Abstract: In complex geological environments, high geo-stress and strong unloading in particular, the rock mass of large hydropower projects in west China presents new phenomena which cannot be explained by the existing theories. New in-site test techniques were developed and imported to study the complicated problems regarding rock mechanics and rock engineering of large hydropower projects in west China, covering the rock mass deformation and failure mechanism, the characteristics of rock mass relaxation, the rheological behavior and characteristics of time-dependent failure of rock. In-site rock mass test techniques, inclusive of the rheological test with flexible bearing plate, the real-triaxial unloading test under high confining pressure with complicated stress paths, the triaxial rheological test and time  dependent failure of hard rock mass, and acoustic emission location technique for the deformation and failure of rock mass are briefly introduced. Initial achievements of applying these new techniques in studying complicated rock mechanics problems of large hydropower projects in west China were also presented.

Key words: in-site rock mass test technique ,    rock mass real-triaxial test  ,   rock mass rheological test    , time-dependent failure of rock mass ,    acoustic emission location technique