Improved Undrained Strength Interpolation Scheme for Rapid Drawdown

Abstract

Linear interpolation between isotropically consolidated undrained strength envelopes and fully drained (effective stress) strength envelopes is commonly used to calculate undrained strengths for slope stability analyses of rapid drawdown. However, the current linear interpolation method presents numerical problems at low effective normal stresses with soils that possess an effective stress cohesion intercept. The resulting undrained shear strength envelopes are unrealistic at low normal stresses. An improved interpolation method has been developed that interpolates a single undrained strength envelope for the entire slip surface. The improved interpolation method produces identical results to the current method for cases where c′ equals zero.