Geomechanical model for asymmetric distribution of deep-seated crack

The spatial distribution, deformation type and geomechanical model of asymmetric deep-seated crack (DSC) are analyzed. Taking Baihetan Hydropower Station as a typical example, the spatial distribution characteristics, deformation characteristics and deformation types are investigated by means of the integration methods of field investigation and fine description. Furthermore, a geomechanical model for DSC is proposed based on the view of energy evolution process. The spatial distribution range of DSC is between about 50 m and 150 m in vertical direction and horizontal direction from the surface of rock slope, and is located in the influence range of stress concentration of valley bottom. According to the deformation characteristics, the deformation types of DSC can be divided into three ones: tensile type, tensile-shear type and slippage-splitting type. The rock mass of the left bank has experienced several cyclic loading-unloading processes accompanied by the migration-incision evolution process of Jinsha River at dam site. Different from that of the right bank, the energy evolution process of the left bank has three significant differences: high storage, high dissipation and high strength degradation degree, which are the primary reason of asymmetric distribution of DSC. The formation-driving force of DSC is the tensile stress caused by differential rebound or stress concentration, and the slippage of shear belt makes DSC remarkable. The geomechanical model of asymmetric DSC can be divided into two types: one type is based on tectonic discontinuities and intact rock bridge; and the other is based on shear belt slippage. The formation process can be summarized into three stages successively: damage and strength degradation, local tensile stress formation and slippage splitting.