Based on Investigation and Statistics of joint surface in field, as well as indoor triaxial unloading experiment and structural plane direct shear, designed several different connectivity rate and different dip angle joint rock mass models, using the discrete element software FLAC3D to simulate triaxial unloading experiment. According to indoor triaxial unloading test and simulation results, figure out the joint sandstone's mechanics parameters under conditions of unloading, studied the influence law which in different connectivity rate and dip angle of the joint influence on rock mechanics parameters at the conditions of triaxial unloading. And on the basis of the above, it amends the relevant parameters of high and steep slope in YINBAZI material yard, JINPING-I hydropower Station. The result can provide references to similar project as geotechnical engineering design and construction et al.
At present, the main body of large water conservancy and hydropower construction projects is mostly buried in deep rock mass. The primary machine rooms' excavation and stability are closely related to unloading rock mass mechanics and the joint rock mass's mechanics parameters formed by engineering excavation are the basis of engineering design, which affects the stability and safety of the whole project. Joints' extension, connection and combination determine rock mass's mechanical properties, and buckling failure mode. Extensive studies have been conducted on joint rock mass mechanics characteristics by scholars at home and abroad. However, most researches are mainly prone to loading mechanical category, like joint rock mass's basic mechanical properties, mechanical constitutive relation, and so on. While unloading mechanics differs from loading mechanics in essence. The mechanical characteristics of joint rock mass under the condition of unloading are the key points in the current engineering research. Due to its complicated structure and obvious size effect, laboratory tests cannot fully reflects its unique mechanics mechanism. But the numerical simulation technology shows incomparable superiority in this aspect (Hu B, et al. & Zhu J.W, et al. 2007) combining with field geological investigation and laboratory tests, different sizes of models can be established according to actual engineering and joint model can be generated in the model by using simulation software. The research on joint mass has been promoted greatly owing to its fast calculation speed and good operability.
