Evaluation of coal bump risk in excavation roadway based on multi-point stress and displacement monitoring system

With the gradual increase of coal mine depth,the coal bump disaster of deep roadway becomes more serious,so it is of great significance for the research on the monitoring and evaluation technology of coal bump. In order to evaluate the impact risk of deep roadway excavation accurately and fulfill the real-time warning of coal bump,the stress and strain conditions of roadway instability were analyzed based on elastic-plastic mechanics mode. Taking the coal with strong outburst tendency as a test object,the author carried out two stress path tests,i.e.,"fixing axial compression-loading confining pressure" and "loading axial compression-unloading surrounding pressure",which were simulating the loading process of coal body during the roadway excavation,for analyzing the stress and displacement evolution during coal failure. By using Bragg grating with distributed measurement,the stress-displacement monitoring system with multi-point of one hole was developed and tested for the measuring function. Taking stress gradient and displacement gradient as the index for roadway impact evaluation,the coal bump evaluation index system of roadway was constructed,on basis of which the real-time impact risk assessment method of roadway excavation is proposed,combining with analytic hierarchy process and fuzzy mathematical theory. Lastly the stress-displacement monitoring system with multi-point of one hole with impact risk assessment technique of roadway excavation was applied preliminarily in a typical coal bump mine. The results show that with the increase of strain gradient and stress gradient,the hazard of roadway excavation coal bump become more serious,making the mining stress (Δσ) and the lateral strain(ε₃) of coal caused by excavation characteristic parameters predicting coal impact. The stress-displacement monitoring system with multi fiber gratings in one hole has been developed successfully. By testing the error of the stress gauge is 1.54% and the maximum error of the displacement gauge is 3.78%. A real-time impact risk assessment method based on stress-displacement monitoring system was applied preliminarily in coal mine,although the evaluation of technical reliability needs further study.