A new approach for non-linear load-settlement assessment of shallow foundations

The use of deep foundations is more common than the use of shallow foundations for highway bridges. This comes from a trust in the reliability of deep foundation behavior when compared to shallow foundations. The lack of confidence in shallow foundations derives from the dearth of well-documented experimental load-settlement and bearing capacity results. However, the use of shallow foundations may save up to 50% of the structure's foundation cost, which amounts to about 25% to 30% of the total cost of a highway bridge. Accordingly, a new approach to assess the combined load-settlement-bearing capacity behavior of shallow foundations is proposed in this thesis. The load-settlement method assumes non-linearity of soil stress-strain behavior. Most of the settlement calculation methods in the literature assume a linear stress-strain relationship and that results in the inaccuracy of settlement calculation. While shallow foundation settlement and bearing capacity are calculated separately in the classical methods, the proposed load-settlement approach provides the link between each of them. The thesis incorporates a calibration of the proposed method against different drained and undrained shallow footing loading cases. These loading cases were performed on circular steel plates and square and rectangular concrete footings. The thesis shows the required inputs to produce the load-settlement curve which include foundation geometric data and soil engineering properties. An approximate method for calculating the apparent cohesion resulting from capillary tension and the angle of internal friction for rectangular footings resting on sandy soils are also introduced in the thesis.