Unique onsite assembly of a 12.43 m Main Beam TBM and back-up system was completed on September 18, 2008 in the remote mountains of the Sichuan province of China. The equipment was assembled onsite, without previously having been assembled and tested in a factory, utilizing a method called Onsite First Time Assembly (OFTA). The Jinping-ll hydroelectric project features four parallel headrace tunnels approximately 18 km long, two of which will be excavated by TBMs and two by drill and blast. A nearby fifth tunnel is being excavated by a 7.2 m TBM to draw down ground water in advance of excavating the headrace tunnels. This paper addresses the following topics: 1. Project description including geology and terrain; 2. The decision process leading to onsite first time assembly, the assembly process and logistics, and lessons learned; 3. Design features of the TBM and back-up system; and 4. Operational history from startup to the writing of the paper.
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