Abstract: The impact of human activity on surrounding rock quality is increasingly remarkable because of largescale and complicated arrangement of underground projects. In order to accurately evaluate engineering rock quality, both the natural impact factors and the engineering factors need to be considered, and the engineering factors should be regarded as the modification indexes of natural factors during the evaluation. With Dagangshan hydropower station as an example, the main engineering factors and their impacts on surrounding rock quality are summarized. On this basis, some targeted factors are chosen to quantitatively describe the quality degradation effect and to analyze the correlation of supports. Furthermore, according to some technical requirements of the surrounding rock classification systems, the flow chart of multi-level surrounding rock evaluation system in construction period is put forward. This research provides theoretical foundation for the quantitative expression of degradation caused by engineering factors and the evaluation system for surrounding rock quality. It also has enlightening significance for the research on the impact of engineering factor on surrounding rocks evaluation system.

Key words: construction period, underground cavern, engineering factors, surrounding rock quality evaluation system, limited degradation