Study on the effects of the ice-filled fissure on the failure features of frozen rock mass
With the promotion of the Belt and Road initiative,strategic corridors are being developed in the western cold regions,necessitating numerous tunnel and slope projects in frozen rock formations. The mechani-cal properties of frozen rock are pivotal for ensuring the safety of construction and operation in such environ-ments,influenced by factors like fracture structure and freezing temperature. However,the impact of fracture structure on the mechanical behavior of frozen rock masses remains poorly understood,particularly the role of fracture ice during rock mass failure. This study aims to elucidate the effects of fracture structure on the mechani-cal properties of frozen rock masses and the mechanism of ice fractures in the failure process. We selected medi-um and coarse-grained saturated yellow sandstone as our research subject and conducted uniaxial compression failure tests on sandstone samples with varying fracture dip angles (α=0°,15°,30°,45°,60°,75°,90°) at freezing (-10 ℃) and room temperature (25 ℃) conditions. We analyzed the variation in mechanical properties of frozen sandstone under different fracture dip angles and discussed the influence mechanism of fracture dip an-gle on crack propagation based on the principle of ice-rock interaction. The findings indicate that:(1) Freezing does not change the trend of strength and elastic modulus variation with fracture inclination. Both parameters show a decreasing-then-increasing pattern as the fracture angle increases,with minima at α=60° and maxima at α=90°. (2) The initiation pattern of samples follows a "tensile cracking→shear cracking→tensile cracking" trend at both room temperature and frozen states,with higher stress levels required for crack initiation in the fro-zen state. (3) The mechanical properties of frozen fissured sandstone are governed by both freezing effects and fracture inclination angles,with changes in fracture angle altering the stress state at the fissure tips and ice-rock interactions affecting fracture initiation and propagation. (4) At smaller fracture angles (0° to 30°),the ice with-in the fissures primarily reinforces the structure through its supporting effect,while at larger angles (45° to 75°),the strengthening effect is mainly due to the bonding action at the ice-rock interface. As the fracture angle approaches perpendicularity,the strengthening effect is attributed to the bonding and supporting effects of the ice. The study of the mechanical properties of compressive failure in frozen fractured rock masses holds signifi-cant engineering and scientific value.
frozen rock massice-filled fissurescrack initiation and propagationice-rock interfacefreezing strengthening effect
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