چكيده به لاتين
The liquefaction-induced lateral spreading has been responsible for severe damages on the pile foundation during major earthquakes. Although in recent years many studies have focused on different aspects of this phenomenon, the complicated nature of the dynamic interaction between piles and liquefied soil is not fully understood yet. The present study is about numerically studying the effect of using finned pile as a protection pile in upstream side of a 2*2 circular group pile which is subjected to liquefaction induced lateral spreading by Opensees which is FEM based. For verification of the numerical model, Wilson (1998) centrifuge model is used. The parameters such as, pile head acceleration, pile head displacement, pile moment time history in three depths, and pore water pressure of soil in three depths are verified and afterwards, based on suggested numerical model, the parametric study is conducted on three new models. These models are comprised of a 2*2 group pile as base model and two other models which have a protection pile in circular shape with same geometry of piles in base 2*2 group pile in one, and a finned shape pile with comparable geometry to circular pile in the other, located in upstream side of 2*2 group pile. By comparing the results of these three models, it can be understood that, by using a protection pile, specially finned pile, in upstream side of group pile, some key parameters such as bending moment and lateral displacement in 2*2 group pile are significantly decreased. It is observed that, using finned pile as protection pile has better function than circular pile with comparable geometry which can be due to the limited movement of soil around pile because of the geometry of finned pile. This limitation in soil movement consequently reduces the kinematic forces applied to the pile. Furthermore, a parametric study is conducted on six parameters such as, ground slope, pile stiffnes, relative density of liquefiable soil layer, surcharge on pile, dominant frequency of excitation, and pile head fixity condition. In all presented models in all conditions, pile bending moment and lateral displacement in 2*2 group pile with a protection finned pile in upstream side, is lower than any other models, which provides good efficiency in using this type of pile in liquefaction induced lateral spreading conditions.
