NUMERICAL SIMULATION OF THE EFFECT OF SEMI-PERMEABLE PROPERTIES OF CLAY ON THE VALUE OF CONCENTRATION JUMPS OF CONTAMINANTS IN A THIN GEOCHEMICAL BARRIER

The process of the distribution of chemical substances in an array of soil containing a thin clay geochemical barrier is considered. Due to the physico-chemical characteristics, clay possesses properties of semi-permeable membranes which is expressed numerically in the ideality coefficient (of clay). The research which experimentally shows the dependence of the ideality coefficient of clay inclusions on moisture and on salt concentration has been analyzed. The dependences that were taken into account under modified conjugation conditions for the concentration of chemical substances and pressure in case of incomplete saturation are given. The conjugation conditions are an integral part of the mathematical model of salt-moisture transfer in the case of heterogeneity of porous media and the presence of thin inclusions differing in their filtration and physico-chemical characteristics from the principal material of the porous medium. The numerical solution of a corresponding non-linear boundary value problem with modified conjugation conditions was found by the finite element method. The schematic algorithm for the software realization of the search for approximate solutions is described. The differences in the value of the concentration of chemical substances for a classical case and the test model case are considered in the article.