Water can percolate to the formation of the track through any of the following methods.
By gravity This includes water that collects due to rains, etc., moving into the subgrade because of the effect of gravity. This movement is resisted by the permeability of the soil. The effective ways of reducing the progress of water by this method are the following.
(a) Provision for drainage on the top of the embankment in the form of cross fall, side drains, lowering of cess, etc.
(b) Turfing of side slopes of the embankment.
By capillary action At times water rises into the subgrade by way of capillary action. The capillary rise of water can be prevented by providing a pervious layer in the embankment which serves a capillary break.
From adjacent areas In this case, water from some nearby source seeps into the subgrade. Water seepage can be reduced by taking the following steps.
(a) Diverting the original source of water
(b) Providing effective paved catch water drains
(c) Providing inverted filters and underground drains
By hydroscopic action from atmosphere The moisture present in the atmosphere is comparatively very small and has very little effect on the total moisture content of the soil.