Abstract
Due to the extensive excavation of the mine pit, a special frozen rock slope is formed, which transforms the permafrost (coal rock) of certain thickness in the frozen state to the melting state. To evaluate the dynamic mechanical properties and deformation characteristics of coal under cyclic freeze-thaw conditions, freeze-thaw experiments with different cycle times were conducted. And the mechanical properties of coal under quasistatic and dynamic conditions were investigated by using GCTS multifunctional rock mechanic experimental apparatus and SHPB dynamic loading apparatus, respectively. The results show that with the increase of freeze-thawing times, mass of both water-saturated and dried coal samples gradually decreased, the postpeak becomes gentler, and the specimens show ductile damage characteristics. The damage of the coal samples changed more after 30 freeze-thaw cycles, when deterioration of the coal samples was highest. The elastic modulus of the coal sample after freeze-thawing decreases continuously with the increase of the number of freeze-thaw cycles, and its trend decreases approximately linearly. Dynamic compressive strength of the coal samples decreases after freeze-thaw cycles, and this trend is consistent with the quasistatic loading conditions.
Highlights
With the decreasing amount of coal resources in China and the increasing energy demand year by year, several cities with depleted coal resources have emerged in the Middle East [1,2,3]
Coal resource development has been gradually extended to the northwest planning area, where several large open-pit coal mines are located in the high-altitude perennial permafrost zone
Wang et al [7] investigate the fatigue mechanical characteristics of marble having different interbed orientation subjected to multilevel constant-amplitude (MLCA) cyclic loads
Summary
With the decreasing amount of coal resources in China and the increasing energy demand year by year, several cities with depleted coal resources have emerged in the Middle East [1,2,3]. With the change of temperature and the two-state cycle of freezing and melting, the nature of coal rock medium is changing, making the frozen rock slope of open pit mine in high altitude permafrost area a special slope. The research on the evolution of slope stability under the influence of multiple factors is carried out in a targeted manner, especially the mechanical characteristics of coal rock under the disturbance of external dynamic load after freeze-thaw cycles. It is of great theoretical significance to study the mechanical properties and deformation characteristics of coal rock masses in open pit coal mines in cold regions under the combined effects of freeze-thaw cycles and dynamic load disturbances to ensure the safe mining of open pit coal mines
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