煤体剪切破坏电荷感应规律试验研究

Experimental study on the charge induction regularity in the shearing process of coal

为研究煤体剪切破坏过程中的电荷感应规律,基于变角板法对某矿区煤体在不同剪切角度破坏下进行电荷监测,探究了煤体在剪切破坏过程中的力-电感应变化规律。结果表明:随剪切角增大,煤体发生剪切破坏的强度逐渐减弱,失稳破坏形式由压剪破坏向张拉破坏过渡;煤体剪切破坏过程中有显著电荷感应信号产生,电荷信号异常区域对应于剪应力突变阶段;随剪切角增大,煤体应力峰值前电荷信号逐渐减少并不断向剪应力峰值附近集中,剪应力峰值前累计的电荷量也逐渐减少;提出了煤体剪切破坏过程中产生电荷的机理主要为摩擦作用的观点;电荷感应信号峰值在剪应力达到极限强度之前出现,电荷信号峰值比剪应力峰值提前出现时间随剪切角度增加有减短趋势;在首次出现电荷峰值信号之后短时间内煤体将发生较大幅度的应力跌落过程;可以以电荷信号峰值的出现为基点来预测煤体将要发生变形破坏及通过电荷信号的整体分布特征来揭示煤体剪切破坏规律。

The present paper intends to introduce its study on the charge-inducing regularity of the coal seam in the process of the shear failure.To achieve the purpose,we have done the monitoring test based on the variable angle plate method in hoping to trace and identify the charge-inducing signals of the coal seam mass in different shearing angles.And,then,we have made an analysis of the changing regularity of the electro-sensitive forcecharge induction of the coal seam in the process of the shearing failure on the basis of the experimental results.In the paper,we have also done the theoretical analysis through experiments.The results of our research demonstrate that,first of all,the failure mode tends to transform from the compression and shearing failure and then to the tensile failure with the increase of the shearing angle and the gradual decrease of the shear strength of the coal seam.And,secondly,it would be possible to generate obvious charge induction signals in the process of the coal shear failure in the abnormal areas of charge signals in correspondence with the mutations of the shearing stress.Thirdly,the charge signals tend to get gradually shrunk before the stress peak and continuously concentrate around the shearing stress peak,with the accumulated charge gradually reduced before reaching the stress peak.In accordance with the above situation,it can be concluded that the friction effect should be crucial for the mechanism of the charge generation in the shear failure process of the coal seam.Finally,it would be possible for the peak of charge-inducing signals to take place before the shear stress reaches the ultimate strength.At the same time,with the increase of shearing angle,the time interval between the charge signal peak and the shearing stress peak will be getting shorter and shorter.What is more,a great stress down-drop would occur in a short period of time after reaching the first charge signal peak.With the above study results given in mind,it would be possible for the deformation and failure of coal to be predicted and forecasted based on the evaluation and judgment of the likeliness for the charge signal peak and the shearing failure mode of coal seam by the comprehensive distribution characteristics of the charge signals.