Development of Hybrid Material as Drainage Media and Efficiency Comparison of Various Vertical Drains

Abstract

Vertical drains are extensively used for ground improvement in order to accelerate the consolidation settlement of soft clay deposits. In the case of very soft clay, if sand/aggregate alone is provided, the diameter of the well can be reduced due to necking action and clogging. In order to reduce these effects and increase strength and properties of drainage media, a hybrid mix is developed through experimental model studies. A major limitation of displacement vertical drains is generation of a smeared zone, leading to lower capabilities. This disadvantage could be reduced by penetration of intrusion material in the smeared zone during a second driving at the same point. Efficiency of sand piles with a single or double driving, optimum hybrid mix with a single or double driving, and prefabricated vertical drains is studied by assessing the behavior in the laboratory using large-scale model bed tanks. From the results, it is found that double-driven piles with the hybrid mix show better performance compared with other vertical drains and can be effectively used for ground improvement in very soft clays.