چكيده به لاتين
iesmic response of structores during earthquake is affected by pile performance.Different methods for analysing piles under dynamic loading is presented, but these methods are not sufficiently reliable in areas where the soil has a liquefaction potential.When liquefaction occurs and lateral spreading is created,the pile is placed under the inertial load from superstructure and soil and additionally soil resistance reduces due to excess pore pressure generation.
In this study in order to investigation of piles dynamic behavior at liquefaction and its subsequent lateral spreading,a 3D fully coupled dynamic analysis is done.The afformentioned numerical analysis is done by finite element software OpenSees 2.5.0.The soil medium is modeld in 3D and fully continuous by U-P formulation which governing the saturated porous media by Yang,s multi yield surfaces model (2003) wich can simulate sand behavior under cyclic loading and draind or undraind condition.This material is basically developed for modeling cyclic mobility of sands.
To ensure the finiti element program performance,the results of shake table test (Haeri et.al, 2012) are used.The mentioned test is done in a rigid container on SUT,s large scale shake table under 1G condition due to investigation of neighboring and shadowing effects in piles in a two layerd soil profile in which the upper layer is liquefiable and the underlying layer is nonliquefiable.The results of excess pore pressure, pile head displacement and pile bending moment during earthquake which assesd from FE simulation have good agrement with experimental results,but there is not good matching between numerical and experimental results of soil surface lateral displacement in free field while the liquefied soil is very loose which means that the flow liquefaction has happened.By the suggistion of Dr. Baziar,a centrifuge test (Dobry et.al, 1998), in which satureted sandy soil with Dr=40% under 50g condition and an earthquake excitation has analysed.The comparision between numerical and experimental results shows a greate improvement of the prediction of soil lateral displacement.After verifying the numerical modeling, a parametric study of a single pile which placed in two layerd soil that the upper layer is liquefiable and second layer is nonliquefiable has done.The parameters which their effects has investigated are:ground slope,pile diameter,liquefiable layer depth.
Keywords: Liquefaction, Lateral spreading, FEM, OpenSees.
