为探究冻融作用对条带状磁铁石英岩破裂失稳过程裂纹演化特征的影响规律，对冻融温度区间为-20~20 ℃、最长冻融周期为280次的岩石开展了力学与声发射试验研究。结果表明：单轴抗压强度和弹性模量自干燥状态时的200.93 MPa和21.67 GPa下降至冻融280次时的106.64 MPa和8.24 GPa；低冻融周期（冻融循环≤40次）作用下，岩样在裂纹演化过程中以拉伸裂纹为主、剪切裂纹为辅，裂纹破裂主要发生在微裂隙加速扩展阶段，该阶段中、高频信号的出现时间稍早于中、低频信号，且高频条带所对应的幅值较高；高冻融周期（冻融循环>40次）作用下，岩样裂纹演化同样以拉伸裂纹为主，但剪切裂纹占比低于低冻融周期岩样，随着冻融周期的增加，岩样裂纹总量呈降低趋势，在微裂隙加速扩展阶段，中、高频信号与中、低频信号基本上同时大量出现，岩样超高频信号所对应的幅值随着冻融周期的增加而降低；低冻融周期作用下，高能信号主要产生于微裂隙加速扩展阶段，而高冻融周期作用下，高能信号的分布较为分散，且岩样自身声发射能量跨度以及大能量声发射事件出现的概率相较低冻融周期岩样均有所下降。

To investigate the impact of freezing and thawing on the crack evolution characteristics during the fracture instabiligy processes of banded magnetite quartzite，mechanical and acoustic emission tests were conducted on the rock subjected to a temperature range of -20~20 ℃ and a maximum of 280 freeze-thaw cycles.The results indicate that the uniaxial compressive strength and modulus of elasticity decreased from 200.93 MPa and 21.67 GPa in the dry state to 106.64 MPa and 8.24 GPa after 280 freeze-thaw cycles，the reduction in strength and modulus of elasticity exhibited a tendency to stabilize during the later stages of freeze-thaw cycles，resulting in the establishment of a new dynamic equilibrium between the skeletal structure of the rock samples and their internal microcracks.Additionally，under conditions of low freeze-thaw cycles （defined as ≤40 cycles），the evolution of cracks in the rock samples primarily involved the development of tensile and shear cracks，with crack rupture predominantly occurring during the accelerated expansion phase of microfracture. The high freeze-thaw cycle （defined as exceeding 40 cycles） significantly influences the crack evolution process in rock samples，predominantly resulting in tensile cracks，while shear cracks are less prevalent compared to those observed in samples subjected to low freeze-thaw cycles.Notably，as the number of freeze-thaw cycles increases，there is a discernible trend toward a reduction in the overall cracking of the rock samples.Furthermore，during the accelerated expansion phase of microfractures in rock samples exposed to low freeze-thaw cycles，high and medium frequency signals emerge slightly earlier than their medium and low frequency counterparts，the amplitude associated with the high-frequency bands was elevated.During the phase of accelerated microfracture expansion in rock samples subjected to extensive freeze-thaw cycles，there was a simultaneous emergence of middle and high-frequency signals alongside middle and low-frequency signals.Furthermore，as the freeze-thaw cycle period increased，the amplitude corresponding to the ultra-high frequency in the rock samples progressively diminished.Under the influence of a low number of freeze-thaw cycles，high-energy signals predominantly emerge during the accelerated expansion phase of microfractures，characterized by a more concentrated distribution and increased frequency.Conversely，with a higher number of freeze-thaw cycles，the distribution of high-energy signals becomes more dispersed，and their frequency diminishes as the number of cycles increases.These signals are observed throughout the entire loading process. The rock samples subjected to a low number of freeze-thaw cycles exhibit fewer microfractures during the compression stage，the elastic deformation stage，and the microfracture development stage，with no apparent correlation to the location of fracture aggregation at the point of rupture.In contrast，for rock samples exposed to a high number of freeze-thaw cycles，there is a significant relationship between the cracks formed during the initial three stages and the locations where cracks aggregate at the time of rupture.The range of acoustic emission energy and the likelihood of high-energy acoustic emission events in rock samples subjected to a high number of freeze-thaw cycles were reduced compared to those subjected to a low number of freeze-thaw cycles.This observation further suggests that rock samples experiencing fewer freeze-thaw cycles are primarily characterized by the development of large and mesoscale fissures.In contrast，those subjected to more frequent freeze-thaw cycles are predominantly influenced by the expansion，merging，and fusion of localized fissure networks.

http://www.goldsci.ac.cn/article/2024/1005-2518/1005-2518-2024-32-6-1030.shtml