Abstract:

 The determination of mechanical parameters for columnar jointed rock mass is challenging due to its complex structure. Accurately estimating the strength and deformation of such rock masses is crucial for ensuring engineering safety. To address this issue, the authors developed a photosensitive resin mould using Voronoi diagrams and three-dimensional printing technology to create regular and irregular jointed rock mass specimens. Regular and irregular columnar jointed rock mass specimens with different dip angles were prepared and subjected to uniaxial compression tests. The resulting deformation and strength mechanical behaviors of the two types of rock masses were analyzed. The failure modes and mechanisms were summarized based on the final appearance of the specimens. Furthermore, the influence of joint surface materials on the failure mode and strength of columnar jointed rock mass was explained by combining the findings with existing research results. The authors proposed a modified joint coefficient method that better accounts for the structural characteristics of columnar jointed rock mass, building upon the traditional joint coefficient method. Using this modified method, empirical relationships were established between laboratory test results of regular and irregular columnar jointed rock mass and field deformation and strength parameters. The proposed calculation formula was then applied to the Baihetan Hydropower Station project, and the predicted results were compared with field measurements as well as predictions from the RMR (RMR is a rock quality evaluation index) and Q (Q is the quality index of rock mass) methods. The results demonstrated that the modified joint coefficient method provided the closest agreement with field measurements in terms of deformation and strength parameters.

Key words: cross-sectional regularity, columnar jointed rock mass, deformation and strength characteristics, physical model test, empirical relationship