Calculation of Settlements of Shallow Foundations on Sand and Silt Based on In Situ Test Results

Calculations of settlements of foundations on sand and silt are often made with methods that do not take into account the curved load-settlement relations. With reasonable accuracy, these methods can be used to calculate settlements only for the “normal” ground pressures for which they have been elaborated. For lower ground pressures the settlements become overestimated and for higher pressures they become increasingly underestimated. However, new design rules often contain varying demands for acceptable settlements depending on the type of structure. The failure criteria for bearing capacity are also more often defined in terms of large relative settlements than of actual failure. This leads to higher demands for accurate predictions of settlements over a wide range of possible ground pressures. New methods of predicting the load-settlement curves for shallow foundations have been proposed and two of these methods have been compared and calibrated against the results of a series of plate load tests in Sweden. Both methods appear to greatly improve the possibilities of accurate predictions of settlements and failure loads based on settlement criteria.