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原文传递 PREDICTING SCOUR IN WEAK ROCK OF THE OREGON COAST RANGE

题名：	PREDICTING SCOUR IN WEAK ROCK OF THE OREGON COAST RANGE
作者：	Stephen E. Dickenson and Michael W. Baillie
关键词：	scour, rock, abrasion, slake durability, stream power
摘要：	Recent experience in the Coast Range Province of Oregon demonstrates that weak sedimentary bedrock in stream channels can be vulnerable-to scour. The presence of erodible rock adjacent to bridge foundations and abutments necessitates monitoring of the channel to preclude costly repairs, or in an extreme case undermining of the foundations and bridge collapse. Current design methods are not well suited for evaluating the potential for scour in weak rock, nor can the rate of scour be estimated. A design method for the latter would be useful for identifying the depth that the foundation should be socketed into the potentially scourable rock given the design life for the bridge. In an effort to relate the rate of scour in weak sedimentary rocks to the geological and geotechnical characteristics of the rock, as well as the hydraulic characteristics of the streams, a pilot study of eleven bridge sites was conducted. Geomechanical index tests were performed on bedrock specimens and the hydraulic properties of the stream channels were evaluated. A preliminary model has been proposed wherein the rate of degradation of die stream channel is related to the abrasive resistance of the bedrock and the hydraulic power of the stream. The proposed method can be used to obtain an approximate estimate of the degradation of unobstructed channels in weak sedimentary rock due to abrasion by bedload and flood events. The effects of local, or contraction, scour were not evaluated.
报告类型：	科技报告