A. Khoshghalb - Academia.edu (original) (raw)
Papers by A. Khoshghalb
Geotechnical Earthquake Engineering and Soil Dynamics V, 2018
International Journal of Geomechanics, 2021
Computers and Geotechnics, 2020
In this study, computational efficiency and performance of the smoothed point interpolation metho... more In this study, computational efficiency and performance of the smoothed point interpolation methods (SPIMs) in coupled problems of geomechanics are examined and compared with those of the standard linear finite element method (FEM). In the SPIMs, the problem domain is first discretised using a triangular background mesh, and the smoothing domains are then constructed using the cells of the background mesh. Different approaches for construction of the smoothing domains result in different SPIMs including Edge-based SPIM (ESPIM), cell-based SPIM (CSPIM), and node-based SPIM (NSPIM), each featuring different computational characteristics. For each type of the SPIM, only the simplest and most widely used supporting node selection technique is adopted in this study. The field function is approximated using shape functions constructed adopting either the polynomial point interpolation method (PIM), or radial point interpolation method (RPIM). The governing equations are derived from the equilibrium equation of the solid phase, and momentum and mass balance equations for the flow phase. The equations are then discretised in space using the generalized smoothed Galerkin (GS-Galerkin) method, and in time using the three-point time discretisation technique. The performance of the SPIMs in coupled geomechanical problems are then thoroughly assessed and compared to those of the linear FEM through extensive numerical analyses of four benchmark problems in saturated porous media covering both linear and non-linear material behaviours, and the conclusions drawn by analysing the results.
Computers and Geotechnics, 2018
A smoothed point interpolation method (SPIM) for the numerical modelling of saturated porous medi... more A smoothed point interpolation method (SPIM) for the numerical modelling of saturated porous media in axisymmetric conditions is proposed, aiming to overcome the singularity problem encountered when using SPIMs in axisymmetric settings. The singularity is circumvented in this study by decomposition of the property matrices of the system to sub-matrices with smoothed terms and non-smoothed terms. The salient feature of the proposed method is that it neither incurs additional computation nor compromises on the accuracy of the method. The proposed method is examined by numerical modelling of several benchmark axisymmetric problems, along with a set of convergence studies.
Geosynthetics International, 2018
In this study, the effect of fibre reinforcement on the small-strain shear modulus (Gmax) of sand... more In this study, the effect of fibre reinforcement on the small-strain shear modulus (Gmax) of sandy soils is investigated. A comprehensive set of 47 specimens composed of different types of sand reinforced with variable percentages of polypropylene fibres were tested using a Hardin-type resonant column apparatus embedded with bender element inserts to study the effect of fibre inclusion and content on the Gmax of sands with different particle shapes and gradations. Accordingly, an expression of Gmax for sands, previously proposed by the last two authors and their colleagues, was systematically modified in this study to include the effect of fibre content to estimate the small-strain shear modulus of fibre reinforced sands. An additional set of dynamic tests was performed to verify the newly proposed expression. It was shown that the newly developed expression can predict the Gmax of sand-fibre mixtures with an accuracy of around ±20%, with the error being limited to ±10% in the major...
International Journal for Numerical and Analytical Methods in Geomechanics, 2016
An elasto-viscoplastic constitutive model for asphaltic materials is presented within the context... more An elasto-viscoplastic constitutive model for asphaltic materials is presented within the context of bounding surface plasticity theory, taking into account the effects of the stress state, void binder degree of saturation, temperature and strain rate on the material behaviour. A stress state dependent non-linear elasticity model is introduced to represent time-independent recoverable portion of the deformation. The consistent visco-plasticity framework is utilised to capture the rate-dependent, non-recoverable strain components. The material parameters introduced in the model are identified, and their determination from conventional laboratory tests is discussed. The capability of the model to reproduce experimentally observed response of asphaltic materials is demonstrated through numerical simulations of several laboratory test data from the literature.
International Journal for Numerical and Analytical Methods in Geomechanics, 2011
The Crank-Nicolson scheme has second-order accuracy, but often leads to oscillations affecting nu... more The Crank-Nicolson scheme has second-order accuracy, but often leads to oscillations affecting numerical stability. On the other hand, the implicit scheme is free from oscillation, but it has only first-order accuracy. In this work, a three-point discretization scheme with variable time step is presented for the time marching of parabolic partial differential equations. The method proposed has second-order accuracy, is unconditionally stable and dampens spurious oscillations of the numerical results. The application and effectiveness of the new method are demonstrated through several numerical examples. It is shown that, unlike the Crank-Nicolson method, the approach proposed produces no oscillatory response irrespective of the time step adopted.
