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Study on damage characteristics and internal variable modeling of single-fracture sandstone under coupling effect of freeze-thaw and fatigue load
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  • PENGBO CHANG CHANG,
  • Kun Zhang,
  • JianXi Ren,
  • Zheng Liu,
  • Ke Wang
PENGBO CHANG CHANG
Xi'an University of Science and Technology
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Kun Zhang
Xi'an University of Science and Technology
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JianXi Ren
Xi'an University of Science and Technology

Corresponding Author:[email protected]

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Zheng Liu
2、China Construction Third Engineering Bureau Group Co, Ltd Wu han
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Ke Wang
Xi'an University of Science and Technology
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Abstract

To strengthen the disaster prevention and control of engineering fractured rock mass in the cold region of western China due to freeze-thaw cycles, 20 freeze-thaw cycles were performed on fractured sandstone samples with different inclination angles of 30°, 45°, 60°, and 90°. Subsequently, conventional triaxial and fatigue loading tests were conducted to explore the mechanical properties and fracture morphology evolution mechanism of freeze-thaw fractured sandstone during compression. At the same time, nuclear magnetic resonance technology was used to analyze the microscopic damage characteristics. Based on the internal variable theory of continuum mechanics, a fatigue model of freeze-thaw fractured sandstone with different inclination angles was established. The results show that the sandstone strength is negatively correlated with the fracture dip angle, the axial deformation and shear failure angle are positively correlated with the fracture dip angle. The mechanical properties of the sandstone are deteriorated by fatigue loading. The T 2 spectrum distribution of the fractured sandstone mainly has three peaks, and the pore distribution is mainly medium and small pores. There is a small leftward shift after freeze-thaw cycles and fatigue loading. The T2 spectral area is significantly affected by freeze-thaw cycles and fatigue loading, and the rate of change of both tends to increase. Through the fine correspondence between the axial residual deformation and the deformation modulus, a fatigue model with different crack inclination angles was established using the axial residual deformation as the internal variable, and the rationality of the model was verified by fatigue loading tests.