Experimental p-y curves for liquefied soils from centrifuge tests

The present study aims to obtain p-y curves(Winkler spring properties for lateral pile-soil interaction)for liquefied soil from 12 comprehensive centrifuge test cases where pile groups were embedded in liquefiable soil.The p-y curve for fully liquefied soil is back-calculated from the dynamic centrifuge test data using a numerical procedure from the recorded soil response and strain records from the instrumented pile.The p-y curves were obtained for two ground conditions:(a)lateral spreading of liquefied soil,and(b)liquefied soil in level ground.These ground conditions are simulated in the model by having collapsing and non-collapsing intermittent boundaries,which are modelled as quay walls.The p-y curves back-calculated from the centrifuge tests are compared with representative reduced API p-y curves for liquefied soils(known as p-multiplier).The response of p-y curves at full liquefaction is presented and critical observations of lateral pile-soil interaction are discussed.Based on the results of these model tests,guidance for the construction of p-y curves for use in engineering practice is also provided.

Dynamic p-y curves for vertical and batter pile groups in liquefied sand

In this study,centrifuge model tests of vertical and batter pile groups in liquefied sand were conducted on a centrifuge shaking table.The dynamic p-y curves for these pile groups before and during sand liquefaction were obtained from calculations based on test data.The results confirm that liquefaction contributes to a reduction in the energy consumption of pile foundations,with the degradation effect being more pronounced for batter pile groups.At shallow depths,the difference in the backbone gradients of the p-y curves after liquefaction for vertical and batter pile groups indicates that the lateral stiffness of a batter pile group is greater than that of a vertical pile group.As shaking intensity increases,the lateral stiffness of a vertical pile group increases with depth during the late stage of sand liquefaction.However,the lateral stiffness of a batter pile group during liquefaction does not vary with depth.The results of this study provide a reference for the seismic design of vertical and batter pile groups in liquefied soil.

Centrifuge tests for seismic response of single pile foundation supported wind turbines in sand influenced by earthquake history

This paper reports on two sets of centrifuge model tests of wind turbines in dry sand and saturated sand subjected to earthquake sequences.The wind turbine system is composed of a single pile foundation and a wind turbine.All tests were applied with liquefaction experiments and analysis projects(LEAP)waves to simplify the analysis.The objectives of the tests are to investigate:(1)the influence of earthquake history on the seismic response of wind turbines;(2)the influence of earthquake history on the dynamic pile-soil interaction;and(3)the influence of two different foundation types on the seismic response of wind turbines.The tests indicated that earthquake history has a significant influence on the natural frequency of the pile and the soil around the pile in the saturated sand,but has no obvious influence on the dry sand.The shear modulus of the soil and the acceleration amplification factor of the pile top in both tests increased and the maximum bending moment envelope of the single pile foundation shrunk.The stiffness of the p-y curve in saturated sand was increased by the earthquake history,while that in dry sand was not significantly affected.

Interface Mechanical Behavior of Flexible Piles Under Lateral Loads in OWT Systems

This paper investigates the interface mechanical behavior of flexible piles with L_p/D>10 under lateral load and an overturning moment in monotonic loading conditions.To modify the beam-on-Winkler-foundation model of piles in offshore wind farms,the energy-based variational method is used.The soil is treated as a multi-layered elastic continuum with the assumption of three-dimensional displacements,the pile modeled as an Euler-Bernoulli beam.A series of cases using MATLAB programming was conducted to investigate the simplified equations of initial stiffness.The results indicated that the interaction between soil layers and the applied force position should be taken into account in calculating the horizontal soil resistance.Additionally,the distributed moment had a limiting effect on the lateral capacity of a flexible pile.Moreover,to account for the more realistic conditions of OWT systems,field data from the Donghai Bridge offshore wind farm were used.