Developments in quantifying the effect of water table rise on additional settlements of shallow foundations resting on granular soils

Settlement calculation is an important part in the design of shallow foundations on cohesionless soils. The designers have to ensure that the settlement is within tolerable limit. Any future rise of water table may cause additional settlement, which can jeopardize the integrity of the structure. There is no widely accepted procedure for predicting additional settlement because of water level rise. This paper reviews the current state of the art for additional settlement prediction techniques for footings subjected to water table rise. Theoretical background, analytical studies, field tests, laboratory modeling, and recent developments in predicting the effect of submergence on settlement are briefly discussed. Terzaghi (1943) suggested that the settlement is doubled when the water level rises to the footing level. This was supported by analytical studies and field experiments. Laboratory modeling of the shallow footings indicated much larger additional settlements for saturated soils. A few rational methods for predicting settlement of submerged soils have been developed based on the laboratory test results. Numerical modelings reveal that the water table correction factor can be more than two and it depends on stress level, angle of friction, and soil relative density. The shape of water table correction factor diagram and its extent below the footing level have been discussed based on the previous studies