Slope stabilisation of railway embankments over loose subgrades using deep-mixed columns

Abstract

An investigation was undertaken into the stability of railway embankment slopes over soft subgrades stabilised by deep-mixed columns (DMCs). Three 1 : 10 scale laboratory embankments were constructed over unreinforced and reinforced subgrade with DMCs in square and triangle patterns. The load–settlement responses of both embankments and columns were measured. The laboratory embankments were then mathematically modelled and the results were compared. After validation, a comprehensive parametric study was carried out to evaluate the factor of safety (FoS) of the embankment side slopes against sliding. Five embankment soil types from poor to high strength, three heights from 1.5 to 10 m and various DMC improvement area ratios from 0 to 65% were considered. The experimental outcomes indicated an increase of nearly 63% in the bearing capacity of both DMC-supported embankments compared with the unreinforced one. Regarding the parametric study, a minimum required FoS of 1.5 was observed for 1.5 m embankments of all soil types stabilised with a 60% improvement ratio. The greatest safety increase was associated with a 1.5 m height embankment with poor soil type, which showed a 36% increase.