Observations on the Seismic Loading of Rigid Inclusions based on 3D Numerical Simulations-Article

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The study uses three-dimensional numerical simulations to investigate how rigid inclusions (RIs) interact with surrounding soil during earthquakes, particularly when liquefiable layers are present. The simulations examine ground-motion variability, area replacement ratio, surface-crust thickness, embedment, liquefiable-layer thickness, and steel reinforcement. Nonlinear soil behavior, RI flexure, and soil–inclusion interfaces are modeled to capture interaction mechanisms often omitted in earlier studies.<br /><br />Results show that RIs do not necessarily prevent liquefaction. However, their interaction with soil can delay liquefaction onset and mitigate strong, short-lived ground-motion amplification caused by dilation in liquefied sand. Static arching before shaking alters soil stresses and plays a major role in subsequent cyclic stress redistribution and pore-pressure development. As liquefaction develops, the soil may transfer foundation loads from the RI to pore water, temporarily reducing RI axial load.<br /><br />Kinematic bending demands can, in turn, produce transient increases in axial load as the inclusion engages with surrounding soil. This raises grout confinement and moment capacity, so the simulations did not show flexural failure in the cases examined. Thicker surface crusts and greater embedment can increase restraint and seismic bending demand; deeper embedment should therefore be considered carefully when it is not needed for static or settlement performance. Reinforcement effects depend on liquefiable-layer thickness and the resulting nonlinear flexural response.<br /><br />The authors caution that the results are not directly applicable to individual designs. The analyses use a unit-cell model, exclude inertial loading and pore-water flow, and examine a limited set of conditions; some predictions, especially high-frequency amplification, also have modeling uncertainties. The findings are intended to clarify mechanisms and inform site-specific design, not replace it.

Keywords

three-dimensional numerical simulations

rigid inclusions

liquefaction

earthquake ground motion

soil–inclusion interaction

area replacement ratio

surface crust thickness

embedment depth

steel reinforcement

pore pressure development