An Analytical Method for Estimating Hydraulic Parameters of a Nonlinear Consolidated Aquitard Considering Secondary Consolidation

Abstract

The estimation of groundwater released from aquitards is important for the groundwater resources assessment and disaster prevention. In this study, a mathematical model for water release from a nonlinear consolidated aquitard was established considering that the change of the void ratio is caused by effective stress and creep effect, and the corresponding analytical solutions for water release were derived while the water level in adjacent aquifers decreases. The analysis results utilizing the analytical solution show that, with the development of consolidation, the contribution of secondary consolidation to total consolidation continuously increases and dominates during the latter stage of consolidation, where the increase in thickness of aquitards and the decrease in consolidation coefficient postponed this stage. Based on this property, a quantitative method to calculate the completion time of primary consolidation and a new multi-parameter inversion method for calculating hydraulic parameters and coefficient of secondary consolidation were proposed. The consolidation test of aquitard under drawdown condition was conducted to prove the practicality and accuracy of the analytical solutions and parameter inversion methods. Compared with the traditional linear consolidation theory, the estimated water release from aquitards using the proposed non-linear analytical solution is in better agreement with experimental results. The estimated water release from aquitards without considering secondary consolidation apparently underestimated, especially during the latter stage of consolidation.