The failure type-dependent characterization of liquefaction resistance by small-strain shear modulus for saturated sand

In this study, a re-visit of existing laboratory tests was carried out to study the relationship between the liquefaction resistance (CRR) and the small-strain shear modulus (Gmax) of saturated sands with consideration of the failure types of both cyclic mobility and flow liquefaction. The result indicates that the relationship between CRR and Gmax is failure type-dependent, and the liquefaction resistance of cyclic mobility grows faster than that of flow liquefaction. Then discrete element method was used to explore the relationship between the liquefaction resistance and the small-strain shear modulus for a typical saturated granular material, with consideration of different liquefaction types. A series of undrained stress-controlled cyclic tests together with shear wave velocity measurements were simulated, and results similar to the laboratory studies were obtained. Then a new expression is proposed to describe the relationship between CRR and Gmax for granular material. The corresponding micromechanical mechanism is further explored, which shows that there are two kinds of distinct behaviors of the particle contact structure when the granular material changes from loose to dense state under the same confining stress. Compression behavior is dominant for flow liquefaction while collapse behavior is dominant for cyclic mobility type of liquefaction. The different behaviors of the particle contact structure influence the growth of the mechanical contacts, which further leads to the failure type-dependent growth of liquefaction resistance for a saturated granular material.