3-DIMENSIONAL ANALYSIS OF GROUNDWATER-FLOW IN NEOGENE ROCKS THE ROKKASHO LOW-LEVEL RADIOACTIVE-WASTE DISPOSAL CENTER, JAPAN

As a preliminary step for predicting groundwater flow in a plateau 30- 50 m above sea level, a model for three-dimensional analysis of ground water flow was formulated and its validity was verified. The plateau c onsists of Neogene sedimentary rocks and a Quaternary deposit. Most of the groundwater originates in precipitation, with the groundwater tab le lying in the Quaternary deposit. Steady-state analysis was conducte d by using the finite element method. The results of pore-water pressu re measurement and water examination were useful in verifying the vali dity of the model. In constructing the model, reducing the hydraulic c onductivity according to the depth on the basis of the results of the actual measurement was important. (C) 1998 Elsevier Science B.V. All r ights reserved.