A study on the influence of ground water level on foundation settlement in cohesionless soil

Settlement calculation is an important part in the design of shallow foundations resting on granular soils. Rise of ground water level is believed to increase the settlement significantly and has been a topic of research for many years. Terzaghi (1943) suggested that the submergence of soil mass reduces the soil stiffness to half, which in turn doubles the settlement. Since then, various researchers proposed correction factors to account for the additional settlement due to water table fluctuation. However, a comprehensive settlement testing and its numerical modeling to account for the influence of ground water level has not been reported in the literature. The objective of this paper is to quantify the effect of water table rise on settlement through laboratory testing over wide range of footing shape, soil density, water table depth and stress level. The tests were carried out within a settlement tank. The footings under working load were subjected to water table rise, and the additional settlements were measured. The experimental setup was modelled in FLAC and the results were compared with the laboratory tests. The results obtained will be valuable in verifying Terzaghi's intuitive reasoning and explaining the observed additional settlement of footings found in the literature