二维任意裂隙网络裂隙–孔隙渗流模型的两种解法

 与裂隙网络渗流模型相比，裂隙–孔隙渗流模型(双重介质渗流模型)假定裂隙及裂隙切割而成的岩块均透水。这样可以只考虑较大裂隙形成的裂隙网络，而岩块及其内部的较小随机裂隙均作为连续孔隙介质进行渗流分析，从而减少裂隙网络中的裂隙数量以增加计算容量。讨论裂隙–孔隙渗流模型研究存在的问题，归纳剖析2种解法，即整体求解法与流量交换法。整体求解法中，裂隙作为有一定宽度的介质并划分为实体计算单元，与岩块单元的单元渗透矩阵合并成总体渗透矩阵进行求解。裂隙实体单元无需在网格划分时划出，只需在计算程序中对裂隙节点进行扩展。流量交换法中，裂隙系统和岩块系统分别形成渗透矩阵和渗流方程组，分别计算2个系统的渗流，2个系统之间通过流量交换，最终实现流量平衡和同一节点的水头一致，并指出水交换量只修正下游节点的渗流平衡方程。通过算例，比较2种解法的特点。还提出任意封闭回路在不增加节点前提下的三角形划分法。

TWO-DIMENSIONAL FRACTURED POROUS FLOW MODEL OF ARBITRARY FRACTURE NETWORK AND ITS TWO SOLUTION METHODS

In comparison with fracture network flow model,fractured porous flow model,which is also called as dual medium seepage model,assumes that the fractures and the blocks cut by fractures are all permeable.With this kind of model,only the determinate bigger fractures are considered in fracture network simulation,and the rock blocks and their inner stochastic small fractures can be treated as continuous porous media.So the fracture quantity can be decreased and the calculation capacity can be increased.Therefore,this kind of model has a significant development prospect in discontinuous rock mass fluid flow model.At first,the problems of fractured porous flow model are discussed.Then,two kinds of solution methods are summarized,which are called as global solution method and flow exchange method,respectively.In the global solution method,the fractures are considered as media with definite widths and modeled with solid elements.The conductivity matrices of fracture elements and block elements are incorporated to form the global conductivity matrix.The fracture solid elements are obtained by expanding fracture nodes in calculation codes,and needn t to be generated in meshing.In the flow exchange method,the fluid flow of the fracture network system and the rock block system are calculated separately by forming conductivity matrices and flow functions respectively.Then,by means of flow exchanges between these two systems,the calculation results can be iterated with the balance of flow and the unique hydraulic head in one node.It is pointed out that the flow exchange influences only the flow balance function of the downstream node.At last,the characteristics of these two methods are contrasted by means of cases study.Additionally,arbitrarily shaped loop triangulation method without adding any node is put forward.