Abstract: With the increase of buried depth in underground caverns, the phenomenon of strain softening is more obvious. In order to research the deformation characteristics of the fractured rock mass from deep underground after excavation, we set up a new constitutive model in association with strain softening model and constitutive model of fractured rock mass. Based on the secondary development function of FLAC software, this constitutive model was developed in VC++ programming environment. Excavation of the underground circular tunnel of a mine was taken as an example. Numerical simulation was carried out for the example by using strain softening model and self-developed constitutive model respectively. Analyses on deformation, plastic zone and safety factor in the surrounding rock show that the model can reflect the damage action of strain softening and cracks on rock mass, and the model can provide a reference for maintaining stability of surrounding rock.

Key words: fractured rock mass, damage of rock mass, constitutive model;strain softening effect, numerical simulation;safety factor