Structures founded on dense, compacted sands are currently designed based on the shear stress - shear strain (γcs) - volumetric strain (εv) response of clean sands primarily obtained from unidirectional element tests. This may lead to underestimation of εv under multidirectional seismic loads and incorrect settlement estimation for sands with fines. This paper presents results from first of a kind strain-controlled unidirectional (sinusoidal) and bidirectional (circular, figure-8) cyclic simple shear tests. Clean Ottawa sand and a non-plastic Mississippi River silty sand were tested at modified Proctor relative compactions (RC) of 92 to 99%. At the same RC, presence of non-plastic fines decreased εv. Volumetric strain under bidirectional loading normalized by εv under equivalent unidirectional loading (comparable γcs, RC, overburden pressure) was found to be a function of the number of loading cycles, load path and γcs. A figure-8 loading path yielded higher settlement than an equivalent circular loading path.
ASJC Scopus subject areas
- Civil and Structural Engineering
- Building and Construction
- Geotechnical Engineering and Engineering Geology