Development of Torque Logging System for Predicting Rockburst and Coal Outburst

为了提供冲击地压或煤突出预测的备选措施，研制了一种扭矩测井系统，用于记录试钻或超前钻孔过程中的扭矩。该系统具有本质安全的特点，可用于煤矿井下，既可用于干钻，也可用于湿钻。传感器检测到的扭矩通过无线电波传输并记录在安装在防火箱中的录音机上。试验证明，该系统能够在井下钻孔过程中无故障地采集扭矩数据，并在研制扭矩测井系统的基础上，进行了钻孔扭矩与钻屑量、煤的力学性质和煤层应力状态的关系的实验研究。钻孔模拟结果表明，钻孔扭矩和钻屑体积均随作用在煤样上的平均应力的增大而增大，当平均应力大于煤体单轴强度的3倍以上时，就会发生卡钻现象。理论分析也证实了钻孔扭矩与钻孔周围远场应力的关系。由线性弹性和应变软化材料表示。该力学模型使我们能够预测弹塑性边界半径的钻孔周围，以及径向位移的钻孔内表面。

A torque logging system for recording the torque during the test boring or the advance boring has been developed to facilitate an alternative of predicting measures for rockburst or coal outburst. The system is intrinsically safe for use in underground coal mine, and it is available for both the dry boring and the wet boring. The torque detected by a transducer is transmitted via a radio wave and recorded on the taperecorder which is housed in a flame-proof box. The tests have proved that the system is capable of torque data acquisition during underground boring without any sorts of trouble.In addition to developing a new system for torque logging, a laboratory experiment has been carried out to comprehend the relation between the torque during boring, the volume of drillings, the mechanical properties of coal and the stress state in coal seam. The boring simulation has demonstrated that both the torque and the volume of drillings increase with increasing of the mean stress applied to the coal specimen, and resulted in jamming when the mean stress was over three times as large as the uniaxial strength of the coal.The relation between the torque during boring and the remote stress around the borehole has also been confirmed by the theoretical analysis in which the coal seam was represented by means of a linearly elastic and strain-softening material. This mechanical model enables us to predict the radius of elastic-plastic boundary around the borehole as well as the radial displacement at the inner surface of the borehole.