Influence of Multi-Structure Foundation on Evolution Law of Leakage Dissolution of Cutoff Wall

The change of permeability and thickness of deep overburden foundation would affect the seepage field of dam foundation, and then change the erosion evolution process of cutoff wall in dam foundation. In order to study the influence mechanism of multi-structure foundation change on leakage dissolution of cutoff wall, a coupling analysis model of seepage and corrosion of concrete cutoff wall in overburden foundation was proposed by combining fluid mechanics theory, chemical dynamics theory and convection-diffusion equation. The effects of thickness and permeability coefficient of strong permeable layer, weak permeable layer and third permeable layer on calcium ion concentration, porosity and seepage characteristics of cutoff wall were presented. The results show that, with the increase of service years, the calcium ion concentration of the cutoff wall increases rapidly to the peak at first, and then decreases continuously. The porosity and permeability coefficient increase exponentially, and the total seepage flow of the dam increases continuously. Among the influencing factors, the permeability coefficient of weak permeable layer has the greatest influence on the calcium ion concentration, porosity and total seepage flow of the cutoff wall, followed by the thickness and permeability coefficient of strong permeable layer. The service life of concrete cutoff wall under various conditions is from 38.46 a to 44.00 a. The research results can provide theoretical basis for the long-term service performance evaluation of earth-rock dams on multi-structure foundation with deep overburden.