Composite element algorithm of seepage-normal stress coupling for fractured rock masses with drainage holes

A composite element algorithm of seepage-normal stress coupling for fractured rock masses with drainage holes is proposed. The coupling relation between fracture seepage and normal stress makes use of “air element” and “filled model”, which regards the drainage holes and fractures as “filled media” with high porosity. The existence of the drainage holes and fractures is not considered in the mesh generation, but it will be considered explicitly in the mapping composite element by means of the composite element pre-processing work program. The computational mesh generation is simple without restriction. Based on the composite element method, the seepage-normal stress coupling is achieved by applying the cross iterative algorithm. The proposed algorithm considers the flows in the drainage holes and fractures and the flow exchange between the drainage holes and fractures and the adjacent rock masses. The verification of the proposed algorithm is conducted through a simple numerical example, from which the advantages and the reliability of the proposed algorithm are illustrated.