| Mineral resources are important material basis for human survival and social development. Henan province is one of the most important mineral resources in China, the development and utilization of mineral resources of which occupy a pivotal position in the national economy. However, due to the limitation of cognition, while the national economy development is satisfied and huge economic benefits are created, the large development and utilization of mineral resources has caused prominent environmental problems, which has severely hampered the sustainable development of the mining province.In the mine geological environment of western Henan province, the disaster caused by collapse, landslide, debris flow and mined out area breakdown are of most severe in both quantity and damage level, which have gradually become the main geological hazards of the western Henan Province affecting the sustainable development. Due to the complex regional structures, deep-cutting valleys, large terrain elevations, sparse vegetations, and vulnerable geological environment in western Henan Province, and coupling with the mine activity and the susceptibility of the area, the metal mining in those areas has exacerbated the region’s geological disasters. The most typical and outstanding issues within the mine geological environment are slag debris flow, slag heap slump, ground subsidence, avalanches and landslides caused by underground mining as well. Although some treatments have been taken on the key projects, little mitigation effects have played their role on the overall mine geological environment problems.In this paper, the mine risk analysis was carried out from the two aspects of theoretical model and case analysis. The hazard evaluation model of regional and site of mine geo-hazard, the vulnerability assessment and risk assessment model of elements at risk including economics and population were studied respectively. Taking the Luanshigou located in Zaoxiangyu, Qinling metal mining area of western Henan as examples, the hazard evaluation model, vulnerability assessment model and risk assessment model were proposed in this paper. Considering the superposition of two geological disasters and the geological disasters chain effect of valley basin, the mine geological disaster risk assessment system and model were studied and practiced. And the paper proposed that the mine geological disasters treatment should consider the impact on the next level treatment project when the peripheral or upper level geological disasters occurred and that the safety factor of treatment project should be overall arrangement, comprehensive considered and appropriate increased. Through the analysises and researches above, this paper mainly achieved the following results and conclusions:(1) The geological environment problems and governance in the metal mine in western Henan Province. The main geological environment problems of mine are slag debris flow, collapse and landslide. The mine geological environment conditions include physical geography, topography, geological structure, stratigraphy and lithology, hydrogeology and primary geological environment.The mine geological environment governance include the history of mine geological disaster, the present situation of mine geological environment problems, the prediction of mine geological environment trend and the current situation of mine geological environment governance.(2) The study of mine hazard assessment. According to the research scale, the mine debris flow and landslide hazard evaluation were divided into regional and local risk assessment. In the regional hazard evaluation of debris flows, the evaluation indexes, including the topography, material source, geological conditions, meteorology, hydrology and vegetation, human activities and the effect factors, were proposed to establish the regional debris flow risk assessment index system; In the site hazard evaluation of debris flows, the maximal hazardous dimension forecast model was established, and the risk evaluation index system of the debris flows of the formation area, circulation area and the accumulation area was adopted as well. In the regional and site hazard evaluation of landslide, the corresponding evaluation indexes were extracted from the geological environment, dynamic environment, human engineering and economic activities factors, and the landslide hazard assessment index system of region and site were established. The AHP-FCE method, which is combined with analytic hierarchy process (AHP) and fuzzy comprehensive evaluation (FCE), was applied to the hazard evaluation of mine geological disasters, and the basic principles, steps and calculation models of the two models were introduced respectively.(3) The study of the mine hazard vulnerability assessment. It was divided into vulnerability composition, the content of vulnerability evaluation, value evaluation of elements at risk and vulnerability evaluation. According to the characteristics and the various destructive effect of mine geological disasters, the vulnerability was divided into the economic vulnerability and the population vulnerability. The main contents of vulnerability assessment were composed of type, quantity, distribution, value, damage degree, value loss rate and failure probability of elements at risk. Value assessment of elements at risk was mainly used in the calculation of loss expectations, which means risk value. The monetary method was used to calculate the value of economic elements at risk. The population density was used to evaluate the target value of population elements at risk. In the vulnerability value calculation model, for the economic elements at risk, the position relationship between the elements at risk and the disaster body, the escape possibility of elements at risk and the vulnerability coefficients were comprehensive considered, and the damage possibility and the loss degree of the elements at risk were totally described. In the population elements at risk, the factors of population age structure, the awareness of geological disaster risk, the structures and types of houses, the government’s attention degrees of geological disasters and the perfect degree of geological disasters early warning and forecasting system were comprehensive considered.