Using an analytical solution of seepage discharge of rectangular and triangular blankets based on the Bennett model (1945), the thickness and the length of the blanket, which minimize the volume of the blanket on condition that the design seepage discharge is given, are derived as an optimum solution. Based on the decrease rate of the seepage discharge with the blanket length, it is shown that the optimum solution can be used as a design value. The optimum solution demonstrates the ratios of the optimum length, the optimum thickness and the minimum volume for triangular blanket to those for rectangular one become constant. It also shows that if the triangular blanket instead of rectangular one is employed, 31% of blanket material can be saved, keeping the same seepage discharge.
Using an analytical solution of seepage discharge of rectangular and triangular blankets proposed by Bennett (1946) and Yoshitake et al. (2011), respectively, the thickness and the length of the blanket which minimize the seepage discharge under given volume of blanket material are derived as optimum solutions and characteristics of them depending on the blanket volume are described. The results show the ratios of the optimum length and the optimum thickness for triangular blankets to those for rectangular ones are constant. The results also demonstrate that minimum seepage discharge through the optimum triangular blanket is always less than that through the optimum rectangular one under the same volume of the soil blanket.