Design Optimization of Underground RCC Tanks Governed by Hydrostatic Uplift

Depth of underground tanks in reinforced concrete used for collection of water or other liquids by gravity is in principle governed by invert level of inlet. Depending on process requirements, supply to the tank could be either through open drains as in the case of settling ponds or through pipes which convey sludge into these tanks. Where freeboard height is relatively more than liquid depth, overall depth of the tank increases considerably as compared to the actual storage capacity required. Owing to this increase in depth below ground level, stability of the tank against uplift turns out to be critical for design if ground water table must be considered up to ground level. The following discussion explores a design alternative which is quite easier, when site conditions do not suit use of traditional under-reamed piles. This concept had been adopted in coal based thermal power plants engineered and executed.