Stone Soling:
One of the early practices in road construction was to provide a stone soling 150-225 mm in thickness. The stones are laid by manual labour, and stone spalls are inserted and driven by hammer to fill up the voids. The layer is then rolled, applying blinding material such as sand, gravel, murram or screenings and watering. This specification is not practiced in India now because of the following disadvantages:
(a) It is practically impossible to fill up all voids. The voids left are then liable to be filled by the sub-grade soil working up. This will cause loss of strength when wet.
(b) There is no interlocking resistance because the stones are single size.