层理对煤体破坏中磁信号特征影响的数值模拟研究

为进一步完善煤矿动力灾害磁信号监测预警技术的相关机理,根据弹性力学、损伤力学、统计学等学科建立了煤体静载破坏中磁信号的力-磁耦合模型,结合RFPA2D软件,研究了层理性质、数量对试样破坏特征及磁信号变化特征的影响。结果表明:(1)不含层理试样以单斜面剪切破坏为主,含垂直层理试样以顺层理滑移剪切-拉伸破坏为主,含水平层理试样先产生局部拉伸破坏,随后裂纹出现发散状扩展;(2)整个加载过程中累积磁脉冲数及磁能可划分为4个阶段,其变化过程呈"零值段—缓慢增加段—跳跃增加段—平稳变化段"的趋势;(3)含垂直层理试样累积磁脉冲数及累积磁能远低于含水平层理试样,且两类试样累积磁能的差值幅度远高于累积磁脉冲数;(4)含水平层理试样,层理数量与其累积磁能及脉冲数呈现出很好的正线性相关关系,且累积磁能增幅远高于累积磁脉冲;对于含垂直层理试样,层理数量与累积磁能之间存在较好的线性负相关关系,而与累积磁脉冲数之间不存在明显关联特征。

Numerical simulation of the influence of bedding on characteristics of magnetic signals emitted from coal failure

In order to improve the mechanism of the technique used to monitor the coal mine disasters by magnetic signals,a magnetic mechanical coupling model was built based on elastic mechanics,damage mechanics and statistics.Combining with the RFPA2D,the influence of bedding on failure pattern and magnetic signal char acteristics was studied.The results show that:① Coal samples without bedding exhibit the characteristics of single slope shear failure,while samples with vertical beddings experience a process of slip shear tensile failure along the beddings.Samples with horizontal beddings suffer local tensile failure firstly,and then cracks propagation in a shape of divergence.② Magnetic pulses and energy accumulated in the whole process of sample failure can be divided into four stages,which are zero stage,slow increase,rapid increase and smooth change,respectively.③ Accumulated magnetic pulses and energy of samples with vertical beddings is much lower than that of samples with horizontal beddings,and the difference value of magnetic energy is much higher than that of magnetic pulses.④ The quantity of bedding of the sample with horizontal beddings has a good positive linear correlation with magnetic pulses and magnetic pulses respectively,and the increase amplitude of magnetic energy is higher than that of magnetic pulses;for the samples with vertical beddings,the quantity of bedding also has a negative linear correlation with magnetic energy,while no correlation characteristics between beddings and magnetic pulses can be seen.