ROCK CLASSIFICATION AND TUNNEL SUPPORT SYSTEM FOR EXCAVATION OF HEADRACE TUNNEL IN KARORA HYDROPOWER (11.8MW) PROJECT, BESHAM, PAKISTAN

Abstract

Karora Hydropower (11.8MW) project site is located in Kuz Kana / Karora area on the Khan Khwar River about 25 km from Besham and 30 km from Alpuri Town – which is the district headquarter of Shangla District – Swat. The Project is accessible through Besham – Mingora road. The 2960m long Headrace tunnel is designed as a Horse shoe shape of diameter 2.6m concrete lined. The tunnel is constructed by Ghulam Rasool and Company (GRC) under the supervision of Pakistan Engineering Services (PES) as a consultant. Conventional methods like drilling and blasting were used for the excavation of headrace tunnel. This study is focused upon evaluating rock mass classifications such as RMR, RQD and Q system. This tunnel is situated in the geological settings of Karora Group which comprises of meta-sediments.The field surveys were conducted to analyze the lithology, shows the lithology is complex, contain highly sheared zones, wedges and quartz veins that were encountered during the excavation of Tunnel. During the study RMR and Q system results show the rock categorization along the tunnel route from “Good to Very Poor” Quality. The support system designed for headrace tunnel consists of Rock bolts, Shotcrete, Lattice girders and Wire meshes.