Numerical analysis of the effect of sand and silt stratification on liquefaction potential

Liquefaction is a destructive earthquake-induced ground failure that can cripple infrastructure within seconds. It arises when saturated, cohesionless soils lose strength and stiffness as excess pore water pressure accumulates during shaking, triggering abrupt ground deformation. Coastal and low-lying areas with loose to medium-dense sands and high-water tables are especially at risk; the 2018 Palu earthquake starkly illustrated the neighborhood-scale consequences. This study investigates the influence of sand and silt stratification on liquefaction potential using numerical modeling. Calibrated with laboratory data, Plaxis 2D dynamic analyses modeled two relative densities (40% and 60%) across two stratigraphies: sand–silt– sand (S–M–S) and silt–sand–silt (M–S–M). Results show relative density is a primary control: Dr 60% markedly reduces excess pore pressure buildup, settlement, and liquefaction susceptibility compared with Dr 40%. Stratigraphy also matters; the M-S-M profile is most vulnerable, reflecting impeding drainage pathways and amplified pore pressure development in the sand core. These findings clarify the mechanics of layered deposits during seismic loading and highlight practical mitigation strategies, including densification of sand layers and attention to low-permeability interbeds, when screening sites, prioritizing investigations, and designing ground improvement in earthquake-prone settings.