Comparison of performance of single- and double-core prefabricated vertical drains for thick reclaimed ground improvement

The performance of a double-core prefabricated vertical drain (PVD), which could reduce the well resistance via its large cross-sectional area and structural stability, was investigated experimentally and numerically. The double-core and the conventional single-core PVD, which has been widely adopted in reclaimed ground improvement, were compared in this study. In the experimental investigation, modified Delft tests and a calibration chamber test were carried out in a laboratory to determine the discharge capacities of the PVDs. Thereafter, single- and double-core PVDs were installed in the Busan New Port site, which had a 40 m thickness of clay deposit, and the performances of the PVDs estimated through surface settlements were compared. In addition, a numerical program named ILLICON was applied with field measurements, and a parametric study was conducted for different discharge capacities of the PVDs. The result of the laboratory tests and field measurements indicated that there was no difference in the performance between the two types of PVDs for improving the soft ground, considering actual ground conditions. Similarly, the parametric study results also implied that both PVDs could be satisfactorily applied in thick reclaimed ground, and there is no significant difference in the performance of single- and double-core PVDs.