Stability Evaluation And Parameter Optimization Of Complex Structural Slopes In HuShuoTu Open-pit Mine

Open pit mining projects often encounter complex tectonics such as faults,folds and steep slopes in the process of advancing,which have important effects on mine production technology,mining dumping engineering design,slope stability,etc.During the process of excavation,the working face is located in a different time and space domain from the tectonic zone.The tectonic zone is subjected to excavation unloading,which will have a significant impact on mining engineering and slope stability,and directly affect mining production safety and economic benefits.Based on the open-pit mining project in the Hu Shuo Tu complex tectonics zone of Mongolia,this paper uses comprehensive research methods such as data collection,field investigation,geological exploration,mechanical test,numerical simulation,theoretical analysis and slope stability evaluation to study the east and west of B-B’section of Hu Shuo Tu open-pit mine Study the deformation law and seepage path of the west end slope(containing faults,fold structures,and steeply inclined rock formations)during groundwater seepage and mining disturbance processes.Based on the deformation and failure characteristics of the slope,propose dynamic optimization plans for slope angle and other parameters,as well as landslide prevention and control measures The main research content is as follows:(1)By analyzing the engineering geology and hydrogeological conditions of the mining area,we have mastered the occurrence characteristics of the mining area and strata lithology,the development of fault structures,the distribution characteristics of inward and anticlinal fold structures in the mining area,and the underground hydraulic connections.Targeted engineering geological exploration research and indoor testing work have been carried out,typical engineering geological profiles have been established in the mining area,rock and soil mechanical tests have been conducted on drilling samples,and mechanical parameters of slope rock and soil have been summarized for mechanism research and stability evaluation.(2)A three-dimensional simplified calculation model was established,represented by the B-B ’section in a typical engineering cross-section.Fully considering the structural characteristics of faults,synclines,anticlines,and reverse dip rock layers within the slope,an excavation plan was designed for distribution within the structural zone.FLAC3 D was used to simulate and calculate the deformation characteristics of the eastern and western slope distribution during the mining stage.The maximum shear stress in the western slope during the syncline downward mining stage occurs at the structural bend of the syncline axis,and the slope is prone to layered shear slip failure;During the mining phase of the anticline,the overall deformation on the east side is greater than that on the west side,and the stress shows a phenomenon of "west pressure and east pull".The deformation and damage are concentrated on the two wings of the anticline;The main deformation of the east end slope occurs at the inverted rock layer,manifested as tensile failure at the top of the slope and shear failure of the internal strip shaped inverted weak layer.(3)The distribution and variation characteristics of seepage field during the mining process of the east and west slopes of the mining area were analyzed using Geo Studio software.The simulation results showed that the internal seepage path of the west slope was concentrated in the sandstone layer at the bottom of the fault,and there was a stepped change in pore water pressure at the fault,which decreased with the decrease of water level.As the excavation depth increases,there are three potential water gushing points on the slope surface;As the excavation depth and water level change,the location of the water inflow point and the maximum hydraulic gradient change area of the east end slope are concentrated in the middle of the anti inclined coal seam and mudstone.The anti inclined structural rock layer of the entire east end slope is a key factor affecting the stability of the slope.(4)The stability calculation of the slope contour of the original mining and stripping plan of the B-B ’section in the mining area was carried out using the limit equilibrium method,and the safety factor change during the process of groundwater level lowering from+360m to+300m was investigated.The results show that when the groundwater levels on the east,west,and left and right slopes of the anticline are controlled below+330m,+320m,and+340m respectively,the safety factor of the slope tends to remain unchanged,and the overall slope belongs to an unstable state;Based on the simulation analysis results,the parameters of single step and overall slope angles were optimized for the east and west slopes.Through calculation,the slope angles of the upper and lower stages of the east slope were determined to be 33° and29°,respectively,and the overall final slope angle was 31°;The slope angles of the upper and lower stages of the western slope are 26° and 30°,respectively.The final slope angle of the western slope is 29°,and the stability of the optimized slope meets the requirements of the safety reserve coefficient.