Reliability-Based Geotechnical Engineering

The ground is a complex engineering material and how to characterize it realistically is a very difficult problem. It is well known that the engineering properties of the ground can vary quite dramatically from point to point throughout a site, and even more so from site to site, and that these properties are highly uncertain. It is also well known that the ground, when subjected to an imposed or self-load, will fail along its weakest path, however tortuous that might be. Given the complexity of the ground, it makes sense to characterize the ground using models which allow for its quite uncertain spatial variability. It also makes sense to use response prediction models which take both spatial variability in ground properties and the tendency of failure to follow weakest paths through the ground into account. The Random Finite Element Method (RFEM) combines spatially varying random field ground models with the finite element method to yield a reliability-based geotechnical methodology which accounts for both spatial variability and weakest path failure mechanisms. Besides being able to realistically model spatial variability in ground properties along with being able to follow the weakest path through the soil, mass, RFEM also provides the significant advantage of being able to account for site understanding in the design process. This paper describes the Random Finite Element Method along with a few of its significant results over a variety of common geotechnical problems. The latter include ground-water modeling, shallow foundation settlement and bearing capacity, deep foundation capacity, and slope stability. LRFD code development will be discussed along the way.