Numerical modelling of soft ground improvement by vacuum preloading considering the varying coefficient of permeability

Increasing the accuracy of numerical prediction of vacuum preloading methods is very urgent to the geotechnical design engineers. This paper describes the application of the finite element program method incorporating the varying coefficient of permeability with changes in suction (like the variation of permeability in unsaturated soil) to increasing the accuracy of numerical prediction of an axisymmetric single vacuum well point and one case history with prefabricated vertical drains combined with vacuum preloading. The axisymmetric single vacuum well point was modeled using four numerical models: Model 1 with the hydraulic permeability of saturated soil, Model 2 with a thin layer of unsaturated elements activated at the vacuum well boundary, Mode 3 where hydraulic conductivity function was defined as permeability of unsaturated soil, Model 4 where vacuum pressure value remained a constant along the vacuum well drain. Afterward, the case history was modeled using two numerical models: one was created to verify input parameters, and the other was with the application of the varying coefficient of permeability with changes in suction. The results obtained by comparing all the numerical models data with the measured data indicate that the proposed method improved the accuracy of numerical prediction and using the exact distribution of vacuum pressure value or constant vacuum pressure value along the vacuum wellpoint did not make a significant difference in the numerical prediction in the case of shallow vacuum wellpoint. © 2016 Informa UK Limited, trading as Taylor & Francis Group.