A multi-objective optimal method for polymer cut-off wall of earth dam based on response surface methodology and desirability function analysis

Polymer cut -off wall (PCOW) technology as a new -type reinforcement technology has been widely used in medium and small-sized earth dams. However, the density and thickness of the PCOW of earth dams are usually determined based on engineering experience. In order to establish a design method for the density and thickness of PCOW, a multi-objective optimal method based on response surface methodology (RSM) and desirability function analysis is proposed. In the framework of the proposed method, the density and thickness of PCOW are selected as the influence factors; the maximum horizontal gap length and the maximum vertical displacement difference are selected as the response values for deformation index; the maximum Mises stress of the PCOW and the stability coefficient of the earth dam slope are selected as the response values for strength index; the construction cost of the PCOW is selected as the response values for economic index. Then, nine experiments are designed using the central composite design, and response surface function models are constructed for each response value. The optimal problem of the PCOW with five response values is solved by using desirability function analysis. The weight of each response value is determined based on the possible failure mode during the dam operation period. An earth dam with height 15 m is taken as an example, the optimal density and thicknesses of the PCOW are 2.29 cm and 0.3 g/cm3 under strength failure mode, 2.15 cm and 0.29 g/cm3 under deformation failure mode. The proposed method comprehensively considers the control indexes such as deformation, strength and economy and provides an effective method for the optimal design of PCOW.