Surcharge loading rate for minimizing lateral displacement of PVD improved deposit with vacuum pressure

A series of laboratory radial drainage odometer and triaxial tests were conducted to investigate the deformation behaviour of clayey soils under combined vacuum pressure and surcharge loads. Based on the test results, a method for determining the optimum surcharge loading rate (SLR) which will result in minimum lateral displacement of a deposit under combined loads has been proposed. The method using a dimensionless parameter, α, defined as the ratio of SLR and the parameters controlling the rate of consolidation of a deposit improved by prefabricated vertical drains (PVDs). The ratio between surcharge load (Δσs) to the vacuum pressure (Δσvac) is designated as (LR=Δσs/|Δσvac|)(LR=Δσs/|Δσvac|). Values for the optimum SLR increase with increasing of initial effective stress in the soil and with reducing LR. It is suggested that the method can be used for design the preloading project with combined vacuum and surcharge loads.