Influence of soil variability on differential settlements of structures

The paper addresses the interaction of a structure with spatially varying soil properties. In particular, the problem of a two-span continuous beam founded on a heterogeneous soil is solved analytically. The geometrical and stiffness characteristics of the structure interact strongly with the spatial properties of the heterogeneous soil. For a certain value of the correlation distance, a feature of the heterogeneous soil formation, the uncertainty and the risk of high values, not predicted with deterministic models, in estimating differential settlements and forces (bending moments, shear forces, etc.) on the structure becomes maximum. The analytical solution uses a series expansion of the soil properties relative to those of the structure. The error in the solution, due to the truncation of the series expansion, is estimated by relevant numerical results. The paper shows clearly that the forces on the structure founded on a heterogeneous soil can differ widely from those usually predicted by a deterministic model. Furthermore, a usual deterministic approach can underestimate the safety level of the structure significantly.