珊瑚骨架灰岩三轴压缩声发射特性研究

Experimental study of acoustic emission characteristics of coral skeleton limestone under triaxial compression

通过对珊瑚骨架灰岩在不同围压条件下的声发射监测试验,获取珊瑚骨架灰岩三轴压缩力学特性及其声发射(AE)基本特征。研究表明,珊瑚骨架灰岩强度特性符合Mohr-Coulomb强度准则。珊瑚骨架灰岩在三轴压缩作用下的宏观破坏特征表现出较明显的围压效应,即单轴压缩表现为劈裂式张拉断裂面;随着围压的增大,由两级台阶式宏观断口逐渐过渡呈现为单斜面剪切带。珊瑚骨架灰岩在三轴压缩作用下的AE时序演化规律与其应力-应变曲线特征基本吻合,等效破坏时间所对应的累计振铃计数、累计能量计数与围压之间呈良好的对数函数关系。峰前累计振铃计数、累计能量计数在长期强度σcd之前表现出稳定的平缓现象,符合岩石的线弹性变形特征,并在约90%处呈现剧增现象,即为岩石内部微裂纹快速不稳定扩展的开始。珊瑚骨架灰岩在单轴压缩作用下的峰前能量演化规律与其应力?应变曲线特征基本吻合,峰前弹性能、峰前耗散能同样在约90%处出现转折现象。

Through acoustic emission monitoring tests of coral skeleton limestone under different confining pressures,mechanical properties of coral skeleton limestone under triaxial compression and basic AE characteristics were obtained.The study shows that the strength characteristics of coral skeleton limestone accord with Mohr-Coulomb strength criterion.The macroscopic failure characteristics of coral skeleton limestone under the action of triaxial compression show obvious confining pressure effect.In other words,uniaxial compression is shown as split tension fracture surface;with the increase of confining pressure,the"two-stage stepped"macroscopic fracture gradually turns into a single inclined shear zone.The AE time series evolution law of coral skeleton limestone under the action of triaxial compression is basically consistent with the stress-strain curve characteristics,and there is a good logarithmic function relationship between the cumulative ringing count and the cumulative energy count corresponding to the equivalent failure time and the confining pressure.The cumulative pre-peak ringing and cumulative energy counts show a stable and gentle phenomenon beforeσcd,which is in line with the linear elastic deformation characteristics of the rock,and presents a sharp increase at about 90%,which is the beginning of the rapid and unstable expansion of micro-cracks in the rock.The evolution law of pre-peak energy of coral skeleton limestone under uniaxial compression is basically consistent with the characteristics of stress-strain curve,the pre-peak elastic energy and pre-peak dissipated energy also appear the turning point at about 90%.