Liquefaction mitigation methods for existing shallow-founded elongated structures on horizontal or mildly-inclined ground

Abstract

This numerical study investigates the effectiveness of selected ground improvement methods for existing elongated structures that are shallow-founded on horizontal or mildly-inclined liquefiable ground. It employs non-linear dynamic fully coupled 2D ground response analyses performed with the finite-difference method. When the mildly-inclined ground remains unimproved, narrow structures prove more susceptible to horizontal displacement and rotation than wide structures with the same load. However, settlements develop regardless of the width of the structure and the (mild) inclination angle of the ground. Focusing on the improvement of existing structures, the paper studies prefabricated vertical drains or stiff containment walls implemented solely at their perimeter. Reinforced concrete walls (diaphragm or secant pile walls) prove much more effective in reducing structural settlements, horizontal displacements and rotations than prefabricated vertical drains, provided that their tip reaches the bottom of the liquefiable layer. Constructing these walls with deep soil-cement mixing proves a viable (less costly) alternative, at least for horizontal ground conditions.