Dong, Y, Fatahi, B, Khabbaz, H & Zhang, H 2018, 'Influence of particle contact models on soil response of poorly graded sand during cavity expansion in discrete element simulation', Journal of Rock Mechanics and Geotechnical Engineering, vol. 10, no. 6, pp. 1154-1170.View/Download from: UTS OPUS or Publisher's site
The discrete element method (DEM) has been extensively adopted to investigate many complex geotechnical related problems due to its capability to incorporate the discontinuous nature of granular materials. In particular, when simulating large deformations or distortion of soil (e.g. cavity expansion), DEM can be very effective as other numerical solutions may experience convergence problems. Cavity expansion theory has widespread applications in geotechnical engineering, particularly in problems concerning in situ testing, pile installation and so forth, explaining why cavity expansion simulation using DEM has been adopted in this study. In addition, the behaviour of geomaterials in a macro-level is utterly determined by microscopic properties, highlighting the importance of contact models. Despite the fact that there are numerous contact models proposed to mimic the realistic behaviour of granular materials, there are lack of studies on the effects of these contact models on the soil response. Hence, in this study, a series of three-dimensional numerical simulations with different contact constitutive models was conducted to simulate the response of sandy soils during cylindrical cavity expansion. In this numerical investigation, three contact models, i.e. linear contact model, rolling resistance contact model, and Hertz contact model, are considered. It should be noted that the former two models are linear based models, providing linearly elastic and frictional plasticity behaviours, whereas the latter one consists of nonlinear formulation based on an approximation of the theory of Mindlin and Deresiewicz. To examine the effects of these contact models, several cylindrical cavities were created and expanded gradually from an initial radius of 0.055 m to a final radius of 0.1 m. The numerical predictions confirm that the calibrated contact models produced similar results regarding the variations of cavity pressure, radial stress, deviatoric stress, volumetric st...
Dong, Y, Fatahi, B, Khabbaz, H & Hsi, J 2018, 'Impact of Initial In-Situ Stress Field on Soil Response During Cavity Expansion Using Discrete Element Simulation', New Developments in Materials for Infrastructure Sustainability and the Contemporary Issues in Geo-environmental Engineering, GeoChina International Conference, Springer, Hang Zhou, China, pp. 1-10.View/Download from: UTS OPUS or Publisher's site
Discrete element method (DEM) is gaining its popularity in investigating many complicated geotechnical related problems due to its discontinuous nature in simulating granular materials. Particularly when simulating the processes involving large deformation and displacement of soil (e.g. pile penetration), DEM demonstrates distinct advantages over other numerical solutions that may confront convergence problems. Despite the facts that DEM analysis has been conducted to study the mechanism of the cavity expansion, there is a very limited number of investigations conducted to study the effects of the initial stress field on the soil response. Hence, in this study, a three-dimensional numerical analysis has been conducted using PFC3D to investigate the soil response under different initial stress conditions during cavity expansion. A large-scale model containing an adequate number of particles has been constructed to simulate the soil medium, in which, microscopic contact properties were calibrated against existing experimental data to mimic the realistic behaviour of a sandy soil. To examine the effects of the initial in-situ stresses, several cylindrical cavities were created and expanded gradually from an initial radius to a final radius, while stress and strain variations were monitored during the entire simulation. It should be noted that the internal cylinder boundary was loaded using a constant strain rate, while the outer boundary was controlled through a servo mechanism to maintain a constant external pressure adopting appropriate subroutines. The results obtained confirmed that the initial stress conditions have significant effects on the soil response during cavity expansion.
Dong, Y, Fatahi, B, Khabbaz, M & Kamruzzaman, AHM 2018, 'Investigating Effects of Particle Scaling for Cavity Expansion Simulation Using Discrete Element Method', PROCEEDINGS OF GEOSHANGHAI 2018 INTERNATIONAL CONFERENCE: FUNDAMENTALS OF SOIL BEHAVIOURS, GeoShanghai International Conference on Fundamentals of Soil Behaviours, SPRINGER-VERLAG SINGAPORE PTE LTD, Tongji Univ, Shanghai, China, pp. 938-946.View/Download from: UTS OPUS or Publisher's site
Dong, Y, Li, D, Fatahi, B, Zhang, X & Khabbaz, H 2017, 'Small-strain shear modulus of soft clay treated with Saccharomyces cerevisiae and cement', ICSMGE 2017 - 19th International Conference on Soil Mechanics and Geotechnical Engineering, International Conference on Soil Mechanics and Geotechnical Engineering, pp. 2507-2510.View/Download from: UTS OPUS
© 2017 19th ICSMGE Secretariat. All rights reserved. Soil stabilisation by means of microorganisms is an emerging and novel technique in geotechnical engineering. On the other hand, cementation, as one of the conventional ground improvement techniques, has been proved to be an effective method to enhance the engineering properties of soils. Hence, it is believed that the combination of these two approaches can be extremely valuable and offer a novel, cost effective, environmentally friendly and practical engineering solution. In this study, the Saccharomyces cerevisiae, a species of yeast, has been selected owing to abundance and production cost to conduct the experiment in order to investigate its influence on the shear wave velocity and the small-strain shear modulus of cement stabilised clays using bender element test. It is observed that an appropriate amount of Saccharomyces cerevisiae can adequately improve the stiffness of soft clays treated with cement and microorganisms in long term.