Study On The Gas Migration In The Goaf Filling Of Full-mechanized Mining Working Face

Recently, environment and energy issues become more and more prominent, coal mining tends to be non-pollution, so that, green technique is proposed in coal mining. Conventional mining technique causes to serious subsidence, huge gangue volume and serious pollution. If rainwater permeated into self-igniting gangues, the heated air will rapidly expand,which will result in explosion,and cause greater damage. Thus,coal gangue must be comprehensively controlled. To realize backfill mining,through filling waste material like coal gangue,clinker and etc into coal mine, is the effective way to solve subsidence, and treat varieties of waste material. In addition,the volume of coal under three circumstances(three under)is rather huge, with gradually depleting coal resource,the problem of unexploited coal of three under will be confronted with in lots of mine areas,and backfilling mining is used to solve this.However,at present,gas migration of goaf under filling condition comes.At home and abroad,there are many research findings on gas migration,but fewer researches on gas migration under filling condition.Nowadays,it is of great significances to research gas migration under filling condition in coal goaf.In this thesis,focusing on gas migration regulation under filling condition,by aid of rock mechanics,fluid mechanics,gas seepage theory,porous media seepage theory and corresponding theories,by applying theoretic analysis,physical mathematic modeling analysis,computer simulation and etc,in coal mine,equipped with U shaped and Y shaped ventilation system,influence of backfilled coal gangue,clinker and sediment on gas migration is researched.Research tasks are as follows:(1)Theoretic analysis on backfilling mining technique,backfilling methods, backfilling ratio are carried out.(2)Theoretic researches on distribution regulation of gas migration in goaf.Basic parameters,storage and migration,distribution regulation of gas migration are theoretically researched,when gas flows in coal seams.(3)Establishment of physical model of backfilled goaf and seepage mechanic model of porous medium.3-dimentioned physical model of backfilled goaf is constructed; mass transfer process of porous medium is analyzed,controlling equation of goaf gas migration is obtained,and mathematical model of gas migration is established.(4)Models of U-shaped and Y-shaped ventilation system are constructed with Gambit,which are brought into FLUENT software to numerically simulate the gas migration situation in goaf that filled with coal gangue,clinker and sediment.The simulation is divided into two parts according to distribution of porosity,it means the whole goaf is divided into homogeneous distribution of porosity and heterogeneous distribution of porosity.In Y-shaped system,gas migration situation is simulated under drainage condition.When theoretic analysis and numerical simulation have been finished,the conclusions are as follows:(1)Influence of coal gangue,clinker and sediment on gas migration is obviously different.(2)As to coal gangue,diameter is big,compressive strength is large,porosity changes less,backfilled coal gangue contributes to decrease gas accumulation in deep goaf,its effect is better than filling clinker and sediment.(3)In U-shaped ventilation system,in goaf with three fillings,there is gas accumulation of varying degree in return airway and upper corner;Y-shaped ventilation system can solve the problem better.(4)Under drainage condition,gas accumulation can be worked out with Y-shaped ventilation system.