DRAINAGE ASPECTS IN ROAD MAINTENANCE

Adequate drainage enables the road to be used in all types of weather and prevents damage to the road pavement, embankments and structures. The author discusses the various important aspects of the installation and maintenance of subsoil and surface water drainage. Sub-soil drainage is very important in soils which rapidly lose their shearing strength with increased water contact. The positioning of side drains, under drains is discussed. Surface water drainage is effected by the amount of crossfall; impervious bituminous or concrete pavements are given a two per cent crossfall, water bound macadam and gravel surfaces three per cent and unpaved surfaces four per cent. Factors affecting the design of side ditches and drainage channels are examined. Special recommendations are given for the drainage of ghat roads and roads in urban systems. Catch drains, side drains, drains in curves, drains in bridges as well as underdrains and interceptor drains are used for ghat roads. Urban roads require suitable underground drainage systems. (TRRL)