Two effective parameters in determining the length of reinforcements in the reinforced soil slopes are, the one, the length of reinforcement located in the active zone till to the location of failure surface and the second, the length of reinforcement located after the failure surface. Generally, the first one is calculated based on the angle of failure wedge by Rankin method. In this method the effect of reinforcement on the location of failure surface is ignored, while the presence of reinforcement is effective.In order to assess the location of the failure suface, the horizontal slice method based on Spencer assumption is used. In this method, slippery mass with the presence of reinforces is divided into a number of horizontal slices parallel to reinforcement direction. Inter-slice forces are computed by using Spencer basic rules. Earthquake load is affected on the center of each slice by horizontal and vertical pseudo-static coefficients. In the presented method, unlike the other existing methods, all of the critical slip surfaces are examined and are reinforced. In this paper, Genetic Algorithm (GA) optimization method is used to optimize the objective function for the produced non-circular slip surface of each horizontal for the safety factor of one. By comparing the results of Genetic Algorithm optimization approach introduced in this research with the results of the other investigators for the same geometry, material properties and loadings of the slopes it is indicated that the introduced and utilized method is more critical for the estimation of the length of reinforcements and the design of reinforcements with the proposed method is more reliable.
