Ultimate settlement by hyperbolic plot for clays with vertical drains

Abstract

The rectangular hyperbola method (Tv/U versus Tv) is extended to the case of drains and surcharge by considering the hyperbolic plots for combined vertical and radial flow consolidation in clays of varying thickness and drain spacing ratio for typical soil properties of cv of 1-5 m2/yr. The results indicate that the hyperbolic plots are linear between U50% and U90%. For the lines radiating from the origin to U50% point, the slope is (1/0.5 = 2.0), and to the U90% point, the slope is (1/0.9 = 1.11). Thus, the ratio of the slopes of these radiating lines to the slope of the linear portion of the hyperbolic plots identifies the U50% and U90% for any settlement record using drains and surcharge. It is found that the estimate of ultimate settlement from the U50% and U90% is more accurate than the conventional inverse slope approach of the hyperbolic method, especially for data between the 50% and 90% consolidation points. This finding is demonstrated by applying it to a well-documented case history of the long-term full-scale loading tests at Ska-Edeby, Sweden.