Numeric Hydro-Geo-Chemical Modeling Of Dam Foundation Ageing

Dam ageing is one of the main causes of various abnormal problems and even accidents occurred in many dams. Presently, the research on dam ageing is mainly focused on the ageing of dam concrete and metal structures, however there is a lock of systematic research, especially quantitative research, on dam foundation ageing. Due to this reason, aiming at the numerical simulation of dam foundation ageing, the following studies are carried out in this paper:1. Through generalizing various abnormal problems and accidents occurred in dams, the concept and nature of dam foundation ageing are summarized; From the point of different aspects, the necessity and significance of systematic research on dam foundation ageing are emphasized; The present status, existing questions and trends of dam foundation ageing research are set forth; The scope, aim and study line of dam foundation ageing research are brought forward, according to the effect of mechanical and chemical processes (which are arose from the stress, water and chemical environment changing after construction of the dam) to the dam foundation material properties.2. From the point of hydro-geochemistry, various adverse engineering problems arose from dam foundation ageing are detailedly classified and profoundly discussed; The hydro-geochemical process of dam foundation ageing are clarified; Equilibrium and kinetic formulation methods of chemical reactions in the dam foundation water-rock interaction system are put forward, and their advantages, disadvantages and the Local Equilibrium Condition required for the equilibrium formulation are discussed; The numeric Hydro-Geo-Chemical modeling system of dam foundation ageing are established, and main ideas, principles, advantages, disadvantages and applicability of Inverse, forward and coupled hydro-geo-chemical models in the system are discussed in detail.3. The inverse model for dam foundation ageing is established by using mole balance and charge balance equations; By using Barrodale—Roberts algorithm, numerical solution to the model is performed; Applying the model to the ageing status analyses of Xin an Jiang Dam foundation, satisfactory results are obtained.4. The forward model for dam foundation ageing is established by using mass action, mole balance and charge balance equations; By the incorporated using of Newton—Raphson and Barrodale—Roberts algorithms, numericalsolution to the model is performed; Applying the model to the temperature dependency analyses of grout curtain ageing and status analyses of Three Gorges Dam foundation ageing, practicability and reliability of it are certified.5. Based on the real interaction modes between flow, transport and water-rock chemical reactions in the dam foundation ageing process, the coupled hydro-geo-chemical model for dam foundation ageing is established; Numerical solution to the model is performed by incorporated using of Finite Volume Difference method, iterative algorithm for linear equations, Newton — Raphson algorithm and Barrodale—Roberts algorithm; Applying the model to the 2-dimensional ageing analyze of a dam foundation, the ultimate target of comprehensive characterizing of dam foundation ageing process in space and time is achieved.