Experimental Study On Preparation Of Goaf Filling Paste By Synergistic Utilization Of Coal-based Solid Waste

With the increasing attention to environmental protection in china,the resource utilization of solid waste in backfill mining has become an inevitable choice for environmental protection and economic development.A large number of studies have shown that filling mining is the most effective way to solve the problems such as surface collapse,gangue accumulation,surface water loss and other environmental damage caused by coal mining.Based on paste filling technology in wuhai area,this paper makes full use of solid wastes in mining area and around the power plants,and actively seeks to select filling materials with low cost,wide sources and good performance,so as to reduce cement consumption,further reduce filling costs and improve economic benefits.It can provide reference for the backfill mining in wuhai area,so as to reduce the mining cost and realize green mining.In this test,the chemical and mineral components of each filling material were analyzed by X-ray diffraction,and the hydration mechanism of filling material was deeply studied.Finally,coal gangue,fly ash,42.5 ordinary Portland cement,desulfurized gypsum,stone powder and water were selected as raw materials.Several groups of single factor control experiments were used to find the optimal ratio which not only met the filling requirements but also realized the lowest economic cost,so as to realize the green and effective filling,so that the overburden of the goaf would not be deformed,so as to achieve the purpose of controlling the surface subsidence.Finally,according to the specific needs,the economic cost of filling materials is calculated,and the following results are obtained.（1）Under the condition of natural curing,the optimal mass ratio of filling materials is determined.When the ratio of coal gangue,fly ash,cement,desulfurized gypsum and stone powder is 12:10:2.4:4:2,the compressive strength of filling body formed in 28days reaches 5.62Mpa.At the same time,the strength under 15 and 30 freeze-thaw cycles is 5.77Mpa and 5.46Mpa espectively.（2）In accordance with the reaction mechanism of each filling material,the reaction between different materials will influence each other.The hydration products of ordinary cement are composed of Ca（OH）₂.Calcium silicate hydrate and calcium sulfoaluminate hydrate.Ca（OH）₂ provides an alkaline environment for the hydrolysis of admixture and participates in the secondary hydration reaction of minerals.（3）According to calculation,the cost of filling material is 12.48yuan/t,and the dosage of cement is reduced by 30%compared with the original,which meets the demand of mine filling mining.