New perspectives on preshearing history in granular soils

Abstract

The design of deep dump slopes for opencast mines usually requires information about the soil resistance to liquefaction during earthquakes. This resistance depends not only on the initial stress, the initial density, and the amplitude of the cyclic loading, but also on the preshearing, that is, the deviatoric stress path applied to the soil before the cyclic loading. To explore the influence of preshearing on the subsequent soil behaviour, a set of triaxial tests with a combination of undrained preshearing and drained stress cycles using two sample preparation methods is presented. It is shown that the preshearing as well as the preparation method have a major influence on the strain accumulation upon cyclic loading. Simulations of the experiments with four advanced constitutive models reveal that neither the long-lasting effect of preshearing nor the preparation method can adequately be captured by all of the models. This deficiency of the constitutive models can lead to unsafe designs due to the overestimation of the cyclic resistance to liquefaction and to the underestimation of long term settlements.

On the influence of cyclic preloadings on the liquefaction resistance of sands: A numerical study

“…For instance, the work by Wichtmann et al [1] evaluated the prediction capabilities of three advanced constitutive models for sands considering a large database of standard monotonic and cyclic experimental results on Karlsruhe fine sand. Even though this methodology validates the consistency of the models with experimental results, their extended validity should be also judged on tests including paths with more realistic and complex nature [13][14][15][16][17]. A typical example of that is the numerical reproduction of the influence of preloadings on the subsequent monotonic and cyclic response, to which soil deposits are usually presubjected.…”