Development of Torque Logging System for Predicting Rockburst and Coal Outburst

为便于选择冲击地压或煤与瓦斯突出的预测措施，研制了用于记录试验钻孔或超前钻孔过程中的扭矩的扭矩记录系统。该系统在煤矿井下使用具有本质安全性，干式和湿式均可使用。传感器检测到的扭矩通过无线电波传输，并记录在装有隔爆盒的磁带记录器上。试验证明，该系统能够实现井下掘进过程中扭矩数据的实时采集，并开发了新型扭矩记录系统，并进行了室内试验，了解了掘进过程中扭矩、钻井量、煤体力学性质与煤层应力状态之间的关系。钻孔模拟表明，随着施加在煤样上的平均应力的增加，扭矩和钻头的体积都会增大，当平均应力大于煤体单轴强度的3倍以上时，就会出现卡钻现象。通过用线弹性应变软化材料来描述煤层的理论分析，也证实了钻孔扭矩与钻孔周围的远应力之间的关系。这一力学模型使我们能够预测井筒周围弹塑性边界的半径以及井筒内表面的径向位移。

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.