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Abstract Many hydropower stations in Southwest China are located in regions with high geostresse or brittle rock masses. Deep fracture zones occur often in the sidewalls of the underground caverns. The theory and method of fracture and damage mechanics are adopted to study this phenomenon. This model can take into account area and orientation of fractured surfaces of multiple joint sets，as well as spacing and density of joints. Under the assumption of equivalent strain principle，a damage constitutive model is established based on Mohr-Coulomb criterion. The theory of fracture mechanics is applied to analyze the occurrence of secondary cracks during cavern excavation. The failure criterion for rock bridge coalescence and damage evolution equation are derived. A new subprogram for the above-mentioned damage constitutive model and damage evolution equation is developed. The program is then applied to stability analysis of an underground cavern group of a hydropower station. The results are compared with the depth of the relaxation and fracture zone in surrounding rock obtained from field monitoring. The distribution of splitting zone obtained from the proposed model is consistent with the field monitoring data. Therefore，the proposed model is validated.
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Received: 13 May 2010
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2010, Vol. 29 
