Abstract: The study on rock mass weathering and unloading characteristics in the high and steep slope of Yaojiaping hydraulic engineering mainly include two parts partition of unloading zones in the slope and evaluation of unloading rock mass quality. By employing small arrangement of refraction wave method, we effectively eliminated the effect of excavation disturbed zone (after test adit excavation) on the partition of unloading zones. We also obtained the original rock wave velocity which is directly related to the weathering and unloading. According to national standard of rock mass classification, we carried out wave velocity test and indoor rock mechanical test, and obtained the BQ value of unloading rock mass and its distribution rule.

Key words: Yaojiaping hydro power station, rock slope, hydropower engineering, unloading zone