Assessment of group efficiency in sands using finite element method

While designing a deep foundation system in different soil conditions, many uncertainties related to the group efficiency of the pile group is of concern. Especially for the barrette foundations, the main concern is the relation between group efficiency and the shape factors like the length, width or minimum net spacing between the barrettes. In this work, the behaviour of the barrette pile group is modelled using finite element program to analyze uncertainties described above and to obtain a simplified solution method that can be applied to similar cases. In the scope of this study, the Plaxis 3D Foundation software was used to analyze the group efficiency of the barrette piles in sands having different densities. The barrette dimensions are chosen as Bb = 1.0 m, Hi, = 3.0 m and L=25.0 m (width, height and depth). Each model consists of 16 barrette piles. The barrettes are placed parallel and peipendicular to each other to analyze the effect of the shape and placement of the piles. In order to ignore the pile cap rigidity, the piles are modelled as free standing piles, thus each pile is loaded separately and equally until the failure load. The failure load is considered as the load at the 10%D vertical displacement value. As a result of this study, it was found that the group efficiency behaviour is not affected by the parallel or perpendicular arrangements of the barrette piles. High group efficiency factors are achieved as the density of sand increases.