Experimental research on low and strength characteristics of coal slime based cemented filling material

To study the flow and strength characteristics of coal slime based backfill materials, orthogonal tests were used to design one cemented backfill material combining coal slime, high-water-content materials, cement, and fly ash. By using range, analysis of variance, and multi-variate regression analysis, influences of four key factors on the initial setting time, bleeding ratio, diffusivity, compressive strength, and shear strength of the backfill material were studied. These four factors include coal slurry water mass per cent concentration (A), high water material mass / slurry water mass (B), cement mass / slurry water mass (C) and fly ash mass / slurry water mass (D). Results show that initial setting time, diffusivity, compressive strength, and shear strength of the backfill material are 52−67 min, 42.0−76.5 cm, 0.076−0.247 MPa, and 0.033−0.139 MPa, respectively, all distributed in wide ranges. For initial setting time, the four factors are listed in a descending order as B>C>A>D according to their influences; for the compressive strength, the four factors are ranked as D>C>A>B; for the shear strength, the four factors are listed in an order as C>D>A>B. Mathematical equations between A, B, C, D and initial setting time, diffusivity, compressive strength, and shear strength were gotten, initial setting time and A, B presents quadratic function relation, and C, D present exponential relation; diffusivity and A, B, C presents quadratic function relation, and D presents trigonometric relation; compressive strength and A, D presents exponential relation, and B, C presents quadratic function relation; shear strength and A, B presents quadratic function relation, and C, D presents exponential relation.One prediction model for characteristic parameters, namely, fluidity and strength, of the coal slime based backfill material under action of various factors was established and calibrated.