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Numerical investigations of the strain localization in geotechnical engineering within the framework of micropolar theory

Abstract : Most of the progressive failures of geotechnical structures are associated with the strain localization phenomenon, which is generally accompanied by strength softening. Many experimental observationsshow that significant rear rangements and rotations of particles occur inside the shear bands. The aim of this thesis is to investigate numerically the strain localization phenomena of granular materials. Considering the mesh dependency problems in finite element analysis caused by strains oftening within the classical continuum framework, a sand model based on critical-state has been formulated within the framework of the micropolar theory, taking into account the micro rotations, and implemented into a finite element code for two dimensional problems. Then, the simulations of the shearband in biaxial tests are comprehensively studied in terms of onset, thickness, orientation, etc. At the same time, the efficiency of the micropolar approach, as a regularization technique, is discussed. This is followed by an instability analysis using the second-order work based on the micropolar continuum theory. Finally, for a wider application in simulating failures in geotechnical engineering, the 2D model has been extended to 3D model. Based on the entire study, both the 2D and 3Dmodel demonstrate obvious regularization ability to relieve the mesh dependency problems and to reproduce reasonably the shear bands in geostructures.
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Submitted on : Wednesday, December 12, 2018 - 2:11:18 PM
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Jiangxin Liu. Numerical investigations of the strain localization in geotechnical engineering within the framework of micropolar theory. Civil Engineering. École centrale de Nantes, 2018. English. ⟨NNT : 2018ECDN0005⟩. ⟨tel-01952827⟩

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