| There are various types of water-filled aquifers in coal measures strata of China.The water-filled aquifers have the characteristics of uneven water abundance and discontinuous distribution owe to the heterogeneity,anisotropy and discontinuity,which would cause a lot of trouble in effectively preventing mine water disasters.Therefore,the work of water abundance evaluation for mine water-filled aquifer is pivotal to mine water prevention work.It can effectively avoid the possibility that water inrush accidents occur in local water abundance areas with higher water abundance.Meanwhile,the hydrogeological conditions are becoming more and more complex owe to the increasing of mining depth and extension of mining level in recent years.A series of problems like the rising the water head pressure of the coal floor aquifers with water supply,the docking between coal seams and thick limestone with the regional faults,which seriously restrict the safe production of mine.Therefore,it is vital and necessary to master water abundance law of mine water-filled aquifers and predict mine water discharge owe to the changing of mining conditions.All of these work have great practical significance to ensure the safe production of coal mine and the sustainable development for China coal industry.In this paper,according to the types and characteristics of water-filled aquifers,we established a new practical mathematical model called a comprehensive water abundance evaluation index system of mine water-filled aquifers to evaluate the water abundance of different types of water-filled aquifers in the situation of lacking hydrogeological drilling.Some cases in Danhou and Ningtiaota mine were carried out and analyzed by using this new evaluation method.And then a method of dynamic prediction of water discharge based the production bridging program of mine working faces by scientifically analyzing the karst development law and groundwater flow field,which have practical engineering value and theoretical guidance for safe production of mine.The results obtained are as follows:(1)According to the types and characteristics of water-filled aquifers,a comprehensive water abundance evaluation index system of mine water-filled aquifers was established from five aspects of sedimentary environment and lithologic structure,geological structure and karst development,weathering characteristics,hydraulic characteristics and hydrogeological geophysical characteristics.The aspect of sedimentary environment and lithologic structure included five indicators: sedimentaryenvironmental impact index,sand-shale ratio,thickness of gravel,layers of gravel and aquifer thickness.The types and distribution of sedimentary(micro)phases were used to analyse the spatial distribution laws of aquifers(includes)in plane and profile and distribution laws of water abundance of mine water-filled aquifers.The other four indicators were the most direct control factors of groundwater occurrence,which determined the size of the groundwater storage space and the strength of hydraulic connections.The geological structure and karst development included five indicators:faults distribution,influence zone of fold axis,structure fractal dimension index,linear ratio of cavern in drilling hole and percentage of drilling hole encounting cavern.The weathering characteristics composed of the weathering influence index and lithologic combination index reflected the influence of weathering on water abundance of aquifers.And the hydraulic characteristics included four indicators: unit inflow,permeability coefficient,consumption of flushing fluid and coring recovery rate.The geophysical characteristics composed of geophysical anomaly index and logging anomaly index can accurately reflect the distribution of water abundance of the study area.They can effectively make up the gaps in the regional data,and reduce the error of data interpolation in the water abundance evaluation.(2)The types and distribution of sedimentary(micro)phases were used to analyse the spatial distribution laws of aquifers(includes)in plane and profile and distribution laws of water abundance of mine water-filled aquifers.And the macroscopic occurrence conditions of groundwater and the structural characteristics of groundwater system were revealed.Through the study of depositional environment and sequence stratigraphy of Zhiluo Formation aquifers of Ningtiaota mine,multi-phases and multi-cycles sedimentary models were analyzed in Zhiluo Formation of the study.The braided river delta deposit is the most important part of the lower member of Zhiluo Formation.The sequence is composed of single or multiple channel sand bodies.The combination of lithology is simple,which is mainly composed of medium-coarse sandstone.And there is no mud,silty sand layer between sand bodies.Therefore,the sand bodies have good connectivity,which provide a good space for the storage of groundwater.The meandering river deposition is the most important part of the upper member of Zhiluo Formation,which mainly develop flood plain sediments and small channel sand body.Some of the sand bodies have a certain thickness,so that have a certain water storage space,but the connectivity is poor,which is not conducive to groundwater storage and runoff.(3)A new evaluation method was proposed to evaluate water abundance of the bedrock fissure aquifer,which was based on the coupling of types and distribution of sedimentary(micro)phases and PNN neural network model.Take fractured aquifer of Zhiluo Formation of Ningtiaota mine as an example,in the absence of hydrogeological drilling conditions,the evaluation index system was established,which included four indexes of sedimentary environment influence index,weathering degree index,aquifer thickness and core recovery rate.The PNN neural network model,which can consider many factors simultaneously,and can deal with the fuzzy information problem,was used to evaluate water abundance of the bedrock fissure aquifer.Compared with the conventional water abundance evaluation method,the results showed that the method can get a better effect to water abundance zoning of Zhiluo Formation fractured aquifer,which was in good agreement with the actual situation.It can provide reference for the water abundance evaluation of the bedrock fissure aquifer in the lack of hydrogeological test area.(4)A new evaluation method was proposed to evaluate water abundance of loose pore aquifer,which was based on the coupling of sedimentary characteristics,lithologic structure and multi index comprehensive unascertained measure theory.Take the lower part of the Quaternary loose pore aquifer of Danhou mine as an example,in the absence of hydrogeological drilling conditions,the evaluation index system was established,which included four indexes of sand-shale ratio,thickness of gravel,layers of gravel and aquifer thickness.A new comprehensive evaluation model was developed to evaluate the water abundance of loose pore aquifer by using the multi index comprehensive unascertained measure model which can deal with the fuzziness and uncertainty of influence factors.The types of safety coal and rock pillar under water body were rationally set according to the evaluation results of aquifer water abundance.The results showed that the method can get a better effect to water abundance zoning of loose aquifer and the evaluation results were consistent with actual situation.Therefore,the model can provide a new idea for water abundance evaluation of loose aquifer in the lack of hydrogeological test area.(5)In order to overcome the irrationality of the weight distribution in the constant water abundance evaluation model,a new method based on variable weight theory was proposed to evaluate the water abundance of carbonate karst aquifer.Take a case study of Ordovician limestone karst aquifer as an example,in the condition of less hydrogeological drilling,the evaluation index system was established,which includedfive indexes of fault distribution,fault dimension index,geophysical anomaly index,unit inflow and permeability coefficient.A new evaluation model was developed to evaluate the water abundance of Ordovician limestone aquifer by using a segmented strong incentive-penalty variable weight synthetic function.Compared with the conventional water abundance evaluation method,the results showed that the method can get a better effect to water abundance zoning of Ordovician limestone karst aquifer and the evaluation results were consistent with actual situation.The new method makes the evaluation result more discrete,which can easily divide the quality grades of aquifer water abundance.Thus,it can be concluded that the new method can greatly improve the accuracy and practical value of water abundance evaluation of aquifers.(6)On the basis of rationally generalizing the conceptual model of hydrogeological of Ordovician limestone aquifer,the water discharge with the production bridging program of mine working faces was predicted under complicated hydrogeological conditions.In view of the boundary conditions and internal structure of the Ordovician limestone aquifer difficult to describe,take the Danhou mine as an example,the paper established regional natural boundary model,depicted the hydraulic nature of boundary conditions and heterogeneity of internal structure of Ordovician limestone aquifer based on the analysis of many data,such as pumping test,geological section and water inrush.According to the production bridging program of mine working faces,the model forecasted water discharge of Ordovician limestone aquifer after it was identified and verified.This method can improve the precision and practicability of water discharge prediction to a certain extent. |
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