Quality evaluation of engineering rockmass is essentially stability analysis based on engineering geology analogue. As national standard of China

BQ qualification is ubiquitous. However

rockmass with intercalated bed is mechanically unique

so it is reasonable to modify Formula BQ in order to match its feature. Taking underground cavities of a large hydropower station in Southwest China for example

rockmass structure and quality evaluation are studied. The result agrees basically with the one acquired by RMR System.