【摘要】 为研究裂隙岩石破坏强度及裂纹扩展特征,采用MTS岩石力学试验机对单裂隙岩石进行单轴压缩试验,同步进行声发射、声波及摄像测试,研究裂隙岩石应力应变行为、声波及声发射特征与裂纹扩展、聚结的变化关系。结果表明,起裂应力、峰值强度及模量随裂隙倾角α变化一致,均先减小后增大,起裂应力和强度受α影响较大;裂纹间断性加速扩展引起的应力转移和释放(应力降),导致裂隙岩石应力-应变曲线呈阶梯状上升;应力降伴随着能量释放、刚度劣化和AE振铃计数的激增,随着α的增大,首次应力降和振铃计数陡增对应的应力逐渐增大,且振铃分布向峰值强度附近集中;裂纹起裂、扩展引起波幅和波速衰减,且波幅下降早于应力降的发生。α=0o岩样峰前波速降高达50%,随α的增大,波速下降点的应力逐渐增大,峰前波速降幅不断减小,α较小时峰前裂纹发育程度高,随着α的增大,峰前裂纹发育程度减弱,裂纹加速扩展、聚合向峰后转移;裂纹长度扩展到临界值时扩展速率会发生快速增大,随着α的增大,裂纹临界长度逐渐降低。更多还原

【Abstract】 In order to study the failure strength and crack propagation characteristics of fractured rocks, the uniaxial compression experiments on rocks with single fissure were carried out by MTS rock mechanics system. Acoustic emission(AE), ultrasonic testing and camera recording were monitored simultaneously to study the relationships between stress-strain behaviors, acoustic emission characteristics, the propagation and coalescence of cracks. The results show that the variations of crack initiation stress, peak strength(PS) and modulus are consistent with the inclination angle α of fissure, which decreases firstly then increases later. Crack initiation stress and peak strength are affected greatly by α. The stress-strain curves of fractured rocks rise stepwise before peak strength attributed to the stress transference and stress release(stress drop) induced by intermittent accelerated propagation of cracks.The stress drop is accompanied with energy release, modulus deterioration and sharp increase in ring counts of acoustic emission.With the increase in α, the stress corresponding to the first stress drop and sharp increase in ring counts of α coustic emission gradually increases. Besides, the ring distribution gradually shifts to peak strength. The initiation and propagation of cracks result in the attenuation of wave amplitude and velocity, and the amplitude decrease occurs earlier than that of stress drop. The velocity decrease of rock sample with α = 0o reaches up to 50% before peak strength. With the increase in α, the stress increases at the moment corresponding to the velocity drop, and the drop rate of wave velocity before peak strength decreases gradually. When α is small,crack propagation is highly developed before peak strength of rock. It shows that with the increase in α, crack development before peak strength subsides. Thus the accelerated crack propagation and convergence transfer to post-peak stage. When the crack length is extended to a critical value, the expansion rate will increase rapidly. The threshold of crack length gradually decreases as α increases.更多还原