A method for non-linear analysis of pile groups under vertical loads

摘要

The mechanism of load transfer in pile groups involves many interaction factors such as: soil properties, single pile and pile group geometry, pile cap, surrounding soil, single pile-soil interaction. In most of available prediction methods, the pile group settlement is related to the settlement of a single pile. The "hybrid" approach (O'Neill et al., 1977; Lee, 1993), for example, models the single piles using the load-transfer (t-z) method, and the interaction between the piles, through the soil, is then evaluated using the Mindlin's solution (Mindlin, 1936). The load-transfer curves for the individual piles are modified to take into account the group effects by "stretching" the curves, involving the displacement of a single pile and an additional induced displacement due to pile interaction. The representation of a pile group by an equivalent pier (Randolph, 1994; Clancy and Randolph, 1996; Horikoshi and Randolph, 1999) for estimating the settlements behavior of pile groups has been adopted. Naturally, the equivalent pier approach furnishes an estimation of only the average settlement of the pile group. A simplified non-linear method to predict the behavior of a pile group under vertical loads is presented in the paper. The model employs hyperbolic load-transfer (t-z) functions, by which the non-linear behavior of shaft and base resistance is simulated.