Study On Rheological Properties And Mechanical Properties Of Paste Filling Materials With Solid Waste In Coal Mine

As a new green mining technology,paste filling in the coal mine has an application prospect.However,the pipeline blockages are often caused by materials,which affected coal mining efficiency.Coal gangue,fly ash,and other large amounts of solid wastes were produced in energy and resource development and utilization.Stacking up for a long time occupied a large number of land resources and polluted the environment.It is a step for China’s current sustainable development strategy to realize the resource utilization of solid wastes.In this paper,coal gangue,fly ash,and other industrial solid wastes were used as raw materials of paste filling materials.Rheological properties and mechanical properties of paste filling materials were studied from the aspect of material ratio,which provided scientific basis for the resource reuse of solid coal waste,the treatment of goaf subsidence,and the release of "Three coal mining on the next" compressed coal.The main research contents and conclusions of this paper were as follows:(1)Through 23 groups of single factor rheological properties and mechanical properties tests,such as mass fraction,admixture content,aggregate content and aggregate particle grading,the change rule of different factors on yield stress,plastic viscosity,compressive strength and shrinkage of paste filling materials were obtained.Moreover,the appropriate value range of mass fraction,fly ash content,and fine coal gangue content was optimized.(2)By collecting the rheological parameters,the rheological models of each fresh sample were constructed to verify that paste filling materials conformed to the rheological behavior of Bingham plastic fluid.(3)The regression model of yield stress,plastic viscosity and compressive strength was derived by the Box-Behnken Design response surface method based on the results of single-factor rheological properties and mechanical properties tests.The effects of interaction with different factors on yield stress,plastic viscosity and compressive strength of paste filling materials were analyzed.The optimal ratio of paste filling materials was obtained by using response surface methodology that was the mass ratio of cement,fly ash and coal gangue was 1:3.3:9,the mass fraction was 80.3 %,and the fine gangue content was 40.15 %.(4)The influence mechanism of material ratio on the rheological properties and mechanical properties of paste filling materials were analyzed by comparing the hydration exothermic rate,main hydration products and microscopic morphology of samples with the optimal ratio and the benchmark ratio.