Study on mechanical characteristics of cemented backfill under dynamic load

To study the mechanical characteristics of cemented backfill with different batching ratio and mass fraction conditions under impact loading, a 50 mm rod diameter split Hopkinson pressure bar test device was used to carry out impact loading tests on the cemented backfill, and at the same time, according to the results of the SHPB experiments, the damage process of the cemented backfill and coal rock affected by the impact pressure in the underground backfill mining was simulated with the help of Holmquist-Johnson-Cook (HJC) model. The results show that the dynamic compressive strength of cemented backfill shows a good strain rate effect. In the lower strain rate range (46.21-79.85 s−1), the higher the coarse aggregate content, the lower the peak stress, and the maximum strength of the filling body decreased by 87.94%; in the higher strain rate range (145.01-197.48 s−1), the peak stress increases obviously with the increase of coarse aggregate content, and the strength of backfill increases by 53.56%; the increase of mass fraction and gray-sand ratio has a significant strengthening effect on the strain rate effect of compressive strength. The increase of mass fraction and ash-sand ratio makes the dissipation rate of the cemented backfill specimen show a tendency to increase; the numerical simulation results of SHPB are in good agreement with the experimental results, and the simulation results of impact ground pressure verified that the cemented backfill has a certain protective effect on the coal rock mining in the backfill mining.