Abstract: The Central Yunnan Water Diversion Project features extremely complex geological structure background and seismic geological conditions. With a total length of 62.60 km and a maximum buried depth of 1 450 m, Xianglushan tunnel crosses the Hengduan Mountains in northwest Yunnan, the watershed of Jinsha River and Lancang River, and several regional deep faults. It is the longest single tunnel with the largest buried depth in the Central Yunnan Water Diversion Project and is also the most difficult to construct large, deep and super long tunnel with the most complex geological condition in water conservancy projects under construction in China. In view of the major engineering geological problems and the potential risks of groundwater environmental impact, we systematically summarize the key survey technologies including 3S-based geological remote sensing interpretation, magnetotelluric sounding, kilometer-level deep hole exploration and testing, route selection of large deep-buried and super long tunnels in complex karst areas, and numerical simulation of three-dimensional seepage field of groundwater. We also developed some key technologies of advanced geological prediction applicable for large, deep-buried, and long tunnels in complex geological conditions, kilometer-level deep hole geostress testing technology, as well as deep rock hydrogeological parameter testing technology. Such technologies form a whole set of systematic and comprehensive research methods for investigating large buried and super long tunnels.

Key words: Xianglushan tunnel, super long tunnel with large buried depth, complex geological conditions, key technologies of investigation, key technologies of advanced geological prediction