| With the national policy of "green mountains are golden mountains",the construction of green mines has become a top priority in mine construction.For open pit mining enterprises,the problem of large open pits formed by long time mining needs to be solved.Some open pit mines have chosen to backfill the tailings discharged from mineral processing with cemented tailings into the open pit,but the impact of cemented tailings backfill on the stability of the open pit is unclear,while the risk of new pollution to groundwater from the backfilling of metal mine tailings into the open pit is still to be assessed.In view of this,this paper establishes a numerical model of the open pits with/without seepage field for moulded retaining walls and slopes and a groundwater pollution prediction model based on the current situation of the open pits and the physical properties of the tailings and rocks,combined with indoor and field backfill tests,rock mechanics tests and toxic leaching tests,and investigates the safety and stability of the open pits with tailings cemented backfill and the impact of groundwater pollution.The main research elements are as follows.(1)Analysis of the current status of the open pit,geological conditions and the current status of the tailings cementing backfill based on mine engineering data,and assessment of the current status of the groundwater environment in conjunction with the main technical solutions for open pit cementing backfill.(2)The 7d and 28 d uniaxial compressive strengths of the indoor/in-situ backfill and the rock mechanics parameters of the slope were compared and analysed through indoor cemented backfill proportioning tests,in-situ backfill sampling tests and rock mechanics tests,which were used as the basis for the numerical simulation study.(3)The numerical model of open pit cemented backfill was constructed by Slide numerical simulation software under two conditions of no seepage field and seepage field,and it was concluded that for the moulded bag retaining wall above the closure circle,the safety factor of the moulded bag retaining wall was 1.766(>critical safety factor 1.25)and 1.682(>critical safety factor 1.682)under the conditions of no seepage field and seepage field respectively when the backfill was 28 m above the closure circle.(>Critical Safety Factor 1.10).The safety factor of the moulded retaining wall is 1.424(>1.25)and 1.159(>1.10)for backfilling up to 68 m above the closure circle.This indicates that the moulded bag retaining wall remains stable at a certain height of backfill,but the stability of the moulded bag retaining wall gradually decreases as the backfill height above the closure circle increases.In terms of slope stability,the slope safety factor is 1.243(<1.25)and 1.188(<1.20)for the case of no seepage field and seepage field respectively when the backfill height of tailing sand is 0m.When the tailings were backfilled to 48 m,the slope safety factors for the open pit were 1.663(>1.25)and 1.547(>1.20)respectively.This indicates that there is a risk of stability of the open pit slope without backfilling,and the safety factor of the open pit slope increases with the increase of the cemented backfill height.(4)Based on the analysis of the groundwater pollution characteristics of the open pit colluvial backfill,the groundwater pollution risk of the tailings colluvial backfill was evaluated by comparing the groundwater safety standards with the toxic leaching test of the tailings colluvial backfill and the monitoring of the tailings colluvial backfill embodiment site.This is combined with a groundwater contamination prediction data model under extreme conditions to quantify the groundwater contaminant dispersion patterns.Finally,the risk of groundwater contamination is evaluated comprehensively. |
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