Analysis of fracture characteristics and energy consumption of full tailings cemented backfill under impact load

In order to study the fracture characteristics and energy consumption characteristics of the fully tailings cemented backfill under impact loading, uniaxial impact tests on fillers with different cement-sand ratios at moderate strain rates were carried out with the help of a split Hopkinson pressure bar (SHPB) test system. The results show that the pre-peak strain energy, absorbed energy, prepeak strain energy density and absorbed energy density of the backfill body all increase exponentially as increase of incident energy when the cement-sand ratio is the same. When the incident energy is less than 16 J, the absorbed energy density, pre-peak strain energy density, absorbed energy and pre-peak strain energy of the backfill body with the cement-sand ratio of 1:6 are greater than those of the cement-sand ratio of 1:4 and 1:8. The fracture toughness of the backfill body gradually grows with the increase of the cement-sand ratio for the same peak strength, incident energy, pre-peak strain energy and absorption energy. The fracture toughness of the backfill body increases linearly with the increase of dynamic peak strength, absorbed energy density and pre-peak strain energy density, and increases exponentially with the increase of incident energy, pre-peak strain energy and absorbed energy. The increase of fracture toughness with energy absorption density and pre-peak strain energy density of the filled body with cement-sand ratio of 1:4 is two to three times that of cement-sand ratios of 1:6 and 1:8. Based on the growth law of strain energy density, energy consumption and strain, the damage and failure evolution process of the backfill can be divided into four stages: nonlinear compression, linear elastic deformation, elasto-plastic deformation and post-peak damage. Through regression analysis of the backfill body test results, a calculation formula for the fracture toughness is derived from the perspective of energy consumption, which can provide a reference for the stability analysis of the underground backfill body.