Due to the arching behavior of concrete arch dams, the hydrostatic loads imposed on dam body are
transferred to the abutments. Accordingly, an accurate evaluation of the stability of abutments is
very important. The failure mechanism of abutment is substantially governed by a network of
discontinuities crossing the abutment. Meanwhile, the flowing water through discontinuities
provides an easier condition for discontinuities to slide and/or open. In this paper, the effects of
fluid flow and mechanical characteristics of joints are treated on safety of abutments. Though, a full
3D simulation of dam body and its surrounding rock mass is needed for a complete understanding
of the problem, but in general, the 3D jointed abutment stability analysis considering hydromechanical
interaction are too time consuming and complicated. Therefore, in this study, a 2-D
DEM model for the most critical region of a typical arch dam abutment resulted through a 3D FE
modeling is considered to evaluate the abutment safety. In this research, the effects of fluid flow
and mechanical characteristics of joints on the safety are investigated through SRF and increasing
water pressure methods in both dry and saturate assumptions. In order to recognize the conditions
leading to failure in abutments, the values of maximum sliding, maximum opening, opening and
sliding intensity and maximum resulting water flow rate along discontinuities are used as failure
criterions. The results demonstrate that the assumption of dry abutment is not proper for evaluating
the stability condition and may submit the safety factors much larger than the real values.
Moreover, the strength characteristics of rock joints are less significant on the stability of abutment.