Dr Majid Nazem
Honorary Associate Professor
School of Engineering (Civil Engineering)
- Email:majidreza.nazem@newcastle.edu.au
- Phone:(02) 4921 6048
Career Summary
Biography
Research Expertise
Computational Geomechanics Finite Elements Method Finite Plasticity Contact Mechanics Dynamic Soil-Structure Interaction .
Teaching Expertise
CIVL3280 – Geomechanics II. CIVL4110 – Theory of Structures III. CIVL4201 – Geotechnical and Geoenvironmental Engineering. CIVL4830 – Stress and Finite Element Analysis. GENG1001 – Introduction to Engineering Mechanics. GENG1002 – Engineering Computations.
Administrative Expertise
Representative of Discipline of Civil, Surveying, and Environmental, Marketing Committee Group (MCG) of the Faculty of Engineering and Built Environment.
Collaborations
Numerical analysis of reinforced concrete structures Dynamic analysis of geotechnical problems Adaptive finite element methods Multi-seam mining/ land subsidence.
Qualifications
- PhD, University of Newcastle
Keywords
- Adaptive Finite Element Methods
- Contact Mechanics
- Engineering Mechanics
- Finite Elements
- Finite Plasticity
- Fortran programming language
- Geotechnical Engineering
- Large deformations
- Nonlinear Dynamic Analysis
- Soil Mechanics
- Stress Analysis
- Theory of Structures
Languages
- Persian (excluding Dari) (Fluent)
Professional Experience
Academic appointment
Dates | Title | Organisation / Department |
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1/12/2010 - | University Research Fellow | University of Newcastle Engineering & Built Environment Australia |
1/3/2009 - 1/3/2012 |
Fellow UON UoN Research Fellowship |
University of Newcastle School of Engineering Australia |
1/6/2007 - 1/3/2009 | Postdoctorate | University of Newcastle Engineering & Built Environment Australia |
Awards
Research Award
Year | Award |
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2006 |
D. H. Trollope Medal Australian Geomechanics Society |
Publications
For publications that are currently unpublished or in-press, details are shown in italics.
Chapter (2 outputs)
Year | Citation | Altmetrics | Link |
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2015 |
Zakrzewski N, Nazem M, 'The Maximum-Entropy Meshless method for dynamic and coupled analysis of offshore geotechnical problems', Frontiers in Offshore Geotechnics III 1145-1149 (2015) There exist many problems in the offshore geotechnical setting which necessitate a dynamic analysis or a consolidation analysis. In recent years literature on this topic has been ... [more] There exist many problems in the offshore geotechnical setting which necessitate a dynamic analysis or a consolidation analysis. In recent years literature on this topic has been dominated by the application of Finite Element Methods to solving such problems and addressing the inherent shortcomings associated with their use. These issues include, but are not limited to, the occurrence of mesh distortion in problems involving large deformations and the inability to adequately capture discontinuities. The intrinsic nature of meshfree methods, however, makes them a more appropriate means of solving offshore geotechnical problems. This study presents a robust Maximum-Entropy Meshless method for nonlinear analysis of offshore problems in which the effect of time-dependent behaviour cannot be ignored. The Generalised-a time integration scheme and the Backward-Euler method are respectively employed for dynamic analysis and coupled analysis of such problems. The applicability of this meshless method is presented by studying the undrained soil behaviour under a circular footing subjected to dynamic loading as well as static loading. |
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2010 |
Nazem M, Carter JR, 'Parametric study of a free-falling penetrometer in clay-like soils', Frontiers in Offshore Geotechnics II 293-298 (2010) A free-falling penetrometer (FFP) is a useful apparatus for providing information on the mechanical properties of soil layers, especially where the site in question is inaccessibl... [more] A free-falling penetrometer (FFP) is a useful apparatus for providing information on the mechanical properties of soil layers, especially where the site in question is inaccessible, which is normally the situation for many seabed, river and swamp deposits. FFP tests can provide useful data such as the total depth and time of penetration and the deceleration characteristics of the penetrometer, provided it is suitably instrumented. The main quantities of interest measured in FFP tests, viz., the time and depth of penetration, depend on the mechanical properties of the soil, such as its shear strength and rigidity index, as well as those parameters associated exclusively with the penetrometer, such as its geometry and the energy with which it first impacts the soil. Potentially, these penetration data can be used to deduce strength parameters for the soil in situ, either through empirical correlations or else by application of a rigorous numerical solution for the ideal penetration problem. A robust finite element analysis