LAUSR

Construction of foundations close to each other, which results in substantial interaction between them, has become a common practice. However, not much literature is available for practicing engineers to analyse and design deep and shallow foundations when they are constructed adjacent to each other. This study analyses one such scenario where a structure supported on drilled shafts was supposed to be constructed adjacent to another structure supported on a large mat foundation with heavy floor load. A detailed parametric study using finite element techniques was performed to better understand stress distributions and develop simplified methods to analyse this type of problems. Lateral stress and drag forces on the shafts resulting from the heavy load on the mat foundation were identified to be the key factors. This paper is focused on estimating the drag forces. A deformation bulb under a uniformly loaded square foundation, similar to the well-known pressure bulb, is proposed. A new term ‘Isodefers’ has been proposed to refer the lines of equal deformation. Isodefers are a significant tool for practicing engineers to understand vertical deformation distribution below a uniformly loaded square area and estimate drag forces on nearby deep foundations by determining its neutral plane.