Analysis of rate effects induced by cavity expansion in silty soils using a Drucker-Prager cap plasticity model
Gracieli Dienstmann1; Samir Maghous2; Fernando Schnaid2
1 Department of Civil Engineering, Federal University of Santa Catarina, Florianópolis, Brazil; 2 Department of Civil Engineering, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
doi:10.20906/CPS/CILAMCE2017-0125
Resumo
The drainage conditions during cone penetration tests is a critical factor in the assessment of tailings properties, since they often involve materials with permeability ranging from 10-5 to 10-8 m/s, which are typical values for silty soils. In such materials, a partially drainage behaviour is likely to occur during the standard penetration test, which leads to errors in interpretation. Aiming to understand the processes that control the drainage behaviour during penetration, a simplified model was formulated in Dienstmann et al. (2017). The model provides semi-analytical solutions for pore-fluid pressure, displacement and stress distributions around an expanding rigid infinite cylinder embedded within a saturated porous medium. The poromechanic approach is based on the local equivalence between the response of a perfectly plastic behavior to the monotonic loading process and an appropriate fictitious nonlinear poroelastic behaviour. A Drucker Prager yield condition is adopted in the formulation. In the present work, results of the model predictions are directly compared with poroplastic finite element solutions using both a Drucker-Prager and Drucker-Prager Cap plasticity models. The analysis allows to quantitatively discuss the impact on the model predictions, as well as their correlation with the drainage conditions, when a cap is introduced to limit the domain of elastic compressive stresses. Useful recommendations for Interpretation and analysis of in situ measured properties will be formulated in light of the present study.
Palavras-chave: expanding cylinder; Non-linear poroelasticity; Porous medium; Transient flow; Finite element analysis