Study On Ecological Restoration Technology And Effect Evaluation Of Open-pit Mines

China is a big country in mineral resources and mining industry.According to many years of practice,the exploitation of mineral resources is one of the most prominent types in the development and utilization of natural resources that affect and destroy the ecosystem.General secretary Xi Jinping pointed out that after all,the ecological environment problem was caused by excessive exploitation of resources,extensive utilization and extravagance and waste.The exploitation of mineral resources must follow the principles of respecting nature,conforming to nature and protecting nature,especially dealing with the relationship between development and protection.To explore a variety of governance models and restoration mechanisms,according to the requirements of ensuring safety,restoring ecology and taking into account the landscape,reduce costs,and do not engage in"bonsai",so it is imminent to do research on ecological restoration of open-pit mines.The methods commonly used in mine ecological restoration generally need to consume a lot of soil resources,which will not only cause damage to the original land resources,but also have high cost,so it is difficult to popularize and use on a large scale.At the same time,most of the mine ecological restoration effect evaluation systems can not objectively and comprehensively reflect the real situation of the evaluated mine ecological restoration,which is divorced from the essence of mine ecological restoration projects.Also,it does not consider the rationality of the system,and lacks the long-term and continuous tracking and evaluation of the whole ecological restoration process.In order to reduce the amount of cultivated soil,broken shale gravel soil was added into the substrate.The optimal ratio of each component of the substrate was determined by the orthogonal test,queuing scoring method and range analysis method.Two representative open-pit mines were selected to carry out field tests to verify the applicability of the substrate.A set of evaluation system for ecological restoration effect of open-pit mine is put forward,and the rationality and accuracy of the evaluation system are verified by combining with practical engineering.The main work and conclusions are as follows:(1)Through the orthogonal test of 5 factors and 4 levels,the physical properties,chemical properties and plant growth of the substrate in each experimental group were detected and observed,and the influence of the amount of each factor on the physical and chemical properties of the substrate was analyzed through the advantages and disadvantages of each index.By using the queuing scoring method and range analysis method,the optimal ratio of each component of the substrate was determined as follows:the ratio of shale gravel soil to cultivated soil was 1:1,the amount of organic fertilizer was 0.2kg/m~2,the amount of oil was 0.15kg/m~2,the amount of straw was 0.15kg/m~2,and the amount of polymer material was 0.85kg/m~2.The physical index,chemical index and mechanical index of the optimal ratio substrate were determined by laboratory tests.The results showed that the physical and chemical properties of the substrate were in a good level,which can fully meet the needs of ecological restoration of open-pit mines and help to establish a long-term stable plant community.(2)Two representative construction sites,shale slope and limestone waste dump,were selected to carry out ecological restoration field tests.By analyzing the lithologic characteristics,geological environment,climatic conditions and other factors of the two sites,appropriate construction methods were selected correspondingly.After the completion of the field tests,samples were taken from the substrate,and the physical,chemical and mechanical properties were determined.The results showed that the physical and chemical properties of the developed substrate were excellent,and the nutrient content was at a high level,which was far greater than that of ordinary farmland soil,which was suitable for plant growth and development.Through the long-term tracking of the vegetation growth and development of the two sites,it was found that the pioneer grass seeds began to germinate in about a week,and the coverage rate reached a high level in about a month,so as to achieve the goal of fast greening and covering the slope.As a result,it proved that the developed substrate can be applied to the ecological restoration of open-pit mines,with good physical and chemical properties,long-term nutrient supply capacity,anti erosion ability and strong adhesion.(3)Combined with the characteristics of open-pit mine and the principle of evaluation index selection,a set of evaluation system with 18 indexes was established from four aspects of soil quality,vegetation quality,water and soil quality and landscape quality.By analyzing excellent engineering cases,consulting relevant literature and asking for experts’opinions,the evaluation grades of each index were divided into five grades:"excellent,good,general,poor and extremely poor",and the specific scope of each grade was given.The advantages and disadvantages of several commonly used evaluation methods were summarized,and AHP-fuzzy comprehensive evaluation method was chosen as the comprehensive evaluation method of this paper.(4)The weight value of each index was calculated,and the results showed that the evaluation system attached the most importance to"vegetation quality".Through AHP-fuzzy comprehensive evaluation method to evaluate the effect of ecological restoration,the results showed that the restoration effect was"good".Because the sampling time was short from the completion of the field test,but the soil recovery was good.With the passage of time,the vegetation growth is complete,and the ecological restoration effect will be further improved.Compared with the actual effect,the results obtained by the evaluation system were basically accurate,which also proved the rationality and scientificity of the established evaluation system.