Modeling Essential Elastoplastic Features of Compacted Silty Sand via Suction-Controlled Triaxial Testing

Abstract

Experimental results from a comprehensive series of suction-controlled, consolidated drained (CD) triaxial tests, conducted on statically compacted specimens of unsaturated silty sand, are presented. The experimental program was accomplished in a newly implemented, fully automated double-walled triaxial test system via the axis-translation technique. Results were thoroughly analyzed to gain critical insight into some of the essential elastoplastic features of compacted intermediate geomaterials under controlled suction states, including the effect of suction on yield stress, apparent cohesion, tensile strength, and critical state line, as well as postpeak softening and strain-induced dilatancy under suction-controlled monotonic shearing. Constitutive parameters postulated by the Barcelona basic model (BBM) were then experimentally calibrated and used for prediction of compacted silty sand response at matric suction states that varied from 50 to 750 kPa. Predicted values of deviatoric stress at critical state are reasonably close to those experimentally assessed from suction-controlled conventional triaxial compression tests; however, given the distinct brittle and dilatant nature of the test soil, its postpeak softening behavior was not adequately captured by the BBM framework. The results therefore are primarily valuable to unsaturated soil constitutive modelers in validating more suitable frameworks for compacted intermediate geomaterials, including bounding surface plasticity models, when subjected to suction-controlled monotonic shearing.