Abstract
Exponential development of post-yield strain (epsilon(post)) is a pivotal indicator of failure in embankments constructed on soft saturated clays. This paper characterizes saturated clay stratum comprising very soft to very stiff stratigraphy, with plasticity index (PI) ranging from 19% to 31%, by performing widely used geotechnical engineering tests, i.e., the prebored pressuremeter (PMT) test, the triaxial (TXL) test, and constant-rate-of-strain (CRS) consolidation. PMT, TXL, and CRS tests were performed at a strain rate range of 0.18%/min to 0.21%/min to explore the yield stress (sigma'y), the pre-yield strain (epsilon(pre)), and the post-yield strain (epsilon(post)). Results indicate that epsilon(post)/epsilon(pre) for PMT, TXL, and CRS stressstrain curves range from 2.7 to 19 in the loading phase and 2 to 21 in the unloading phase. An exponential increase in epsilon(post)/epsilon(pre) is observed in the range of 10 to 21 for very soft to soft clay which is congruent with the realistic sustainable range of 4 to 30 for embankment failure on soft clays worldwide. The evaluated epsilon(post)/epsilon(pre) can be applied for sustainable prediction of post-failure evolution of strains in embankments on soft clays. Simplistic correlations are developed for approximation and prediction of epsilon(post) as a function of epsilon'y, epsilon(pre) and maximum applied pressure (P-max) for loading and unloading phases with reasonable accuracy. The intuitive zone of critical Epost is quantified for impending failure in embankments for maximum applied pressure (P-max), ranging from 36 kPa to 100 kPa for very soft to soft clay for use in sustainable embankment design and construction. Variation in predicted versus measured results of an individual site is observed to be within +/- 10% of line of equality.