Study On The Precursory Characteristics And Warning Methods Of Rockburst In Laohutai Coal Mine

In recent years,the depth and intensity of coal mining in China are increasing,the mining conditions of coal seams are becoming more and more complex,and the rockburst disaster is becoming more and more serious,which seriously restricts the safe production of coal mines in China.Although the risk of rockburst is reduced,the floor fault activation impact,coal pillar impact and so on are still severe and more complex.The study on the precursory characteristics and early warning methods of rockburst in Laohutai coal mine is lacking.In this paper,the dynamic behavior and law of the impact failure of Laohutai coal sample are experimentally studied,the precursory characteristics of micro earthquake,acoustic emission and electromagnetic radiation signals of the impact ground pressure in Laohutai coal mine are analyzed,and the comprehensive early warning method of the impact ground pressure is proposed and verified on site.The main research results of this paper are as follows:(1)The dynamic behavior and law of impact failure of Laohutai coal sample are tested and analyzed.The mechanical properties of coal body are closely related to the dynamic and static loads.When the dynamic load is fixed,the dynamic strength of coal body increases with the increase of axial static load,while the peak strain decreases with the increase of axial static load.When the axial static load is fixed,the dynamic strength and peak strain of coal body increase with the increase of dynamic load,and the coal body is more tolerant when the dynamic load is larger Prone to damage.In addition,the dynamic load acts on the coal sample with the stress wave of half sine wave,and the reflected wave amplitude value is positively related to the axial static load and dynamic load.(2)The acoustic emission law of coal impact failure is analyzed.The acoustic emission signal of the impact fracture of coal sample has a good correspondence with the load,but the change rule of the dynamic load and the static load is different.When the dynamic load is fixed,the peak AE count and peak energy decrease with the increase of the axial static load;when the axial static load is fixed,the peak AE count and peak energy increase with the increase of the dynamic load.(3)The occurrence rule and main influencing factors of rockburst in Laohutai coal mine are analyzed.Based on the statistical analysis of the rockburst events in Laohutai coal mine,combined with the data of mine geology,mining methods and techniques,support methods,etc.,the main factors of rockburst in Laohutai coal mine are: fault structure,mining activities,burial depth,rock properties and support conditions,etc.The stress of coal and rock mass in the fault structure is more concentrated,and it is easier to activate and produce rockburst;the mining activity will cause the activity of overlying strata,and it will also produce far-field stress wave.The superposition of the disturbance wave and the high stress of coal and rock mass will cause the deformation wave of coal and rock mass to a greater extent,thus causing the instability of coal and rock mass and rockburst;the high-strength support of Laohutai Coal Mine To a certain extent,it reduces the stress gradient of the surrounding rock of the roadway,and also resists the destructive force of a certain strength impact ground pressure.(4)The precursory characteristics of rockburst in Laohutai coal mine are analyzed.In the process of evolution of rockburst in Laohutai coal mine,the change trend of acoustic electric signal has good precursory law.Before the occurrence of rockburst,the acoustic electric signal has obvious fluctuation.The overall change trend is “ / ”、“ V ” and “ N ” type.The common feature is that there is an energy accumulation process in the evolution process of the impact pressure;the change trend of the microseismic signal is mostly “∧” type,which will rise and fall before the impact event,and it is easy to have an impact in the process of the microseismic energy decline,which should be paid attention to when the microseismic energy shows such a trend.This is the main law of acoustic signal response of coal and rock mass under load.(5)Based on the laboratory test and analysis results and the acoustic electric and microseismic data before the occurrence of the rockburst in Laohutai coal mine,an early warning criterion of the rockburst with the critical value and the dynamic rate of change as the index is proposed,and a multi index comprehensive early warning method of the rockburst based on the acoustic electric signal and microseismic signal is established,and the method is applied to the on-site monitoring of the rockburst in Laohutai coal mine The results show that the early warning method is effective.The research results are helpful to further improve the accuracy of prediction of rockburst in Laohutai coal mine,to ensure the safety of production in the coal mine,and to improve the mine dynamic disaster prevention system in China.There are 43 figures,10 tables and 82 references in this paper.