Multiaxial testing and analytical constitutive characterization of granular materials

Abstract

A new 250 psi capacity stress-controlled, fluid cushion multiaxial cubical apparatus has been described. Its load application and deformation measurement capabilities were explored and found suitable for most soil testing applications. Other new generation laboratory equipment was surveyed and compared with the aforementioned apparatus. Constitutive laws based on incremental plasticity theory including "Cap models" were examined relative to observed soil behavior. The apparatus was used to characterize the constitutive behavior of two soils. This characterization included the generation of cap model parameters. A two dimensional finite element code incorporating a cap model was used to predict experimental test results. This work demonstrated the need for precise laboratory testing techniques in geomechanics which is satisfied in part by the multiaxial cubical test apparatus.