Capillary Cut-off

When there are certain chances for the water to reach the level of subgrade and sometimes, ingress into the subgrade layer due to the “capillary action”, so it becomes important to cut this action of capillary rise by providing “capillary cut-off” between the subgrade layer and the topmost layer of the water table.

In other words, it can also be said that the capillary cut-off is usually required at the locations where the soil has the potential for rapid and high migration of moisture “by capillarity action”. 

The capillary cutoff can be in the form of granular layer, coarse or fine sand layer and it can be extended across the full width of the embankment. 

In case the “sand side” needs to be protected then it can be done by placing the filter of graded granular material.

Other material that can be used for capillary cutoff are bituminous impregnation, bituminous stabilized soil, Geo-composite layer, and stabilized soil layer 

·      In case of capillary cutoff, the thickness of – 

Ø Fine sand = 300-350 mm 

Ø Coarse sand and gravel = Minimum 150 mm

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