Pre-Liquefaction and Post-Liquefaction Responses of Axially Loaded Piles in Sands

This paper presents a methodology for predicting the mobilized response of axially loaded piles in sands in the states of pre-liquefaction and post-liquefaction. The proposed procedure calculates shaft and skin resistance of axially loaded piles in sands with and without liquefaction. Sands with limited liquefaction (mostly medium-dense sands), in which the shear strength of the sand drops under a cyclic loading (seismic events), were the focus of this study. The proposed approach provides the load transfer-settlement (t-z) curve and the pile-head axial-load versus pile settlement in sands before and after the development of soil liquefaction. It also considers the variation of pore-water pressure (PWP) in the near-field soil caused by axial loading combined with free-field PWP that is generated by cyclic loading as a postseismic event. The mobilized pile skin and tip resistances were determined on the basis of two constitutive models (of stress–strain relationship) for sands under drained and undrained conditions. A computer code was developed to implement the presented technique.