The failure behavior of prefabricated fractured sandstone with different rock bridge inclination angles under freeze-thaw cycles

Abstract

In this paper, the fractured rock samples with different dip angles of rock bridge are taken as the research object, and the freeze-thaw cycle test and uniaxial compression test are carried out successively. Combined with digital image correlation technology (DIC) and numerical simulation, the failure process of prefabricated fractured sandstone with different rock bridge dip angles was studied. The results show that the frost heaving force caused by freezing and thawing will cause irreversible damage to the rock sample. Especially at the tip of the prefabricated crack, macroscopic frost heaving cracks will occur. Frost heaving cracks can reduce the stress concentration at the crack tip, which leads to a decrease in tensile cracks during loading. With the increase of the inclination angle of the rock bridge, both the modulus and the peak stress show an inverted “spoon-shaped” trend of increasing first and then decreasing. The tensile effect of the frost heave force generated by the freeze-thaw process leads to the early development and expansion of the prefabricated cracks. Under the action of external load, according to the law of crack development, the failure mode of rock bridge can be divided into shear failure (S type), tensile failure (T type) and tensile-shear composite failure (M type). The relative displacement evolution curve of the characteristic points on both sides of the fracture surface is basically consistent with the evolution characteristics of the strain field. According to whether the x-direction and y-direction displacement curves of the feature points deviate from each other, the type of driving force of fracture propagation can be judged.