Diffusion mechanism of quick-setting slurry in water-rich fractured rock mass based on circle-outburst diffusion model

Grouting is the most commonly used methods in dealing with water inrush issue in mine and tunnel engineering. In order to better predict the grouting effect, research on slurry diffusion mechanism became a hotspot for scholars. At present, the mainstream theoretical model used to study the slurry diffusion mechanism are the circle diffusion model and the modified ones in plane plate fracture. However, these models cannot explain the “contradiction” between the rapid setting characteristics of quick-setting slurry and the continuous long-term injection of slurry in grouting engineering, which cannot accurately predict the grouting pressure or grouting diffusion range. Therefore, a “circle-outburst diffusion model” which can explain the above “contradiction” was proposed in this paper. Based on the new model, stepwise algorithms were developed to predict the grouting pressure and slurry diffusion range. By means of conducting fracture grouting simulation test and collecting grouting pressure data in an actual grouting project, the new model was verified and the slurry diffusion mechanism was studied. Comparison results indicate that the new model can reveal the intrinsic reason for the irregular diffusion phenomenon of the slurry and forecast the outburst moment accurately. The circle diffusion stage and outburst diffusion stage elaborated in the new “circle-outburst diffusion model” were consistent with the staged characteristics of the grouting process presented in the grouting simulating test. Differences between theoretical and experimental pressure value were within 10 %, indicating a high degree of consistency. The number and distribution of outburst diffusion points determine slurry diffusion form and significantly influence the diffusion range. The grouting pressure and the length of slurry flow path increase nonlinearly with time in each diffusion stage. It is hoped that the new model can provide a theoretical basis for the study of diffusion mechanism of quick-setting slurry.