Experimental Study on Grouting Diffusion and Reinforcement Law of Grouting Backfilling mining in Caving Zone

Abstract Grouting filling in a caving zone has always been a "black box" project due to its complexity and unpredictability. The filling space, slurry flow characteristics, and the bearing capacity of the mixture formed by broken rock mass and slurry in the caving zone after grouting filling are difficult to visually express. To investigate these issues, experiments were conducted on the flow characteristics of fly ash slurry under different gangue particle grading schemes and confined compression tests before and after grouting in various gangue particle gradation scenarios. The research results indicate the following: 1) Under different gradation schemes, the theoretically calculated porosity is similar to the measured porosity, providing a preliminary means to assess the filling space. The injection amount of fly ash slurry is proportional to the porosity of the gangue bulk, but high slurry concentration or close particle combination within the gangue may lead to grouting infiltration. 2) Under different gradation schemes, the stress-strain curve of both gangue bulk and gangue-slurry mixture follows an exponential relationship. The maximum strain value in both gangue bulk and mixture tests is influenced by porosity and the proportion of large particle size gangue. 3) The internal energy changes of gangue bulk and mixture exhibit pronounced time series characteristics. The energy change in the early and late stages of the gangue bulk is relatively weak, while the medium-term shows a strong change trend, indicating that the internal structure adjustment in the initial and end stages is relatively gentle, and the energy fluctuation in the intermediate stage is more significant. 4) Creep tests on the mixture show a gradual axial strain change during the stable stress stage, suggesting that the mixture has better stability and bearing capacity.