A damage and fracture model for jointed rock masses and application in stability analysis on an underground cavern group

Numerous hydropower stations are located in high mountain-canyon areas in southwestern China. A number of deeper cracking zones frequently appear in the side walls of the underground caverns in these hydropower stations. The related principles and methods in fracture and damage mechanics are applied to study this phenomenon. A damage constitutive model is initially put forward using geometry damage principles. In this model, the initial geometry damage of jointed rock masses can be considered, which involve the major influencing factors such as joint plane areas, directions, and so forth. This constitutive model is derived according to the equivalent strain hypothesis. A failure criterion for crack coalescence and a damage evolution equation are deduced considering secondary cracks using the principles of fracture mechanics. Then the above model and analysis methods are programmed. Eventually, this new damage constitutive model is utilized to study on the stability of a group of underground caverns at a hydropower station in Sichuan Province. The obtained splitting depths from this model are close to the in-situ monitored ones using the deformation-electric-resistance-rate technology monitoring method, which validate the effectiveness of this fracture-damage constitutive model.