饱水时间对含黏土矿物岩石声发射特性影响的试验研究

Experimental Study on Influence of Immersion Time to Acoustic Emission Characteristics of Mud Bearing Sandstones

为研究饱水时间对含黏土矿物岩石力学行为与声发射特性的影响,对含蒙脱石的砂岩开展干燥、饱水及不同浸水时间条件下的单轴压缩力学和声发射试验,重点分析浸水时间对岩石各受力阶段声发射计数率、能率等时域参数的影响.结果表明:饱水时间对含泥质矿物岩石的强度、声发射参数均产生显著影响,饱水岩样的强度由干燥时的53.52 MPa下降到49.51 MPa,浸水超30 d,水岩耦合作用逐渐减小;岩样在破裂前存在微裂隙快速发育阶段,声发射信号开始活跃并迅速增长,随浸水时间的增加,信号活跃增长期的应变量逐渐减少,浸水90 d后,岩样破裂前能率增长期基本消失,表现为失稳破坏时的骤然释放;饱水岩样声发射累积计数和累积能量分别为干燥岩样的20.8%和30.9%;岩石在破裂过程中的声发射信号总数随浸水时间的增加持续减少,浸水120 d后,声发射累积数和累积能量分别为干燥岩样的0.24%和0.39%.

In order to investigate the influence of immersion time to rock mechanics behavior and acoustic emission(AE)characteristics of rocks that contain mud minerals,uniaxial compression strength(UCS)tests and AE tests are conducted on montmorillonite bearing sandstones under different conditions,i.e.dry,saturated,and unequal immersion time.The influence of sandstones immersion states to the time domain parameters of AE,such as counting rate and energy rate,in the different work stages is the key analytical point.The results are as follows.The immersion time has a significant impact over the strength of rocks that contain mud minerals and AE parameters.The UCS is 53.52 MPa for dry specimens,while this value declines to 49.51 MPa for saturated ones.Water-rock coupling appears inapparent when the immersion time is over 30 d.The rapid development of cracks and active AE signals coexist before fracture.As the immersion time gets longer,the strain becomes smaller in the signals actively increment stage.But after 90 d of immersion,the energy rate growth period is not obvious,and the energy is released suddenly when the rock sample is unstable.The cumulative number and energy of AE of saturated rock samples are 20.8%and 30.9%of that of dry rock samples respectively.With the immersion time increment,the total number of AE signals keeps decreasing during the rock failure process.After 120 d of immersion,the cumulative number,and energy of AE are 0.24%and 0.39%of dry rock samples,respectively.