Abstract
A finite element modeling for three-dimensional analysis of saturated-unsaturated steady state seepage flow in hydrogeological complexity is attempted in order to investigate the effect of grouting works on seeping water losses from the damsite and reservoir of the Nakadake Dam, Japan. In the left hillside of the reservoir, the area where groundwater level is lower than the full water level of the dam reservoir stretches far from the damsite and therefore how to design the grouting works becomes a crucial problem. To clear up the effect of the rainfall recharge on seepage flow, two series of analysis are carried out: Series A and B with and without rainfall recharge, respectively. For the respective series, total flow rates and seepage losses are estimated in relation to the length of the grouting works. To investigate in more detail flow rates across the grouting limb, the partial flow rates across seven fragmented limbs are compared. As a result, the total flow rate for Series A is larger than that for Series B, but there is a slight difference in flow rate characteristics between both series. When the limb length is 1.20 and 1.88 times as large as the magnitude of full reservoir water depth, the total flow rate becomes about 43% and 55% of that without grouting works, respectively. In the latter case, however, seepage loss is not so effectively reduced although the limb is longer. This is because the flow taking a detour without going through the grouted limb significantly contributes to the aggregate seepage loss.
