花岗岩Kaiser效应的实验验证与分析

Experimental Verification/Analysis of Kaiser Effect in Granite

应用八通道的声发射系统,实验研究了10个花岗岩试样(150 mm×150 mm×150 mm)在单轴压缩循环荷载作用下的Kaiser效应,同时研究了保载、旋转(90°)加载和延时加载对Kaiser效应的影响.应用单纯形算法对声发射事件进行定位,研究裂纹扩展过程.结果表明:在初次加载条件下,声发射事件连续急剧产生,反映岩样本身的损伤程度;在岩样线弹性循环加载阶段,花岗岩表现出明显的Kaiser现象,同时表明岩石具有一定的受载记忆能力;声发射事件定位结果明显显示出裂纹的初始、扩展过程,与实际观察到的岩样破坏结果是一致的.同时发现保载、旋转(90°)加载和延时加载对Kaiser效应没有影响.但是,一旦岩样被加载至非线性阶段,再对岩样进行重复加载,声发射事件急剧增加,超过前几次加载过程产生的声发射数,这个结果与Kaiser效应试验结果完全不同.

A 8-channel acoustic emission （AE） system was employed to investigate the Kaiser Effect. It was investigated using 10 150 ram-cubic granite specimens monitored under the action of uniaxial-compression cyclic load, of which the AE sensors were surface mounted. A simplex algorithm allows AE events to be located from its first arrival time determined by AE sensors, and then the crack propagation is further studied. The influences of delay time between subsequent loading cycles, 90°-turned loading and load holding time on Kaiser effect were examined in granite samples. The experimental results showed an obvious Kaiser effect, and the continuously increasing AE events in the initial loading cycle can reflect how the granite samples were damaged. Crack initiation and propagation were monitored by AE functions and compared with visual observation, and AE events were located. The delay, 90°-turned loading and load holding time can not strongly affect Kaiser effect. But, when rock comes into nonlinear loading phase and then to failure loading, it will not follow the Kaiser effect, which is slightly different from the theoretical analyzing result.