(4) The risk evaluation study of mine hazard. The basic risk evaluation system of mine geological disaster is composed of hazard prediction, vulnerability assessment and risk prediction. The hazard prediction is to put forward the different failure probability of different hazard levels for regional mine geological hazard. The hazard evaluation model in various kinds of geological disasters occurred in the same research area at the same time was proposed based on the geological hazard assessment of the single mine disaster. The vulnerability assessment included risk area determination, characteristics evaluation of elements at risk and the analysis of the ability to resist disasters of elements at risk. The risk prediction was divided into economic risk prediction value and population risk prediction value. The economic risk prediction value calculation model was composed of probabilities of geological disaster occurrence, the total economic value and the vulnerability of elements at risk. While the population risk prediction value calculation model was composed of probabilities of geological disaster occurrence, population density and the population vulnerability.(5) The mine hazard risk evaluation at Luanshigou watershed in Zao Xiangyu. It was divided into three parts, including hazard evaluation, vulnerability assessment and risk assessment.For the purpose of hazard assessment, we adopted a new assessment method which synthesized the advantages of the Analytic Hierarchy Process method (AHP) and Fuzzy Comprehensive Evaluation method (FCE). Using this new method, slag type debris flow hazard assessment map, collapse hazard assessment map and a comprehensive geological hazard assessment map that overlay the former two hazard assessment maps were made. Hazard assessment map was divided into four levels, namely high danger zone, medium danger zone, low danger zone and very low danger zone. High danger zones were mainly distributed in the west trenches, the west side of the top in the middle trenches, the east trenches DE33, DE31 slag accumulation site and 1280 slag heap area. Medium danger zones were mainly distributed at the bottom of the west trenches, in the east side of the top in the trenches and the main ridge distribution area in the Luanshigou area. In addition to the distribution area of three branch lander in front of the divergence, the other area in Luanshigou is of better stability.To make vulnerability assessment, we calculated and analyzed the value assessment and vulnerability values of the economic elements at risk and the population elements at risk respectively.To make the risk assessment, the risk assessment of economic elements at risk and population elements at risk were made respectively, the assessment levels were divided into levels of high risk, medium risk, low risk and very low risk. For the risk prediction results of economic elements at risk, high risk zone were mainly distributed in the residential areas of the miners at the back of the 1620 slag heap. The medium risk zone were mainly distributed in the middle trenches, divergence area, the back of 38 and 1280 slag heap. The low and very low risk zone were mainly distributed in simple gravel roads, the mine roads, the residential areas nearby the 1120,1140 and DW4 slag heaps and some part of the three branch lander.For the population risk prediction results, the high risk zone were mainly distributed in the residential areas of the miners at the back of the 1620 slag heaps. The area of medium risk zone was the smallest of all risk zone, which was only distributed in the local district of the back of 1280 slag heap. The area of low risk zone was very large, including the middle trenches, east trenches, divergence area, the and residential areas of the miners at the back of 1280、D385 and DW2 slag heaps. The very low risk zone were mainly distributed in the simple gravel roads, the mine roads, the residential areas nearby the 1120,1140, DW4 slag heaps and parts of divergence.(6) The mine geological hazard management system at Luanshigou watershed in Zao Xiangyu. In the treatment programs of the geological hazards in the Luanshigou area, the following engineering measures were taken:The retaining wall for holding back slags, wastes clearing and removing and drainage channel projects. In the treatment programs of geological disasters of mining valleys basin, the safety factor of the geologic disaster treatment projects should be taken into consideration. For example, when designing the lower level block slag dam, the safety factor should consider not only its own safety reservation, but also the impact of dam break of slag dam block at the upper level. Therefore, the safety factor of treatment project should be raised. For the valleys types of tailings dam, when designing the lower level dam, the damage caused by the dam break of slag dam block at the upper level must be considered, meanwhile, the collapse disasters happened in the surrounding rock mass must be prevented. The safety factor of mine disaster treatment project should be studied and arrangement comprehensively, and improved appropriately. |
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