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寒区饱水裂隙岩体受反复冻融作用影响,沿裂隙端部出现裂纹萌生、延展、偏转、分叉等现象,造成裂隙端部局部化区域损伤,进而诱发端部断裂造成岩体整体失稳。现采用相似材料配制0°,30°,45°,60°,90°的单裂隙类砂岩试样,并对裂隙内部充分饱水,展开10,20,30,50次冻融循环试验,而后观测裂隙端部区域在不同裂隙倾角、冻融循环次数下局部化损伤效应差异规律。藉此,对裂隙岩体在冻融循环作用下的局部化损伤效应进行分析,并结合断裂力学应力叠加理论,验证了因局部化损伤效应造成的裂隙端部断裂特性及扩展路径规律。结果表明:(1)冻融循环作用下单裂隙岩体存在局部化损伤效应,按照局部区域宏观裂纹发育状况,可将裂隙端部划分为:断裂区、渐进损伤区、系统损伤区;(2)随着裂隙倾角增大,冻融循环过程造成的局部化损伤效应越不显著,对应的声波波速值越大;(3)冻融循环过程中,主要在30°,45°,60°斜裂隙岩体出现主裂纹分叉、偏转现象;(4)裂隙角度愈缓,冻融循环作用造成的主裂纹偏转现象越早产生,偏转方向逐渐趋于水平,且沿初始裂隙走向的延展长度越短;(5)冻融循环引起局部化损伤在上下端部存在差异,裂隙下端部较早发生宏观断裂,且倾角越大,差异现象越明显。研究将为冻融作用下裂隙岩体局部损伤及端部断裂演化规律提供技术参考。
The cold-water saturated fractured rock masses are affected by repeated freeze-thaw cycles. Cracking, spreading, deflection and bifurcation occur along the ends of the fractures, causing localized damage to the ends of the fractures, which in turn induce the entire failure of the rock mass stable. The single-fractured sandstone samples of 0 °, 30 °, 45 °, 60 ° and 90 ° are prepared with similar materials, and the inside of the fractures is fully saturated with water and the freeze-thaw cycles of 10, 20, 30 and 50 times are carried out. The difference rule of localized damage effect at different crack dip angles and freeze-thaw cycles was observed. In this paper, the local damage effect of fractured rock mass under freeze-thaw cycles is analyzed. Combined with the stress superposition theory of fracture mechanics, the fracture characteristics and propagation path of the fractured rock due to the localized damage effect are verified. The results show that: (1) Localized damage effect exists in single-fracture rock mass under the action of freeze-thaw cycles. According to the development of macro-cracks in local area, the fracture tip can be divided into fracture area, progressive damage area and system damage area. ) As the fracture angle increases, the localized damage effect caused by the freeze-thaw cycles is less significant, and the corresponding acoustic velocity value is larger. (3) During the freeze-thaw cycles, the main damage occurs at 30 °, 45 ° and 60 ° (4) The farther the fissure angle, the earlier the main crack deflections caused by the freeze-thaw cycles occur, the more the deflection direction tends to be horizontal, and the longer the fissure along the initial fissure direction Short; (5) Localization damage caused by freeze-thaw cycles is different at the upper and lower ends, macroscopic fracture occurred earlier at the lower part of the fracture, and the greater the inclination, the more obvious the difference phenomenon. The research will provide a technical reference for the local damage of fractured rock mass and the law of the evolution of tip fracture under the action of freeze-thaw.