冻融循环作用下含裂隙砾岩力学特性及宏微观破坏机理OA

Freeze-thaw cycles are critical factors influencing rock landslides in high-altitude mountainous regions.In this study,rock samples from the Lagangcun landslide in a high-altitude area are collected to conduct triaxial unloading tests on fractured conglomerates subjected to varying freeze-thaw cycles.The mechanical properties,energy evolution,acoustic emission characteristics,and multi-scale structural features are systematically analyzed to elucidate the freeze-thaw degradation mechanism of conglomerate with prefabricated fissures.The results demonstrate that the peak strength of the samples progressively decreases with increasing freeze-thaw cycles.After 60 freeze-thaw cycles,compared to untreated samples,the peak strength of intact specimens under confining pressures of 10 MPa,20 MPa,and 30 MPa decreases by 44%,48%,and 70%,respectively.Under identical confining pressure and freeze-thaw cycles,samples with longer pre-existing fractures exhibit lower peak strength and greater susceptibility to failure.Both the absorbed and dissipated energies during rock failure decreased with freeze-thaw cycle,indicating that less energy is required to induce failure.As freeze-thaw cycles increase,the average acoustic emission energy per second diminishes,the number of rupture points declines,and the failure duration is shortened.The failure mode transitions from X-shaped shear failure to tensile-shear conjugate failure.At the macroscopic scale,the secondary cracks or fractures are closely associated with pre-existing fissures.Microscopic analysis reveals that crack propagation intensified with freeze-thaw cycles.Compared to untreated samples,4 cm pre-fractured specimens after 40 and 60 cycles show crack volume increases of 1.71%and 1.83%,respectively,with more pronounced cracking along pre-existing fractures,highlighting the exacerbated damage in fractured rocks.These findings clarify the strength degradation law of conglomerates under freeze-thaw conditions,providing critical insights for engineering construction and rock mass stability in alpine regions.