RURAL DEVELOPMENT DEPARTMENT PROVIDING AMBULANCE ROADS TO LOCAL STRETCHES WHERE (PMGSY) COULD NOT BE AVAILABLE MUST HAVE MINIMUM MODULUS OF SUBGRADE REACTION, UNDER SURFACE.

Rural development department is doing development through road net work for the villages and sub villages where the PMGSY is not being constructed by the department of HPPWD , as people are compelling to their representatives for doing  needful under the provision made by the RD department, but it is regretted to point the various shortcomings in the said road net work connectivity where curves are not properly designed and grades of the roads are not being maintained ruling gradients more over there is no appropriate provision of the cross drainage works in said roads of the emergency duty declared as the Ambulance roads. As for the road pavement is concerned the department of Rural development maintaining Ambulance roads as concrete roads, where it is very necessary to have good solid foundation of well consolidated and non -absorptive materials under the concrete road and a concrete slab, being a rigid type of construction, however loose boulder stones are laid on the road surface, liable to crack over a yielding and flexible base when loaded. The load carrying capacity of a concrete road structure lies mainly in the structural rigidity of the slab and the uniformity of the subgrade support. It is therefore necessary to prepare the base in such a way that the concrete slabs are supported as uniformly as possible. Subgrade failure is a common cause of cracking and subsequent tilting or disruption of the slabs. As such base, sub base, or subgrade together act as a unit for supporting the concrete pavement, where it is necessary to follow the foundation under concrete pavement. The width of the base should project out at least 30 cm beyond the proposed edge of the concrete slab if kerbs are not set on the slabs. The base under the concrete pavement must be properly levelled, hollow patches filled up and consolidated with hard core, cambered and cross falls or longitudinal slopes must be given and there should be no soft spots present either in the base or the subgrade. For concrete pavement the minimum modulus of subgrade reaction of the under surface obtained with a plate bearing test should be 5.5 kg /cu.cm, where the type of the soil in the formation of the road is of this quality, no intermediate sub grade need be provided. The top 15 cm should be thoroughly compacted at the minimum moisture content to the exact profile of the road. Where the natural subgrade is weak but it doesn't consist of highly expansive soil, such as black cotton soil, the thickness of the consolidated base need not be more than 15 cm. Where lime -puzzolana concrete or lean concrete is proposed to be used, the thickness then may be only 10 cm. 10 cm thick concrete slabs laid over 15 cm well consolidated existing WBM crust have been found adequate to stand an axle load of 8100 kg or single wheel load of 4100 kg, as the case may be:-- Er Fateh Chand Guleria, RTI welfare Association registered number HPCD 3552 Bilaspur Himachal pradesh phone number 9459334377