The Research Of Seepage Flow Through Dam Based On The Distributions Of Waterhead And Saturation

Seepage flow is a motion law that exists in porous media impersonally.It has important effects for the stability of water conservancy building,the using of groundwater resource,the pollution controlling,the exploitation of rock oil and natural gas.And the needs of projects for those fields are increasing home and abroad.So the research of seepage flow becomes focuse.In this article,a saturated and unsaturated seepage model has been established which includes double variables:piezometric tube waterhead and saturation.The model theory bases on the saturated theory and unsaturated theory.The form of Darcy velocity is changed according to the production of unsaturated hydraulic conductivity in the model.The seepage field was divided into two regions:saturation and unsaturation.The saturation equals 1 in saturated region.The piezometric tube waterhead equals position head by neglecting the effect of capillarity in unsaturated region.So the nonlinear parabolic equation of seepage flow will degenerate to Laplace equation about piezometric tube waterhead in saturated region and convective equation about saturation in unsaturated region respectively.The equations are discretized with the Galerkin FEM in space and the implicit difference method in time.And the equations are solved coupling iteratively whith PCG method for Laplace equation and Gauss—Seidel method for convective equation.So the distribution of piezometric tube waterhead and saturation can be obtained.And the seepace free surface will be captured automatically according to the distribution of saturation with the concept of VOF.An experiment of unsteady seepage flow through dam is done in laboratory.In the experiment,the changes of seepage surface and pressure head in dam are mensurated.By analyzing the result of experiment,the characteristic of physicsdynam is gotten for unsteady seepage flow with movement boundary on staunch groundwork.Three analytical solutions are given including the wet front analysis solution of double medium soil column,the analytical expression of piezometric tube water head and saturation for steady state and the analysis solution of seepage in unconfined aquifer with a periodic boundary condition.The problems of analysis and experiment are modeling by the seepage model that presented in this paper.The dependability and accuracy of model are proved by comparing with the analytical solutions and experiments results. The model is used to count several engineering example.Comparing the 2D numerical results with electrical simulations,it is proved that the seepage model can count the seepage surface and the location of search results in dam well and truly.Comparing 3D results with 2D results at close section,the results are tally well except the difference of meshes and the interceptive position of section.So the model is credible and has upper practicality value.In the projects,the spending of account is increasing because of the bigger account field.In this article,the seepage field is parallelly solved rapidly by changing serial program to parallel program with OpenMP API.It was proved that the parallel result is reliability and accuracy by comparing the results of 3D and 2D at close position.It is proved that the parallel program can account the seepage field well and rapidly by comparing the speedup of different scale.And the paralle program will do well in works.