Effect of deformation of prefabricated vertical drains on discharge capacity

The effects of deformation on PVD discharge capacity remain discrepant among investigators. This study investigates the discharge capacity behavior of deformed PVDs using a laboratory performance test. Four different PVDs were tested, and two different soils were used for confinement. The reduction of the discharge capacity of PVDs varied with the type of PVD and percentage settlement, and reached up to 99% at a maximum percentage settlement of 41%. Hydraulic gradient also appreciably affects discharge capacity, owing to the non-steady-state flow in the core of the PVD. Soil type impacts on the deformation pattern of PVDs, but its effect on discharge capacity appears to be slight in this study. Soil type, however, has a significant influence on required discharge capacity. For a 20 m long drain in example calculations, one of the PVDs would result in restriction of water flow and cause significant increases in time for consolidation. Additionally, if soils with a higher hydraulic conductivity, such as 1 x 10(-8) m/s occur at a site, significant increases in consolidation time could occur at percentage settlements in excess of approximately 30% for all drains tested.