Modelling the load-deformation response of deep foundations under oblique loading

Abstract

Deep foundations are slender pile elements used to transfer loads from structures into deeper soil strata below the ground. Deep foundations have a variety of loads including axial, lateral and moment loads. Often these loads will act together to form a combination of loads, such as oblique forces that have a component of axial and lateral forces. Due to the pile's length, which can extend past 30 m, it is difficult and expensive to carry out full-scale testing. Any full-scale test data are limited to the area conditions and soil properties at the testing site. Small scale testing can be used as an alternative to full-scale testing, although scaling effects will influence the conclusions from this type of study greatly. Computer simulations of finite element modelling allow for in-depth studies into the complex pile–soil interaction under combination loading in deep foundation structures. This work used three-dimensional finite element modelling using ABAQUS to explore the effect of pile shape, sand properties, pile length and loading conditions on the capacity of a pile. Using trends discovered by these simulations design charts were developed to aid designers when determining the bearing capacity for oblique interaction for square piles. The final design chart shows the change in capacity for in-plane loaded, square cross-sectioned piles as compared to circular piles. The difference in capacity is shown to be a function of the oblique interaction angle and length to diameter ratio.