To satisfy the need for development of transportation infrastructure, hydropower, water supply, etc., more long, deep, and large diameter tunnels and underground caverns are being, or will be, constructed in China. Commonly, they may be characterised as being under heavy overburden, of complicated engineering design, under difficult geological conditions, requiring sophisticated project management, etc.
This keynote address presents an overview of some practical challenges, recent developments, and technical progress, based on lessons learned from successful construction of deep headrace tunnels at Jinping II hydropower station. Geomechanical challenges overcome during construction are reviewed and summarised: these include the control of large deformations or soft rock squeezing, the prediction of, and risk mitigation against, severe rock-bursts, the forecasting and treatment of high pressure groundwater with associated flow issues, etc. Some innovative and effective analysis methods and engineering approaches are illustrated: they were applied to overcome the aforementioned underground engineering hazards. The experience accumulated during the construction of the tunnels at Jinping II hydropower station provides a valuable reference for similar projects in the future.