| Under the concept of sustainable development and ecological environment protection in the new era,filling mining method,as a key method to deal with tailings and underground goaf,is widely used in underground mines because of its advantages of safety,efficiency,green economy and environmental protection.However,many factors such as the filling law of the mined out area and the filling strength of the mined out area will seriously affect the filling strength of the mined out area,It can provide some reference and reference value for the in–depth application of cemented filling technology in China.According to the four stratification factors of different horizontal stratification number,different interlayer angle degree,different filling time interval and different interlayer lime sand ratio,the uniaxial compression experiment is carried out on the layered structure characteristics of cemented backfill,the strength reduction law and failure form under the influence of stratification factors are analyzed,and the numerical calculation model of layered backfill is established by using particle discrete element software PFC(Particle Flow Code),The strength reduction of cemented paste backfill under the influence of stratification factors is deeply studied from the meso level.(1)Based on the uniaxial compressive strength of cemented layered paste backfill under four influencing factors: different number of filling layers,different angle between filling surfaces,different filling time interval and different interlayer ratio,the strength of cemented layered backfill is fitted and analyzed by using different functions,and the complex correlation coefficient of fitting curve between cemented paste backfill and different number of horizontal layers,different angle between filling surfaces and different filling time interval is obtained,Polynomial function can better characterize the quantitative relationship between the strength of layered paste backfill and different influencing factors.(2)The concept of strength reduction coefficient is introduced to calculate the strength reduction of cemented filling under the influence of different stratification factors,and the strength reduction interval distribution of filling under the influence of different stratification factors is obtained.When the filling concentration is 68%–74%,the corresponding value of horizontal layered filling is between 0.3322–0.9500,and the corresponding value of included angle layered filling is between 0.3380–0.7720.The reduction coefficient of layered backfill at different time intervals is between 0.2572–0.3527.Different interlayer angles and different time intervals have a great impact on the reduction of cemented backfill.(3)The strength of the upper filling body obviously lags behind that of the lower filling body.By analyzing the failure form of layered filling body,it is found that most of them have broken swelling failure,and the lower layer basically remains in good shape.Compared with the non stratified filling specimen,the failure is more longitudinal cracking.At the stratification plane of the layered filling body specimen,there are separation and dislocation phenomena in varying degrees.The influence of the angle factor on the separation and dislocation is much greater than that of the number of layers on the layered filling body.(4)The particle discrete element software PFC is used to simulate and calculate the cemented backfill with different layers and angles between layers with mass concentration of72% and ash sand ratio of 1:8,explore the reduction law of water bisection and angle layered cemented backfill at the micro level,analyze the distribution of meso cracks and force chain network after the failure of cemented backfill,and explore the failure mechanism of backfill model under different friction coefficients.This paper contains 47 figures,21 tables and 81 references. |
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