Approaches for modelling transient unsaturated-saturated groundwater flow during and after construction

White, M. J.*; Guimer, J.*; Oyama, Takuya ; Kosaka, Hiroshi; Robinson, P.*; Saegusa, Hiromitsu

JAEA has been developing modelling techniques to overcome these problems as part of the Mizunami Underground Research Laboratory. An integrated geological and hydrogeological modelling, and visualization system referred to as GEOMASS has been developed, which allows for transient unsaturated groundwater flow modelling in the presence of dynamic underground excavation models. The flow simulator in GEOMASS, FracAffinity, allows for such modelling by the application of sophisticated gridding techniques, allowing for modification of hydraulic conductivity in key zones, and by suitable modification of water retention models. The approaches that have been developed in GEOMASS have been tested through a series of models of increasing complexity, and the testing has demonstrated that there is no significant impact on estimates of regional groundwater flows or local estimates of flow into underground excavations.