不同节理起伏角的非贯通岩样拉伸剪切过程声发射演化特征

Acoustic emission characteristics in tensile-shear failure of non-persistent jointed rocks with different undulation angles

拉伸剪切破坏通常发生在深层现浇隧道施工过程中。本文利用自主研发的多功能岩石力学试验系统,对含有规则锯齿状节理的类岩试样进行直接拉伸剪切试验,研究节理起伏角度变化对拉伸剪切强度、温度和声发射的影响。结果表明,试样的峰值剪切强度随着节理起伏角的增大而降低,节理起伏角的增大导致岩桥更容易拉伸破坏,同时也使裂缝轮廓呈现出明显的阶梯状特征。在接近失效时,试样都产生了强烈的声发射信号,并产生了更多的裂纹,同时伴随能量耗散和温度降低。在三个试样的加载过程中,声发射b值呈现出先增大后减小的总体趋势,在接近峰值强度时急剧下降。根据RAAF值对裂缝进行分类,结果显示,在初始加载过程中,裂缝主要为纯拉伸类型。当试样接近失效时,剪切裂纹和复合裂纹的数量明显增加。

Tensile-shear failure commonly occurs during the construction of deep in-situ tunnels.In this paper,direct tensile-shear tests were conducted on rock-like specimens containing regular serrated joints using a self-developed multifunctional rock mechanical test system.The influence of joint undulation angle variation on the tensile-shear strength,temperature,and acoustic emission(AE)was investigated.The results showed that the peak shear strength of the specimen decreased with the increase of joint undulation angle,and the increase of joint undulation angle led to the rock bridge being more prone to tensile failure and made the crack contour exhibit an obvious step-like feature.When approaching failure,the specimens all generated vigorous AE signals and yielded more cracks,which were accompanied by energy dissipation and manifested a decrease in temperature.During the loading process of the three specimens,the AE b values exhibited an overall trend of first increasing and then decreasing,with a dramatic fall near the peak strength.Cracks were classified by RA-AF values,and the results showed that in the initial loading process,the cracks were primarily of pure tensile types.The number of shear and composite cracks increased significantly when the specimens were close to failure.