Investigating the deformability of grouted rock mass under static and dynamic loading conditions

One of the remedial techniques to strengthen fractured rock mass is the grouting method. There are several direct and indirect methods to investigate the mechanical properties of a fractured rock mass. Among other indirect numerical methods, the discrete fracture network-discrete element method (DFN-DEM) encompasses a more realistic fracture pattern and takes into account the mechanical properties of both intact and rock joints and their interactions. A sensitivity analysis on the effect of joint stiffness ratios (JKn/JKs) and grouting grades with water-to-cement (W:C) ratios of 1:1 and 2:1 on different DFN realizations with different sizes and in various directions were conducted. The deformability moduli of natural and grouted models and representative elementary volume (REV) of models were approximated under static and dynamic loadings. The results show that, in natural and grouted models, the effects of the considered JKn/JKs ratios on the deformability moduli in different geographical directions are smaller than 15%. If models are subjected to dynamic loading, horizontal moduli are increased by 25% compared to static loading, while in grouted models, they do not vary significantly. Under static loading and grouted models with a W:C ratio of 1:1 slurry, the maximum and minimum horizontal deformability moduli are recorded in the NW-SE and NE-SW directions with improvement rates of 103% and 54%, respectively. However, in grouting with diluted slurry, the improvement ratios in almost all directions are 105% and 60% in the horizontal and vertical deformability moduli, respectively. This condition is also seen under dynamic loading, and weak grout has a better improvement ratio compared to the strong slurry. Grouting causes a decrease in the anisotropy of deformability moduli, particularly under dynamic loading.