ESTIMATING UNSATURATED HYDRAULIC PROPERTIES OF SOFT ROCK BY THREE DIFFERENT FLOW MODELS

Abstract

Several countries utilize the sedimentary soft rock for nuclear waste disposal because it has a potential to use as a host rock. Therefore, the analytical researches on the unsaturated flow of this type of rocks have been increased to assure the safety of the disposal. In this study, the applicability of three models; Brooks-Corey/Burdine (BC), Campbell (CB) and van Genuchten (VG) that have been used commonly for soil was studied, by applying these to one dimensional flow induced by evaporation in six disk shaped soft rock samples. The best parameters in each model were inversely estimated by adopting genetic algorithm (GA). It was clearly found that the best parameters in BC and CB models can be easily estimated and the measured evaporation change could be well analyzed. However, the parameters in VG model could not be estimated easily. It was found that BC and CB models are more robust than the VG model for the analysis of unsaturated flow in soft rock.