压缩作用下岩石预置裂隙贯通机制的研究

Analysis of mechanisms of crack coalescence based on pre-cracked rock under compression

运用岩石破裂过程分析系统(RFPA2D),结合室内实验研究了预置双裂隙试样在不同岩桥倾角影响下的破坏过程及裂隙的贯通机理。对单轴加载下岩桥断裂特征的研究表明:随着岩桥倾角(0°~90°)的增加,贯通模式呈现由压剪混合贯通过渡到剪切贯通最后到拉伸贯通的趋势。从贯通强度和能量的角度,分析了岩桥倾角分别为0°、30°、60°、90°下的贯通模式,研究了岩桥长度、非均匀性对裂纹扩展的影响。结果表明:岩桥倾角为0°时,贯通强度最高;岩桥倾角为60°时,贯通强度最低;随着岩桥长度(8mm^42mm)的增加,贯通由简单模式过渡到复杂贯通最后到未贯通;当均匀性系数较小(m=3),即均匀程度较低时,裂纹往往沿着强度较弱的部位进行扩展,裂纹路径较为曲折;当均匀程度较高时(m=7、m=15),主裂纹路径较为集中,宏观上表现为越来越光滑。

With the help of Rock Failure Process Analysis(RFPA) and combined with laboratory experiments, the study of the rock failure process of pre-existing double flaws under different bridge angles and the mechanism of coalescence is made. It is shown that with the increase of bridge angle(0°~90°), there appears a trend that transition from the mixed compression/shear mode to the shear mode, and finally to the tension mode. Moreover, the four coalescence modes of bridge angles α=0°, 30°, 60°, 90° are analyzed at the view of the coalescence force and energy. The coalescence force is maximum when bridge angle is 0°, and the coalescence force is minimum when bridge angle is 60°. Then, the research on what the influence of ligament length and inhomogeneity on the crack propagation shows that with the increase of ligament length(8mm^42mm), the coalescence mode transforms from simple mode to complicated mode, and finally to no coalescence. When the uniformity coefficient is small(m=3), the propagation also happens at the lowstrength part, and the trajectory is twisting. Conversely, when the uniformity coefficient is high(m=7, 15), the trajectory is concentrated and it is smooth from a macro standpoint.