孔隙水压对分级循环加载灰岩声发射Felicity效应的影响

Effect of Pore-water Pressure on Felicity Effect of Acoustic Emission in Limestone Under Graded Cyclic Load

利用渗透-应力耦合试验装置不同孔隙水压下的灰岩试样进行了单轴压缩和分级循环加载试验,探讨了孔隙水压对分级循环加载的灰岩强度特征和Felicity效应的影响,并基于Felicity比变化路径分析了灰岩变形特征.结果表明,孔隙水压对应力-应变曲线有显著影响,软化作用导致压密阶段延长而弹性阶段相对缩短,其峰值应力呈指数衰减.随孔隙水压增加,平均循环峰值应力和循环寿命均为指数衰减,疲劳破坏“门槛值”为峰值应力的67.50%~78.75%,疲劳曲线近似线性减小.每级循环加载声发射的“活跃-平静”期的阶段分界点为上限应力.随孔隙水压增大,Felicity比的变化路径明显缩短且随循环次数近似线性减小,其变化系数与孔隙水压为二次函数关系.Felicity比的稳定阶段预示着发生疲劳破坏,最小Felicity比随孔隙水压呈线性减小.

In this study,uniaxial compression and graded cyclic loading tests of limestone under different pore-water pressures were carried out by usinghydro-mechanical coupling tests,then the effects of pore-water pressure and graded cyclic load on the strength characteristics and Felicity effect of limestone were explored,and the deformation characteristics of limestone were analyzed based on the change path of Felicity ratio.The test results show that the pore-water pressure has significant effect on the stress-strain curve,its softening effect causes the compaction stage to lengthen and the elastic stage to shorten,and the peak stress shows exponential attenuation.With increasing pore-water pressure,the averages of cyclic peak stress and cyclic life are both exponential decay,its“threshold value”of fatigue failure is greater than 67.50%and less than 78.75%of the peak stress,and the fatigue curve decreases approximately linearly.The boundary stress point of the active stage and quiet stage of acoustic emission is the upper limit stress during the cyclic loading.With increasing pore-water pressure,the change path of Felicity ratio is obviously shortened and decreases approximately linearly with the graded cyclic load times,and its variation coefficient is the quadratic function of pore-water pressure.The stable change trend of Felicity ratio indicates the occurrence of fatigue failure in limestone,and the minimum Felicity ratio decreases linearly with pore-water pressure.