冲击扰动下泥页岩块剪切蠕变损伤特性研究

Study on Shear Creep Damage Characteristics of Shale Block under Impact Disturbance

矿体爆破是大多数露天矿山开采作业中的必要环节,然而持续爆破作业产生的冲击扰动作用会降低露天边坡的长期稳定性,甚至促使滑坡灾害的发生.为研究冲击扰动效应对边坡岩体蠕变特性的影响,以露天石灰石矿山二叠系软弱夹层中的炭质泥页岩为研究对象,利用自主研发的岩石冲击-剪切蠕变试验系统开展了不同冲击能量扰动下的剪切蠕变试验.试验结果表明:(1)冲击扰动对软岩剪切蠕变破坏具有明显的促进作用,随着冲击扰动能量的增加,软岩进入加速蠕变历时缩短,蠕变破坏总时长与剪切蠕变破坏强度亦随之降低.(2)冲击能量可改变泥页岩剪切破坏面的发育特征,冲击扰动能量越大,剪切面裂隙发育越充分且岩样结构形态越破碎.(3)岩样总体变形量与冲击能量呈正相关关系,随着冲击能量的增加,其造成的总变形中塑性永久变形占比越大而弹性变形占比越小,当冲击能量为7.09 J时两次冲击后的塑形永久变形占比均不小于73.1%.根据试验结果,引入基于冲击能量的损伤因子D,建立了考虑冲击扰动效应的软岩剪切蠕变损伤模型.采用BFGS算法和1stOpt通用全局优化数学软件进行了模型参数辨识,采用损伤模型对试验结果进行拟合后发现,所建立模型能够较好地描述冲击扰动下泥页岩剪切蠕变变形的全过程,可为爆破扰动效应下的矿山边坡长期稳定性研究提供一定的理论基础.

Blasting is an essential part of open-pit mining, but the impact disturbance produced by continuous blasting operations will weaken the long-term stability of open-pit slopes. In order to study the influence of impact disturbance on the creep characteristics of rock, we prepared rock samples 150 mm × 75 mm × 75 mm in size with the argillaceous shale from the weak interlayer, and carried out shear creep tests under different impact energy disturbances with the self-developed rock impact-shear creep test system. The following conclusions are drawn based on the test results:(1) The impact disturbance has a significant interference effect on the shear creep failure of soft rock. With the increase of impact disturbance energy, the accelerated creep duration and the total creep failure time of the soft rock are shortened, and the shear creep failure strength decreases.(2) The impact energy can affect the spread characteristics of the shear failure surface of rock samples. The impact disturbance energy destroys the rock sample structure, resulting in an increase in the number of shear cracks.(3) The total deformation of the rock sample is positively correlated with impact energy. With the increase of impact energy, the proportion of plastic deformation becomes larger and the proportion of elastic deformation becomes smaller. After applying a disturbance of impact energy of 7.09 J, the ratio of plastic deformation to total deformation is no less than 73.1%. According to the test results, a damage factor D based on impact energy is introduced, and a shear creep damage model of soft rock considering the impact disturbance effect is established. The Broyden-Fletcher-Goldfarb-Shanno(BFGS) algorithm and the 1 stOpt mathematical software for general global optimization are used to identify model parameters. It is found that the established model can well describe the whole process of shale creep deformation under impact disturbance. This study provides a certain theoretical basis for the research on long-term stability of mine slope under blasting disturbance.