SUB SOIL DRAINAGE AND MOISTURE CONTROL OF THE SUB GRADE IS AN ESSENTIAL FEATURE OF THE GOOD ROAD

The useful life of a road depends upon, the type of construction of road structure, intensity and nature of traffic, bearing capacity of the soil, climatic conditions and the maintenance. The sub-grade or formation and the pavement are the structural elements and the base may be surfaced either with a concrete or a bituminous surfacing. The surface of the natural ground, in its final shape after completion of earthwork on which the entire road structure rests, fails the performance of the whole road if it is not able to resist the after affects of both traffic and the weather. The base course is the major structural component of a road and is composed of stone aggregate well consolidated. The main consideration of a base are, its thickness, stability under traffic loads and resistance to weathering. The stability of the base depends upon its thickness and the thickness of the base construction is mainly a function of the strength of the sub grade and maximum wheel loads that are anticipated with the intensity of traffic. Good drainage system is required to protect the base of the road surface combined with the pavement. It must be realised that it is the sub grade which really carries the weight of the vehicles and that the function of the road surface (road structure) is merely to distribute that weight over a large area. If the sub grade is composed of unsuitable material, or if water has access to it, the earth underneath will move and the road surface will fail. As such the character of the sub grade has a great effect upon the stability of a road surface therefore a study of the soil structure is a very important factor. In hilly areas the land slides of the hill side of roads must have appropriate slope for the protection of land slides during the heavy rains which may obstruct the vehicular traffic during the rainy season , if proper slopes of cutting are not maintained . Sub soil drainage and moisture control may increase the strength of the sub soil. This effect of the moisture content is more marked in the case of clay soils than with granular soils such as sands and gravels so the control of the moisture content of the sub grade is an essential feature of a road surface:-- Er Fateh Chand Guleria, RTI welfare Association registered number HPCD, 3552 , Bilaspur Himachal Pradesh phone number 9459334377