Settlement correction for future water table rise in granuular soils: a numerical modelling approach

Shallow foundations are designed such that their expected settlements are limited to 25 mm, and the safety factor against possible bearing capacity failure is 3. When the water table is close to the footing, appropriate design parameters are used to reflect the less stiff soil beneath the water table. When future rise in water table is expected, substantial additional settlement might occur. Terzaghi (1943) suggested that the Young's modulus of saturated granular soil is ∼50% of that of the dry soil, which leads to doubling the settlement in saturated soil when the water table rises to the foundation level. In this paper, an explicit finite difference code FLAC was used to simulate the rise of ground water table in granular soil and the resulting additional settlement was studied. Using linear elastic model gives two times settlement in saturated soil, agreeing with Terzaghi's (1943) statement. Using hyperbolic nonlinearly elastic soil model shows that the correction factor varies with the stress level as well as soil strength and stiffness. The Mohr-Coulomb elastoplastic model gives high additional settlements, as observed in the laboratory model tests