Investigation of the Accuracy of the Elastic Settlement Estimation Methods and the Extrapolation Techniques of Plate Load Test Results

Accurate estimation of the settlement of shallow foundations is an important aspect in the design of such foundations. Most often elastic settlement estimation methods are used in the estimation of settlement of shallow foundations. In addition, plate load tests are also performed to estimate the settlement of shallow foundations. Since a smaller size plate is used in the plate load test, the settlement obtained from such tests should be extrapolated to the actual size footings. Even though there are large number of settlement estimation methods and extrapolation techniques for plate load test results, the verification studies of the accuracy of the methods are very rare. It is very often observed that the settlement of shallow foundations are estimated based on the plate load tests carried out in layered soil medium, where a stiff fill soil layer overlying a soft soil. Extrapolation techniques of the plate load test results are highly questionable under such situations. A finite element model was developed using the software called PLAXIS to simulate the settlement of footings. The developed model was used to model some case studies presented in the literature to investigate the accuracy of the model predictions. Thereafter, parametric studies were carried out to investigate the accuracy of: (i) commonly used elastic settlement estimation methods; (ii) the commonly used extrapolation techniques in the homogeneous subsurface conditions; and (iii) the commonly used extrapolation techniques in the two layered medium with a hard layer overlying a soft layer.