Three-dimensional numerical modelling of soft ground improved by prefabricated vertical drains

摘要

ABSTRACT: A prefabricated vertical drain (PVD)-improved ground under embankment surchargenloading at the Second Bangkok International Airport was modelled using a three-dimensional finitendifference program and proposed matching schemes. The matching schemes used an equivalent wellnradius and an equivalent permeability to account for the cross-section of band-shaped drains andnthe smear effect, respectively. The well resistance of the PVD was taken into account by imposingna finite discharge capacity throughout the consolidation process. The numerical methodnincorporating the matching schemes satisfactorily simulated the drainage behaviour of the PVD unitncell and of the full-scale PVD improved ground. The three-dimensional numerical modelling alsonshowed that the degree of consolidation of the PVD-improved ground in terms of settlement ratenwas higher than that in terms of excess pore pressure dissipation rate. In addition, after the PVDnimprovement, the undrained shear strength of the clay layers below the centre of the embankmentnwas numerically estimated to be approximately twice the value before the improvement.