ABSTRACT
Twin 8.5 m diameter, 10 km long parallel headrace tunnels under overburdens of up to 1870 m were excavated for the Neelum Jhelum Hydroelectric Project located in the Azad Kashmir region of northeast Pakistan using two open gripper Tunnel Boring Machines (TBMs). Both TBMs started headrace tunnel excavation in early 2013 with completion in May 2017.
This paper briefly outlines the shotcrete application procedure in different zones on the TBM, and the issues encountered during construction that led to the need for remedial works to the shotcrete lining. The paper then details the sequence for implementing the remedial works, which was complicated by limited access, and describes the various methods employed to carry out the finishing works, such as grouting operations and repair of construction joints. Details of quantities used for the Neelum Jhelum project are provided for use as a guideline for similar projects in the future.
