Optimal hydraulic design of barrage considering the challenges of the presence of collapsible soil

This study aims to find the solution to the optimization problem for the safe and, eventually, the most cost-effective hydraulic design of the barrage laid on gypsiferous soil foundation. The proposed barrage section is with upstream and downstream sheet piles, as well as to an inverted filter provided at the end of the barrage. A multi-objectives optimization problem for the optimal hydraulic design in this study considers minimizing the cost of the barrage construction by minimizing the total volume of construction material in addition to minimizing the seepage flux beneath its floor foundation. The objective function for minimum cost was computed from the volume of the barrage floor, and the objective function for minimum seepage flux underneath barrage was computed by proposed multiple non-linear models. These objective functions are subject to constraints to preserve a safe exit gradient; the uplift pressures exerted by seepage; and the hydraulic adequacy of stilling basin length. All dimensions of the barrage were converted to non-dimensional form to facilitate solving the optimization problem by dividing on high flood head H_F._h to obtain a dimensionless parameter. The optimization problem was solved using the Genetic Algorithm (GA) with MATLAB software R2015a, and with different population sizes of 200, 600, 1000, and 1400. The results indicated that a population size of 600 was sufficient to provide a satisfactory solution for the constrained nonlinear optimization problem of the optimal hydraulic design in which it gives minimum construction volume (4.9341), and seepage flux (0.0021) in non-dimensional state. Finely the results are introduced as design charts and all details are present in this paper.