Application of a genetic algorithm for the optimization of a cutoff wall under hydraulic structures

Abstract

A genetic algorithm (GA) model coupled with finite element modeling was developed here to find the optimal values of inclination angle and cutoff location for a hydraulic structure of a given cutoff depth to floor length ratio. The objective function to be minimized is the exit gradient function. The main constraint models are those that satisfy a factor of safety against uplift pressure which correspond with minimum floor thickness. More than 3500 different cases were modeled and analyzed using SEEP2D modeling. Statistical Procedures for Social Sciences software was used to obtain a nonlinear regression model for estimating pressure head at nodal points and the exit gradients behind inclined cutoff walls for a given relative depth (d/b), relative location (b1/b) and angle of inclination (θ), using the data obtained from SEEP2D modeling. A Matlab code was used to perform a GA optimization modeling. The results indicated that the optimum location of cutoff is at upstream with an inclination angle from 59° to 68° for a (d/b) equal to or more than 0.4. For other relative depth values studied, the optimum location is at the last third of the concrete floor. The obtained optimum solutions were compared with the SEEP2D modeling to find the uplift pressure and exit gradient for the optimum solutions. Values estimated were found to be comparable to the obtained values from the GA model.