Optimization of circular ground reservoirs

Abstract

Ground reservoirs of various types are often used as water storage reservoirs in major water supply schemes. Mainly there are two types of ground reservoirs viz. circular and rectangular. Circular type ground reservoirs are the most efficient reservoir form for enclosing space and at present these are widely used throughout the world. There are various types of structural forms available for circular type ground reservoirs; It is very important to select the most economical structural form and optimum wall height when designing a ground reservoir. Also it is necessary to have an idea about the cost of the structure as well. The main aim of conducting this research is to introduce a method to find the most economical structural form and optimum dimensions for a circular ground reservoir when the capacity is known. Circular ground reservoirs of different capacities were selected for the analysis and several structural forms were considered for each capacity. Different wall heights were considered for each capacity and structural form in order to find the optimum height for each case. In the case of domed circular reservoirs, in addition to the wall height, various roof angles, were also considered to find the optimum cost of the reservoir. Finally, variation of the cost with respect to capacity was obtained for each structural form. Similarly the variation of optimum tank height to diameter ratio with, respect to capacity for each structural form was also obtained. These relationships can be used to determine the most economical structural from, for a given capacity and also the cost of the reservoir. Once the economical structural form is selected, the optimum height of the reservoir can be decided based on the relationship developed for optimum tank height to diameter ratio with respect to capacity and this would be very much helpful to the designer when designing ground reservoirs. It was found that flat roof pinned type ground reservoirs are the most economical structural form for larger than 2000m3 and there is not much in cost for small capacities.