The structure of a rock mass directly controls its mechanical and hydraulic properties

and the distribution of rock block volumes can directly reflect the structural characteristics of the rock mass. Currently

many studies simplify the joint surfaces as planes and ignore the influence of roughness on the volume of rock blocks. In this study

the Hurst exponent (H) and root-mean-square height (Rq) were used to characterize joint roughness

and the influence of joint roughness on the quantity and volume distribution of rock blocks was investigated. The results show that: (1) H and Rq control the roughness of the joint

and the roughness increases with the increase of Rq and decreases with the increase of H; (2) the quantity of rock blocks is generally positively correlated with joint roughness

that is

it increases as the roughness increases; (3) the influence of Rq and H on the distribution of rock block volumes is mainly achieved by changing the proportion of small-volume blocks

and the mean and median volumes of rock blocks decrease as the roughness increases; (4) when the joints are orthogonal and spaced closely

the variation in the quantity of rock blocks can be divided into three stages with respect to the roughness: a stable stage

an initial growth stage

and a rapid growth stage

where Rq and H jointly control the relative distribution range of each interval. Finally

based on the data collected by photogrammetry

we establish a joint model of the rock mass

and study the distribution of rock block volumes in a slope along a certain highway in Dalian

which verifies the correctness of the above conclusions.