Cracking behaviors and strength of rock-like samples with steps of different geometries under shear stress

Steps are distinctive features for estimating the movement of the upper and lower block of faults.However,studies about the influence of steps as a special type of discontinuity on cracking behaviors and strength of rock masses are limited.In this research,rock-like samples with steps and preexisting flaws were fabricated.Step height h and the inclination angle of gentle slope of the stepαwere set to different values.Direct shear tests were conducted on these samples under different normal stresses.The experimental results reveal that the inclination angle of the gentle slope of the stepα,step height h,and normal stress have an influence on the strength,crack initiation,and crack propagation of the samples.The experimental results show that crack behaviors and shear strength were affected by step inclination anglesαand step height h.As the normal stress increases,the improvement of the strength of samples with a large step height is larger than that of samples with a small step height,the improvement of the strength of samples withαof 10°is larger than that of samples withαof 0°and-10°.The discrete element method was used to simulate the shear test.Numerical results show five different types of displacement vectors,which can be used to determine whether the cracks are tensile cracks or shear cracks.The above conclusions can provide help for estimating mechanical properties and failure modes of rock masses with steps of different geometries.

平行双裂隙类石灰岩试样注浆前后的力学特性和开裂行为

本文对几何形态不同的张开平行双裂隙类石灰岩试样和水泥充填平行双裂隙类石灰岩试样进行了单轴压缩试验,发现试样的力学特性和开裂行为受岩桥角度和裂隙倾角的影响。通过分类,总结了四种岩桥贯通方式。在观察试验过程中发现在裂隙倾角较小的试样中,加载前期产生的张裂纹在加载过程中会闭合,这是一个未被提及的新现象。结果表明,张开裂隙试样和水泥充填裂隙试样的峰值强度、起裂应力和聚结类型不同,产生这种现象的原因是水泥灌浆可以传递应力,从而减少裂隙尖端和岩桥区域的应力集中。