservoirs. Totally, we can classify the main applicable caverns in five groups, including the hydropower plants and pumped storage, liquid storage, storage of nuclear waste disposal, waste water and sewage systems and alsomiscellaneous applications. The aim of studying Pumped Powerhouse - open-damstorage project isexploring the possibility of establishing Pumped - storage powerhouse systems inopen range of reservoir dam and assessing the potential of hydroelectric energy generation in this system. Open Reservoir Dam, is under construction inKurdistan and on Kumasi river (Cham Goure) of the major branches of Sirvanriver and near the Bani village.Pumped-storage power plant include the reservoir zone of power plant,lateral constructions and water tunnel on plant, which is following we will addressed the stability analysis and calculating the optimal distance of powerhouse cavernand transformer by using numerical and experimental analysis.The optimal distance of about 40 meters is estimated.