Parameter optimization and analysis on strength, fractal-permeability of gob backfill made of construction waste

Abstract The application of permeable backfill made of construction waste could maintain effectively regional hydrogeology balance and reduce land occupation. The study analyzed the relationships of permeability coefficient, porosity, fractal dimension and strength of non-cemented and cemented construction waste backfill by permeability test and mechanical one on the specimens with different aggregate and cement content, identified the strength of ones with different fine-aggregate and cement content, and determined the optimal parameters. The porosity of non-cemented specimens and cemented ones were 5.007 ~ 7.029% and 3.230 ~ 6.508% respectively. Permeability coefficient was negatively correlated with fine-aggregate content and linearly positively correlated with porosity. Both particle-size fractal dimensions of non-cemented and cemented specimens were fine > medium-coarse > coarse aggregate, and one of non-cemented specimens was less than that of cemented ones. Compressive strength reached the maximum 12.30 ~ 12.79 MPa and good permeability coefficient 1.17 × 10 –2 cm/s in aggregate gradation 3:3:4:1, and cement content 7 ~ 15% was key range for strength improvement.