Assessment of cyclic stability of cohesive deposits using cone penetration

Unlike cohesionless soils, cohesive deposits are not susceptible to near-complete loss of shear strength under cyclic loading. Nevertheless, cohesive deposits are known to soften during earthquake-related cyclic loading that results in severe ground deformation and structural distress. Available frameworks for assessing cyclic stability of cohesive soils do not account for the intensity of cyclic shear stress, These procedures are based on very approximate indicators of cyclic soil strength. As a result, their performance is not always satisfactory. A framework has been proposed in this paper for assessing cyclic stability of cohesive soils utilizing a worldwide database of laboratory tests, earthquake-related ground failure case-histories and cone penetration tests in cohesive, fine-grained silts and clays. The proposed framework indicates that a Critical Stress Ratio (CSR) of less than 0.125 is unlikely to trigger large deformations in cohesive deposits even during great earthquakes. Nor are deposits characterized with a normalized total cone tip resistance of more than 70 susceptible to deform appreciably during such seismic events.