Development and Application of Probabilistic Liquefaction Susceptibility Models

Liquefaction susceptibility, the inherent capability of a soil to lose all of its strength transiently or in a sustained manner, is a fundamental material characteristic best assessed from cyclic undrained laboratory tests. We assembled an inventory of cyclic tests paired with co-located CPT soundings and added them to the NGL database, following recommendations from a 2022 PEER Workshop. To interpret these tests objectively, quantitative metrics representing salient features of cyclic response (pore pressure generation, stress-strain pinching, cyclic degradation) are proposed and computed automatically, departing from prior reliance on visual inspection. Expert assessments link test metrics to a cyclic behavior type index (0 for clay-like, 1.0 for sand-like) via Bayesian inference. Models conditioned on index properties and CPT results are proposed. Finally, a three-step logic-tree framework for seismic ground failure assessment is presented, illustrated through cyclic strength and lateral spreading examples.