Cyclic Simple Shear Size Effects

Abstract

Cyclic simple shear testing is considered to be one of the most appropriate ways of reproducing in the laboratory the stresses that would be experienced by an element of soil in level ground subjected to earthquake loading. The main drawback in cyclic simple shear testing concerns the lack of complementary shear stresses on the specimen vertical boundary. Therefore, a selection of the proper specimen size, i.e., proper diameter versus height ratio, must be carefully considered. To investigate the specimen size effect on the primary dynamic (cyclic) soil properties, namely the shear modulus and damping, a large‐scale simple shear apparatus was constructed. In it, specimens having diameters from 3–12 in. and heights from 0.25–4.0 in. could be tested. Thus a wide range of diameter to height ratios could be obtained. The paper presents a comprehensive study of the effect of the specimen size on the cyclic properties of dry sand tested in such an apparatus at different strain levels, vertical pressures, void ratios, and number of stress cycles. From this study, the size of specimens that would provide cyclic properties that are independent of size were determined.