Abstract: The calculation formula of rock quality index in slope engineering (hereafter referred to as BQ (basic quality)), together with the valuing of correction factor in the formula, is given in Standard of Engineering Rock Mass Classification(GB/T 50218-2014) for the rock quality rating and self-stability evaluation of slope engineering in China. With other commonly used rating methods as reference, we pointed out that the evaluation index of correction term and correction factor in the BQ formula needs to be improved. On the basis of the current BQ formula, we propose the correction factor of slope height influence and the correction factor of stress state influence, and give the corresponding calculation formulas and valuing criteria. We also refined the evaluation indexes and valuing criterion of the correction factor of structural plane influence for high and steep slope in complex geological conditions. Finally, we give the optimized BQ formula and the corresponding stability evaluation system for BQ method. The research results are conducive for a correct rock quality rating, and offer reference for slope stability evaluation and reinforcement design work.

Key words: BQ method, correction factor, slope engineering, rock mass quality classification, stability evaluation