In practice, analysis of laterally loaded piles is often carried out using a “Beam on Non-linear Winkler Foundation method” whereby the lateral pile-soil interaction is modelled as a set of non-linear springs (also known as p y curves). During seismic liquefaction, the saturated sandy soil changes its state from a solid to a thick fluid like material (solid suspension), which in turn alters the shape of the p-y curve. Typically, p-y curves for non-liquefied soil looks like a convex curve with initial stiff slope which reduces with pile-soil relative displacement (y). However, recent research conclusively showed that p-y curve for liquefied soil has a different shape, i.e., upward concave with near-zero initial stiffness (due to the loss of particle to particle contact) up to a certain displacement (y), beyond which the stiffness increases due to reengaging of the sand particles. This paper presents a practical method for construction of the newly proposed p-y curves along with an example

Understanding the behaviour of soils under cyclic/dynamic loading has been one of the challenging topics in geotechnical engineering. The response of liquefiable soils has been well studied however, the post liquefaction behaviour of sands needs better understanding. In this paper, the post liquefaction behaviour of sands is investigated through several series of multi-stage soil element tests using a cyclic Triaxial apparatus. Four types of sand were used where the sands were first liquefied and then monotonically sheared to obtain stress-strain curves. Results of the tests indicate that the stress-strain behaviour of sand in post liquefaction phase can be modelled as a bi-linear curve using three parameters: the initial shear modulus ( ), critical state shear modulus ( ), and post-dilation shear strain ( ) which is the shear strain at the onset of dilation. It was found that the three parameters are dependent on the initial relative density of sands. Furthermore, it was observed that with the increase in the relative density both and increase and decreases. The practical application of the results is to generate p-y curves for liquefied soil

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Collapse of Showa Bridge during the 1964 Niigata earthquake has been, throughout the years, an iconic case study for demonstrating the devastating effects of liquefaction. Inertial forces during the initial shock (within the first 7seconds of the earthquake) or lateral spreading of the surrounding ground (which started at 83 seconds after the start of the earthquake) cannot explain the failure of Showa Bridge as the bridge failed at about 70seconds following the main shock and before the lateral spreading of the ground started. In this study, quantitative analysis is carried out for the various failure mechanisms that may have contributed to the failure. The study shows that at about 70 seconds after the onset of the earthquake, the increased natural period of the bridge (due to the

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