ABSTRACT
An effective stress method for the evaluation of the undrained stress-strain-stress path behavior of loose sands based on drained triaxial test response is presented here. Understanding peak undrained resistance and residual strength in terms of characteristics of rebounded (i.e. overconsolidated) standard drained test response proves extremely useful. This approach works for both triaxial compression and extension tests and shows that these undrained paths control or bound the undrained cyclic triaxial test stress path. Hooke’s Law posed in terms of drained test confining and deviatoric stress response can be used to demonstrate why the extension test resistance of a loose sand measures less than the undrained compression peak resistance and residual strength. The characterization works for both contractive (i.e. steady-state or complete liquefaction) and dilative (i.e. quasi steady-state or limited liquefaction) behavior. Formulation of the standard drained test stress-strain and volume change response based on confining pressure, OCR, peak friction angle, void ratio, uniformity coefficient, and particle shape allows the direct assessment of undrained behavior (compression and possibly, in the future, extension and simple shear response) based upon the same variables. Such undrained response characterization from drained test formulation has direct application to a number of practical problems.
