加载方向变化对细晶花岗岩凯塞效应的影响

Influence of rotation angle of principal stress axes between loading cycles on aplite granite's Kaiser effect

进行了单轴压缩试验条件下重复加载时加载方向变化对细晶花岗岩凯塞效应的影响试验研究。试验发现,加载方向不变或加载角度变为7°时,岩石的凯塞效应明显;加载角度为10°和15°时,部分试件由于受试验环境、试件加工等因素的影响观测不到凯塞效应。试验统计数据表明,重复加载时加载方向变化越大,其凯塞效应越弱。研究同时发现:加载方向变化对凯塞效应的影响还取决于岩石的受力状态,单轴压缩状态下,岩石受力状态单一,重复加载时加载方向的轻微变化不会影响岩石对历史应力的记忆能力;劈裂状态下,圆盘试样应力状态复杂,加载方向的轻微变化足以引起试样内应力的重分布,进而影响岩石的凯塞效应。

Uniaxial compressive tests on aplite granite were carried out under the conditions of changing rotation angle of principal stress axes between first and second loading cycle for investigating the existence or attenuation of rock＇s Kaiser effect.It is found that when the principal stress axes doesn＇t change or rotates 7°,pronounced Kaiser effect can be detected;when rotating to 10° and 15°,some specimens lost Kaiser effect due to the environment changes,specimen processing or other factors.Test statistics indicate that the greater the rotation angle changes when reloading,the weaker the Kaiser effect is.The study also find that the influence of rotation angle of principal stress axes between first and second cycle on the Kaiser effect also depends on the stress state of rock.Under pure uniaxial compressive state,a slight change of angle of principal stress axes when reloading does not affect rock＇s ability of memorizing the historical stress.While the stress inside rock discs under Brazilian tests is more complicated,a slight rotation of loading direction will be enough to cause a redistribution of stress,thus weakens rock＇s Kaiser effect.