Overburden failure induced by instability of coal pillar in strip Wongawilli mining

In order to study the failure mechanism and movement characteristics of overburden induced by coal pillar instability,the first continuously-extraction area of No． 15 coal seam in Zhaowu Mine was taken as a geological model, and theoretical analysis,similar simulation,site measurement and formula calculation were combined to build a system-atic model in strip Wongawilli mining,and the coal pillar instability and its effect on overburden failure were analyzed. The results show that in the pillar system of strip Wongawilli mining,some damaged or irregular pillars would become instable under the coupling effect of mining pressure,ground water immersion and other unfavorable factors,corre-spondingly,relevant pillars would be affected and become instable. Therefore,“Domino effect” occurred and the whole pillar system invalidated. Overburden failure was aggravated by pillars instability,the mining condition transformed in-sufficient mining stage to sufficient mining stage,which resulted in surface subsidence.