A practical method for construction of p-y curves for liquefiable soils

Abstract

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

Hazard considerations in the vulnerability assessment of offshore wind farms in seismic zones

“…The moment and lateral resisting capacity values were estimated using the methodology presented in Aleem et al 27 For the estimation of the liquefied soil the p – y springs were removed to represent the loss of the soil strength in that regions. For an accurate representation of p–y springs the readers are referred to Lombardi et al 11 or Dash et al 34 —the depth of liquefied soil presented by the removal of p–y springs. API 35 p–y springs are used to represent the non‐liquefiable depth.…”

Seismic Design of Offshore Wind Turbines: Good, Bad and Unknowns

“…A bilinear stress-strain model (see Figure 10b) is proposed in [25] that was used by [26] to recommend a new family of p-y curves with a characteristic strain hardening behavior, also referred to as S-shape p-y curves [26]. A step-by-step method for constructing S-shaped p-y curves is given in [4,27]. The use of an appropriate p-y curves, which are consistent with the soil response as observed in laboratory testing, is paramount since the typical p-y curves for liquefied soils tends to significantly overestimate the initial stiffness of the curve, therefore leading to un-conservative approximation of foundation tilting and the response of overall system (see Figure 11).…”

Physical Modelling of Offshore Wind Turbine Foundations for TRL (Technology Readiness Level) Studies

“…This can be carried out by linking results from element tests (triaxial, simple shear) to results from small-scale model tests carried out either at 1× g or in the centrifuge. The readers are referred to [59] for more details on the derivation of the p-y curves for liquefiable soils shown in Figures 36 and 37.…”