三轴循环加卸载下花岗岩损伤的声发射特征及能量机制演化

Acoustic Emission Characteristics and Energy Mechanism Evolution of Granite Damage Under Triaxial Cyclic Loading and Unloading

利用TYP-500型三轴试验机进行三轴常规及循环加卸载试验,借助PCI-2声发射系统记录花岗岩破坏过程的声发射信号。试验结果表明：循环加卸载试验使花岗岩的弹性模量变大,较常规三轴压缩强度,循环加卸载强度大致提高了3.5%;随着循环加卸载次数的上升,花岗岩不可恢复的变形量变大,为最大变形的5%左右,表明花岗岩具备明显的“记忆性”功能;花岗岩声发射振铃计数突变点大致在峰值应力的90%处,可将此作为判断花岗岩破坏的前兆;围压越大,弹性能所占比越大,说明围压影响岩石内部能量的分配;在峰值强度的0.3～0.4处,弹性能所占比达到0.9左右,说明在荷载达到试件峰值强度之前,岩样内部的能量演化已经发生转变,并保持在一定水平。

TYP-500 triaxial testing machine was used for triaxial conventional compression test and triaxial cyclic load- ing and unloading test, and the PCI-2 acoustic emission system was applied to record granite acoustic emission char- acteristics. Experimental results showed that, the granite e- lastic modulus increased test, and compared with after cyclic loading and unloading the conventional triaxial compres-sion strength, the cyclic compressive strength increased by 3.5 % or so; with the increasing number of cyclic loading and unloading, the unrecoverable deformation quantity of granite increased as large as 5% of the maximum deformation, which indicated that the granite had obvious memory func- tion; the mutation point of acoustic emission ringing count, which was at 90% or so of the peak stress, could be consid- ered as a judge for early signs of granite damage; the larger confining pressure, the greater proportion of elastic energy, which illustrated that the confining pressure had effect on rock internal energy; in about 0.3～0.4 of the peak intensity, the proportion of elastic energy reached around 0. 9, which meant that rock internal and maintain at a certain energy evolution had been changed level before the load reaching peak strength.