Cyclic simple shear behaviour of saturated and moist sandy soils

Liquefaction and settlement of sandy soils cause significant damage during earthquakes. In this research, cohesionless soils of Kutch region with history of large earthquakes are explored. Twenty-six soil samples were collected from different locations of Kutch region and tested under saturated and moist conditions by performing two series of Electromechanical Dynamic Cyclic Simple Shear (EMDCSS) tests. In series I, the liquefaction characteristics of saturated samples were observed to be dependent on fines content and plasticity index. Kutch soils with non-plastic fines exhibited low liquefaction resistance and showed increased resistance at higher FC; however, for sands with plastic fines, PI rather than FC controlled the cyclic degradation. Saturated sandy soils with non-plastic fines exhibited lower shear stress mobilisation, higher pore pressure and larger degradation as compared to sands with clay content. In series II, the settlement characteristics of moist samples at constant normal stress revealed decreased axial deformation and increased mobilised shear stress with increased FC and PI.  Silty-sands exhibited higher deformations and larger strength as compared to clayey-sands. The EMDCSS tests at saturated and moist conditions revealed Kutch soils to be prone to liquefaction and large settlements, respectively.