Abstract:
As sedimentary soft rock has a potential to store hazardous nuclear waste, several countries utilize it as a possible and
safe way of hazardous nuclear waste disposal. Therefore, precise estimation of unsaturated hydraulic properties is
needed on the unsaturated flow of this type of rocks to assure the safety of the disposak In this study, Tertiary
sedimentary soft rock samples were collected from Rokkasho Low Level Waste Disposal site in Japan. Applicability of
an empirical model; Campbell (CB) model, which use commonly for soil hydraulic property estimation was studied.
This model was applied to one dimensional flow induced by evaporation in three Pumice Tuff specimens and three
Sandstone specimens. The inverse estimation technique was used to select the best parameter in each model by
adopting Genetic Algorithm (GA) as an optimization tool. From the results it was clearly found that the unsaturated
hydraulic properties could be easily estimated by CB model and the measured evaporation change could be well
analyzed. According to the results the CB model is robust for unsaturated flow analysis in soft rock.
