Study On Static Dissolution-dynamic Dissolution Characteristics Of Rock Salt And Fluid Transportation Mechanism In Solution Mining Cavern

Owing to the need of national energy security and strategic reserve, along with the growing demand for nuclear waste storage, the basic research of rock salt has become one of the hot topics in geotechnical engineering in recent years. In view of this, based on national 973 project and other scientific research projects, this paper would use a combination method including theoretical derivation, indoor testing research and numerical simulation to study the dissolution characteristics of rock salt(static dissolution model under different influence factors, dynamic dissolution model at different flow rates, and the dynamic dissolution model under gravitational effect), and the numerical solution and analysis of rock salt fluid transportation. The main research work and achievements of this paper were as follows:① According to calculating the concentration of water-salt solution, a constant differential equation was established. On the basis of this, static dissolution models of rock salt under three conditions were derived, including different dissolution areas, different solution concentration and different solution temperature, whose corresponding analytic solutions were solved. Analytic solutions were used to fit the dissolution experimental data of other researchers, and explained conclusions of static dissolution test in terms of the theoretical point of view.② Apparatus were custom-designed to test the dynamic dissolution process for rock salt samples at different flow rates, and obtained the dynamic dissolution test characteristics and change rule for different flow rates at different time. Apparatus were also designed to test the dynamic dissolution process for rock salt samples under gravitational effect, in which obtained the dynamic dissolution test characteristics and change rule for different flow rates at different time under the effect of gravity.③ Based on the dissolution characteristics of rock salt, being simplified and hypothesized the dynamic dissolving process of rock salt, combined conditions between dissolution effect and seepage effect in establishing a dynamic dissolution model of rock salt for different flow rates. Then, utilized finite-difference method to find the numerical solution of the dynamic dissolution model. Particle Swarm Optimization algorithm(PSO) was introduced to conduct parameters inversion on the established model, whose calculation results agreed with the experimental result, indicating the dynamic dissolution model of rock salt established in this paper can describe the dynamic dissolution mechanism of rock salt well.④ According to the dissolution characteristics of rock salt, rock salt dynamic dissolution process under gravitational effect was assumed and simplified. Based on this, after analyzing the influence of different parameters on the dissolution model, a linear relationship between D/δ and flow velocity was proposed. Using finite difference method, a numerical solution of the rock salt dynamic dissolution model under gravity was numerically solved, and parameters of the model were inversed, whose results agreed with the experimental results.⑤ The mathematical model and numerical solution of fluid transportation and dissolution process of rock salt was introduced. A difference scheme of two dimensional convection diffusion equations was established by means of exponential transformation. A two dimensional incompressible Navier-Stokes equation was discretized by using a multigrid method, a SIMPLE algorithm and a three order upwind type. Numerical experiments were carried out using above methods, whose results were close to others’ results according to comparing, which verified the reliability of above numerical methods.⑥ Numerical simulation of fluid transportation process was studied by establishing a mathematical model of fluid transportation, and corresponding influence factors of fluid transportation were deeply discussed and studied. Then combined with the test results of this paper, numerical study on the two cases of static dissolution and dynamic solution were simulated, whose simulation results proved the analytic solution of static dissolution model and dynamic dissolution test result.