Abstract:

For the fact that rock mass degradation is not taken into account in the appraisal method for surrounding rock stability and the insufficient norms reference to deformation characteristics of the large underground powerhouse, considering the fact that the actual rock mass properties change in the excavation of underground powerhouse, based on strength reduction method idea, a new stability analysis method of surrounding rock for large underground powerhouse is proposed. At first, yielding approach index is used to appraise the excavation degradation zone of surrounding rock in numerical simulation. Secondly the deformation modulus and cohesive strength are reduced in the degradation damage zone. Then the failure criterion could be determined through the displacement, damage zone and energy release amounts mutation. Meanwhile, the early-warning displacement is analyzed in the process of rock degradation, and it can distinguish the stability of surrounding rock rapidly. At last, by analyzing an example of underground powerhouse, it is shown that the proposed method can provide quantitative basis for underground powerhouse stability; and it meets the need of underground projects fairly.

Key words: rock mechanics, underground powerhouse, rock degradation, stability evaluation, deformation early warning