三维静载与循环冲击下煤岩组合体的动态本构模型及其损伤特性研究
Dynamic constitutive model and damage characteristics of coal-rock combined body under three-dimensional static and cyclic impact loading
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摘要: 为探究三维静载与循环冲击下煤岩组合体的力学与损伤特性,以岩-煤-岩组合结构试样为研究对象,利用改进型霍普金森压杆试验系统,进行三维静载与循环动态冲击试验,分析煤岩组合体的应力-应变曲线与破坏特征,建立反映应变率、煤岩受力特征及围压的动态本构模型,探讨冲击入射能、围压等对煤岩组合体损伤的影响规律。结果表明:煤岩组合体应力-应变曲线呈非线性特征,破坏主要发生于煤体,表现为剪切-拉伸复合破坏,且破碎程度呈应变率效应。所建本构模型计算结果与试验数据吻合良好。煤岩组合体损伤演化可分为3个阶段:弹性阶段,损伤增长速率较低;裂纹稳定扩展阶段,损伤逐渐累积;峰后阶段,损伤急剧增加。当围压恒定时,煤岩组合体的累积损伤值随冲击次数或入射能的增加而增大;当入射能恒定时,累积损伤随围压增大而减小;采用Logistic方程的逆函数形式能有效表征煤岩组合体的损伤演化特征。研究结果可为深部煤岩体动力灾害控制提供理论参考。Abstract: To investigate the mechanical behavior and damage characteristics of coal-rock combined body under three-dimensional static and cyclic impact loading,this study employs an improved Split Hopkinson Pressure Bar (SHPB) testing system to conduct experiments on rock-coal-rock structured specimens. The stress-strain curves and failure modes of the specimens were analyzed under varying strain rates and confining pressures. A dynamic constitutive model was established to reflect the strain rate,stress characteristics of coal-rock,and confining pressure effects. The influence of impact incident energy and confining pressure on damage evolution was systematically examined. Results demonstrated that the dynamic stress-strain curves exhibited nonlinear characteristics,with failure primarily occurring in the coal interlayer through shear-tensile composite failure modes. Specimen fragmentation severity displayed pronounced strain rate dependence. The proposed constitutive model achieved high consistency with experimental data. Damage evolution progressed through three distinct phases:an elastic phase with a low damage growth rate,a stable crack propagation phase characterized by gradual damage accumulation,and a post-peak phase featuring abrupt damage escalation. Under constant confining pressure,cumulative damage increased monotonically with an increase in either the number of impacts or the incident energy. For a fixed incident energy level,cumulative damage decreased with increasing confining pressure. The inverse logistic function effectively quantified damage evolution patterns. These findings provide critical theoretical insights for controlling dynamic disasters in deep coal-rock engineering.
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