procedure was developed at the University of Newcastle, Australia, especially for the analysis of geotechnical problems, including problems that involve soil penetration. This method of analysis is based upon the Arbitrary Lagrangian Eulerian (ALE) finite element technique and takes into account material nonlinearity and rate dependence, large deformations, changing boundary conditions, and time-dependent loading, including an allowance for dynamic forces when necessary. The present study aims to provide some numerical results describing the effect of the mechanical properties of the soil and the energy of the penetrometer on the penetration response. This goal has been achieved by performing a wide range of FFP analyses using the proposed ALE finite element method. |
Journal article (64 outputs)
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2024 |
Rong J, Nazem M, Chow SH, Zhou A, Moridpour S, 'Design and application of dynamic seabed penetrators in offshore geotechnical engineering: A review', Ocean Engineering, 293 (2024) [C1] Dynamic seabed penetrators are increasingly utilised for offshore site investigation and mooring offshore floating infrastructure. This paper presents a state-of-the-art review of... [more] Dynamic seabed penetrators are increasingly utilised for offshore site investigation and mooring offshore floating infrastructure. This paper presents a state-of-the-art review of dynamic seabed penetrator designs, performances, and data interpretations developed after the 2000s. The goal of this study is to provide essential insights into dynamic seabed penetrators, aiming to elucidate the strengths and constraints associated with various designs based on applications. This facilitates the prospective common advancements and potential refinements discussion. A brief introduction is provided on existing dynamic seabed penetrator, along with the advantages and drawbacks of their physical design. The dynamic seabed penetrators are grouped and reviewed according to their prototype model investigations, field studies, and practical applications, i.e., free-falling penetrometer (FFP) for offshore site investigation; and dynamically installed anchor (DIA) for mooring offshore infrastructure. The influence of penetrator geometry, weight, instrumentation, and the target soil type and state on the penetrator performances are also presented. Existing data interpretation models are then discussed, which take into consideration the strain rate effects, including consolidation and viscous rate effects, and the non-linear variation in capacity factor. Through the review, some research gaps are identified and highlighted, leading to potential future research opportunities.
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2023 |
Barari A, Zhou J, Bo Ibsen L, Nazem M, Nielsen K, 'A theoretical and practical framework based on plasticity theory for the drained behavior of single and multiple shallow footings', International Journal for Numerical and Analytical Methods in Geomechanics, 47 2872-2898 (2023) [C1] With the shift of the offshore wind energy sector to deeper waters, demand for the development of more complex foundation solutions, particularly suction bucket ¿ supported tripod... [more] With the shift of the offshore wind energy sector to deeper waters, demand for the development of more complex foundation solutions, particularly suction bucket ¿ supported tripod/tetrapod and jacket foundations, has increased. This paper is divided into two main sections. The first part comprises a comprehensive review of the performance of circular surface and shallow foundations under combined loading (VHM), and how it can principally be understood in a theoretical framework of plasticity theory. Examination of the considered data suggested that the general assumption of over-estimated non-association degree with constant failure surface parameters and increasing vertical load may require further investigation. This may be attributed to the complex interplay of multiple properties such as stress level, soil strength profile and foundation geometry. The existing data in the literature were also used to provide practical guidance for a successful implementation of the elasto-plastic constitutive relationships in offshore foundation design. In second part of the paper, the suitability of the non-associated plasticity formulation for a baseline multi-pod system in H-M load space was investigated using three-dimensional (3D) finite element (FE) analyses and not verified. Furthermore, the failure envelopes and hardening law for caissons with different embedment ratios differed from those recommended in the literature were established. Parametric studies of multi-caisson foundations revealed that the failure mechanism of multi-bucket foundations under horizontal loading depended greatly on the bucket spacing. The horizontal bearing capacities increased with the bucket spacing until they reached a threshold. Meanwhile, analyses of the multi-bucket foundation under moment loading confirmed the occurrence of a push-pull failure mechanism.
