Cyclic liquefaction screening of sand with non-plastic fines: Critical state approach

Abstract

There have been significant advances in the application of critical state, CS, in liquefaction potential assessment. This was done by comparing state parameter, ψ with estimated characteristic cyclic stress ratio, CSR due to an earthquake. A cyclic resistance ratio, CRR curve, which can be determined from cyclic liquefaction tests, separates historical liquefied and non-liquefied data points (ψ, CSR). On the other hand, the concepts of equivalent granular state parameter, ψ*, which was developed for sands with fines, can be used in lieu ψ to provide a unifying framework for characterizing the undrained response of sands with non/low plasticity fines, irrespective of fines content (fc). The present work combines these two propositions, and by merely substituting ψ* for ψ into the aforementioned CS approach to capture the influence of fc. A series of static and cyclic triaxial tests were conducted, separately and independently of the concept of ψ*, for sand with up to fc of 30%. The clean sand was collected from Sabarmati river belt at Ahmedabad city in India which was severely affected during the Bhuj earthquake, 2001. The experimental data gave a single relation for CRR and ψ* which was then used to assess liquefaction potential for a SPT based case study, where fc varies along the depth. The prediction matched with the field observation.