Importance of Joint Geomerical Parameters on the Safety of Concrete Arch Dam Abutments

Concrete arch dams often need sound and strong foundation and abutments due to the usually large hydrostatic pressure imposed on the abutments. Moreover, it is required to limit the water leakage through the abutments and foundation. On the other hand, a hard rock mass often contains joints and discontinuuites, wich are partially created during the thermal and techtonical activities. Several researches have shown that in most cases, the stability and permeability of rock masses are governed by the joints. Therefore, it is necessary to consider the joint roles for preliminary evaluation of a rock mass as abutment and foundation of a concrete arch dam. In addition, the interaction of hydraulic and mechanical behaviour of joints causes the saturated rock masses to act more omplicated, hence, it must be considered in the estimation of stability and leakage. In this paper, the effects of geometrical parameters of joints including joint orientations and initial apertures on the safety of a concrete arch dam were evaluated using UDEC software. A two-dimentional model including the waterflow through the joints and a loading from dam and the reservoir was simulated in the analyses. In this study, the dam stresses imposed on the abutment were applied instead of dam body modeling. In all analyses, the hydromechanical interaction effects were considered. The values of maximum sliding, maximum opening and the maximum resulting waterflow along the discontinuities were adopted as criteria for estimating the dam abutment safety. The results demonstrate that the joint sets pattern and initial hydraulic aperture of joints dominate the stability of arch dam abutments.