TBM Tunnel Friction Values for the Kerckhoff 2 Projectby Richard D. Stutsman, Pacific Gas & Electric Co, San, Francisco, CA, USA,
Abstract: In the mid-1970's Pacific Gas and Electric Company began design of the Kerckhoff 2 Hydroelectric Project, which supplements the Kerckhoff 1 project built in 1919. The Kerckhoff 2 project is located near the end of a chain of hydroelectric plants on the San Joaquin River in the foothills of the Sierra Nevada mountains foothills of California. In comparing the hydraulic characteristics of the TBM tunnel to the other tunnel systems, a Mannings 'n' friction factor of 0. 015 was assumed for expected friction value. This value was selected based on input from in-house engineers as well as several outside engineering companies. During construction of the power tunnel, two plaster casts were made of the actual excavated tunnel surface. In 1983 and 1984 startup testing was performed on the plant. From tunnel headlosses, turbine pressures and the manufacturers expected performance curves, calculations determined the actual friction factor. The results indicate that the average Mannings 'n' calculated from 1983 and 1984 startup test data is 0. 0154.
Subject Headings: Tunnels | Friction | Hydro power | Construction equipment | Power plants | Tunneling | Rivers and streams | North America | United States | Nevada | California
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