Differential Settlement of Foundations

ABSTRACT: The allowable settlement of a foundation must account for maximum deformations at both serviceability limit states (SLS) and ultimate limit states (ULS) of the supported structure. The resulting design of foundations typically proceeds by limiting the total settlement of individual foundations and by doing so, hopefully restricting the differential settlement between pairs of foundations. In fact, it is often the differential settlement which is of more importance to the performance of the supported structure. Unfortunately, due to the random nature of the supporting ground, the magnitude of differential settlement is also random, and is typically much more difficult to characterize than is the total settlement of individual foundations. For a group of four foundations arranged in a square pattern, this paper investigates the distribution of the pair-wise maximum differential settlement as a function of the degree of spatial variability and correlation. In particular, the effect of increasing correlation length between elasticity of the ground, and loads applied to the foundations, on the maximum differential settlement distribution is investigated. The end goal is to develop probabilistic design requirements which allow for acceptable target reliabilities against excessive differential settlement.