Estimation of Ultimate Bearing Capacity of Footings on Soft Clay from Plate Load Test Data Considering Variability

Abstract

The ultimate bearing capacity of a foundation can be determined from the load–settlement response obtained from plate load tests. For clayey soil it is known that the ultimate bearing capacity of footing is equal to that of a test plate. However, the present study shows that it varies with the variation of type of loading, size and shape of test plate and soil consistency. For reaction type of loading, the load is observed as normally distributed random variable with an average co-efficient of variation of 0.018. For different shape and size of plates, the bearing pressure–settlement curves show a high degree of variation. Subsequently the bearing pressures and settlements are normalized to dimensionless parameters and the normalized plot shows a reduction in variability. Further, the normalized curves are fitted to the hyperbolic model by nonlinear regression with non-constant variance. The model parameters, their standard errors, 95% confidence intervals and co-efficient of determination are quantified. The horizontal asymptote of the hyperbolic model has been used to estimate the ultimate bearing capacity. This method yields a value very close to other conventional bearing capacity methods. A sensitivity analysis shows the influence of various parameters on the bearing pressure.