Stress-Dependent Shear Strength of Resedimented Nile Silty Clay

Abstract

The variation of clay undrained shear strength with consolidation stresses is of paramount importance to geotechnical engineers. For several decades, the normalized shear strength of clays has been the cornerstone of geotechnical design in many applications, such as staged construction of embankments. Recently, different trends of shear strength dependency on consolidation stresses have emerged indicating nonlinear variation. Resedimentation has been a useful and reliable method to investigate stress dependency by generating lab test specimens of fine-grained soils with a minimum sample to sample variation for benchmark studies. Previous work on resedimented Nile silty clay (RNSC) has shown unique features, such as high sand fraction and contradicting index properties used for soil classification. The shear strength of Nile silty clay (NSC) and the effects of the consolidation stresses are explored through a laboratory program on resedimented samples from material excavated within the Nile River flood plains. A portion of the material was processed using mechanical energy, which exhibited a significant increase in the liquid limit and a larger clay-sized fraction of particles from grain-size distribution tests. The measured engineering parameters are compared with comparable studied soils and established empirical correlations to provide insights on mechanical behaviors of the NSC. NSC is found to have a rapid decrease in the undrained shear strength ratio and a rapid increase in the lateral stress ratio with increasing consolidation stress.