Blockiness is a new index to evaluate the integrity of rock mass

and it can represent the degree of rock mass fracture in three dimensions. However

current blockiness evaluation methods have not considered the cutting degree of rock mass

the size of the block

unrestricted basic application conditions and unreasonable ratings of blockiness levels. In this study

the causes of these limitations were analysed in-depth. Moreover

the concept of block volume percentage was defined referring to the calculation principles of the rock mass cutting degree

three-dimensional (3D) block modulus and volume RQD. A comprehensive percentage calculation method of block volume was proposed

in which the scale effect of rock blocks was considered. The ratings of blockiness levels and the values of the classification index were determined

and the improved blockiness evaluation method was developed. By comparing the rating results of the modified blockiness evaluation method and the Chinese codes for geotechnical engineering

the rationality of the modified blockiness evaluation method was analysed. Based on the Tongkeng Zn polymetallic orebody and Wudongde Hydropower Project

the case studies of the modified blockiness evaluation method were conducted. The results showed that the block volume percentages of No. 4 testing area at the 255 m level in the Tongkeng Zn polymetallic orebody

the PD49-1 adit and PD4 branch adit in Wudongde Hydropower Station were 11.18%

12.847% and 10.168% by using the modified block evaluation method

respectively. In addition

they all belonged to slight-blockiness categories

and the rock mass was moderately integrated. Compared with the conventional blockiness evaluation method

the block volume percentage calculated by the modified blockiness evaluation method can more accurately represent the integrity of the rock mass from a 3D perspective. The findings in this study are significant for accurately characterising the 3D integrity of rock mass.