Research On Safe And Efficient Disposal Technology Of Underground Goaf In Hequ Open Pit Mine

In the process of open-pit mining,the sudden collapse of goaf poses a serious threat to the safety of personnel and equipment.Hequ open-pit mine was formed by the integration of eight mine resources,with the mined out areas densely distributed in the mine area.The safety prevention and control and disposal technology for the influence of goafs are studied in this paper,so as to ensure the safe and efficient resource development of Hequ open-pit mine.The engineering geological conditions and goafs exploration data of Hequ openpit mine are compared and analyzed,the location of the suspected goafs is determined,and the actual location and size of the seven goafs are determined by combining the drilling verification,on-site monitoring and the stability evaluation of the overlying strata in goafs.According to field investigation and borehole data analysis,the key strata in the upper part of the goaf are 12# coal roof calcareous mudstone and 13# coal roof calcareous sandstone.The physical and mechanical parameters of the surrounding rock mass in the goaf are measured by uniaxial compression,variable angle shear and point load.According to size of goafs,the numerical model and theoretical model of goafs and overlying strata are established,and the settlement of overlying strata in different spans of goafs is obtained through analysis.The results show that: the goaf with a span of more than 50 m will cause apparent destruction on the surface,the span range of single goaf with the biggest influence on the production safety of open-pit mine is 0~40m,and the influence of vibration load on rock displacement is positively correlated with the span.The modeling analysis of double goafs is carried out,and the results show the spacing range of stress superposition effect in multiple goaf is 0~20m.Combined with the failure rules of different spans of goaf,the seven proven stratas that can be safely mined are determined,which provides a basis for the safe and efficient recovery of the overlying thin coal seam in the goaf.According to the goafs with different spans and failure characteristics,four kinds of deep hole blasting methods are proposed to deal with the goafs,the selection and mining equipment model,equipment layout and mining method of mixed coal and rock in goafs are optimized.The research results are successfully applied in Hequ open-pit mine,with 7 mined out areas treated and 5.5Mt residual coal recovered,ensuring the stable production capacity of Hequ open-pit mine during the period of passing through the mined out areas in 2019,with a direct economic benefit of 28 million yuan.There are 54 figures,20 tables,70 references in this thesis.