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Numerical analyses of vegetated slopes subjected to rainfall

In recent years, soil bioengineering methods started to be taken into consideration as fully ecological and economically efficient solutions of slope stabilisation. Moreover these measures can be effectively used in combination with geosynthetics or classical, structural slope protection.
In the developed model, two main factors which govern the improvement of slope stability due to the presence of vegetation are incorporated, namely: mechanical reinforcement and root water uptake (evapotranspiration). The Cam-Clay model by Tamagnini (2004) for the partial saturation conditions is implemented in Finite Element software, in order to make possible to describe the multi-phase nature of the mentioned phenomena. The mathematical formulation, based on non-equilibrium thermodynamics is widened by introducing a new constitutive parameter. This allows defining the influence of plant roots, present in elementary volume of soil. Root water uptake is defined as a volumetric sink term in the flow continuity equation. To account for this phenomena, an Abaqus subroutine, developed by Fatahi (2007), is incorporated and adapted to use for slopes and for different shapes of root architecture. The developed numerical model allows simulation of a rainfall induced landslide of the vegetated slope. The improvement of stability due to the vegetation presence is highlighted. The slope performance is evaluated by the time at which the collapse occurs.
Obtained results confirm that the use of soil-bioengineering methods can be very effective and can delay the occurrence of rainfall induced landslide. Vegetation removal can have serious consequences, especially considering stability of steep, forested slopes.

Author(s):

Barbara Maria Switala    
Institute of Geotechnical Engineering, University of Natural Resources and Life Sciences (BOKU), Vienna
Austria

Roberto Tamagnini    
Institute of Geotechnical Engineering, University of Natural Resources and Life Sciences (BOKU), Vienna
Austria

Wei Wu    
Institute of Geotechnical Engineering, University of Natural Resources and Life Sciences (BOKU), Vienna
Austria