Soil deformability. Settlement. Consolidation

All soils deform under the loads applied to them, with amplitudes ranging from a few millimeters to several meters. New calculation standards require us to predict these displacements, to ensure that they will be acceptable for the structures to be built.

The amplitude of ground deformation depends on the nature and condition of the soil and the loads applied. These loads are limited by the stability conditions that must be respected when designing structures. In practice, the surface foundations of buildings are built on relatively resistant soils and are subject to low levels of deformation, which can usually be estimated using linear calculations. The most significant deformations are those of saturated soft clays, which can last for long periods (from a few months to several decades). In this case, a non-linear (semi-logarithmic) deformability law is used to evaluate the final amplitude of settlement and horizontal deformation, and the evolution of settlement over time is analyzed, taking into account the effect of limited soil permeability on the rate of deformation (consolidation) and soil viscosity (creep).

This article deals successively with soil deformability (odometric compressibility, estimation of deformability moduli), calculation of the amplitude of final settlements and description of the evolution of deformations over time. It concludes with some considerations on the practical calculation of settlements.