抄録
In recent years, strong random earthquake motions have become a matter of great interest among earthquake engineers concerned with the design earthquake of important civil engineering structures such as fill dams. The influence of a strong random earthquake on fill dams is characterized by large accelerations (body forces) in both vertical and horizontal directions.The following four kinds of experiments are conducted in order to investigate the dynamic strength and deformation characteristics of rockfill material : (1) static shear tests; (2) static shear tests with vertical vibration; (3) dynamic shear tests and (4) dynamic shear tests with vertical vibration.The following results are obtained;(1) The body force affects significantly the dynamic deformation behaviours, but only slightly the static deformation and strength.(2) If the ultimate dynamic strength is defined as the maximum shear stress by which the specimen fails in the same way by the static shear stress, the ultimate dynamic strength of a dense rockfill material becomes larger than the static strength in a range of lower sustained stress.(3) The rockfill material becomes unstable with a disturbed grain structure and a large deformation when it is subjected to the dynamic loads exceeding the yield stress ratio, (τs/σn)y.Thus, the yield stress ratio becomes an important criterion for the dynamic stability of earth-structures, and the yield stress ratio can be obtained from the static shear test.
