Experimental Study On Filling Material Performance Of Coal Gangue Fiber Foamed Concrete

Surface subsidence caused by coal mining is posing a serious threat to people's lives and property,therefore,it is necessary to fill some goaf while reducing the cost as much as possible.However,because of the limitation of filling cost,filling mining has not been widely used.A large amount of coal gangue and fly ash are discharged every year in China,which not only encroaches on land resources,but also has a bad effect on ecological environment.Therefore,coal gangue and fly ash are used as the main raw materials and a small amount of polypropylene fiber is added to prepare the foam concrete filling material.The material has positive significance for filling in coal mine.The research content and test results of this paper are as follows:(1)Firstly,different concentrations of foaming agent and foam stabilizer were configured.The results of measurement of foaming multiple and foam stability showed that when the concentration of 0.4%sodium dodecyl benzene sulfonate particles solution was used as the foaming agent,the foaming effect was the best,but the foam stability was poor.When 0.04%modified silicone polyether microemulsion was added as foam stabilizing agent,the foam stability was the best,and the foaming multiple could reach 23.7,meeting the foaming requirements.(2)The corresponding gangue fiber foamed concrete test blocks were prepared according to the designed proportion.The effects of gangue fiber foam content,fiber content and foam content on slump,linear shrinkage,28d compressive strength and dry density of gangue fiber foam concrete were studied respectively.The results show that slurry slump increases with the increase of gangue content,but decreases with the increase of fiber content and foam content.The shrinkage rate decreases with the increase of gangue and fiber content,and increases with the increase of foam content,and fiber content has obvious effect on controlling early shrinkage.The 28d compressive strength first increases and then decreases with the increase of gangue and fiber content.The 28d compressive strength and dry density decreased with the increase of foam content.(3)By studying the water absorption and stress-strain curves of coal gangue fiber foamed concrete,it can be obtained that the water absorption process is a process in which the water absorption increases rapidly at the beginning and then gradually becomes gentle and close to saturation.And with the increase of coal gangue content,water absorption decreases first and then increases.The residual stress can still maintain a large value and decrease slowly after the maximum stress reached.With the increase of foam content,the residual stress is more stable.By observing the failure process,it is concluded that the nature of the failure is the result of the micro-cracks produced in the process of stress and the main cracks formed by continuous extension.(4)Finally,combined with the geological conditions of a mine,the numerical model was established by FLAC3D numerical simulation software.The maximum subsidence value and horizontal movement value after filling mining are respectively 57.1mm and 17.91mm.It is concluded that the filling material can effectively control the surface subsidence.At last,the design of field application of filling technology and the material cost are analyzed.