Study On The Precursor Information And Forecasting Inedices Of Pillar-rockburst In Fold Area

The geological tectonic movement in the northwestern of China is active,and the fold structure is developed.The rockburst caused by the composite factors of folds and coal pillar is more and more common in the coal mine,but there are few studies on the pillar-rockburst in fold area.Therefore,this paper takes the pillar-rockburst in fold area of Hujiahe Mine as the research object,and study the precursor information and forecasting indices of pillar-rockburst in fold area,by theoretical analysis,on-site observation and identification,laboratory test and fuzzy mathematical calculations,etc.Achieve accurate monitoring and warning during the mining process,and take effective measures to prevent the occurrence of pillar-rockburst in fold area.The stress state and rockburst characteristics of fold structure and pillar structure are analyzed theoretically.The horizontal static load stress is concentrated in the fold region,and the coal pillar is concentrated by the vertical static load stress.The pillar and its surrounding rock mass in fold area is superimposed by vertical and horizontal high static load stress,at the same time.When the static load stress,or the dynamic stress and static load stress such as excavation and microseism overlap the critical stress level of the rockburst,the rockburst disaster will be induced.The rockburst of Hujiahe Coal Mine belongs typical fold and pillar type.According to the precursory information characteristics of monitoring and warning in the stage of coal pillars and folds,the selected parameters,like A(b)?A(t)?S??F?EEM?TSE are presented with high-value anomaly,b and AC are presented with low-value anomaly when the rockburst occurs.The whole stress-strain curve of coal sample failure process in Hujiahe coal mine was obtained by laboratory test.According to the experimental observation results,during the failure of the sample,the parameters determined on-site show obvious rising or falling characteristics,and have a very high positive or negative coupling relationship with the stressstrain curve.Thus,the precursor information of rockburst can be identified from the coupling relationship between these parameters and stress and strain,and the feasibility of forecasting pillar-rockburst in fold area can be revealed.Based on the mechanical response of coal and rock in the process from loading deformation to instability failure,the relationship between stress and strain in the elasto-plastic transition stage and plastic deformation stage,the dimensionless standardized treatment was carried out to obtain the monitoring and warning indexes and risk discrimination criteria of pillar-rockburst in fold area.Based on the in-situ observation and experimental results,a comprehensive forecasting indicator system consisting of 8 indicators was constructed.The Gaussian model is combined with the exponential distribution function of the sample failure time in the reliability theory to establish the membership function of each index in the comprehensive monitoring and early warning system.Applying the F-score method of confusion matrix to determine the weight of each index in the comprehensive forecasting index system.Finally,through the principle of maximum membership degree principle(MMDP)and variable fuzzy pattern recognition mode(VFPR),obtain the comprehensive forecasting results of pillar-rockburst risk in fold area.Using the comprehensive monitoring and warning method of pillar-rockburst in fold area to monitor the tremors in the 401103 working face of Hujiahe Coal Mine,and obtained a good application results.