Arch Effect And Case Analysis Of Goaf Under High Mining Stress

Deep mining is the developmental direction of mine at present.The high temperature and high pressure of mining gradually rise with the increase of the depth,which easily induce a series of geological accidents such as roof cracking;surrounding rocks falling,overburden rock slippage,etc.,resulting in major personnel injuries and economic losses.The arch effect of rock is a mechanical phenomenon of self-adjustment and stress transfer due to the internal stress resistance of the rock body.The stability of deep mining can be improved by making the most of the self-bearing capacity of the rock arch and the mining cost will be then reduced.Therefore,the study on the theories and key technologies in this field is of great significance.In this paper,the deep mining goaf of a large mine was taken as the research object.The study on the correlation between the arch effect of the goafs and the size of the stope structure under high stress was carried out through theoretical analysis,field investigation and displacement monitoring and engineering verification methods,based on the theory of arch effect and safety factor.The main work of this paper was summarized as follows:(1)Based on relevant theories and methods of research on arched structures,including the mechanical model and internal force analysis method of two hinged arch,three hinged arch and non-hinged arch,and combined with the complex environment of deep underground mining in a large copper mine,the internal factors,external factors,and main control factors affecting the arch effect of the goaf were analyzed in detail.Subsequently,the most suitable arch structural mechanics model and analysis method for the mine was selected.(2)The method of comprehensive safety factor calculation of the pillar was put forward.The mechanical model of the pillar was set up by analyzing the failure process of the homogeneous pillar under the complex loadings.Based on the study of the variation rule of comprehensive safety factor under different ore pillar size and height,the reasonable mining size of pillar was determined which provides the basis for stope layout.(3)On the basis of determining the reasonable mining size of the pillar(pillar spacing and width),the mechanical model of the roof free arch was established,and the relation between the arch and the arch axis coefficient was then deduced.The study of the spacing and width of pillar and the variation law of the arch shaft coefficient were conducted,which revealed that the effect of the arch of the goaf was depended on the size of the pillar.This result provides theoretical guidance for the design of the structure size of the mining goaf in the deep mining(4)Based on the dependence of the arch effect of goaf and pillar size and the complexity of deep mining environment,the mechanical model of unhinged arch of rock mass was designed.The dependence between the arch effect of goaf and the structure size of goaf(stope span and pillar width)under the action of high stress was then deduced,which provides a theoretical basis for the design of mining structure parameters in deep mining,improving the safety and recovery rate of the goaf.The present study provides theoretical guidance for the structural parameters design of deep high stress mine stope,the inherent safety level of goaf improvement and the recovery rate of metal mineral resources increase.