Abstract
To discuss the nonlinear pile-soil interaction of offshore pile foundations under cyclic lateral loading in soft clay, the p-y curve method proposed by Matlock for the pile shaft under cyclic lateral loads were introduced and modified to reflect the weakening effect of the ultimate lateral bearing capacity of soft clay and the cyclic deformation of offshore pile shaft. In the modified p-y curve method, influences by cyclic loads on the lateral bearing behavior of subsoil around the pile shaft were approximately simulated by using a decreased undrained shear strength of the soft clay. And a bigger lateral deflection of the pile shaft was considered to reflect the impact by cyclic loads than the equivalent static load. Based on the formula proposed by Hettler to predict the horizontal displacement of pile shaft after N cycles of loading in sandy soil, a modified formula was established for offshore piles in soft clay to involve the cyclic deformation of pile shaft. The feasibility of modified p-y curve method presented in this paper was verified by comparing the more reasonable calculated result with those available achievements from the models of Matlock. Furthermore, a detailed parameter analysis was carried out to find out that, the value of the correlation coefficient ζ used to calculate the Y50 in the modified p-y curve is 1.5, and the reduction of the ultimate lateral bearing capacity of soft clay increased only 6% when the plasticity index increased from 10 up to 60. Finally, a simplified formula was proposed to calculate the undrained shear strength of soft clay under cyclic loading.
Published Version
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