| At present,the depth of mining in China,underground temperature continues to rise.At the same time,a large number of mine solid waste piled on the surface not only pollutes the surrounding environment,but also brings certain security risks.Solid waste filling is an effective way to dispose mine waste stone tailings,and it is also an important part of building green mines.In this paper,based on the deep high temperature environment of Gaofeng Mine,the optimal ratio parameters and optimization of waste rock and tailings mixed filling materials meeting the requirements of pumping technology and high strength filling body were studied by means of field investigation,literature retrieval,laboratory test and algorithm analysis.The main findings are :(1)Through the analysis of physical and chemical properties of waste rock and tailings,the feasibility of waste rock as underground filling materials is evaluated.The results show that waste rock do not contain toxic substances,and can be used as underground filling materials.When the waste-tailing ratio is 7:3,8:2 and 9:1,the mixed aggregate composed of waste rock and tailings has good compactness.According to the actual situation of Gaofeng Mine and the characteristics of filling material,the scheme of underground mobile pumping filling system is proposed.(2)The orthogonal test at room temperature was carried out,and the filling ratio meeting the requirements of the mine was preliminarily obtained as follows : slurry concentration 86%,cement-sand ratio 1:4,waste-tail ratio 9:1,and pump dosage 1%.According to the orthogonal test data,the multi-objective optimization model of the compressive strength,slurry bleeding rate and slump of the filling body is established.The multi-objective optimization algorithm based on the improved gamultiobj function of NSGA-II is used to optimize the ratio of waste rock and tailings mixed filling materials.The results show that the optimized target values meet the requirements of the mine,and the cost of the optimized material is reduced by 12.7% compared with that obtained by the orthogonal test.(3)In view of the high temperature environment under the Gaofeng Mine,the ratio test of waste rock and tailings mixed filling materials with different curing temperatures was carried out.The results show that when the temperature of filling area under the Gaofeng Mine is lower than 40°C,the ratio of filling materials with high waste-tail ratio is recommended.When the temperature exceeds 40°C,the ratio of filling material with low waste tail ratio is recommended,which can ensure the long-term strength of the filling body and improve the stability of the filling body.(4)The mechanical properties and microstructure of the filling body under different curing temperatures were studied by pressure testing machine,nuclear magnetic resonance,XRD diffraction and scanning electron microscopy.The evolution law of the strength of the filling body under different curing temperatures was analyzed,and the relationship model between the curing temperature and the uniaxial compressive strength of the filling body under different waste-tailing ratios was established.The variation law of the stress-strain curve and the failure mode of the filling body under different curing temperatures was explored.The evolution law of the pore structure of the filling body under different curing temperatures was studied,and the consolidation characteristics of the mixed filling material of waste rock and tailings were revealed. |
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