Study on coupled seepage and stress fields in the concrete lining of the underground pipe with high water pressure

When an underground pipe works in high water pressure, cracks often occur in the concrete lining and cause the inner water flowing out to the rock mass. For simulating the hydraulic–mechanical interaction in the process of cracking, a coupling method which based on the three-dimension elasto-plastic finite element method (FEM) is proposed in this paper. The coupling principle can be described as follows: the change of stress field leads to the change of permeability coefficient and the redistribution of the seepage field; the new seepage field will produce new seepage force and lead to the change of stress field. The crack expansion and its influence on the seepage and stress fields are studied in paper. As an engineering example, the coupling model is applied in the structural analysis of the lower bifurcated pipes and the surge chamber of Xiaowan Hydropower Station in China, and the computation results show the coupling method is reasonable.