Effects of Spatial Variability on Reliability-Based Design of Drilled Shafts

Inherent spatial variability is a major source of soil property variability, and it affects the analysis and design of geotechnical structures, such as drilled shafts. The current reliability-based design (RBD) approaches, however, commonly address the inherent spatial variability in an indirect and implicit manner using an equivalent single random variable. Recently a Monte Carlo simulation (MCS)-based RBD approach, namely the expanded RBD approach, has been developed, and the inherent spatial variability can be conveniently modeled in a direct and explicit manner using the expanded RBD together with random field theory. This paper integrates the expanded RBD approach with random field theory to account, directly and explicitly, for inherent spatial variability of soil properties in the RBD of drilled shafts. The proposed methodology is illustrated through a drilled shaft design example and is applied to explore effects of inherent spatial variability on the RBD of drilled shafts. It is straightforward and convenient to integrate the expanded RBD approach with random field theory, and the inherent spatial variability of soil properties is shown to affect the RBD of drilled shafts significantly. Such effects are more profound for drilled shafts with relatively long shaft length.