Effects Of Polymer Materials On The Mechanical Properties Of Tailings

Tailings?artificial sand?,the byproducts of mineral processing,are special solid wastes.With the development of the mining industry,a large amount of tailings are piled up into the tailings pond.The tailings pond is dangerous source of debris flow with high potential energy.It is like a“bomb”,threatening the life property safety and living environment of the resident of towns and villages downstream of the tailings reservoir.The safety situation of tailings pond is serious and needs to be solved urgently.Among the factors that affect the stability of tailings dam,the mechanical properties of stored tailings are the key one.In order to improve the severe safety and environmental situation of tailings ponds in China,it is necessary to carry out a research on the mechanical properties improvement of tailings.In this paper,the copper mine tailings with relatively large stockpiles were taken as research objects.A comprehensive method combining theoretical analysis,laboratory test and numerical simulation was used to carry out this research.Firstly,the particle shape,mineral composition,occurrence environment of tailings and effects of common compounds on mechanical properties of tailings were studied.Secondly,the study of improved tailings was carried out by selecting polymer materials as additives.It was found that the polyacrylamide was the most effective additive.The mechanical properties,aging characteristics and improvement mechanism of tailings improved by polyacrylamide?PAM?were studied.Then,the mechanical properties and improvement mechanism of tailings improved by polyacrylamide and basalt fiber?PAM-BF?were studied.Finally,the improvement effect of the tailings dam constructed by PAM improved tailings and PAM-BF improved tailings was analyzed.The research results could provide theoretical and technical support for improving the stability of tailings pond.It can also provide service for the construction of safe and harmonious mines.The main research work and achievements are as follows:?1?In order to reveal the differences of particle shape between tailings and natural sands,the microscopy and image processing technologies were used to quantify four indicators?flatness,roundness,convexity and roughness?which can well quantify the shapes of particles.Furthermore,four tailings?gold,tin,copper and iron?and two natural sands?river sand and sea sand?were selected for such comparisons.?2?The mineral composition and chemical composition of tailings,the water quality of tail water and the potential chemical action between tailings and tail water were analyzed.Based on the idea of soil chemical improvement method,the effect of common compounds?acid solution,alkali solution,CaCl₂ solution and FeCl₃ solution?on the mechanical properties of tailings was studied.The results show that the improvement of common compounds on mechanical properties of tailings was not ideal.Thus,it is necessary to find other types of materials to carry out research on the mechanical properties of the improved tailings.?3?Based on the idea of chemical improved soil method and the existing research of soil improved by polymer,four polymer materials?polyacrylamide,sodium carboxymethyl cellulose,polyvinyl alcohol and calcium lignosulfonate?were selected as additives.Firstly,the effect of polymer material type,polymer material content and curing time on the mechanical properties of tailings was studied by geotechnical test?direct shear test?.In order to further test the influence level of external factors on the mechanical properties of tailings improved by polymer materials,the water stability and anti-aging ability of tailings improved by polymer materials were studied through soaking test,wetting-drying test and freeze-thaw cycle test,respectively.It was concluded that polyacrylamide?PAM?behaves the best improve the mechanical properties of tailings.Moreover,the tailings improved by PAM have good water stability and aging ability.?4?The improvement effect of polyacrylamide?PAM?on three kinds of tailings?silty clay,silty and silty sand?were systematically studied by consolidation test,triaxial test and dynamic triaxial test.The research contents include consolidation characteristics,shear strength?cohesion and internal friction angle?,dynamic strength,dynamic shear modulus,damping ratio,dynamic pore water pressure,etc.It was concluded that PAM can effectively improve the compressibility and antiliquefaction performance of tailings.The improvement effect of the shear strength of tailings improved by PAM was also related to the type of tailings.?5?The interaction between polyacrylamide?PAM?and tailings particles was analyzed by means of CT scanning technique and X-ray diffraction technique.The results show that PAM can make the inner structure of tailings more uniform.However,there was no chemical reaction between PAM and tailings particles to form new substances.It indicates that the principle of PAM improved tailings should be adsorption.The adsorption performance and influencing factors of PAM in tailings were studied by adsorption test.The mechanism of PAM improved tailings was further explored.?6?The mechanical properties of tailings improved by polyacrylamide?PAM?and basalt fiber?BF?were studied by geotechnical test?direct shear test and triaxial test?.In addition,the interaction among PAM,BF and tailings was studied at a microscopic level by means of scanning electron microscopy and CT machine.The results show that the PAM could further enhance the improvement ability of tailings improved by single BF.And the shear strength of the tailings was effectively improved.?7?The stability of the tailings dam constructed by unimproved tailings,PAM improved tailings and PAM-BF improved tailings was calculated.It was concluded that the stability of tailings dam constructed by PAM improved tailings and PAM-BF improved tailings can be effectively improved.Furthermore,the anti-seismic liquefaction of tailings dam constructed by PAM improved tailings can be improved.