LATERAL CAPACITY OF AL NAJIBIYA BRIDGE PIER FOUNDATION

Al-Najibiya Bridge was designed to be constructed on Shat Al Arab River in Basra district, Iraq. The bridge consists of five spans 33m length each with four intermediate piers. Each pier is supported on pile cap of 9m width, 17m length and 2m depth. The pile cap is stand over six cast in drilled hole piles of 1.8m diameter arranged at five meter center to center in both directions. The piles are stand 10 to 12m above river bed and embedded 30m in an over consolidated clayey soil with stiffness vary linearly with the depth. Each pier was designed to carry a maximum of 10000 KN lateral forces. The design engineer considered the average lateral capacity of each pile in the group as 70% of the lateral capacity of a similar single pile. In this paper, the justification of the efficiency factor of (0.7) was studied by analyzing the single pile and the pile group in a finite element model with the soil represented in two ways, as linear elastic and elastic-plastic material (Drucker- Prager plasticity model). The ANSYS 12.1 finite element program was employed for the analysis; the results are given based on displacements at the piles head, shear forces and bending moments throughout the pile length.