Numerical evaluation of embankment partition wall reinforced by PVD–DMM in Matarbari

This study presents a novel ground improvement approach combining the deep mixing method (DMM) and prefabricated vertical drains (PVDs) with surcharge preloading to reinforce soft coastal soil beneath an embankment partition wall constructed to contain leachate migration from an ash pond and prevent environmental pollution. In the proposed configuration, deep mixing columns (DMCs) were installed along the outer edges of the wall, with PVDs placed internally at a particular spacing to accelerate consolidation, including a geotextile layer at a particular height of the wall. This integrated system aims to improve the foundation performance while ensuring long-term containment stability, leachate migration, and excessive settlement and embankment stability. Field evaluation was conducted along a 558 m-long embankment partition wall. Geotechnical investigations, such as SPT, cone penetration test, and VST, and laboratory testing, including field settlement, slope instability, and pore pressure monitoring, have confirmed notable improvements in soil behaviour. Three-dimensional numerical analyses were performed for the combined DMC–PVD, including geotextile reinforcement, to assess their influences on the composite foundation system. The numerical analysis results closely matched the field settlement and lateral displacement but some discrepancies have been observed in the excess pore water pressure. A rigorous sensitivity analyses have been performed. The analysis also revealed that the combined ground improvement method significantly reduced settlement and lateral deformation, enhanced soil arching, and improved the bending resistance of DMCs.