A fast and robust numerical solution for the positioning design of horizontal drains in a saturated-unsaturated soil ground system

This paper proposes an implicit difference solution to design the position of the horizontal drain in a saturated-unsaturated soil ground system (SUSGS).A complete system of classic diffusion equations is used to describe the transient flow of air and water phases in the soil system.Consolidation equations and boundary conditions are discretized by using the Crack-Nicolson (C-N) and virtual grid methods, respectively.The numerical scheme has been verified to be unconditionally stable based on von Neumann's theorem.The comparison with existing analytical predictions confirms that the proposed solution is effective and accurate.According to the verified numerical solution, the optimum position of horizontal drains is designed to elevate the consolidation rate of the saturated-unsaturated soil ground system.