Undrained Strength Characteristics of Cohesionless Soils

In most practical cases where saturated cohesionless soils are involved in stability problems, the rate of application of disturbing forces is so slow that any changes in pore water pressure induced by the loads are dissipated as the loading progresses. In cases where rapid loading occurs, even cohesionless soils may not have time to drain during the loading process and the undrained strength must be determined. Under general earthquake conditions, cohesionless soils may be undrained during loading but the stress or strain applications will be cyclic in nature. Cyclic loading effects are quite different from those in which the stress or strain is increased progressively until failure occurs. Conventional strength determinations are only made for this latter condition, and one-directional load applications of this type are the only condition considered.