Numerical Analysis of Soil Deformation in Earth Dams Using a Stiffness Variation Technique




UNSTRUCT, Unsaturated soils, Dam collapse


Small earth dams have been used since ancient times and are often the main source of water in semi-arid regions. In this particular type of engineering work, soils saturated by water present changes in their mechanical properties (especially in the first filling), which usually cause a simultaneous loss of stiffness and shear strength. In this context, the software UNSTRUCT presents itself as a very useful tool, as it allows calculating the final state of stress x strain for a plane strain state, using the Finite Element Method, both for saturated and unsaturated embankments, considering an elastic model and the effect of suction (and its variation), through a stiffness variation technique. The present research used UNSTRUCT to assess the behavior of the embankment of a hypothetical earth dam, varying the features of its typical cross-section: homogeneity; internal drainage structures; geometry along a longitudinal profile; and the influence of the compaction level. The results showed that the soil responded better to strains for the scenario of better compaction along the dry branch of the compaction curve, as well as with the use of a vertical drainage element. It was also observed that the strains were higher when greater sections considered, which, in a real situation, would cause distortions along the longitudinal profile of the dam. The software UNSTRUCT proved to be efficient in obtaining and visualizing the modeling results, also making it possible to analyze the development of failure over time after the dam was filled. With UNSTRUCT, a more realistic analysis of the behavior of the hypothetical dam – considering factors that are specific to unsaturated soils – was possible. Worth mentioning also that the software allowed the appraisal of multiple changes in the dam’s geometry and parameters.

Author Biography

Francisco Chagas da Silva Filho, Federal University of Ceará, Department of Hydraulic and Environmental Engineering (DEHA)

Civil Engineer with a Master's degree in Geotechnics from the Federal University of Rio de Janeiro (1991), a PhD in Geotechnics from the Federal University of Rio de Janeiro (1998), and also a Post-doctorate in Geotechnics from the Federal University of Rio de Janeiro (2002).

Currently works as an Adjunct Professor at the Federal University of Ceará, a Supervisor of PhD, MSc, and undergraduate students (Civil Engineering and Geotechnics).

Experienced with Civil Engineering, emphasis on Soil Mechanics, mainly: dams, unsaturated soils, constitutive modeling of the mechanical behavior of soils and waste, and instrumentation of geotechnical works.


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