Seepage Analysis Based On Natural Element Method

According to the survey, the main reason of dam collapse is the seepage,so in-depth study of seepage is crucial. In the seepage problem, the flow withfree surface is a difficulty of study, because the changing free surface needs toiterate.This thesis uses natural element method for seepage analysis,supplyinga new thinking of seepage with free surface.Natural element method(NEM) is one of Meshless methods. Itscomputing is based on node information and the influence domain of judgingis based on Voronoi diagram and its dual Delaunay triangles.The computationof shape functions is based on natural neighbour(n-n) interpolation and it’sdivided into Sibson interpolation and non-Sibson interpolation. Thecomputation formula of these two methods is simple and with highcomputational accuracy. Because the influence domain of shape functions andintegral domain are not consistent,the integral error is unavoidable.According to combining the Sibson shape function and the flow balanceequations based on variational principles to solve algebraic equationgs andcalculate head, velocity, and flux of flow. This thesis introduces two kinds ofinterpolation and choose Sibson interpolation approach for the analysis ofseepage calculations. In order to ensure the normal computation of shapefunctions, this paper introduced some notices.Based on the above theory, develop a seepage analysis softwareNEMSEEP and introduce main subroutines, basic input parameters andjudgement criterion of convergence. According to parameter sensitivityanalysis,compare different stationing schemes and integral schemes how toeffect the calculation result. In order to reduce calculation error, choose Gaussintergral with seven guass points. Then we use this software to calculate thesteady seep and unsteady seep of rectangular dam, and solve the steadyseepage problems of dam with slanted face, and dam of anisotropic materials.The calculation results show that the natural element method has high efficiency and high precision, combing the advantages of finite elementmethod and other meshless methods. Finally, through the analysis the coredam of project Nuozhadu, supply the calculated head contours of steady seepand provide the basis for project desigh and safety assessment.