Energy-Work-Based Confined-Unconfined Seepage Modeling Using Numerical Manifold Method

Wang, Yuan (College of Civil and Transportation Engineering and Hohai University and Lawrence Berkeley National Laboratory (LBNL) ) | Hu, Mengsu (College of Civil and Transportation Engineering and Hohai University and Lawrence Berkeley National Laboratory (LBNL)) | Rutqvist, Jonny (Lawrence Berkeley National Laboratory (LBNL))

OnePetro 

Abstract: In this paper we present developments and applications of a new code for confined-unconfined seepage analysis based on the Numerical Manifold Method (NMM). We approach the problem using an energy-work-based seepage model which provides a clear definition and physical meaning of the seepage energy terms when assembling the governing equations. A unique feature of our approach is that it enables the application of the NMM to non-homogenous seepage analysis, based on our pipe model analogous to the penalty spring commonly applied in mechanical analysis. We verified the proposed model and the NMM code by comparison of our simulation results to analytical solutions for confined seepage and to available numerical models for a number of unconfined fluid flow examples, including a case with non-homogeneous material domain. We show that NMM, based on a two-cover-mesh system, can in the case of unconfined seepage achieve high accuracy and convergence speed with rather coarse meshes and without the need for remeshing as the phreatic surface changes.