Tapered piles have not often been considered as a design option due to the lack of knowledge about their behavior. Last researches were focused on the axial behavior of these piles; However, their lateral was rarely considered. The main objective of this thesis is to evaluate static and lateral behavior of battered tapered piles, under monotonic loading. A proper constitutive model capable to predict the behavior of soil in different stress states, could evaluate a more accurate results in a numerical modeling. In this research, the unified bi-surface elasto-plastic model developed by Maleki et al was employed to simulate the soil behavior. The constitutive model was implemented in a finite difference code, FLAC 3D . To verify the constitutive model, different experiments were simulated. The results showed significant ability of the model to predict behavior of drained and undrained sand and clayey soils. To assess lateral behavior of battered tapered piles, several models including single and group piles were developed. Emphasizing on slenderness, inclination angle, soil type and pile spacing ratio in group piles, and comprehensive parametric analysis were performed. The results showed that applying battered, tapered piles led to increase the lateral capacity of these piles; moreover, axial stress distribution and soil lateral pressure on the pile approved that distribution of tapered pile material, is more efficient than uniform section piles.
