Numerical study of the effect of thermal ice loads on concrete dams

Abstract: It is essential to understand the mechanics of ice load and how it affects concrete dams located in a cold climate, such as Sweden, where the temperature becomes sufficiently cold to freeze the surface of the reservoir. The purpose of this thesis is to study ice load distribution along concrete dams, and its response during the application of an ice load. Two types of concrete dams were analysed, an arch dam and a buttress dam. For these dams, the influence from different parameters on the ice load distribution along the dams is studied. In addition to this, a study on how the ice load affects dam stability had also been performed. Stability analyses based on the finite element method were performed using both linear and nonlinear formulation of the interaction behaviour between the base of the dam and the underlying rock. A parametric study of ice sheet expansion on different dam types and geometries were performed. The expansion of the ice sheet was assumed to either be caused by a constant temperature 15 ˚C uniformly distributed over the ice thickness, or by a temperature gradient from 15 ˚C at the top surface of the ice sheet and 0 ˚C at the bottom. The parametric study also includes an investigation about influence of the shape of the reservoir beaches, where it either had a perpendicular shape towards the surface of the dam, or it had an angle of 30˚ with the dam surface. In the linear stability analysis, the structure continued to deform with increasing of the resultant pressure until it reached nonlinearity. The dam deflection had a linear relation with the applied ice load force until it reached the point when structure behaviour was nonlinear. The structure failed due to sliding, overturning or combination of both sliding and overturning. A material failure can also occur if the nonlinear material behaviour is considered, however this was not considered in this study. The parametric study showed that the ice load distribution was less near the beaches, and the distribution of the load on the concrete dam was higher near the top surface of the ice sheet. It was also shown in the study that the distribution of the ice load along the dam was as a cosine function where it had the maximum value at the buttress and the minimum at monolith connections. The result also showed that the load distribution over the thickness of the ice sheet was the same along the dam, regardless of the shape of the beaches or the length of the ice sheet.