Assessment And Dynamic Monitoring Of Mining Geo-environment In Ningxia

Based on finding out the main mining geo-environmental problems and its potentialhazards, the mining geo-environment of Ningxia was evaluated by use of comprehensiveassessment method on ArcGIS. Referred to the quantitative evaluation results, the mininggeo-environment problems of Ningxia zonation was comprehensively evaluated and itsdevelopment trend was analyzed. The GPS deformation monitoring system was established inShizuishan mining area and deformation could be monitored automatically and uninterrupted.The ecological environment of Shizuishan mining area was dynamiccally monitored byapplication of remote sensing technology. In this paper, the surface deformation in Shizuishanmining area was analyzed by means of superposition of two different period DEM, numericalsimulation and probability integration method, the trends of ground subsidence was predictedas well. One typical profile was selected and finite element models was simulated to indicatethe stress changes in overlying rocks and to reveal deformation characteristics. Mechanism ofground subsidence was analyzed to set an example for evaluating of mining geo-environmentin Ningxia. New ideas and new methods were provided for mine geo-environment monitoringand the study of ground subsidence mechanism. Therefore, the study was of importantacademic significance and application value on rational exploration of mineral resources, andmuch contribution to the effective protection of the mining geo-environment and ecologicalrecovery. The main conclusions are as follows:(1) Based on finding out the main mining geo-environmental problems in Ningxia,evaluation index system was established following principles of comparability, briefly,integrity and operability, according to distribution, present situation and development trend ofvarious types of geo-environment problems. It includes7criteria layers and21indicator layers. The criteria layers consisted of geological environment conditions, geological disasters,mining conditions, resource damage, waste discharge, water environmental impacts andenvironmental governance rate.(2) Mining geological environment of Ningxia was quantitatively evaluated by use of comprehensive evaluation method based on ArcGIS. The weight of evaluation index wascalculated combining AHP with rough set theory. Based on quantitative evaluation results andfield survey data, the study area was divided into3regions and34sub-regions, namely theseriously influenced area, the more serious influenced area and the lighter influenced area.The geological environment background and main mining geo-environmental problems ofeach sub-region were reviewed comprehensively.(3) GPS deformation monitoring system was established in Shizuishan mineral area. OneGPS reference station,67GPS monitoring stations and16traditional geodetic monitoringpoints were set up in the area. The technical indicators, the overall design, various subsystemsand the implementation process of automated monitoring were mainly introduced in thepaper.(4) Dynamic monitoring of the ecological environment in Shizuishan mining area hadbeen achieved by using remote sensing technology. Three period remote sensing image datawere interpreted and superimposed respectively, obtaining the dynamic changes of the landtype map and matrix. Analysis of the interpretation results showed that: firstly, from1970s to2003, the main change of lands in Shizuishan mining area was that vegetation coverage areaand cultivated land had been transformed to residential areas and wastelands by infrastructureconstruction and soil erosion. What’s more, the areas of gangue, coal pile, water etc. increasedgreatly because of mining activities. Secondly, the areas of vegetation coverage area increasedthe fastest during2003to2009from wasteland and residential areas whereas areas such asgangue and coal pile decreased sharply as a result of integrated renovation of mininggeo-environment.(5) Changes of surface elevation were obtained by overlay analysis of two period DEMdata of Shizuishan mining area. It could be summarized as: from1970s to2003, the largestdecline of the elevation was27.5m. Larger subsidence areas were located at the collapse pitwith the elevation decreasing from10to27.5m leading to the maximum vertical displacementand collapse range of seven large collapse pits. More intuitive changes of the displacementand range of ground subsidence were obtained by overlay analysis of two period topographic lines by selecting four typical profiles with correspondence to the collapse pit.(6) Discrete element model of three typical cross-sections in Shizuishan mining areawere established to obtain the maximum vertical displacement and the collapse range of eachmining level in accordance with the actual mining condition. The surface deformation of themain strike section and inclination section were predicted by use of probability integrationmethod. The calculated results were in consistence with the numerical simulation and DEMsuperimposed results. It can be deduced that the impact of mining activity on the surfacedeformation would gradually decrease when the ratio of the mining depth and thickness wasgreater than120and the possibility of causing ground subsidence and cracks would becomesmaller, gradually becoming stabilized.(7) The variation and distribution of the rock stress in the mining process were analyzedaccording to establish two-dimensional finite element numerical simulation model of threetypical cross-sections in Shizuishan mining area. The deformation characteristics and failuremechanism of the overburden rocks were revealed combining with the geological conditionsand mining current situation.