Experimental study on ethanol/bentonite slurry injection into synthetic rock fractures: Application to seepage control

Transmissive fractures or rock discontinuities (micro and macro) are mostly encountered when shafts and tunnels are excavated during the construction stage of underground space development or repositories for high level radioactive waste (HLW) disposal. These fractures may become flow paths to groundwater seepage and affect the stability of the excavated structure. For safe, effective construction and operation of such facilities, these fractures need to be sealed. In this study, the effect of ethanol on the injection characteristics of bentonite slurry as an effective grouting material is investigated. Various levels of ethanol concentrations (60%, 50% and 40%) were mixed with bentonite at liquid/solid ratios L/S (10, 8 and 6) by weight, w/w and injected into synthetic fracture of aperture sizes 100, 80 and 60 µm to investigate the penetrability of various concentrations of ethanol/bentonite slurries (EBS) into fractures of small aperture. Viscosity tests were also carried out to characterize the effect of ethanol on the rheological characteristics of the slurries. The results indicate that EBS is an effective grouting material capable of penetrating fractures of aperture sizes (100 µm–60 µm) and effectively sealing them for seepage control in the construction and operation stages of HLW repository. The results also showed that dynamic injection is more effective than static injection as it was able to inject high dense slurry into fractures better than static injection.