For many decades the ‘classical’ method has been used to design gravity dams. This method
is based on the Bernoulli shallow beam theory. The finite element method (FEM) has become
a powerful tool for the dam design engineer. The FEM can deal with material properties,
temperatures and dynamic load conditions, which the classical method cannot analyse. The FEM
facilitates the design and optimisation of new dams and the back analysis of existing dams.
However, the linear elastic FEM has a limitation in that computed stresses are sensitive to
mesh density at ‘singularity points’. Various methods have been proposed to deal with this
problem. In this paper the Drucker-Prager non-linear finite element method (DP NL FEM) yield
model is presented as a method to overcome the problem of the stress peaks at singularity
points, and to produce more realistic stresses at the base of the dam wall.
The fundamentals of the DP NL FEM are presented. Benchmark studies of this method
demonstrate the method’s viability to deal with zones in a structure with stresses beyond the
elastic limit where yielding of the material occurs.
A case study of a completed gravity dam is analysed, comparing several analysis techniques.
The service and extreme load cases are investigated. Different material properties for the
concrete and rock, including weathered material along the base of the wall, are considered. The
application and merits of the DP NL FEM are presented. The calculation of the critical factor of
safety against sliding is done with a more realistic determination of the conditions along the
base of the wall.