基于CT扫描的煤岩试件破坏加载速率效应数值模拟研究

Numerical simulation study of failure loading rate effect of coal-rock specimens based on CT scanning

加载速率效应是岩石力学和地质领域的研究重点之一。非均质结构与加载速率效应的耦合,将使得煤岩体呈现更为复杂的破坏特性。基于微焦点工业CT对煤岩试件进行了微米尺度上的扫描,构建了反映试件内部结构信息的三维数值模型,并导入FLAC^(3D)软件进行了5种不同加载速率下(2.5×10^(-7)、5.0×10^(-7)、2.5×10^(-6)、5.0×10^(-6)、10.0×10^(-6)mm/step)的单轴压缩实验数值模拟。结果表明,5种加载速率下,弹性阶段的应力-应变曲线基本重合,但在荷载接近试件承载极限时,不同加载速率的应力-应变曲线变化明显,加载速率增大时,峰值应力相应增大,对应的应变值也增大,在一定范围内增大加载速率使得试件的承载能力有所提高。受材料非均质性影响,塑性区分布并不对称,且峰值应力后,加载速率对塑性区的分布影响更为明显。应力达到峰值前,剪切应变率较大区域均未贯穿试件,而加载速率越大,剪切带形状越趋于不规则;应力达到峰值后,加载速率越大,试件破坏越突然,破坏形式也更复杂。

The loading rate effect is one of the research focuses in the field of rock mechanics and geology.The coupling of the heterogeneous structure and the loading rate effect will make the coal-rock mass show more complex failure characteristics.Based on micro-focus industrial CT,the coal and rock specimens were scanned at the micron scale,and a three-dimensional numerical model reflecting the internal structure information of the specimen was constructed.Uniaxial compression experiments under 5 different loading rates including 5.0×10^(-7),2.5×10^(-6),5.0×10^(-6),10.0×10^(-6)mm/step numerical simulation.The results showed that under the five loading rates,the stress-strain curves in the elastic stage basically overlap,but when the load was close to the bearing limit of the specimen,the stress-strain curves at different loading rates changed significantly,and when the loading rate increased,the peak stress increased accordingly.The corresponding strain value also increased.Increasing the loading rate within a certain range improved the bearing capacity of the specimen.Affected by material heterogeneity,the distribution of plastic zone was not asymmetric,and after peak stress,the effect of loading rate on the distribution of plastic zone was more obvious.Before the stress reached the peak value,the area with a large shear strain rate did not penetrate the specimen,and the larger the loading rate,the more irregular the shear band shape becomes.After the stress reaches the peak value,the greater the loading rate,the more sudden the failure of the specimen and the more complex the failure form.