Based on the 3D joint network simulation

the structure classification was carried out on the left bank dam foundation in Baihetan hydropower station on Jinsha River. Firstly

the dam foundation was separated into several statistical homogeneous subsections

according to the group distribution and density distribution of joints. Then

a 3D joint network model was established for each subsection by considering the statistics and probability theory. Secondly

uniform angle rotating measuring-lines were arranged on the positive

side and top surfaces of the model

respectively. Subsequently

a certain RBI value of each line and 3 rose diagrams for each orthogonal surface were obtained. Finally

the mean value of these RBIs from 54 measuring-lines was defined as 3D equivalent rock mass block index RBI3D. Moreover

the RBI3D

as an evaluation index

was used to classify the structure of dam foundation. Results showed that the integrity of No.10 bench in the left bank was relatively good. It was found that the ratios of the whole blocky structure

blocky structure and sub-blocky structure were 53.3%

26.7% and 20.0%

respectively. The analytical results agreed well with the actual situation. Therefore

the presented method has been proven to be scientific rationality and engineering practicability

as the space anisotropy of joint distribution was fully considered and a single quantitative evaluation index was employed to determine the rock mass structure type.