Improvement of Soft Organic Clay Soil Using Vertical Drains

The design of foundations based on soft clay is still a very challenging problem. Three experimental cases were performed to examine the action of soft clay: the first case without drains, the second case with sand drains and the third case with prefabricated vertical drains (PVDs). Two-dimensional finite element analysis was carried out using PLAXIS 2D and its findings were compared to previous experimental results where good consistency was found. Parametric study was conducted with a variation in the size, length and diameter of sand drains. The length and spacing of the PVD, the diameter of the smear zone and the permeability of the smear zone were also studied. Results have shown that PVD is preferable to the improvement of soft clay rather than sand drainage systems. The sand drains decreased the time of 90% consolidation by (90.8%) using 50 cm diameter, 2 m spacing and 25 m length, and the PVDs decreased the time of 90% consolidation by (94.4%) using 4 mm × 10 cm dimensions, 2 m spacing and 25 m length. Both sand drains and PVD are effective in decreasing the consolidation time. The results of this paper concluded analytical formula that indicate the percentage of wick drain consolidation.