The Mixing Ratio And Acoustic Emission Characteristics Of Cemented Backfill Materials Added With Coal Gangue And Wasted Concrete

Filling mining in coal mines are the main technical means to liberate thecoal resources of "three-below" and control the ground surface subsidence atpresent. What is more, it can solve fundamentally the environmental problemcaused by solid waste. However, the deficiencies in filling materials seriouslyconstrain the full implementation of filling mining technique. In addition, a largenumber of wasted concrete are produced every year, and it not only take upmuch land, but also pollute environment. The preparation of cemented backfillmaterials by using wasted concrete, which turns waste into valuables, haveimportant practical significance. This paper are for the mixing ratio and theacoustic emission characteristics of cemented backfill materials added with coalgangue and wasted concrete. The research contents and the conclusions asfollows:Firstly, the grain composition, bulk density, apparent density, moisturecontent, water absorption and crushing index value of coal gangue and wasted concrete aggregate were analyzed. The results show that:1. The graincomposition of coal gangue and wasted concrete fine aggregate have littledifference. The grain composition of coal gangue and wasted concrete coarseaggregate are difference, but they are continuous grading.2. The bulk densityand apparent density of wasted concrete aggregate are less than the coal gangueaggregate, but its moisture content, water absorption and crushing index valueare far greater than the coal gangue aggregate.Secondly, the single factor analysis method was used to study the influenceof wasted concrete aggregate on slump, slump flow, plastic viscosity, yield stress,bleeding rate, compressive strength and constitutive relation of cementedbackfill materials. The results show that:1. With the increase ofwasted concrete fine aggregate replacement rate, the slump flow of cementedbackfill materials is generally increasing, while the slump first decreases slightlyand then keep constant, plastic viscosity and yield stress show a arising trend,but the fluctuation range of yield stress is very small.2. With the increase ofwasted concrete coarse aggregate replacement rate, the slump and slump flow ofcemented backfill materials show a descending trend, while plastic viscosity andyield stress are a rising trend in general.3. With the increase of wasted concreteaggregate replacement rate, the bleeding rate of cemented backfill materials isgenerally descending, the compressive strength show a trend of first increaseand then drop. When wasted concrete aggregate replacement rate is50%, thecompressive strength of cemented backfill materials is maximum. Comprehensive analysis, coal gangue aggregate of cemented backfillmaterials can be replaced30%~70%by wasted concrete aggregate.4. Thestress-strain curves of cemented backfill materials include rising stage anddecline stage, the rising stage changes is small. Due to the effect of wastedconcrete aggregate, the decline stage fluctuation is greater.Thirdly, on the basis of the single factor analysis, through response surfaceanalysis methodology to select the reasonable proportion of cemented backfillmaterials added with coal gangue and wasted concrete. The results show that:1.Getting the additive proportion of wasted concrete fine aggregate replacementrate, coarse aggregate replacement rate and cement content, as follow:37%、49%、156kg/m3；2. When wasted concrete coarse aggregate replacement rate is40%~50%, with the increase of cement content, the slump of cemented backfillmaterials decrease rapidly, while its compressive strength increase more slowly.When wasted concrete coarse aggregate replacement rate is more than50%,with the increase of cement content, the slump of cemented backfill materialsdecreases trend become smaller, while its compressive strength increase rapidly.Finally, the acoustic emission characteristics at different stages ofcompressive failure of cemented backfill materials added with coal gangue andwasted concrete are researched, when wasted concrete aggregate replacementrate is different. The results show that:1. When wasted concrete aggregatereplacement rate is30%, ringing count and energy rate of cemented backfillmaterials mainly concentrated in the early days of elastic stage.2. When wasted concrete aggregate replacement rate is50%, ringing count and energy rate ofcemented backfill materials has been in a steady state in loading each stage.3.When wasted concrete aggregate replacement rate is70%, ringing count andenergy rate of cemented backfill materials mainly concentrated in the early daysof elastic stage and failure stage.