Multi-parameter while-drilling monitoring experiment of loaded coal and while-drilling outburst prediction method

The prediction results of coal and gas outburst are directly related to the safe mining of coal seams and the scientific implementation of outburst prevention measures. However, it is difficult for the current outburst prediction index system to reflect in advance the changes in the stress and physical and mechanical properties of the coal in front of the working face. A large amount of information reflecting the outburst hazard of the coal is contained in the drilling process. In order to deeply explore the relationship between the drilling information and the stress and physical and mechanical properties of the coal, a simulation drilling and multi-parameter while-drilling monitoring test system for the loaded coal has been independently developed. In this system, The mine-used hydraulic rotary drilling rig can restore the drilling ability of the underground drilling rig. The three-way independent loading and one-way differential loading and unloading module can restore the non-uniform distribution of the stress of the underground coal. The four test spaces of 300 mm×400 mm×400 mm can realize the continuous drilling of the heterogeneous coal. At the same time, the test system can realize the while-drilling acquisition of the drilling parameters and the acoustic emission signal. Using this test system, the while-drilling monitoring experiments under different coal stress/physical and mechanical property conditions have been carried out. The results show that as the coal stress increases, the torque and the pushing force increase correspondingly, and the rotational speed decreases correspondingly. The response sensitivity of different drilling parameters to different physical and mechanical properties of the coal is different. The torque is positively correlated with the triaxial compressive strength of the coal, the rotational speed is negatively correlated with the uniaxial compressive strength of the coal, and the pushing force is positively correlated with the internal friction angle of the coal. The while-drilling acoustic emission frequency band distribution of coal bodies with different physical and mechanical properties is different, and the peak frequency is negatively correlated with the uniaxial compressive strength, the triaxial compressive strength, and the internal friction angle. The further theoretical analysis and experimental research explored the feasibility of evaluating coal stress, physical and mechanical properties of coal, and coal seam gas content with drilling, and a while-drilling multi-parameter prediction model for coal and gas outburst is established. The feasibility of the comprehensive while-drilling prediction research of coal and gas outburst is discussed, and a while-drilling acquisition device for the near-bit acoustic and vibration signals is developed, which provides a theoretical basis and equipment support for promoting the development of the while-drilling prediction technology of coal and gas outburst.