Research on the mechanism of overall instability type rock burst of fault coal pillars in deep topsoil fully mechanized top coal caving mining area
Rockburst induced by the overall instability of fault coal pillar in the stope under thick overburden soil exhibits destructive characteristics such as high concealment,strong destructiveness,difficulty in protection,and long duration,which is challenging to predict and prevent effectively in the coal mine field.Taking the 2305S working face of a mine in the Juye coal field as the engineering background,this study adopts theoretical analysis,numerical simulation,and field measurement to investigate the mechanism of rockburst induced by the overall instability of fault coal pillar in the stope under thick overburden soil.The conclusions are as follows:the study discusses the spatial structure and mechanical characteristics of the initial and periodic interactions of rock-soil strata in the stope under thick overburden soil,designs a calculation method for the load-bearing strata to bear the transferred load,overlying self-weight load,and fault structural load,and proposes a mechanical criterion for the rockburst induced by the overall instability of the fault coal pillar in the stope under thick overburden soil.According to the evolution law of simulated stress growth rate,the mining process of fault coal pillars is divided into energy storage stage and critical stage,in which the overall instability shock hazard level rapidly increases during the critical phase.The mechanism of rockburst induced by the overall instability of fault coal pillar in the stope under thick overburden soil is revealed:the fault coal pillar,formed by the intersection of the fault and the goaf,carries a high level of base stress.When the working face advances to the initial interaction phase of the rock-soil strata,the transferred load from the trend strata increases the stress level of the fault coal pillar,while its bearing area decreases continuously under the conditions of continuous mining.When the load exceeds the instability threshold of the elastic bearing zone,a rockburst caused by overall instability occurs.A control plan for this type of rockburst is designed,including pre-mining overall impact risk assessment,well-ground joint regional monitoring-nuclear stress local early warning,and graded bearing multi-layer pressure relief design.
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