Most of our understanding of the nature of the cyclic, and post liquefaction response of sands is derived from controlled laboratory tests on reconstituted specimens. However, the undrained response of soils is dependent on the fabric, in addition to the density, initial stress state, and the stress path during loading. As a result, uncertainties arise when characterizing the response of natural soils in-situ, based on the behaviour of specimens reconstituted in the laboratory, even if appropriate stress states and paths are duplicated. This paper presents the cyclic and post liquefaction response of in-situ frozen, "undisturbed" sands from alluvial environments and compares them to the response of specimens reconstituted in the laboratory by water pluviation using the same sand. The data presented demonstrate that the response of alluvial in-situ sands may be treated within the same framework established in the literature using water pluviated specimens. The various mechanisms of deformation noted in these "undisturbed" sand specimens were consistent with those observed using pluviated specimens. The process of water pluviation mimics the natural deposition process in an alluvial environment, and as a result produces a fabric similar to that of alluvial sands. It is shown that post liquefaction response of sand is dilative, even if the sand is contractive and strain softening during the cyclic loading. As a result, post liquefaction shear results in a continually stiffening response. Post liquefaction response is dependent on the density, stress level, and loading mode. The results presented suggest that the residual post liquefaction strength adopted in current practice (based on the empirical relationship between the back calculated shear strength and SPT N1,60 blow counts) is conservative.
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