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The rock-dilation constant of DuBose Mountain in British Columbia was determined in 1951 byin situ rock tests utilizing a strain-gage-instrumented 10-ft-diam pressurized sphere. This work was the subject of a paper by the author in 1956.5
The purpose of the work was to determine the optimum wall thickness of the two 2500-ft head steel penstocks (each 4450 ft in length) to be built within the mountain. The 11-ft-diam penstocks were planned to power eight BLH Pelton impulse turbines, each rated at 112 megawatts.
The power plant is now in operation, generating 896 megawatts of power. Since the time of the 1951 study, the penstock hydrostatic operating stresses have been measured by ALCAN engineers employing conventional resistance and vibrating-wire-type strain gages. The operating stresses correlated closely with those predicted from the sphere tests.
The operating personnel and families live in a model village at the end of a deep gorge. Communications with the outside world are solely by airplane or boat. The author revisited the site in 1972 to inspect the plant and the 1951 test instrumentation.
The author also revisited the site in March of 1973 measuring the continuity bridge-leg resistance and ground resistance of all of the installed sphere-dilation instrumentation.
Ninety percent of the Carlson strain meters and 19 percent of the strain gages and resistance thermometers were found to exhibit their original bridge and bridge-leg continuity resistances.
KeywordsFluid Dynamics Strain Gage Pressurize Sphere Operating Stress Operating Personnel
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