受载煤体电磁辐射动态非线性特征

Nonlinear dynamic characteristics of electromagnetic radiation during loading coal

为了研究受载煤岩变形破裂过程中电磁辐射动态非线性特征,对不同力学性质的煤样进行了不同加载速率的单轴压缩实验和分级加载实验,发现受载煤体电磁辐射由煤的力学性质、应力水平及加载速率共同决定,煤的强度越高、加载速率或应力水平越大,电磁辐射非线性特征越明显.依据煤的力学性质,受载煤体在变形破裂过程中其破坏前兆信号可以划分为3种类型.应用时变多重分形理论分析了电磁辐射时间序列,结果表明煤岩破裂失稳之前多重分形参数Δαm随载荷的增加呈增大趋势,在破坏后期Δαm有一定程度降低.裂纹扩展越激烈,煤岩内部损伤程度越高,Δfm越小.Δαm,Δfm的动态变化可以用来评价煤岩变形破裂过程及破坏阶段.

The nonlinear dynamic characteristics of electromagnetic radiation （EMR） due to the deformation and fracture development of coal during loading is investigated, uniaxial compres- sion and multi-stage loading experiments are carried out on coal samples with different mechanical properties. Results show that the EMR from coal during loading depends on the mechanics properties of coal sample, the stress level and the loading rate. The dynamic nonlinear characteristics of EMR are more apparent when experiments are performed under higher stress or loading rate, or on coal samples with higher strength. Before the failure of coal samples happens, the EMR from loaded coal can be divided into three types depending on the mechanical properties of coal. The time series of EMR is analyzed using the time-varying and multi-fractal theory, it can be concluded that the multi-fractal parameters △αm increases during enhancing loading level before the failure of coal, but it will decrease after failure. The value of △fm increases with more intense damage and fracture development inside the coal. The dynamic chan- ges of △αm and △fm can be used for evaluating the deformation and failure of loaded coal.