The Numerical Method Of Modeling Non-Darcy Flow In Low Permeability Medium And Its Application

The seepage flow in the subsurface rock masses is the main factor influencing therunning of hydraulic engineering, and it is also one of very important topics in the design ofhydraulic engineering. Currently, the main concern of the researcher studying hydraulicengineering is the basic law and principle of the seepage flow in the subsurface rock, and aproper seepage flow model formulated is the base on judging whether the calculation of theseepage flow is accurate and valid. The characteristic of the low permeability medium is the existence of the thresholdpressure gradient and the nonlinear relationof flowspeed withpressure gradient which doesnot follow Darcy's law at the low pressure gradient. There are disadvantages in simulatingthe flow feature by Darcy's law seepage flow model or non-Darcy equation seepage flowmodel. In order to describe the movement characteristic of the seepage flow in the lowpermeability medium accurately and comprehensively, the paper established the low speednon-Darcy flowmodel which can reflect the flow characteristic in low permeability mediumdirectly. Based on the detailed analysis of the essential rules of seepage flow, this dissertationintroduced and discussed the Darcy flow models founded on the Darcy theory and thenon-Darcy equation flow models founded on the characteristic of non-Darcy flow, andanalyzed them carefully. The dissertation studied the low speed non-Darcy flow model. Iteduced non-Darcy seepage continuity equation by water equipoise theory, and adopted theFinite element method and SOR iterative method which have been used maturely in theDarcy's seepage calculation. This dissertation investigated the characters of variousnon-Darcy dynamical equations in detail. Catching up with the essence of the non-Darcyseepage at low velocity, this model adopted the typical curve of non-Darcy seepage, andtook the conception of variationalhydraulic conductivitycoefficient to the nonlinear seepagenumerical equations. With the alternant iterative method of variational hydraulic conductivity IIcoefficient, the physical non-Darcy seepage problem embodied by various dynamicalequations was turned into pure mathematical problem. Then it calculated the hydraulicconductivitycoefficient and numerical function value of hydraulic head alternately with SORiterative method, and solved the problem in determining the result of nonlinear numericalequation. This model can simulate the characteristic of the non-Darcy seepage flow, and itcan be used on the actual project analysis. In this dissertation, the non-Darcy seepage flow model has been applied to theoptimization analysis of the anti-leakage as well as well as the simulation of the runningcondition seepage flow field for the Lvyinhu reservoir. After proof-testing, the model withthe validity and the practicability in analysis of the low permeability medium can deal withthe appropriate anti-leakage for the project and make some suggestions, along with thesimulation of the seepage flow field for the project under various running condition. Part ofthe calculation and analysis results in the dissertation have put onto the design andconstruction side, which provided references for the formal design and construction methodof the project.