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3D analyses of dynamic LNG tank performance on liquefiable soils improved with stone columns

Yannis Chaloulos, Panagiota Tasiopoulou, Takis Georgarakos, Amalia Giannakou, Jacob Chacko and StéphanUnterseh have co-authored a paper titled: “3D Effective stress analyses of dynamic LNG tank performance on liquefiable soils improved with stone columns” which has been published in Soil Dynamics and Earthquake Engineering. In this paper, the seismic performance of an LNG tank on liquefiable soil improved with stone columns is assessed through 3D effective stress time history analyses. The numerical methodology, which is validated against centrifuge tests, uses the Ta-Ger model to capture the complex sand response under earthquake loading while it simultaneously accounts for Soil-Foundation-Structure interaction by incorporating tank inertial response and both convective and impulsive hydrodynamic actions through a system of properly calibrated oscillators. The methodology introduces a novel technique for incorporating the "improvement" effect of the stone columns by means of "equivalent" soil properties calibrated through separate analyses of a representative remediated 3D soil "cell" explicitly simulating the stone columns within the soil. The analyses show that the presence of the

stone columns substantially reduces shear deformations in the improved soil. During shaking, tank settlements accumulate through a rocking, downwards ratcheting, mechanism, which is however constrained by the formation of a stable, nonliquefied soil zone below the tank. Post-seismic, reconsolidation settlements, primarily originating from unimproved zones below the stone columns, are also assessed. Once the complex soil behavior- and dynamic load- mechanisms are comprehensively addressed, differential settlements remain well below allowable limits, demonstrating adequate structure performance even under the high design shaking levels.

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