THE PENSTOCK PUZZLE

摘要

A project that pieced together years of geotechnical studies and several designs has finally resulted in a construction effort to stabilize the Camino penstock after 40 years of chronic slope movement. From the south fork of the American River in California, the Camino penstock looms as a huge pipe on a steep mountainside. On closer inspection one of the foundations appears to have slid downhill approximately 7 in. (180 mm) so that the steel penstock pipe support is no longer centered on its concrete foundation. The misalignment could be a construction defect, but closer inspection reveals another abnormal condition. Two anchor bolts in the concrete at the upper end of the footing have been sheared off by the penstock support as the concrete foundation moved downhill. This provides convincing evidence that part of the mountain is moving downhill from beneath the penstock. Although many symptoms of distress to the penstock are apparent, years of detailed study were necessary to unravel the complex movement puzzle.