Three-dimensional numerical modeling of water distribution tunnels in karst area

Abstract

Karst physiognomy is a common terrain in mountainous area. The tunnels constructed through these terrains may suffer from stress maldistribution due to the existence of the karst caves. The lining of water distribution tunnels passing through karst caves suffer from both the outer pressure of surrounding rock and the inner water pressure that could cause cracks of the lining and seepage of the water. This study focuses on the influence of exposed karst caves on water distribution tunnels. In order to assess the risks caused by the karst caves, finite element methods are carried out. Test datum of the tunnel in the Water Distribution Project of Qiandao Lake is used to validate the accuracy of the FEM model. The effects of filling the karst cave with concrete and embedding pre-stress steel strands into the lining are studied, respectively. Results show that filling the karst cave with concrete grout can eliminate the inhomogeneity of the tensile stress of the lining, and embedding the pre-stress steel strands into the lining can resist the inner water pressure effectively. Meanwhile, the most appropriate pre-stressing force and the relationship between the pre-stressing force and the inner water pressure are suggested.