Fundamental factors affecting liquefaction susceptibility of sands

Abstract

Liquefaction phenomena in saturated sands are examined. Fundamental factors that influence liquefaction susceptibility are considered from the background of comprehensive experimental evidence from test results on reconstituted specimens. These include those related to the loading system characteristics which do not enable measurements of the true post-peak behaviour. In particular, several issues related to the influence of initial state variables, on which there appears to be a lack of consensus in the literature, are dealt with. It is shown that at identical initial void ratio - effective stress state, undrained (constant volume) behaviour is profoundly affected by the fabric that ensues upon sample reconstitution. Very loose moist-tamped states are unlikely to be accessible to in situ sands. The susceptibility to liquefaction, both static and cyclic, is not only dependent on the initial state variables, but is also strongly affected by the effective stress path during undrained shear. Comparative tests on undisturbed samples retrieved by in situ ground freezing and their reconstituted counterparts show that water-pluviated specimens closely mimic the behaviour of in situ sands. Very small expansive volumetric strains due to pore-pressure gradients during short-duration loading, or after its cessation, could transform a sand into a strain-softening type, which otherwise would be dilative if completely undrained.Key words: anisotropy, laboratory tests, liquefaction, sampling, sands, shear strength.