In normal case, railway track is laid on ballast at formation level over blanket layer which rests on embankment. Strengthening layer of any cohesive material is provided on side slopes of embankment. Between blanket and embankment, there can be embankment sub-grade that would be of defined thickness and follows the required cross slope.
At places where formation level is very high because of design requirement that results in very high embankment. High embankment is achieved at site by providing side slope berms of specific widths at regular depth intervals say around 3 to 6 m. When strengthening layer/layers are provided, those should follow the side slopes with berms.