Vertical Sand Drains for Performance Enhancement of Loose Unsaturated Soils: A Sustainable Solution

Rapid urbanization requires swift infrastructure development, often prioritizing flat areas while leaving behind undulating terrain due to expensive and slow activities required for their preparation. In Pakistan, suburban flat agricultural lands are converted into residential and commercial zones but as demand grows, the undulating areas are levelled hastily sometimes leading to inadequate or no compaction. This study aims to enhance the performance of such loose unsaturated soils by introducing moisture using Vertical Sand Drains (VSDs) in a regulated manner to achieve maximum pre-construction settlement along with shear strength quickly and cost effectively. Simulating freshly levelled areas, indigenous soil was subjected to rigorous testing in an uncompacted and unsaturated state against static loading of self-weight and surcharge to observe the effect of VSDs at various moisture contents. Better moisture distribution and more cumulative settlements were observed when VSDs were used. Maximum enhancement in shear strength was observed when 16-17% moisture content was achieved in the soil mass. Shear strength and cumulative soil settlement increased to 82% and 135.7% respectively when VSDs were used along with surcharge loading. The findings of this study will help in preparing unused lands for infrastructure development on a macro scale rapidly and economically for efficient land usage and thus development of compact and sustainable cities.