Research On Heterogeneous Features Of Tailings Backfill In Metal Mine And Its Mechanism

Mining with tailings backfill can make comprehensive use of mine tailings and realize the purposes of safety management of ground pressure and control of surface subsidence,etc.which is a mining method according with national requirements of green mining industry.To properly backfill filling materials into mined-out stope,it is usually necessary to use water as carrier to make all solid filling materials into slurry so that they can be suspended in the slurry for transportation.After backfilling,solid filling materials will settle down and be layered by gravity,which will cause heterogeneity of backfill body and affect its strength.Therefore,in order to explore the heterogeneous properties of backfill body caused by settlement of filling materials,and to clarify its influence on strength of backfill body,so as to reveal the mechanism of effect of backfill concentration on strength of backfill body,and provide a reference for filling practice of mines,by comprehensively combining experimental researches with theoretical analysis this paper has thoroughly studied the settling and layering process of filling materials in backfill slurry and the heterogeneous properties of backfill body and its influence.Bleeding tests of tailings backfill slurries have been launched,the bleeding water of slurries with different cement content,curing time and particle size distribution(PSD)has been measured,and the influence of above factors on changes of slurry concentration and water content of backfill body because of bleeding have been quantitatively compared and analyzed.Heterogeneous properties tests of backfill body have been launched,by using the method of dividing a backfill body into different layers,the PSD of tailings,cement content and porous properties of backfill body have been measured to quantitatively analyze heterogeneous properties of backfill body.And by analyzing the experimental results,the relations among the heterogeneous properties have been studied,then the comprehensive effects of backfill concentration on heterogeneous properties have been revealed.The settling experiments of slurries with different tailings PSD have been launched,with the guidance of particle settling theories,the settling mechanisms of classified tailings,small particles and mixed materials with different particles PSD have been studied.Based on experimental results,the lay of settling and layering of particles in tailings backfill slurries has been studied,then the mechanism of heterogeneous properties of backfill body caused by settling and layering of filling materials has been revealed.The experimental study of the effect of heterogeneous properties of backfill body on its strength has been launched,through observing the changes of characteristics of internal structures of cemented tailing backfill under uniaxial compression and comparing the experimental results of the heterogeneous properties of each layer of backfill body,the influence of the heterogeneous properties of backfill body on its strength has been analyzed and revealedBased on conclusions obtained from the analysis of heterogeneous properties of backfill,the in-situ backfill of Anqing copper mine has been evaluated by the method of combining similar model tests and in-situ backfill strength tests.