Optimization of the Joint Structure Between Asphalt Concrete Core and Concrete Plinth in Earthen Dams Based on the Response Surface Method

The joint structure between the asphalt concrete core and the concrete plinth is a critical and vulnerable part of the asphalt concrete core dam (ACCD). Shape parameters of the core–plinth joint structure are directly related to joint structure behavior and thus affect the core safety, but there is currently a lack of relevant quantitative research. In this paper, the shape parameters of the joint structure were optimized to obtain an economical joint form under the condition of ensuring the stress safety of the joint structure. Abutment slope ratio i, core enlarged angle θ, and depth of the core embedding into the plinth h were taken as optimization parameters. The maximum shear stress, maximum tensile stress, and minimum arch effect of the core were taken as constraint conditions, and the joint structure volume was taken as the objective function to establish a mathematical optimization model for the joint structure. The regression relationship between the constraint conditions and the joint structure parameters was fitted based on the central composite design and response surface method. A three-dimensional zone of joint structure parameters that can satisfy the constraints was further constructed. Combined with the linear programming method, an optimization calculation method for joint structure parameters was proposed. Taking the dam with the highest core among the ACCDs that have been built as an engineering example, an optimization analysis of the joint structure between the core and plinth was conducted. The results indicated that the stress and the arch effect of the joint structure improve as the abutment slope becomes gentler. As h increases, the arch effect and shear stress at the joint weaken. The increase in θ will increase the possibility of core shear failure and make the core suffer a stronger arch effect. Compared with the original engineering (θ and h are 75.96° and 0.3 m, respectively), when the θ and h are set as 80° and 0.39 m, the joint structure volume reduces by 6.67% under the condition of i of 1:0.33, which can achieve better economic efficiency under the premise of satisfying the core safety.