Fundamental factors affecting liquefaction susceptibility of sands

TLDR

The study examines liquefaction in saturated sands, focusing on fundamental factors and initial state variables that lack consensus in the literature. Using comprehensive experimental evidence from reconstituted specimens, the authors assess loading system characteristics that impede accurate measurement of true post‑peak behavior. Results show that undrained behavior at a given void ratio and effective stress is strongly influenced by reconstitution fabric, very loose moist‑tamped states are unlikely in situ, liquefaction susceptibility depends on both initial state and effective stress path, and water‑pluviated specimens closely mimic in‑situ sands, while small expansive volumetric strains can alter a sand from dilative to strain‑softening behavior. Very small expansive volumetric strains from pore‑pressure gradients during short‑duration loading can convert a sand from dilative to strain‑softening behavior.

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.