Index

Deep Tunneling for the Jinping II Hydropower Project

Itasca Consulting China, Ltd. has been involved in an engineering and research effort for deep tunneling for the Jinping II hydropower project in Sichuan Province, China. The project includes numerous tunnels mined by both drill-and-blast and TBM methods in high quality brittle marble. Under high stresses, brittle failure and rock bursting conditions have been encountered.

The most recent phase of the project has been devoted to extensive use of continuum and discontinuum numerical modeling to characterize the brittle response of the high quality marble to excavation. The brittle-ductile transition and post-peak strength parameters, as a function of confining stress, has been studied to provide a comprehensive peak and post-peak failure envelope for the marble. This failure envelope was used with continuum modeling to capture the mining response in high quality (GSI>70) marble. Discontinuum methods (PFC and UDEC) were used to investigate lower-quality (GSI=50-70) marble. The material was carefully calibrated to peak and post-peak laboratory data and found to represent the EDZ around mined tunnels well.

PFC2D model shows agreement with EDZ measurements (shown superimposed on the bottom right portion of the plot)