Proceedings of the 6th Asia Pacific Conference on Unsaturated Soils (Guilin, China, 23-26 October 2015), 2015
Proceedings of the 6th Asia Pacific Conference on Unsaturated Soils (Guilin, China, 23-26 October 2015), 2015
Computers and Geotechnics, 2016
From Materials to Structures: Advancement through Innovation, 2012
Geomechanics from Micro to Macro, 2014
Numerical Methods in Geotechnical Engineering, 2014
Unsaturated Soils: Research & Applications, 2014
Unsaturated Soils: Research & Applications, 2014
Geotechnical Earthquake Engineering and Soil Dynamics V, 2018
International Journal of Geomechanics, 2021
Computers and Geotechnics, 2020
In this study, computational efficiency and performance of the smoothed point interpolation metho... more In this study, computational efficiency and performance of the smoothed point interpolation methods (SPIMs) in coupled problems of geomechanics are examined and compared with those of the standard linear finite element method (FEM). In the SPIMs, the problem domain is first discretised using a triangular background mesh, and the smoothing domains are then constructed using the cells of the background mesh. Different approaches for construction of the smoothing domains result in different SPIMs including Edge-based SPIM (ESPIM), cell-based SPIM (CSPIM), and node-based SPIM (NSPIM), each featuring different computational characteristics. For each type of the SPIM, only the simplest and most widely used supporting node selection technique is adopted in this study. The field function is approximated using shape functions constructed adopting either the polynomial point interpolation method (PIM), or radial point interpolation method (RPIM). The governing equations are derived from the equilibrium equation of the solid phase, and momentum and mass balance equations for the flow phase. The equations are then discretised in space using the generalized smoothed Galerkin (GS-Galerkin) method, and in time using the three-point time discretisation technique. The performance of the SPIMs in coupled geomechanical problems are then thoroughly assessed and compared to those of the linear FEM through extensive numerical analyses of four benchmark problems in saturated porous media covering both linear and non-linear material behaviours, and the conclusions drawn by analysing the results.
Computers and Geotechnics, 2018
A smoothed point interpolation method (SPIM) for the numerical modelling of saturated porous medi... more A smoothed point interpolation method (SPIM) for the numerical modelling of saturated porous media in axisymmetric conditions is proposed, aiming to overcome the singularity problem encountered when using SPIMs in axisymmetric settings. The singularity is circumvented in this study by decomposition of the property matrices of the system to sub-matrices with smoothed terms and non-smoothed terms. The salient feature of the proposed method is that it neither incurs additional computation nor compromises on the accuracy of the method. The proposed method is examined by numerical modelling of several benchmark axisymmetric problems, along with a set of convergence studies.
Geosynthetics International, 2018
In this study, the effect of fibre reinforcement on the small-strain shear modulus (Gmax) of sand... more In this study, the effect of fibre reinforcement on the small-strain shear modulus (Gmax) of sandy soils is investigated. A comprehensive set of 47 specimens composed of different types of sand reinforced with variable percentages of polypropylene fibres were tested using a Hardin-type resonant column apparatus embedded with bender element inserts to study the effect of fibre inclusion and content on the Gmax of sands with different particle shapes and gradations. Accordingly, an expression of Gmax for sands, previously proposed by the last two authors and their colleagues, was systematically modified in this study to include the effect of fibre content to estimate the small-strain shear modulus of fibre reinforced sands. An additional set of dynamic tests was performed to verify the newly proposed expression. It was shown that the newly developed expression can predict the Gmax of sand-fibre mixtures with an accuracy of around ±20%, with the error being limited to ±10% in the major...
International Journal for Numerical and Analytical Methods in Geomechanics, 2016
An elasto-viscoplastic constitutive model for asphaltic materials is presented within the context... more An elasto-viscoplastic constitutive model for asphaltic materials is presented within the context of bounding surface plasticity theory, taking into account the effects of the stress state, void binder degree of saturation, temperature and strain rate on the material behaviour. A stress state dependent non-linear elasticity model is introduced to represent time-independent recoverable portion of the deformation. The consistent visco-plasticity framework is utilised to capture the rate-dependent, non-recoverable strain components. The material parameters introduced in the model are identified, and their determination from conventional laboratory tests is discussed. The capability of the model to reproduce experimentally observed response of asphaltic materials is demonstrated through numerical simulations of several laboratory test data from the literature.
International Journal for Numerical and Analytical Methods in Geomechanics, 2011
The Crank-Nicolson scheme has second-order accuracy, but often leads to oscillations affecting nu... more The Crank-Nicolson scheme has second-order accuracy, but often leads to oscillations affecting numerical stability. On the other hand, the implicit scheme is free from oscillation, but it has only first-order accuracy. In this work, a three-point discretization scheme with variable time step is presented for the time marching of parabolic partial differential equations. The method proposed has second-order accuracy, is unconditionally stable and dampens spurious oscillations of the numerical results. The application and effectiveness of the new method are demonstrated through several numerical examples. It is shown that, unlike the Crank-Nicolson method, the approach proposed produces no oscillatory response irrespective of the time step adopted.
Proceedings of the 6th Asia Pacific Conference on Unsaturated Soils (Guilin, China, 23-26 October 2015), 2015
Proceedings of the 6th Asia Pacific Conference on Unsaturated Soils (Guilin, China, 23-26 October 2015), 2015
Computers and Geotechnics, 2016
From Materials to Structures: Advancement through Innovation, 2012
Geomechanics from Micro to Macro, 2014
Numerical Methods in Geotechnical Engineering, 2014
Unsaturated Soils: Research & Applications, 2014
Unsaturated Soils: Research & Applications, 2014