Improving the Stability of High Embankments Founded on Soft Marine Clay by Utilizing Prefabricated Vertical Drains and Controlling the Pace of Construction

In many cities worldwide, the development of sites underlain by thick deposits of soft marine clay has become more common to meet the demand for essential transportation infrastructure arising from the current unprecedented urban population growth. Staged construction and ground improvement techniques are two approaches frequently used in constructing high embankments over soft soils. These approaches improve stability, ensuring that the pace of construction does not cause a build-up of excess pore water pressures and an associated reduction in shear strength, which could lead to progressive failure. This study examines the use of prefabricated vertical drains (PVDs) and the pace and sequence of construction, to determine the most suitable method for constructing high embankments on soft soil deposits. The problem was modelled using a Finite Element software called PLAXIS 2D, in which the PVD is available as pre-coded drainage line elements. The modelling was carried out with a staged construction technique. The analyses considered PVD spacing ranging from 1 to 2.5 m, with PVDs extending to the crest, to the toe, or beyond the toe of the embankment. The fill layer thickness and the consolidation time following the placement of each layer were also varied to study the effect of these parameters on overall stability. The results obtained from this study show that PVDs can significantly improve the stability of embankments when combined with an appropriate consolidation time for a faster construction pace.