抄録
Bedrock erosion rate E due to collision of saltating bedload is expressed by E=βqb (1-Pc), where qb is the bedload transport rate, Pc is the areal fraction of bedrock covered with gravel and β is the abrasion coefficient. It is known that bedrock becomes weathered to have many cracks and voids after repeated wet-dry cycles. However, the possible impacts that weathering of bedrock has on the erosion rate have not been elucidated. In this study, laboratory experiments are conducted for understanding how weathering of bedrock would affect the rock tensile strength and the erosion rate. For this purpose, boring cores taken from natural bedrock rivers are exposed to artificial wet-dry cycles. The experimental results suggest the following: (1) the abrasion coefficient is estimated by β=1.4×10-4σ T-2 (d/ksb)0.5, where d is the size of colliding gravel and ksb is the bedrock hydraulic roughness height; (2) the tensile strength of the bedrock decreased exponentially due to repeated wet-dry cycles, σ T/σ T0 = exp (-CdwNWa0/σ T0), where σ T0 is the initial rock tensile strength, Wa0 is the initial water absorption rate, N is wet-dry cycles and Cdw is a constant.
