基于FDM-DEM耦合的岩石动态冲击特征方法

为探究动态冲击作用下岩石的力学特征,根据室内霍普金森冲击试验模型,基于有限差分(finite difference method, FDM)-离散元(discrete element method, DEM)耦合方法构建了三维分离式霍普金森压杆(split hopkinson pressure bar, SHPB)冲击数值模型,在模型入射杆端部施加半正弦冲击波进行动态冲击模拟,对三维离散元试样的动态应力时程曲线、裂纹时空演化等特征进行讨论,从细观力学角度分析岩石的动态冲击破坏过程。结果表明：三维耦合模型在动态冲击过程中能够很好地满足应力有效性检验,保证了冲击过程的可靠性;利用Fish语言编写的半正弦冲击波等效替代室内试验撞击杆的撞击作用可以在一定程度上消除入射波的弥散效应;动态冲击过程中,试样内部的裂纹发展可分为平静阶段、缓升阶段、陡增阶段和稳定阶段,且裂纹主要产生于应力峰后阶段,裂纹总量呈反Z形变化。

Study on rock dynamic impact mechanics method based on FDM-DEM coupling

In order to explore the mechanical characteristics of rock under dynamic impact, according to the indoor Hopkinson impact test model, based on the finite difference method (FDM) -discrete element method (DEM) coupling method to build three-dimensional split hopkinson pressure bar (SHPB) impact numerical model, the model applying half sinusoidal stress wave incident rod end for dynamic impact simulation for three dimensional discrete element sample time history curve of dynamic stress, crack characteristics such as space-time evolution are discussed, from the perspective of mesoscopic mechanics analysis of the dynamic impact of the rock failure process. The results show that the 3D coupling model can well meet the stress validity test in the dynamic impact process and ensure the reliability of the impact process. The half-sinusoidal shock wave written by Fish language can effectively replace the impact effect of the impact bar in laboratory test, which can eliminate the dispersion effect of the incident wave to some extent. During the dynamic impact process, the crack development inside the sample can be divided into calm stage, slow rise stage, steep stage and stable stage, and the cracks mainly occur in the stage after the stress peak, and the total amount of crack changes shows an inverse "Z" shape change.