Analysis And Prediction Of The Failure Causes Of Large Open-pit Mine Slopes

Large-scale closed open-pit mines,characterized by large scale,mining depth and complex slope,exist in large quantities in China and even in the world.Making full use of these huge underground Spaces has become a hot issue in recent decades,such as the establishment of geological museums,mining parks,storage of nuclear waste,extreme sports venues and so on.Such pits have become an important geological resource.However,due to the influence of mining history,mining mode and management mode after pit closure,there are certain risks in safety,especially the slope of pit.Therefore,it is of great practical significance to study the stability of pit slope and predict the time and place of possible failure for rational utilization of large abandoned mines.Taking Huoyanshan open-pit mine in Baiyin,Gansu Province as the research object,the author analyzed and studied the destruction process and causes by using the existing data and the status quo of the mine's local damage.The numerical model of stability prediction is established to predict the stability and safety of the mine in time and space in the future,which provides the basis for the development and utilization and safety management of the mine in the next step.It also provides reference for the use of similar mines.The thesis mainly carries out the work from the following aspects and carries on the research:(1)Conduct data collection and field geological survey on the mining history,mining methods,engineering geological conditions,ore-closing time,and side slope collapse failure after ore-closing.The geological information of open pit is collected by means of UAV and field survey.The numerical analysis and hierarchical evaluation model of the mine slope are established to analyze the reasons for the failure of the slope and further predict the stability of the slope in the future.(2)In order to study the cause of failure of mine slope,the author established a numerical model of mine slope excavation based on the engineering geological conditions of geological survey.The model is used to simulate the changes of the internal stress field and displacement field during the excavation process and the formation process of the excavation slope.Combined with the structure and structural characteristics of the slope,three potential failure slip surfaces are obtained.(3)The main and secondary factors affecting the slope stability of abandoned open-pit mine are determined by using the principle of analytic hierarchy process.Tectonic factors and hydrological factors are the most significant factors,stratigraphic lithology and topographic factors are the second,human and other factors are the second.(4)According to the limit equilibrium principle,the physical and mechanical parameters of the slope failure are inversely analyzed by using the sliding surface near the surface that has been destroyed,and the weakening process of the mechanical parameters of the slope rock mass is deduced according to the continuous period from the formation of the slope to the failure of the slope.(5)Based on the present situation,the numerical model of slope prediction is established.According to the model prediction analysis,the safety reserve of secondary potential sliding surface is only 28%?30%,and the damage may occur within 4?7 years.The combination of three potential sliding surfaces is good,and the damage will not occur in a short time.According to the model,the slope under earthquake condition is predicted.Based on the present situation,the numerical model of slope prediction is established.According to the model prediction analysis,the safety reserve of secondary potential sliding surface is only 28%?30%,and the damage may occur within 4?7 years.The combination of three potential sliding surfaces is good,and the damage will not occur in a short time.According to the model,the slope under earthquake condition is predicted.