Solution methods of hydraulic conductivity in low permeable saturated soil during liquid releasing

Solution methods of hydrogeological parameters in saturated zones for certain geological behaviors have been presented in many studies. Traditional solution methods of hydrogeological parameters, such as hydraulic conductivity and storage coefficient, were acquired by in situ hydrogeological experiment or seepage control equations. However, those two methods obtain a constant value of hydrogeological parameters which is not very suitable in practical cases. This study assumes that hydrogeological parameters to be a variable value because the properties of soil were changed during liquid releasing. An analytical solution for liquid releasing from saturated soil was deduced based on the existing seepage control equation, and the analytical value of hydrogeological parameters was obtained. Moreover, analytical expression for hydraulic conductivity was developed, and variable hydraulic conductivity was gained by analyzing flow quantity during seepage. Different calculation methods were used to get constant and variable conductivity coefficient, respectively. A laboratorial test model of saturated soil under designed conditions was also established to verify the analytical solutions of both constant and variable parameters by fitting the calculated value and measured value curve. Seepage tests and case studies showed that variable hydraulic conductivity value presents higher agreement with the measured data for flux versus time than constant hydraulic conductivity. In order to prove the fact that variable parameter is more reasonable in real cases, we also conducted a group of comparative tests by rising and falling the hydraulic head of seepage model in three periods. Three different hydraulic conductivities were obtained, and then they were substituted to seepage equation for the sake of curve fitting. The correlation coefficient between measured flow versus time curve (obtained from hydraulic conductivity vs. time curve) and calculated flow versus time curve is higher than flow versus time obtained from hydraulic conductivity versus periods. Solution methods suggested in this paper are generally applicable to problems involving the hydraulic conductivity, specific storage and other related hydrogeological parameters calculation of low permeable saturated soil.