AN ENGINEER IS CONCERNED WITH THE CRITICAL (OR DESIGN) INTENSITY FOR A CATCHMENT WHICH CAN OCCUR IN A GIVEN TIME.

It was an occasion today on 30-6-2023 when the inspection of Village road from Kathuin Chowk to Gujrehra was made by the department of public Works where in the cement concrete road has been started and the foundation under concrete pavement was prepared by the contractor and one layer of water bound macadam was laid by the construction agency however two layers of WBM has been described by the design & scope of the work before the final concrete pavement is laid over the water bound macadam surface.The junior Engineer of the department of public works and the Road supervisior of the area and circle were present at the site of work and penetrate the first course of laid water bound macadam to check the thickness of the first layer laid consequently at three places of the work of WBM .As such a good base has to be provided to form a working surface on clays ,silts and Sandy clay soils and the other weak soils,and also to provide a levelling course on roughly shaped formations.A layer of lean concrete may also be necessary on old macadam roads to re-shaping the surface.In such cases a base need only be thick enough to provide a smooth ,hard working face over the formation .The subgrade is prepared and checked at least two days in advance of concreting.The under layer should be in wet conditions but not muddy ,at the time of concrete is laid .If necessary,it may be saturated with water the night before or, not less than six hours ,not more than twenty hours in advance of placing the concrete.There is a proposal of the department of RDD to construct a hume pipe culvert for which the run -off from the drainage area required to be considered for deciding the maximum intensity that is likely to occur with in the duration which can occur in a time interval equal to the concentration time of the catchment area covered .The time to concentration depends upon the slope of the ground,distance to be travelled and the nature of the soil. An Engineer is concerned with the maximum rate of run -off and this occurs when the duration of the storm is equal to the time of concentration, because if the periods are short ,the whole of the watershed will not be contributing the water,and for longer durations the intensity of rain fall will be smaller.