LIQUEFACTION AND RESIDUAL STRENGTH OF SANDS FROM DRAINED TRIAXIAL TESTS

The state of knowledge with regard to static and cyclic liquefaction h as progressed tremendously since the mid-1960s. In fact, it is general ly accepted, based on the steady-state concepts of Casagrande, Castro, and Poulos that the end or steady-state condition of a liquefied loos e sand is the same whether due to monotonic, cyclic, or dynamic undrai ned loading. Even so, a straightforward and fundamental explanation of the initiation and end-state liquefaction behavior is still needed. T oward that end, an effective stress approach that allows the assessmen t of the whole undrained stress-strain curve (including the peak and r esidual strength values) and the undrained effective stress path of a monotonic test from drained triaxial tests is presented. Results from three series of tests are shown to demonstrate the validity of the met hod. This method makes it possible for a geotechnical firm with the ca pability of performing the traditional drained test with volume change measurements to participate in static liquefaction and residual stren gth assessment. More importantly, it provides the conditions and logic for the development of complete versus limited liquefaction (and even dilative) response.