Measured and Predicted Settlement of Shallow Foundations on Cohesionless Soil

Various methods are available to evaluate the settlement of shallow foundations on cohesionless soil. Fifteen numbers of such commonly adopted methods have been selected for the settlement calculations. These methods have been categorized as empirical (nine numbers), semi-empirical (two numbers), and theoretical (four numbers). The settlements of foundations with different footing sizes have been calculated using these methods on improved sandy soil (with the stone columns or vibro compaction) and on unimproved soil. The calculated settlement values are compared with the plate/footing load test results carried out on corresponding plate sizes and full scale RC footings. Among various studied methods, empirical method proposed by Terzaghi and Peck, semi-empirical method proposed by Schmertmann and a theoretical method proposed by Janbu appeared to predict reasonably accurate and reliable settlement values. The stiffness of soil does not appear to be nonlinear with strain and stress level as observed based on the actual settlement values at different stress levels. Almost all the methods overestimated the footing settlements at lower as well as higher stress levels. Though semi-empirical and theoretical methods are preferred over empirical methods due to lack of theoretical study in later, it is also suggested to appropriately select the geotechnical design parameters rather than trying to select the best method for the settlement analysis.