论文部分内容阅读
岩质边坡中岩桥贯通是导致边坡失稳的重要因素,通过开展不同岩桥长度岩样的常规三轴加荷、三轴卸荷以及三轴加卸荷试验,研究在不同应力路径下岩桥贯通破坏过程中的声发射特征,以及围压和岩桥长度对声发射特征的影响。结果表明:岩石压密阶段与线弹性变形阶段声发射事件较少,塑性阶段声发射事件明显增多,破坏阶段声发射计数率、累计能量以及幅值均达到峰值。声发射特征的明显变化可为紧接的岩样破坏提供预警作用,幅值变化较其他指标更为敏感,因此幅值的监测对于各阶段演化以及破坏预警更有效。本试验中,岩桥试样达到峰值强度后不会立即跌落至残余强度,而是出现2次应力跌落,应力跌落均对应声发射特征达到峰值,2次应力跌落中会出现“平静期”或“峰后回升”现象,其声发射特征与塑性阶段相似,但幅值、计数率与累计能量均大于塑性变形阶段,表明在这一阶段岩样裂纹仍以较快速率扩展,最终导致岩桥贯通破坏。不同应力路径下累计能量由大到小依次为:三轴加卸荷、三轴卸荷和常规三轴。随着岩桥长度与围压的增加,声发射计数率峰值和累计能量逐步增长,破坏程度更加剧烈。
Rock slope through rock mass is an important factor leading to slope instability. By carrying out conventional triaxial loading, triaxial unloading and triaxial unloading test on different rock length samples, The characteristics of acoustic emission in the process of rock failure through the lower rock bridge, and the influence of confining pressure and rock bridge length on acoustic emission characteristics. The results show that there are few acoustic emission events during rock compacting stage and linear elastic deformation stage, and the acoustic emission events in plastic stage obviously increase. The acoustic emission count rate, cumulative energy and amplitude at the failure stage peak. The obvious change of acoustic emission characteristics can provide an early warning effect on the subsequent rock sample damage. The amplitude change is more sensitive than other indicators. Therefore, the monitoring of the amplitude is more effective for each stage of evolution and damage warning. In this experiment, rock bridge sample peak intensity will not immediately fall to the residual strength, but there are 2 times the stress drop, stress drop corresponding to the characteristics of acoustic emission peak, 2 times the stress drop will appear "quiet period The acoustic emission characteristics are similar to the plastic phase, but the amplitude, the count rate and the cumulative energy are larger than the plastic deformation phase, indicating that the crack at this stage still expands at a faster rate, Eventually led to rock bridge through destruction. The cumulative energy under different stress paths is as follows: triaxial unloading, triaxial unloading and conventional triaxial. With the increase of rock bridge length and confining pressure, the peak value of acoustic emission count rate and cumulative energy increase gradually, and the degree of damage is more severe.