96. Combined Use of Geosynthetic Reinforcement and Prefabricated Vertical Drains (PVDs)

While there has been empirical evidence that the combination of reinforcement and PVDs can allow safe construction in circumstances where it would not otherwise have been possible, the paper by Li and Rowe (2001) provides theoretically based evidence of the significant synergistic effects of combining these two techniques for soil improvement. The paper presents a design method that allows design engineers to take account of these synergistic effects. This approach provides a means calculating consolidation during construction and incorporating the soil strength gain as part of the reinforcement design process. The design technique only requires hand or spreadsheet calculations to design the PVD system and assess the consolidation. The reinforcement design can then be conducted using existing limit equilibrium programs according to current practice. The Li and Rowe (2001) approach involves selecting a PVD spacing and then calculating the degree of consolidation at any time of interest. All assumptions of Terzaghi's consolidation theory are preserved except that the current approach considers both the change in compressibility as a soil moves from the overconsolidated to normally consolidated state and the time-dependent loading.