Construction scheme of tunneling through F_6 fault during construction of Jinping Hydropower Station II

The diversion tunnel group of Jinping Hydropower Station II has the characteristics of large embedded depth,long length,large diameter,high ground stress,etc.,and along which,the thickness of the overburden upon it is normally 1 500~2 000 m with the maximum of about 2 525 m;which is the only hydraulic water diversion tunnel in the world at present with largest length,largest embedded depth and largest hydraulic head.The tunnel is excavated through a zone with developed faults,among which the F6 fault is the largest one.Therefore,the tunneling though the fault becomes one of the most intractable problems.The successful treatment of this problem during the construction is briefly described herein.