Analysis of Load-Bearing Fills over Soft Subsoils

The protection afforded soft subsoils by the stress-distributing characteristics of load-bearing fills is examined. Using recently developed finite element techniques of analysis, including nonlinear soil properties, a complete stress-deformation solution of a fill-subsoil system is obtained. The proposed method is first examined by applying it to three problems, one hypothetical and two actual load test case histories. The method is then used to study the stress distributing characteristics of granular fills overlying clay subsoils. As would be anticipated, the stiffer the fill relative to the foundation soil, the greater the reduction in stress transmitted to the underlying soil. Although the complexity of the load-bearing fill problem is such that simple charts cannot be prepared to indicate fill-subsoil interface stresses for different soil conditions and geometries, it is shown that approximate values of maximum vertical and shear stress can be obtained by use of an easily applied formula for modulus characterization and a simple geometrical function.