CHARACTERISTIC ANALYSIS OF ROCK MASS QUALITY SURROUNDING UNDERGROUND PLANT CAVERN AT PUMPING STORAGE HUDROPOWER STATION

The rock mass quality surrounding the underground plant of a pumped storage station is classified with BQ and Q classification systems. The distribution of rock masses with poor quality is pointed out. The results indicate that the rock mass quality is commonly at the gradeⅡor Ⅲ. On the other hand, the result of wave velocity testing shows that the wave velocity of the rock mass of gradeⅡor Ⅲ is between 4200~5300 ms-1, and these rock mass has good stability. However, the wave velocity of the grade Ⅳand Ⅴ is less than 4000 ms-1. Especially, the rock mass wave of the grade Ⅴ is less than 2200 ms-1. The rock mass quality indices from the two classification systems have similarities. The two indices have the relationship of exponential function. The relation between wave velocity and \BQ\ is linear. For the same project, the classification results from the two classification systems are different, but the classification bases are similar, which are dominated by the geological elements. So, there are the methods for conversion and comparison between the two classification systems.