Abstract: It is very important for an arch dam to ensure the stability of its abutments.The geomechanical model test, allowing for faults, fissures and joints of foundation,is an effective way to study such problems. In this paper the principles and methodsof such model tests are described. An example dealing with the stability of a higharch dam abutment by this method is presented. It indicates that there is a greatdifference in the rupture mechanism between the results of the model test and thatof the calculation based on the theory of equilibrium of rigid bodies.