Revisiting dynamic earth pressure coefficients: shaking sideways but looking up
Revisiting dynamic earth pressure coefficients: shaking sideways but looking up
Dynamic earth pressure coefficients are widely used in seismic engineering design. Nevertheless, practical approaches have typically assumed either fully elastic or fully plastic soil behaviour. Fundamentally, uncertainty remains over the mobilized and limiting soil stresses that are generated during earthquakes that depend on the ground motion, coupled response of soils and structures, and their relative displacements. Amidst these considerations, the scope for horizontal shaking to lead to influential vertical response of the soil has often been neglected. This study revisits centrifuge experiments that revealed, at odds with longstanding assumptions, predominantly horizontal shaking leads to both horizontal and vertical soil accelerations, and thus dynamic horizontal and dynamic vertical normal stresses due to inertia of the soil body and rocking mechanisms. The findings motivate reconsideration of dynamic earth pressure coefficients and other approaches that implicitly assume geostatic vertical stresses. The implications for physical modelers instrumenting and interpreting centrifuge experiments through the lens of these rocking mechanisms are discussed. Grids of vertical accelerometers enable estimates of the cyclic vertical effective stresses and results in the current study reveal cyclic variations up to 20 % of the geostatic values in a level soil deposit confined between smooth boundaries. 2D acceleration measurements are then used to inform the 2D displacements and estimates of the 2D strain states during the shaking, offering fresh insight into the dynamic mobilization of horizontal stresses at the soil-wall boundary and provoking questions about the fundamental soil behaviour.
S. S. C. Madabhushi
11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)
Keynote Papers
https://doi.org/10.53243/ICPMG2026-464