Numerical prediction of unloading in underground caverns excavation based on damage mechanics

Abstract

Unloading is a quite common phenomenon in the excavation process of large underground caverns, but the formed unloading region in the surrounding rock will bring an extremely adverse effect on the system stability. At present, correlation studies mainly focus on the distribution of the stress field and the displacement field after the excavation completed. However, studies that specifically test the fracturing process with the rock properties weakening during the excavation process are rare. Considering the above reasons and based on the damage mechanics theory, this paper established a numerical model used to analyse the damage-fracturing process of surrounding rock mass, with the nonuniformity properties of rock materials explicitly considered. Taking the underground caverns of Jinping Hydropower Station as the study object, the evolution of the unloading region was simulated dynamically during the excavation process, and good simulating results were presented. In sum, the study findings point out that the developed numerical model is not only applicable to the study of the fracturing mechanism of surrounding rock mass, but also can be used as a new method to analyse problems related to underground caverns excavation.

Keywords:

• underground cavern
• excavation
• unloading region
• damage mechanics

Acknowledgments

This work was supported by the Chinese Natural Science Foundation of China (Grant No. 11132003 and 51079045), and the Scientific Innovation Program of College Graduate in Jiangsu Province (Grant No. CXZZ12_0227). This support is gratefully acknowledged.