The results showed that the dynamic elastic modulus and peak strength of sandstone decreased with the increase of freeze-thaw cycles, and the relationship between porosity and dynamic peak strength was polynomial.

carried out nuclear magnetic resonance (NMR) and dynamic compression tests on the frozen and thawed sandstone. proposed an analysis method of damage evolution process after freeze-thaw cycles. Based on the energy change during the dynamic failure process of red sandstone, Wang et al. carried out a dynamic impact test on sandstone after freeze-thaw cycle, analyzed the change of pore structure after freeze-thaw cycle by combining with nuclear magnetic resonance technology, and explained the reason of degradation of dynamic strength. With the development of coal mining in cold regions, some scholars have paid attention to dynamic mechanical properties of rock under freeze-thaw cycles. Scholars at home and abroad have done a lot of research on changes of static mechanical properties of rock under freeze-thaw cycles. The factors affecting rock freeze-thaw strength mainly include rock type, temperature, water content, and freeze-thaw cycle times. Under the influence of freeze-thaw cycles, the frost heaving force caused by the transformation of fracture water into ice is the main damage mechanism of rock freeze-thaw cycles.

Rock materials are cemented by various mineral particles, and there are holes and fissures in the process of diagenesis. As a result, it is critical to investigate the dynamic impact test of rock under freeze-thaw cycles for coal mining in cold regions. Several investigations reveal that the mechanical response characteristics and failure law of rock mass under dynamic stress differ considerably from those under static load. According to real measurements, the stress wave produced by blasting may cause strain rates in the range of 10 1-10 3вЂ‰s -1 in the rock mass, which corresponds to normal high impact dynamic loading. The intensity of blasting steadily increases in high-intensity mining conditions. In open-pit coal mines, bench blasting is the primary method of production. There have been episodes of low temperatures below 0вЊ in the past 8 months at the Xinjiang Beitashan Pasture Open-Pit Coal Mine. However, due to seasonal variations and the diurnal cycle, freeze-thaw damage is unavoidable in coal mining. To increase the efficiency of coal mining via safety and stability, many scholars have conducted extensive study in areas such as roadway excavation, stability monitoring, and resource utilization. More than 95% of open-pit coal mines are located in cold regions north of 38В°N latitude. IntroductionД¬hina has abundance of coal resources, but they are not evenly distributed. The research results can provide reference for open pit coal mining in cold regions. The analysis results were basically consistent with the damage characteristics of macro mechanical properties. In addition, X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to analyze the changes of mineral composition and microstructure damage of sandstone samples under the coupling effect of acid corrosion and freeze-thaw cycles. The coupling effect of freeze-thaw cycles and acid corrosion weakened the dynamic compressive strength, and elastic modulus but enhanced the peak strain. The results showed that strain rate could enhance the dynamic compressive strength and peak strain but had no significant effect on the elastic modulus. The coupling effects of freeze-thaw cycles with different concentrations of HCl solutions and strain rate on mechanical properties of sandstones were explored. In order to study the effect of hydrochemical corrosion on dynamic mechanical properties of freeze-thaw rocks, dynamic compression tests were carried out on sandstone samples corroded by four different concentrations of HCl solutions with the same number of freeze-thaw cycles using split-Hopkinson pressure bar (SHPB) test system. During the construction of geotechnical engineering in cold regions, the stability of rock is inevitably affected by freeze-thaw cycles and hydrochemical corrosion.

Mass effect 3 scanning