Abstract
Abstract
Determining the uplift pressure at key points including the junctions of the floor and the cutoff wall beneath hydraulic structures and estimating the uplift force in these structures are vital issues in water engineering projects. The purpose of this study is to present a series of explicit and highly accurate formulas for determining these quantities for three different cutoff wall locations (at the upstream end, at intermediate locations, and the downstream end). In practice, the materials related to some types of cutoff walls may not be completely rigid due to their low permeability. In this study, the impact of permeability is incorporated into the analysis, and this is the novelty of this study. In order to include the effect of permeability, the capabilities of the SEEPW2D-numerical model that utilizes the FEM to solve the governing equations are used. After generating data sets, nonlinear regression equations are developed in order to estimate the uplift pressure at key points and the uplift force exerted on the hydraulic structures. To validate the results of the FEM, Khosla’s approach is used. Khosla’s solution is usable only for rigid cutoff walls, while proposed equations can be used for both impervious and pervious cutoff walls as an initial estimate in designs. Also, the results indicate that the decrease in the permeability of the cutoff wall is proportional to the value of the uplift pressure at the key points after the cutoff wall. This reduction is inversely related to the value of the uplift pressure at the key points before the cutoff wall. Accordingly, material that constitutes the cutoff wall has a great effect on seepage characteristics, and it is necessary to consider this in the analysis. Therefore, the permeability of the cutoff wall in any design should be selected depending on the case-specific conditions related to seepage and the stability of the structure.