Study of long-term regional groundwater flow system, 4; Study of influence factors on hydraulic conductivity with experimental hydraulic tests

Sakai, Ryutaro; Munakata, Masahiro ; Kimura, Hideo; Ooka, Masao*; Kameya, Hiroshi*

In the safety assessment for a geological disposal of radioactive waste, it is important to develop a methodology and uncertainties of long-term estimation of regional groundwater flow system. The authors discussed the uncertainties of hydraulic conductivity as a significant hydrological parameter for regional groundwater flow analysis model. This study demonstrated that confining pressure change cased by uplift and subsidence and change of hydraulic gradients under the long-term geological and hydrological environmental change could possibly produce variations more than one order of magnitude in hydraulic conductivity of rock mass. It also clarified that the effect of water quality change on hydraulic conductivity is not negligible and that the replacement of fresh water and saline water cased by sea level change could predict to reduce hydraulic conductivities in rock mass 0.6 times from its present data in case of Horonobe site.