Damage mechanism of composite cemented backfill based on complex defects influence

In order to reduce mining waste discharge and realize efficient application of tailing material in underground backfilling, the characteristics and mechanism of backfill damage is analyzed, and also the composed behavior and failure characteristic of cemented backfill. Five types of backfills were tested under uniaxial compression loading in SHT4206 electro-hydraulic servo testing system. Based on the experimental results, the damage constitutive equations of cemented backfills with five cement-tailing ratios were proposed on the basis of damage mechanics and then validated. Research shows that the damage growth rate of backfills with lower cement-tailing is lower before peak value of stress, but it grows more rapidly after that. In addition, four backfill combination schemes were designed for mechanical test. Combining with research results on fracture characteristic of different backfills, a defects coupled constitutive model based on continuum damage mechanics was established. Research shows that the piecewise nonlinear model can well embodies effect of complex defects in backfills on the stress-strain curve. Accuracy of the model is well verified by measured curve of backfill composite members. The results of this work provide a scientific basis for failure process prediction of backfills and reasonable matching design of framed filling.