Dynamic Hazard Identification And Risk Assessment Of Mine Water Inrush From Coal Seam Floor

The systematic analysis of water inrush from coal floor is an important link in coal mine safety production and is of important significance.Further investigations are needed on the hazard identification of floor water inrush,hazard evolution,hazard evaluation and dynamic risk assessment.Therefore,based on the scientific theory of system safety,fcentered on the scientific and technological issues of hazard evolution and dynamic risk assessment,the dissertation takes hazard analysis of floor water inrush as the access point and with a research main line of hazard analysis,hazard evolution,mechanism of water inrush from coal seam floor,hazard evaluation and dynamic risk assessment to carry out the research.Methods including field investigation,theoretical analysis,on-site test,comparative analysis,scale model test,numerical simulation were used to investigate the systematic hazard classification and identification of floor water inrush,dynamic hazard evolution with different geo-structure floor conditions,hazard evaluation,risk assessment and hazard control strategies.The main achievements are as follows:（1）The hazard of floor water inrush is difined as the potential things or status that may lead to floor mine water inrush accident during coal mine excavation or mining.The dissertation also expounds on the relation among hazard,risk,accident hazard and accident in the triggering mechanism of floor water inrush.（2）A systematic hazard classification method for floor water inrush based on three types hazard theory and trigger status was proposed.The hazard of mine water inrush is divided into dynamic root hazard and static root hazard,which can be further divided into human,equipment and environmental hazard according to the three types hazard theory.According to the hazard classification,the hazard identification method based on fault tree analysis,as well as a method based on MORT and energy release theory were put forward.（3）The spatio-temporal evolution characteristics of the dynamic hazard and the mechanism of floor water inrush under the intact floor,hidden-fault floor and hidden-collapse floor were conducted by using scale model test and numerical simulation.The results show that 1)a confined water lifting zone with a certain height is formed above the confined aquifer.Under the condition of intact floor,the major control factors of floor water inrush are aquiclude thickness and the floor anti-failure ability.Floor water inrush occurs only when the floor failure depth contacts the confined water lifting zone.2)Hidden-fault promotes the development of floor failure zone and confined water lifting zone.In addition,rock mass destruction is easier to occur above the aquifer.Deformation and failure occur in floor strata and fault in the process of coal mining,and the sudden increase of water pressure above the fault proves the occurrence of water inrush accident.3)Under the condition of the hidden-karst-collapse floor,the occurrence of water inrush is earlier and more obvious than that of hidden-fault.4)Comparison results show that the development of hidden structure especially the hidden-karst-collapse obviously increase the floor failure depth.（4）The concept and content of hazard evaluation of floor water inrush were put forward.Hazard evaluation refers to the assessment of the possibility of hazard occurred and the impact to the accident caused by single hazard.It is the intermediate link between the identification of the hazard and the comprehensive risk assessment of floor water inrush.Based on the hazard classification method of floor water inrush,the hazard evaluation of floor water inrush is proposed to be divided into three types based on hazard classification method:static hazard evaluation and dynamic hazard evaluation,human and equipment hazard evaluation.（5）An evaluation method for structure complexity degree based on the relationship of FCI and water inrush rate as well as an evaluation method for floor aquifer water abundance based on set pair analysis and triangle fuzzy number（SPA-TFN）was proposed.The content as well as the method of dynamic hazard evaluation was clarified.The entropy weight method,variation coefficient method and grey correlation method were used to analyze and evaluate the sensitivity of the major controlling factors for floor failure depth by using the statistical data,and the multiple linear regression method was used to get the calculation formula of the floor failure depth under-500m.Besides,an L₁₈（3⁶）orthogonal test was carried out based on numerical simulation to analyze the sensitivity of the six factors for the floor failure depth in deep mining:mining depth,sand coefficient,coal seam angle,mining thickness,the strike length of working panel and water pressure.（6）A qualitative and quantitative method combining entropy weight method and analytic hierarchy process was proposed to evaluate human and equipment hazard.The statistical results of water inrush accidents show the importance of human-induced hazard.Therefore,the influence of human and equipment state on the risk of floor water inrush should be taken into consideration.Human and equipment hazard is hard to be used as an evaluation index of floor water inrush risk assessment,which again clarifies the importance of hazard evaluation in the study of floor water inrush accident.（7）A dynamic risk assessment model of floor water inrush based on an improved dynamic variable weight and unascertained measure theory model as well as a vulnerability-time-scale dynamic assessment method was proposed to further realizes the dynamic risk assessment of floor water inrush.Based on the current researches on the risk assessment of floor water inrush,it is proposed that the risk assessment method of floor water inrush is divided into static risk assessment and dynamic risk assessment.Static risk assessment is focused on the risk of floor water inrush at a certain moment,which is the main evaluation method currently adopted.In view of the fuzzy and uncertainty of the risk of water inrush,a risk assessment method of floor water inrush based on SPA-TFN was proposed and verified with an example.Dynamic risk assessment refers to the risk evaluation of the whole process during coal seam excavation.Therefore,a dynamic risk assessment model based on an improved dynamic variable weight and unascertained measure theory model was proposed.Besides,vulnerability-time-scale dynamic assessment method is proposed,which considers the impacts of multi-factors on floor water inrush and time effect.The dynamic assessment models and methods were used to realize the dynamic risk evaluation of floor water inrush in different stages during coal seam excavation.There are 79 figures,31 tables,200 references.