冲击作用下煤岩动态破坏机理的FDEM模拟研究

FDEM simulation of dynamic failure mechanism of coal rock under impact

为研究煤岩的动态破坏规律,利用Φ50 mm分离式霍普金森压杆(split Hopkinson pressure bar,SHPB)装置,开展了煤岩冲击破坏试验。基于零厚度的内聚力单元建立了煤岩有限离散元方法(finite discrete element method,FDEM),标定了模型参数;最后在LS-DYNA软件平台上模拟了SHPB冲击试验,讨论了FDEM模型在模拟动态破坏时的适用性,并对煤岩的破坏过程进行分析。研究表明:①煤岩动态抗压强度与应变率满足经验关系,当应变率为98.05 s^(-1)、119.22 s^(-1)和135.85 s^(-1)时其动态强度因子(dynamic strength factor,DIF)分别为1.92、2.08和2.23;②冲击作用下煤岩的弹性变形阶段较短,塑性变形能力较强,动态弹性模量的应变率相关性不显著;③FDEM模型通过零厚度内聚力单元的失效能够模拟岩石类材料的脆性破坏,当网格尺寸合理时,由于惯性效应的存在,通过准静态试验标定的模型参数,也适用于冲击破坏的模拟;(4)冲击作用下煤岩的破碎程度与冲击速度正相关,其破坏形式表现为压缩波引起的局部剪切破坏和泊松效应导致的整体张拉破坏。

Here,to study dynamic failure laws of coal rock,50 mm split Hopkinson pressure bar(SHPB)device was used to conduct coal rock impact failure tests.Based on the zero-thickness cohesive force element,the finite-discrete element(FDEM)model of coal rock was established,and its parameters were calibrated.Finally,SHPB impact testswere simulated on LS-DYNA software platform,the applicability of FDEM model in simulating dynamic failure was discussed,and the failure process of coal rock was analyzed.The results showedthat①the dynamic compressive strength and strain rate of coal rock meet the empirical relation,when strain ratesare 98.05 s^(-1),119.22 s^(-1) and 135.85 s^(-1),the dynamic intensity factors(DIFs)are 1.92,2.08 and 2.23,respectively;②under action of impact,the elastic deformation stage of coal rock is shorter,its plastic deformation ability is stronger,and the strain rate correlation of dynamic elastic modulus is not significant;③FDEM model can simulate brittle failure of rock type materials through failure of the zero-thickness cohesive force element,when the grid size is reasonable,due to existence of inertia effect,model parameters calibrated with quasi-static tests are also suitable for simulation of impact failure;(4)fragmentation degree of coal rock under impact is positively correlated to impact velocity,and its failure forms are local shear failure caused due to compression wave and overall tension failure caused due to Poisson effect.