| In this study, a recently proposed settlement calculation method, the "load-settlement-curve" method (Briaud and JeanJean, 1994), is improved and generalized for application to designing any shallow footing in sand. The method can generate the complete load-settlement curve of a footing from the corresponding "average" preboring pressuremeter curve, through a pressuremeter-to-footing transfer function. The method accounts for the influence of footing shape, size, depth, eccentricity or inclination of the load, and the proximity of a sloped ground surface, if any. This study was motivated by the recognition that there exists a tremendous need for a realistic calculation method to predict settlements of footings in sand for shallow foundation designs.; Here, the original transfer function is first standardized with respect to a standard footing and loading condition, and then it is extended to apply to any footing and loading condition by an extensive three-dimensional finite element analyses. The soil was represented by the incrementally linear Duncan-Chang hyperbolic model, which was first modified by developing and introducing a new expression for the tangent Poisson's ratio. A finite element code was written to incorporate the soil model into the general purpose finite element program ABAQUS. The parameters for the hyperbolic model were calibrated by matching the load-settlement curves of the finite element analyses to a set of measured load-settlement curves from a database of full-scale load tests of footings in sand, undertaken at the sand-site at Texas A&M University in College Station in 1994.; Using the back-figured values of the model parameters, the influences of the various footing and loading conditions on the settlement of the footing were analyzed. Based on this analyses, appropriate correction factors, to be applied to the standardized transfer function, were developed for footing shape, size, depth, load eccentricity and inclination, and proximity of a sloped ground surface.; The load-settlement-curve method, as has been improved and extended in this study, works as follows: First, the average preboring pressuremeter curve corresponding to the design footing is obtained. Second, necessary corrections are made to the standard transfer function using the appropriate correction factors. Third, the average pressuremeter curve is converted into the pressure vs. normalized settlement curve of the design footing by using the corrected transfer function. And finally, the pressure-normalized settlement curve of the design footing is re-plotted as the load-settlement curve of the footing. |
