Settlement analysis of prefabricated vertical drain by finite element analysis for treated road embankment

Abstract

Prefabricated vertical drains with incorporated with preloading has been used widely as a ground improvement technique in geotechnical engineering. Prefabricated vertical drains would be essential to speed up the settlement of subsoil in embankment and soft ground construction. The prediction in the embankment settlement is a critically important issue for serviceability of road, especially the pre-construction settlement. In this study, Finite Element Analysis was done for analysing viability of PVD modelling in subsoil using Plaxis 2D 2016 software. Asaoka’s method were used to analyse the field monitoring data that was gathered at a location of an embankments. This method is used to determine ultimate settlement and back calculated coefficient for the horizontal consolidation at a certain location of the embankments. The settlement prediction and the actual measurement at a case study in terms of time to reach 90% consolidation were compared with the field instrumentation results in order to verify the design approach used. Subsequently, the effect of smear disturbance was considered in the parametric study. Various equivalent diameter of influence zone of the PVD are simulated in the modelling of embankment to study the effect of consolidation degree to the drain spacing. Based on the performed analysis, the installation of PVD is proved to improve the rate of settlement and the dissipation of pore water pressures. The rate of settlement decreases as the smear disturbance and drain spacing increase. Modelling of PVD with smear ratio kh/ks of 6.0 and drain spacing of 1.0 m shows good agreement with the field measurement.