含Z型相交裂隙岩体剪切力学行为研究

SHEAR MECHANICAL BEHAVIOR OF ROCK MASS CONTAINING Z-TYPE INTERSECTING FRACTURES WITH LABORATORY TEST

采用水刀切割加工灰岩原样,开展含Z型相交裂隙试样的室内直剪试验,系统地研究了剪应力-剪位移曲线,分析了预制裂隙倾角和法向应力对含Z型相交裂隙试样强度、变形及裂纹扩展的影响,并阐明了含Z型相交裂隙试样破坏演化机制。研究表明:①剪应力-剪位移曲线可分为预制裂隙(孔隙)压实阶段(初期下凹)、准线性变形阶段(中期线性波动)、峰前不稳定断裂发展阶段(后期上凸)及峰后强度残余阶段(陡降)4个变形破坏阶段;②相同裂隙倾角下裂隙岩体的峰值剪应力随法向应力增大而增大(近线性),且相同法向压力下裂隙岩体的峰值剪应力随裂隙倾角增大而减小(趋势渐缓);③裂隙宏观损伤裂纹演化过程可分为初始压密弹性阶段、裂纹扩展增长阶段及贯通断裂破坏阶段,且其破坏模式包括拉伸破坏、剪切破坏及拉剪混合破坏(拉伸-剪切贯通和剪切-拉伸-剪切贯通)。

We aim to investigate the shear mechanical behavior of rock mass containing fractures.We cut the limestone samples with Z-type intersecting fractures by water knife,and carry out the laboratory direct shear tests.We examine the shear stress-displacement curve,analyze the influence of prefabricated fissure angle and normal pressure on the strength,deformation and crack coalescence and explore the failure evolution mechanism.The results indicate the follows:(1)The shear stress-displacement curve can be divided into four deformation and failure stages including prefabricated fracture and pore compaction stage(initial sag),quasi-linear deformation stage(intermediate linear fluctuation),pre-peak unstable fracture development stage(later convex)and post-peak strength residual stage(steep drop).(2)The peak shear stress of specimens increases with the normal stress at the same fissure angle(nearly linear)and decreases with the increase of fissure angle at the same normal pressure(the trend is slowing down).(3)The evolution of macroscopic crack damage can be divided into three stages,including initial compression elastic stage,crack growth stage and through fracture failure stage.The failure modes can be divided into three types,i.e.,tensile failure,shear failure and tension-shear mixed failure.The last one can be divided into two types,i.e.,tension-shear hole-through and shear-stretch-shear hole-through.