Coupled hydro-mechanical analysis for grout penetration in fractured rocks using the finite-discrete element method

Grouting is a widely used geotechnical engineering method to improve the strength and reduce the hydraulic conductivity of rock masses. The grouting process is a typical coupled hydro-mechanical (HM) problem, which should be analyzed by considering the mutual interaction between the grout flow and the rock mass. In this paper, a coupled HM model (Y-grouting) is presented to study the grouting process using the finite-discrete element method (FDEM). This Y-grouting can well explain some typical phenomena observed during grouting operations, which are difficult to be modelled by pure hydraulic analysis. The dilation process experienced by the fracture during grout injection clearly illustrates the necessity of considering the HM coupling effect. The effect of the in-situ stress conditions on the anisotropic grout penetration is properly modelled with the Y-grouting that, together with the stress interaction between neighbor fractures, explains why finer fractures are more difficult to be grouted and whether increasing the grouting pressure could be an effective way to improve the penetration in fine fractures. Ultimately, the results demonstrate importance of considering the HM coupling when simulating grouting and assessing the grouting efficiency.