Stability Analysis Of Slope Affected By Goaf In A Transfer From Underground Into Open-pit Coal Mine

In actual production,due to the change of external environment and engineering conditions,considering the technicality and economy comprehensively,the original coal mine will be converted to open-pit mining.The goaf formed in the period of mining has a certain threat to the slope of open pit.In order to solve this hidden danger,this paper studies the stability of slope affected by goaf.The research work of this paper can not only solve the hidden danger of mine production,but also provide engineering experience for other similar underground open pit mines,which has practical significance and reference significanceIn this paper,numerical simulation and limit equilibrium method are used to analyze the stability of two typical sections(sections with high slope and complex engineering geological conditions)affected by coal seam 6-2.It is concluded that the two typical slopes can not be self stable and need to be filled when the ratio of width to span(the ratio of width of one side coal pillar to the span of goaf)is as high as 1:20 After filling,the safety factor of the slope is greater than the specification requirements,which can meet the stability requirementsIn this paper,the numerical simulation method is used to study the stability of slope under different width span ratio.It is found that when the width span ratio of slope exceeds 1:2,the slope cannot be self stable.When the width span ratio exceeds 1:2,the displacement of roof in goaf increases sharply,and the slope will lose stability When the ratio of width to span is 1:2,the influence of goaf depth on slope is not significantBased on the principle of strength reduction,the paper makes strength reduction for the filler and slope in the goaf.It is concluded that the parameter cohesion of the filler material should be between 19.6kPa and 18.7kPa,and the internal friction angle should be between 21.2 °and 20.1°.According to the economic environment of the mine,the dry filling method is suitableThe stability of two typical sections is analyzed by numerical simulation method and limit equilibrium method,and it is concluded that the safety factor of the filled slope can meet the requirements of the code.And the safety factor calculated by the limit equilibrium method is smaller than that calculated by the numerical simulation method,which shows that the calculation result of the limit equilibrium method is conservative.