Triaxial Tests on Compacted Clays for Consolidated-Undrained Conditions

Abstract

Consolidated-undrained tests must be performed on compacted soils to provide undrained soil properties for embankment design scenarios, such as rapid drawdown. These soils are subject to anisotropic consolidation under field conditions. Laboratory testing of compacted clays must consider the effects of the consolidation stress system as well as the subtleties involved in testing initially unsaturated clay specimens. This study considers the effects of anisotropic consolidation on the undrained strength of a compacted lean clay. Strengths were measured using isotropically and anisotropically consolidated undrained triaxial compression tests. It was found that anisotropic consolidation has little effect on the undrained strength of compacted clay at vertical effective consolidation stresses below 50 kPa. As the consolidation stress increased, anisotropic consolidation was shown to decrease the undrained strength by 30 % at vertical effective consolidation stress of 300 kPa. It was also found that undrained strengths can increase by 50 % of more due to increases in relative compaction of a few %. Recommendations are presented for addressing the challenges of performing consolidated-undrained tests on compacted clays.