Large strain shear modulus of sand as a function of confinement and relative density

Shear modulus of soils (G) is dependent on so many factors, such as, plasticity, mineralogy of soil particles and particle shape, relative density, overburden pressure, shear strain magnitude, number of cycles and some more. Meanwhile, for clean sands two significant factors prevail upon the others; relative density and confining pressure. Investigation on stiffness of soils against induced loads has always been a crucial issue for geotechnical engineers. On the other hand, this critical property of soil can be surveyed through in-situ and laboratory tests, which are costly and a long time is needed to obtain precise results. Due to these problems, engineers often prefer to use simple and straightforward empirical approaches to calculate the value of magnitude of G. In this thesis, nearly 200 Direct Simple Shear tests were conducted on two types of sands to understand and quantify the influences of relative density (RD) and vertical effective stress (?_v^') on shear modulus as a function of shear strain. Additionally, an equation was proposed to estimate G as a function of RD, ?_v^' and shear strain within the range of 0.1 to 10%. The outstanding advantage of proposed equation is that it uses directly measurable and calculable parameters (RD and ?_v^').