ENGINEERING ROCK MASS CLASSIFICATION METHOD BASED ON ROCK MASS QUALITY INDEX BQ FOR ROCK SLOPE

The engineering classification in rock slopes is not included in the current standard of engineering classification of rock masses(GB50218—94). This paper presents the engineering classification method for rock slopes(BQ-R Slope) based on the quality index of rock mass BQ. In this method,several modified factors are employed as to correct rock mass basic quality,and the engineering rock mass classifications for rock slopes are determined by the modified rock mass quality, and the evaluation for stand-up time of rock slope in correspondence with each class of rock mass is further proposed. The employed factors consist of the type and the persistence of major structural planes,the relationship between orientations of structural planes in rock mass and rock slope surface and the groundwater conditions in rock slope. The presented method is verified through applications to four rock slope projects and ten slope sections in total. It is found that the engineering classification and the corresponding evaluation results of each slope section with the method proposed are generally in good agreement with the practical situation. This indicates that the presented method for engineering rock mass classification of rock slopes based on BQ index is appropriate.