循环荷载下花岗岩强度及变形特征试验研究

Study on the Strength and Deformation Characteristics of Granite under Cyclic Loading

为研究循环加卸载作用下岩石的强度及变形特征,以隧道工程区域内的花岗岩为对象,采用室内岩石力学试验方法,得到了以下结论。(1)单轴循环荷载作用下花岗岩的最终破裂面明显多于单调加载,而三轴条件下,两种加载方式的破坏模式较为接近;(2)循环荷载作用下花岗岩的峰值强度显著降低;单调加载下的花岗岩表现为脆性破坏,而循环加载下花岗岩具有显著的延性破坏特征;(3)随着循环次数的增加,花岗岩第一次轴向塑性应变增量较大而后趋于稳定,受循环次数的影响较小;其变形模量随循环次数的增加而增大,随着疲劳损伤的累积,增长速度放缓,在试件接近破坏时,变形模量有下降的趋势;循环加载下花岗岩的黏聚力和内摩擦角较单调加载显著降低。

In order to study the strength and deformation characteristics of rocks under cyclic loading and unloading,taking the granite in the tunnel engineering area as an object and using indoor rock mechanics test methods,the following conclusions were obtained:(1)The final fracture surface of granite under uniaxial cyclic loading is significantly more than monotonic loading,however,the failure modes of the two loading methods are close under triaxial conditions.(2)The peak strength of granite is significantly reduced under cyclic loading Granite,and under monotonic loading it shows brittle failure,and granite has significant ductile failure characteristics under cyclic loading.(3)With the increase of the number of cycles,the first increase of the axial plastic strain of the granite is large and then stabilizes.The influence of the number of cycles is small;its deformation modulus increases with the increase of the number of cycles,and the growth rate slows down as the fatigue damage accumulates.As the specimen approaches failure,the deformation modulus tends to decrease;the viscosity of the granite under cyclic loading Cohesion and internal friction angle are significantly reduced compared to monotonic loading.