| Coal mine filling mining is a method to solve the damage of surface environment and improve the safety of working face.Among them,the performance of filling material is the key factor affecting the filling quality.The cost of fly ash produced by coal-fired power generation is low.It can provide a certain strength with cement,sand and other materials,but also play a role in waste utilization and natural environment protection.In order to improve the performance of fly ash paste,this paper improves the performance of fly ash filling material which has been used in WeiQiang coal mine.Through laboratory experiments,numerical simulation and other methods,using additives to continue to improve the working and mechanical properties of the fly ash paste material,and three groups of better performance ratio of coal mine filling mining simulation to test the filling effect of the material.The conclusions are as follows:The mineral composition and content of some raw materials of fly ash paste were determined,and the hydration reaction was analyzed.The mechanism of cement and fly ash hydration reaction on paste strength was obtained.The hydration process of cement is mainly composed of calcium silicate,calcium aluminate and ferric aluminate,which react with water to form gel material.The bonding strength of paste material is enhanced,and the later strength increases with the increase of calcium silicate cementitious substance.The hydration of fly ash combined with cement can produce hydrated calcium silicate and calcium aluminate,which can improve the early strength and setting speed of paste.The influence of different additives(early strength agent,expansion agent,water reducing agent and accelerator)on the working characteristics(slump,bleeding rate,expansion rate and setting time)and mechanical properties of fly ash paste material was studied by single factor experiment.The optimal parameters were as follows:when the content of early strength agent was 2%,the 3D strength reached 2.63 When MPa,5%expansion agent,1.08%expansion rate,1.0%water reducer,238mm slump,3%accelerator,155 min initial setting time and 255 min final setting time.According to the multi factor orthogonal test,the influence of four different additives on the five inspection indexes of the test piece was analyzed,and three groups of optimal ratio combinations were obtained.The early strength of U1 is the best,and the strength after curing for 3 days is 2.91mpa.The strength,fluidity and expansibility of U2 proportioned specimen are the best in the later stage.The strength after 28d curing is 7.73mpa,the maximum slump of paste is 250mm,and the expansion rate is 1.02%.The setting time of paste with U3 ratio is the shortest,140 min.The density characteristics,compression shear tensile strength,deformation characteristics and failure characteristics of the three groups of specimens with optimal mix ratio are studied.During the curing process,the hydration reaction is exothermic,and part of the moisture is lost,resulting in the density of 28d is generally less than 3D.The strength of U2 is the best.The compressive strength and tensile strength are 8.64mpa and 0.87mpa respectively,and the peak strain rate is 2.6%.In this paper,three groups of optimal mix materials are used to carry out the numerical simulation of underground filling,and the 30303 working face of xuemiaotan coal mine is selected as the simulation background to carry out the filling mining simulation of the surface line coal pressure,and determine the stress and deformation characteristics of different materials. |
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