动载下层状岩体力学特性试验与数值模拟

Test and numerical simulation for mechanical properties of laminated rock mass under dynamic loading

摘要:

为研究冲击载荷作用下层状复合岩体的动态力学性能和破裂机制,基于煤单体和白砂岩构成层状软硬煤岩复合体,利用分离式霍普金森压杆试验装置和LS-DYNA有限元分析软件,结合Holmquist-Johnson-Cook(HJC)本构模型,开展不同速率和不同冲击方向下层状软硬煤岩复合体加载试验。结果表明:静态载荷作用下,层状煤岩复合体的强度不会随加载方向变化,动态载荷下层状煤岩复合体的峰值应力和动态增长因子DIF都随冲击速度增加呈线性增大,并且波阻抗匹配效果更好的HS复合体力学性能始终优于SH复合体(S和H分别代表煤单体和白砂岩),随着冲击速度增加这种现象逐渐减弱；层状煤岩复合体耗散能密度与入射能密度呈二次增长关系,分形维数也随着速度增加而不断增大,其中,应力波由硬入软时得到的效果优于由软入硬；层状煤岩复合体破碎程度随冲击速度增加而愈发剧烈,HS复合体破坏程度大于同条件下的SH复合体,白砂岩多呈剪切状破碎,煤单体多呈粉碎锥形破坏；层状煤岩复合体交界处与其他区域强度不一致,造成复合体破坏顺序改变,复合体整体强度规律从小到大依次为煤单体非交界面区域、煤单体交界面区域、白砂岩交界面区域、白砂岩非交界面区域。

Abstract:

To study the dynamic mechanical properties and rupture mechanism of laminated composite rock mass under the action of impact loading, we carried out loading tests of laminated soft and hard coal rock composites consisting of coal monomer and white sandstone under different rates and impact directions by using the split Hopkinson pressure bar (SHPB) device and LS-DYNA finite element analysis software combined with Holmquist-Johnson-Cook (HJC) constitutive model. Results show that the strength of the laminated coal-rock composite did not change with the loading direction under static loading. The peak stress and dynamic increase factor (DIF) of the laminated coal-rock composite under dynamic loading increased linearly with the impact velocity. The mechanical properties of HS (H and S represent white sandstone and coal monomer respectively) composite with better wave impedance matching were always better than those of SH composite, and this phenomenon gradually decreased with the increase in the impact velocity. The dissipation energy density and incident energy density of the laminated coal-rock composite showed a quadratic growth relationship. The fractal dimension increased with the velocity, and the effect obtained when the stress wave transferred from hard into soft was better than that from soft into hard. The degree of fragmentation of the laminated coal-rock composite became more and more intense with the increase in the impact velocity, the degree of destruction of HS composite was greater than that of SH composite under the same conditions, the white sandstone presented more shear-like fragmentation, and the coal monomer presented more crushed conical destruction. The strength at the interface of the laminated coal-rock composite was not consistent with that in other regions, resulting in a change in the order of destruction of the composite. The overall strength law of the composite from small to large was: coal monomer non-interface region, coal monomer interface region, white sandstone interface region, and white sandstone non-interface region.