卸荷条件下岩石Ⅰ型动态应力强度因子变化规律

Variation Law of Mode-Ⅰ Dynamic Stress Intensity Factor of Rock under Unloading Condition

利用数值模拟软件ANSYS,分析卸荷条件下裂纹尖端Ⅰ型动态应力强度因子(DSIFs)变化规律及其影响因素,研究岩石内部裂纹动态起裂行为。结果表明:围压及其卸荷速率越大,DSIFs峰值越大,卸荷产生的动态效应越明显,轴压对卸荷动态效应无影响;瞬态卸荷时,DSIFs最大值出现在卸荷后的持续阶段,存在滞后效应;卸荷过程中随内部应变能的释放,DSIFs时程曲线呈衰减效应;围岩刚度对卸荷条件下的DSIFs有显著影响,围岩刚度相对于岩爆体越小,DSIFs峰值越大,动态效应越明显;高卸荷速率初期,起裂韧度增率大于DSIFs增率,裂纹不会立即起裂,随卸荷时间的增加,裂纹发生起裂。

The variation law and influencing factors of mode-Ⅰ dynamic stress intensity factors(DSIFs)at the crack tip under unloading condition were analyzed with the numerical simulation software ANSYS,and the dynamic initiation behavior of cracks in rock was studied.The results show that the greater the peak value of DSIFs,the greater the confining stress and unloading rate,the more obvious the dynamic effect of unloading,and the axial stress has no effect on the unloading dynamic effect.During transient unloading,the maximum DSIFs appears in the post-unloading stage,and there is time-lag effect.During unloading,the time-history curve of DSIFs shows attenuation effect with the release of internal strain energy.The stiffness of surrounding rock has a significant impact on DSIFs under unloading conditions.The smaller the stiffness of surrounding rock relative to rock burst,the greater the peak value of DSIFs,and the more obvious the dynamic effect.At the initial stage of high unloading rate case,the increasing rate of crack initiation toughness is higher than that of DSIFs,the crack will not initiate immediately.With the increase of unloading time,the crack will crack.