Coupling Effect and Superposition Law in Soil Treatment Systems Incorporating Vacuum Preloading

In previous published literatures it was stated that superposition law might be valid for ground improvement techniques consisting of prefabricated vertical drains (PVDs) along with surcharge and vacuum preloading. Even some professional geotechnical engineers might think of this false idea that superposition law might be valid in such ground improvement techniques. It was shown that the superposition law is not valid because of the hydro-mechanical coupling interactions which exist between vacuum and surcharge preloading. A case history was presented and Finite Element Modeling (FEM) was used for verification and the demonstration of coupled consolidation interaction between vacuum and surcharge preloading. Three main parameters as settlement, lateral displacement, and water excess pore pressure were evaluated for different scenarios. The results that are based on a macro-element approach can be used for better comprehension of the working mechanism of combined treatment systems. Considering the results of this literature, a complex combined vacuum and surcharge preloading can be broken in simpler cases that can be used for either deriving analytical or empirical solutions.