Stability Assessment and Support Design for Water Deviation Binary Tunnels of Bakhtiyari Dam-Iran

Analysis of the stability of deviations binary tunnels at Bakhtiyari dam situated in the southwest of Iran is presented. The diameter of each tunnel is 13.7 m and they are around 1000 m long. The tunnels are excavated in steps of consecutive cuts. The tunnels pass through seven different geological zones with various specifications. To study the characteristics of these zones nine boreholes of total length of 904 m were drilled and around 140 various laboratory tests were conducted on the core samples. Testing and analysis of the cores from the boreholes have resulted in series of data required for the investigation. These data present physical and mechanical properties of the seven various rock zones, including RQD, joint sets and joint properties. Based on these data the values of RMR and Q and therefore the class of the rocks of all seven zones were determined. Stability analysis has been conducted and appropriate supports were suggested for both tunnels by RMR and Q methods. Based on the ratings ascribed to each zone by the two methods a relationship has been driven between RMR and Q for this particular project.