Stability Analysis And Reinforcement Measures Of High Slopes In A Deep Open Pit Min

A deep depression open-pit ore deposit is a super large gold deposit with copper and iron in synbody and associated lead,zinc and silver.The deposit type belongs to the skarn-hydrothermal gold polymetallic deposit related to the alkali-rich porphyry of Himalaya stage.The minimum design elevation of open pit mining is 1385m,the sealing ring elevation is 1834m,and the total height of the final limit slope reaches 540m.In addition,the geological structure and rocks in the ore section are complex,soluble rocks and loose rocks are widely distributed,strong weathering,large thickness,and strong karstification.In addition,the mining area has undergone multi-stage tectonic and magmatic activities,and the faults are relatively developed.The joint density is5.05～6.62 joints/m,and the geological structure is complex.The open-pit slope,especially in the southwest area,has been affected by F₆,F₃₀,F₁₀₆ and other fault zones under the influence of extended mining and stripping and expanding,which seriously threatens the safety of mine production.Based on the methods of field investigation,laboratory test,numerical simulation and theoretical analysis,the stability analysis of the present slope and the final slope is carried out around the southwest area of the open-pit slope of the mine section.Based on this,a systematic and reasonable reinforcement and treatment scheme is proposed and tested.The main research contents and achievements of this paper are as follows:（1）Through field investigation and indoor rock mechanics experiment,the quality evaluation and classification of ore rock in Zone 5 and 6 of the stope are carried out.After comprehensive analysis,it is finally determined that the quality grade of rock mass in each layer is between gradeⅢand gradeⅤ.On this basis,the mechanical parameters of rock mass in different strata are calculated by Heok-Brown strength criterion.（2）The 3D geological model of the 5,6 area in the southwest of Beiya was established by3D Mine and Rhino,and the finite difference software FLAC^3D was imported for numerical simulation analysis.Considering the influence of fault,groundwater,dead weight,blasting,earthquake and other factors,it is concluded that the safety factor of slope under the condition of dead weight is 1.8,and the slope is in a stable state.Under the action of dead weight+seismic force,the safety factor decreases somewhat（1.1）and is basically stable.Under the action of blasting vibration,the safety factor is 1.2,and the slope is in a basically stable state.（3）In order to study the stability of the slope in the process of stripping and expanding the slope to the final slope design,the excavation of the current slope was conducted successively in six steps from the final slope design,and the numerical analysis was carried out from the aspects of stress,displacement and shear strain increment by integrating the influence of fault,groundwater,self-weight,blasting and earthquake.The results show that the slope is basically stable in the first and second steps,and the local displacement occasionally increases.When the excavation reaches the third step,the slope basically enters the understable state.When the excavation reaches the fourth step,the slope completely enters the unstable state under the influence of earthquake.（4）Combined with geological situation and stability analysis,the slope protection and treatment method of sedum was adopted for Q₁S strata above 1860m in the southwest part of a mine stope;Taking into account the actual situation of the mine and combining with engineering analogy method,the GPS2 SNS active flexible protection system with 1650m～1840m in area 5has crosswise layout with transverse support cord of 16m and longitudinal support cord of 12m,with the gap between them being 4.5m×4.5m.As for the local collapse area affected by F₆ and F₃₀ fault fracture zone at 1550m～1660m in the west of stope,prestressed anchor cable is used to strengthen it.The length of anchor section is 12m,the length of free section is 25m,36m and37m,the dip Angle of anchor cable is 20°,and the distance of anchor cable is 4m.Based on the results of field investigation and indoor rock mechanics tests,a large three-dimensional geomechanical model of the southwest side of the open-pit stope of a deep concave open-pit mine is constructed.The numerical simulation method is adopted to obtain the stability of the current slope in the study area and the stability of the slope in the process of peeling and expanding the slope to the final design by integrating the influence of fault,groundwater,self-weight,blasting and earthquake.Therefore,a protection and reinforcement system for slope instability in the study area is proposed.The research results of this paper can provide references for the research of mine slope stability,the prediction and analysis of slope stability from stripping to final,the long-term safety and stability of slope and the safety warning and disaster control.