加载路径和饱和度对砂岩电阻和声发射响应特征的影响

Variation characteristics of electric resistance in the quiet periods of acoustic emission of sandstone with different saturation

岩石破坏过程的声发射监测常存在信号平静期,给岩石的破坏失稳预警带来极大的困难。为了研究利用电阻监测声发射平静期内岩石损伤发展的可行性,本文对干燥和含水饱和度为40%、70%和100%的砂岩岩样分别开展单轴加载、分级加载和增幅循环加卸载试验,研究加载路径和饱和度对砂岩电阻和声发射响应特征的影响。结果表明,饱和度的增加不仅会显著降低砂岩的强度,还会削弱声发射信号的活跃度。随着饱和度的增加,声发射平静期也逐渐增加,在加载-卸载条件下尤为明显。此外,在含水砂岩的增幅循环加载-卸载试验中声发射出现了Felicity效应。电阻的变化与岩石内部损伤发展具有很好的对应关系,可以有效反映声发射平静期内干燥和含水砂岩内部亚临界裂纹随时间的发展。

The existence of a quiet period in acoustic emission monitoring brings challenges to early warning of timedependent rock failure.In order to understand the effect of rock loading paths and water content on acoustic emission(AE)quiet periods and the corresponding electrical resistivity(ER)changes,uniaxial loading,step loading,and incremental cyclic loading-unloading tests were carried out on dry and water-bearing sandstone samples with saturation of 40%,70%and 100%,respectively.The results show that increasing the water content of sandstone can significantly reduce not only the strength but also the activity of AE signals.With the increase of water content,the quiet periods of AE signals increase,especially in the loading-unloading conditions.Under incremental cyclic loading-unloading conditions,the Felicity effect occurs in water-bearing sandstones.The ER variation is well consistent with stress-induced rock damage and can effectively reflect time-dependent subcritical crack propagation in both dry and water-bearing rocks.ER monitor can be used to compensate for the disadvantages of AE monitor in quiet signal periods.