砂岩循环加卸载下损伤特性及声发射Kaiser效应研究

Study on damage characteristics and acoustic emission Kaiser effect of sandstone under cyclic loading and unloading conditions

为了获得砂岩循环加卸载路径下损伤特性和声发射Kaiser效应特征,开展了不同围压下砂岩循环加卸载声发射试验;从轴向应力、加载应力水平、能量耗散损伤角度,研究了三轴循环加卸载下声发射的不可逆比变化规律;评价了三轴循环加卸载下岩石Kaiser效应判断方法。结果表明:循环加卸载下耗散能损伤参数能较好地反映岩石的渐进损伤破坏,基于耗散能损伤参数的计算,能较好地反映岩石不同阶段的损伤特性,避免了应变参数计算损伤时压密阶段损伤值异常增大的现象。从应力水平、能量损伤角度分析声发射FR,更真实地反映岩石声发射Kaiser效应,随着围压增大Kaiser效应失效的应力提前,同一应力水平、相同能量损伤下,围压越大FR越小,声发射不可逆性随围压增大逐渐变得模糊。

In order to obtain the damage characteristics and Kaiser effect characteristics of sandstone under cyclic loading and unloading conditions,a series of tests on characteristics of acoustic emission(AE) have been performed on sandstone under different confining pressures.From the perspective of axial stress,the loading stress level and the energy dissipation damage,the variation of acoustic emission Felicity Ratio( FR ) are studied under triaxial cyclic loading and unloading conditions.The reasonable judgment methods of rock Kaiser effect are evaluated under triaxial cyclic loading and unloading conditions.The results show that the dissipative energy damage parameters under cyclic loading and unloading can better reflect the progressive damage of rock failure under different confining pressure.Based on the calculation of dissipative energy damage parameters,it can better reflect the damage characteristics of different stages of rock and avoid the damage calculation of strain parameters and avoid the abnormal increase of damage value in the case of calculating damage using strain damage parameter.Evaluating acoustic emission ( FR ) can reflect the Kaiser effect of rock more accurately from aspects of the loading stress level and the energy damage.The stress of Kaiser effect failure increases with the increase of confining pressure.The acoustic emission ( FR ) decreases as the confining pressure increase under the same stress level and the same energy damage,and acoustic emission irreversibility becomes gradually blurry with the increase of confining pressure.