Pore orientation of granular materials during biaxial compression |
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| Institution: | 1. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University，Nanjing 210096, China;2. School of Civil and Environmental Engineering, Nanyang Technological University, Block N1, Nanyang Ave., Singapore 639798, Singapore;3. Department of Civil and Environmental Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Kabanbay Batyr Ave., 53, Nur-Sultan, 010000, Kazakhstan;1. School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore;2. Department of Mechanical and Construction Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, UK;3. Building and Construction Authority, 200 Braddell Road, 579700, Singapore. |
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| Abstract: | The local pore spaces in granular materials tend to be aligned parallel to the major principal stress direction upon particle mobilization. Manifestation of this response has been numerically validated in our previous studies with the aid of discrete element method modeling and image processing techniques during creep and shearing. We now extend the modeling of pore geometry, constructed with spherical particles, to assemblies of particle clumps. Two-dimensional simulations are performed for both loose and dense assemblies of spherical particles and particle clumps. Each particle packing is bound by rigid or flexible walls and subjected to biaxial compression and the particle mobilization effect on the evolution of pore orientation is explored. Randomly shaped pores surrounded by adjacent particles are geometrically quantified by Delaunay tessellation and fitted with ellipses. Results show that localization is apparent in dense assemblies, in particular for clumped particle packing, while loose assemblies exhibit diffusive failure. Small pores within well-defined shear bands tend to align either parallel to the direction of the shear band or perpendicular to the major principal stress. On the other hand, small pores within the blocks and large pores have a tendency to become elongate towards the major principal stress direction. This study reveals for the first time that pore orientation is dependent upon particle shape, pore size, and assembly conditions on the pore and global scales. |
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| Keywords: | Pore orientation Tessellation Principal stress Biaxial compression Discrete element method Particle clump |
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