Comparison of Mohr-Coulomb and hardening soil constitutive models for simulation of settlements in the Karkheh earth dam

This paper presents the settlement behaviour of Karkheh earth dam during its construction and operation stages. Karkheh is one of the largest earth dams in the world in terms of its reservoir capacity and body volume. The settlement of such a large body of soil can affect the performance of the dam elements and endanger downstream areas; should a breach or failure occur in the dam, more than two million people will be affected. It is crucial to know the settlement behaviour of this structure and use the existing results to predict its future settlements and calibrate the existing stress-strain models. For anticipation of dam settlement the measured displacement from the portable probe anchor magnets installed in the dam body are compared to the results of numerical simulations. The available data cover a period of 12 years including construction, and two material impounding and operation periods of the dam. The numerical analysis is performed in 2D plane-strain conditions and two material models are used, including Mohr-Coulomb (MC) and Hardening Soil (HS) models. The comparison between the calculation results and the measured vertical deformations in the dam site reveals that the accuracy of model for the deformations in the middle levels of dam is better than those of the crest for both applied material models in construction and impounding stages. The maximum settlement differences between computed and observed values are 0.05 m for MC model and 0.01 m for HS model. For the operation stage, the error of calculated settlements for the MC model is smaller; hence the results of this model might be more reliable for prediction of future dam settlements. The similar trends, obtained from both material models, exhibit the suitability of the model parameters used in the simulations.