Studies of Upstream Blankets for Control of Under Seepage in Earth Dams


Experimental investigations have been carried out into the efficiency of a blanket design in controlling under seepage. Also, accurate numerical method for the mathematical analysis of the blanket designs for efficiency are proposed. In the experimental investigations, use was made of a seepage tank model under steady flow regimes. The blanket design in each case Was constructed of clay. Five different design shapes are considered in the study. They are; rectangular, triangular and trapezoidal blanket shapes. Others are composite blanket shapes the first of which is the stepped-rectangular and lastly the rectangular trapezoidal blanket. The proposed empirical equations are obtained using Bessel’s functions of the first and second kinds respectively. The final equations are simple and can be readily used for design calculations. The theoretical results are tested against the experimental data, with accurate and physically plausible results. Both results show that the triangular blanket is more effective than the rest blanket design shapes.