scholarly journals Slope stability analysis: Barodesy vs linear elastic – perfectly plastic models

2019 ◽  
Vol 92 ◽  
pp. 16014
Author(s):  
Franz Tschuchnigg ◽  
Gertraud Medicus ◽  
Barbara Schneider-Muntau

The results of slope stability analysis are not unique. Different factors of safety are obtained investigating the same slope. The differences result from different constitutive models including different failure surfaces. In this contribution, different strength reduction techniques for two different constitutive models (linear elastic - perfectly plastic model using a Mohr-Coulomb failure criterion and barodesy) have been investigated on slope stability calculations for two different slope inclinations. The parameters for Mohr – Coulomb are calibrated on peak states of element tests simulated with barodesy for different void ratios. For both slopes the predictions of the factors of safety are higher with barodesy than with Mohr-Coulomb. The difference is to some extend explained by the different shapes of failure surfaces and thus different values for peak strength under plane strain conditions. The plane strain predictions of Mohr-Coulomb are conservative compared to barodesy, where the failure surface coincides with Matsuoka-Nakai.

Author(s):  
Peihua Jing ◽  
Tariq Khraishi ◽  
Larissa Gorbatikh

In this work, closed-form analytical solutions for the plasticity zone shape at the lip of a semi-infinite crack are developed. The material is assumed isotropic with a linear elastic-perfectly plastic constitution. The solutions have been developed for the cases of plane stress and plane strain. The three crack modes, mode I, II and III have been considered. Finally, prediction of the plasticity zone extent has been performed for both the Von Mises and Tresca yield criterion. Significant differences have been found between the plane stress and plane strain conditions, as well as between the three crack modes’ solutions. Also, significant differences have been found when compared to classical plasticity zone calculations using the Irwin approach.


2020 ◽  
Vol 42 (3) ◽  
pp. 191-209
Author(s):  
Lylia Deghoul ◽  
Smail Gabi ◽  
Adam Hamrouni

AbstractIn coastal regions, earthquakes caused severe damage to marine structures. Many researchers have conducted numerical investigations in order to understand the dynamic behavior of these structures. The most frequently used model in numerical calculations of soil is the linear-elastic perfectly plastic model with a Mohr-Coulomb failure criterion (MC model). It is recommended to use this model to represent a first-order approximation of soil behavior. Therefore, it is necessary to accommodate soil constitutive models for the specific geotechnical problems.In this paper, three soil constitutive models with different accuracy were applied by using the two-dimensional finite element software PLAXIS to study the behavior of pile-supported wharf embedded in rock dike, under the 1989 Loma Prieta earthquake. These models are: a linear-elastic perfectly plastic model (MC model), an elastoplastic model with isotropic hardening (HS model), and the Hardening Soil model with an extension to the small-strain stiffness (HSS model).A typical pile-supported wharf structure with batter piles from the western United States ports was selected to perform the study. The wharf included cut-slope (sliver) rock dike configuration, which is constituted by a thin layer of rockfill overlaid by a slope of loose sand. The foundation soil and the backfill soil behind the wharf were all dense sand. The soil parameters used in the study were calibrated in numerical soil element tests (Oedometer and Triaxial tests).The wharf displacement and pore pressure results obtained using models with different accuracy were compared to the numerical results of Heidary-Torkamani et al.[28] It was found that the Hardening Soil model with small-strain stiffness (HSS model) gives clearly better results than the MC and HS models.Afterwards, the pile displacements in sloping rockfill were analyzed. The displacement time histories of the rock dike at the top and at the toe were also exposed. It can be noted that during the earthquake there was a significant lateral ground displacement at the upper part of the embankment due to the liquefaction of loose sand. This movement caused displacement at the dike top greater than its displacement at the toe. Consequently, the behavior of the wharf was affected and the pile displacements were important, specially the piles closest to the dike top.


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