The behavior of clayey soils subjected to initial static shear stress under the monotonic and cyclic loads

Clays have been considered to be stable than sandy soils during cyclic loads. This idea is true for clayey soil layers without structures and without sloping ground surface. However, it doesn?t show that clays are always safe and stable under cyclic loadings. Cyclic failures have been observed on the clays below structures or soil elements in slopes due to seismic effects. In the conditions, soil elements subjected to initial shear stresses before cyclic loadings.In order to simulate these situations, it has been required to perform on anisotropically consolidated triaxial test specimens. Laboratory experiments which have been carried out to understand behavior of clayey soils under cyclic loadings, generally are performed on the isotropically consolidated specimens. However, isotropic stress conditions don?t reflect exactly stress situation under structures. In order to use finding that obtained from isotropically consolidated specimens, it has been required to a correction factor. The correction factor must be used to take into account initial static shear stresses.For this aim, monotonic and cyclic triaxial test performed on the reconstituted clay specimens at different static shear stresses ratios. The results obtained from tests showed that initial shear stress caused reduction on both monotonic strength and cyclic strength of clayey soil. Furthermore, cyclic loading induced pore water pressure decreased as initial static shear stress increased.Ka correction factor has been defined to account for initial static shear stress effect on the dynamic strength. Ka correction factor has been generated in the light of the fatigue analysis. Lower and upper limits for Ka correction factor have been defined by using proposed models. Additionally, the relationship between correction factor obtained from experimental results and these limits are investigated. This correction factor is of great importance, because of determination the dynamic strength of clayey soils.