Wick Drains and Rock Fill Save the Day: A Case for Settlement and Stability Solutions

Greengate Mall was initially developed by placing up to 15 m (50 ft.) of fill. Construction of Greengate Super Center at the same site required additional 15 m (50 ft.) of new fill. The subsurface investigation and analysis indicated possibility of excessive long-term settlement. Wick drains and rock fill were used to solve settlement and time constraint problems and at the same time cut down the overall construction costs. Old concrete was crushed and used as porous blanket over wick drains. Nearby borrow site provided hard sandstone as new fill and a source of pavement base. Rock blasting required monitoring of adjacent dam, bridges, and other buildings. Under new fill the old fill settled by several centimeters (inches) and work was completed on schedule. Thoughtful engineering and careful construction planning saved valuable time and money. The Greengate Super Center and the rock fill embankment have performed well for the last six years with no obvious signs of stress.