冻融循环作用后花岗岩断裂性能的试验研究

Research on fracture performance test on granite under effect of freeze-thaw cycle

对含有不同初始损伤花岗岩的三点弯曲断裂性能展开冻融循环试验研究,分析了冻融后花岗岩的断裂破坏机理;对试样断裂面的形貌进行了重构,并分析了试样断裂特性随其破坏面的分形维数的变化规律。结果表明:冻融循环作用下,试样的起裂荷载、峰值荷载、断裂韧度有不同程度的劣化,其劣化的程度又随试样初始缝高比的增大而加剧;随着冻融循环次数的增大,试样裂纹的扩展机理由遵循最大能量释放原则转变为遵循最小耗能原理。试样断裂面的分形维数与冻融循环次数呈较好的指数函数递增关系。峰值荷载损伤因子、断裂韧度损伤因子与分形维数变量有着较为显著的幂函数关系;峰值荷载损伤因子、断裂能损伤因子与粗糙度系数增量呈较好的幂函数关系。

The three-point bending fracture of granite with different initial damages is carried out under different freeze-thaw cycles,with the fracture mechanism of granite under freeze-thaw cycles discussed.Meanwhile,the fracture surface morphology of the specimen is reconstructed,with the change law of fracture property of specimen along with fractal dimension of fracture surface analyzed.The results show that freeze-thaw cycle exerts deterioration of various degrees on such parameters of three-point bending fracture of granite specimen as initial load of fracture,peak load,and fracture toughness.The degree of deterioration of granite specimen is aggravated with the initial crack-depth ratio increasing.With the increase of freeze-thaw cycles,the crack propagation mechanism of specimen follows the principle of maximum energy release changes into the principle of minimum energy consumption.There is an increasing significant exponential function relationship between fractal dimension and freeze-thaw cycles.The damage factor of peak load and fracture toughness and fractal dimension variable existing in power function relation.