Three dimensional behaviour of an embankment on soft soils incorporating vertical drains is analysed by using the simple approach proposed by Chai et al. (2001). The method uses an equivalent vertical hydraulic conductivity to represent the drainage by PVDs. The method was applied to 3D numerical analyses of a benchmark embankment on soft soils incorporating PVDs, in combination with complex elasto-plastic models, namely Modified Cam Clay, S-CLAY1 and S-CLAY1S. For verification, the simulations were also compared to 3D multi-drain analyses of the same embankment. Based on these results, the method proposed by Chai et al. appears to be a useful tool for engineering practice.