Deterioration laws of Hoek-Brown parameters in freeze-thaw multi-fractured rock mass

The Hoek-Brown criterion can better depict the nonlinear failure characteristics of rock mass, which has been widely used in the fields of large-scaled slopes, deep-buried tunnels, foundations in complex geological condi-tions, hydropower dams, and energy mining. In view of the previous studies mostly focused on the property reduction of freeze-thaw rock, the deterioration study of Hoek-Brown parameters for freeze-thaw multi -fractured rock mass was investigated in this study. Firstly, Monte-Carlo method was used to generate two-dimensional discrete fracture network, according to which the multi-fractured rock-like samples were pre-pared. Freeze-thaw cycle experiments were subsequently designed and executed to observe the apparent damage of freeze-thaw effect on the samples. Then, laboratory direct shear tests on freeze-thaw samples under multi-stage normal loading were carried out. The shear performances of freeze-thaw rock mass were analyzed based on the shear stress-shear displacement curves of samples with different freeze-thawed cycles. Besides, considering the deficiencies of the existing Hoek-Brown parameter estimation methods such as complicated sample prepa-ration and strong subjectivity, a new estimation method based on shear test was proposed by deducing the shear expression of Hoek-Brown criterion, which was programmed in MATLAB and verified by direct shear test results. On this basis, the values of Hoek-Brown parameter of those samples under different freeze-thaw cycles were determined, and the variation law with freeze-thaw cycles was summarized. It turned out that the values of GSI and mi both decrease with the increase of freeze-thaw cycles, and the decreasing rate is also lowering, according with the negative exponential function model.

Automated summary

The Hoek-Brown criterion is widely used in various fields. This study investigated the deterioration of Hoek-Brown parameters for freeze-thaw multi-fractured rock mass and proposed a new estimation method based on shear test. The values of GSI and mi were found to decrease with the increase of freeze-thaw cycles, following a negative exponential function model.