Study On Interaction Between Multi Bores In A Tunnel

Long and deep buried water diversion tunnel, as an important part of large conservancy and hydropower project, has been constructed widely in China. The stress states of diversion tunnel are very complicated because of its buried depth, difficult construction, operating under high water pressure, especially under earthquake. The interaction between multi bores in a tunnel subject to earthquakes is an issue. The scholars have carried out the study on interaction between bores during excavating. However, scarcity of the research on the interaction between bores under earthquake has been published. For the safety operation of water diversion tunnel, it is of necessity to determine the effects of dynamic interaction between multi bores.The research done in this paper can be summarized into four aspects listed as follows.(1) Research on interaction between multi bores under static loads is carried out at first. Based on data of Pangduo project, the finite element model of Pangduo water diversion tunnel is established by ABAQUS. The factors such as bore spacing, buried depth and rock grade are considered to study the effects of the on interaction between bores under internal water pressure on tunnel response.(2) Based on the theory of spring-viscous boundary, equivalent load method, an earthquake ground motion input method, the module considering the boundary reflection and transmission is developed using ABAQUS. The module is validated compared with analytical results.(3) Interaction between bores under dynamic loads is researched. A finite element model with spring-viscous boundary is built. The study on interaction between bores under earthquake is performed. The effects including tunnel spacing, tunnel buried depth and rock grade are analyzed, respectively.(4) Dynamic response analysis of Pangduo water diversion tunnel is carried out finally. Based on the model with spring-viscous boundary, a two dimensional dynamic response analysis by means of equivalent load method is computed. Based on model with simple boundary, a three dimensional dynamic response analysis by inputting acceleration time history is calculated. Further, reinforcement with steel rods along axial and circumferential directions of Pangduo tunnel is proposed.