Geotechnical Investigations at Butt Valley and Lake Almanor Dams

摘要

Two hydraulic fill dams in California, owned and operated by Pacific Gas and Electric Company (PG&E), were investigated as a part of PG&E's on-going seismic safety evaluation program. Recent geologic investigations identified faults showing late Quaternary activity in the region close to the dams. Several of these faults are believed capable of producing earthquakes with magnitudes of 6.5 to 6.8. To address the concerns regarding potential liquefaction of the hydrualic fills and resulting stability of the dams under such severe shaking, and to supplement previously obtained geotechnical information on the dams, extensive geotechnical investigations were performed. The results of these investigations and comparisons with results from other hydraulic fill dams are described herein.