Numerical modeling of vacuum preloading and field applications

This study describes the effect of unsaturation at a drain boundary on the behaviour of a single prefabricated vertical drain subjected to vacuum preloading based on a two-dimensional plane strain finite element model incorporat- ing the modified Cam-Clay model. Unsaturation of soil adjacent to the drain can occur due to mandrel withdrawal or application of vacuum pressure through prefabricated vertical band drains (PVDs). Following initial laboratory simula- tion in a large-scale radial drainage consolidometer, the authors have attempted to explain the observed retardation of pore pressure dissipation through a series of models, which consider the effect of unsaturation at the drain-soil inter- face. The results indicate that the introduction of an unsaturated soil layer adjacent to a PVD improves the accuracy of numerical predictions. Lastly, a multidrain analysis is conducted to study the behaviour of an embankment stabilized with vertical drains subjected to vacuum preloading, and the field measurements are compared with a series of numeri- cal model predictions.