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2023 |
Nofalah MH, Ghadir P, Hasanzadehshooiili H, Aminpour M, Javadi AA, Nazem M, 'Effects of binder proportion and curing condition on the mechanical characteristics of volcanic ash- and slag-based geopolymer mortars; machine learning integrated experimental study', Construction and Building Materials, 395 (2023) [C1] Contradicting natures of volcanic ash (VA)- and ground granulated blast furnace slag (GGBFS)- based geopolymers with regard to their need for being exposed to a heating source for... [more] Contradicting natures of volcanic ash (VA)- and ground granulated blast furnace slag (GGBFS)- based geopolymers with regard to their need for being exposed to a heating source for conducting alkali-reactions make meaningful differences in the strength and flowability of mortars. To address the impacts of types of the geoploymerizing agent, their proportions, and different curing regimes on their strength and shrinkage behavior, three different curing scenarios including curing at room temperature, RT curing; resting under room temperature for various curing periods, and then hydrothermally curing at an elevated temperature for one day, RO curing; and curing in the oven for one day and then resting at the room temperature, for various curing periods, OR curing, are considered. Based on the flowability, setting time, unconfined compressive strength (UCS), and drying shrinkage tests on eight different mixtures, the effects of binder proportion and curing conditions are evaluated. It was observed that with the substitution of 30% VA with GGBFS, specimens cured at RT condition outperformed OR specimens. This threshold was 45% while comparing RT and RO specimens and with higher slag content, RT specimens gain higher UCS. Also, for GGBFS proportion less than 45%, specimens cured at RO conditions showed higher long-term UCS compared to the OR specimens, and this behavior was reversed for higher GGBFS content. Scanning electron microscopy test results indicated that N-A-S-(H) type gel is the dominant geopolymeric gel in VA-based specimens, and as the amount of slag increases, the gels formed change to N-(C)-A-S-H and with further addition of GGBFS, C-A-S-H type gel is the dominant gel which results in strength development in GGBFS-based specimens. Based on the results of 80 UCS and 140 drying shrinkage tests, different machine learning (ML) algorithms and an evolutionary model were employed to present accurate and cost-effective predictive models as useful and capable methods for practitioners and researchers for the preliminary design stages of projects. A comparative study revealed the superior prediction efficiency of the gradient boosting (GB) model with the R2 score of 95% among 8 different ML algorithms and advanced ensemble models. In addition, evolutionary models with the coefficients of determination of 92% and 95% are, respectively, proposed for the drying shrinkage and the UCS. This study advances the field by assessing VA-GGBFS blend and curing effects on geopolymer mortars and developing ML-based models for compressive strength and drying shrinkage, facilitating efficient optimization in practical applications.
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2023 |
Shafiei A, Aminpour M, Hasanzadehshooiili H, Ghorbani A, Nazem M, 'Mechanical characterization of marl soil treated by cement and lignosulfonate under freeze thaw cycles: experimental studies and machine-learning modeling', Bulletin of Engineering Geology and the Environment, 82 (2023) [C1] Calcium carbonate-enriched marl is supposed to lose the bearing capacity while subjected to an increase/decrease in the moisture content and under the effect of multiple freeze¿th... [more] Calcium carbonate-enriched marl is supposed to lose the bearing capacity while subjected to an increase/decrease in the moisture content and under the effect of multiple freeze¿thaw (F-T) cycles. Investigating different weight percentages and curing periods, combination of ordinary Portland cement (OPC) and lignosulfonate is introduced as an efficient method to improve the mechanical strength of the marl soil under the effect of F-T cycles. In this regard, compaction, unconfined compressive strength, and direct shear tests were conducted. It was observed that although the addition of OPC (as the sole binder) can enhance the shear strength, the performance of samples under the action of F-T was not significantly improved. However, samples containing lignosulfonate showed a rectified behavior. Microstructural investigations exhibited the development of new intensity peaks for the calcium-aluminate-silicate-hydrate (C-A-S¿H) products and elaborated a denser structure with a lower porosity, keeping the soil particles closer. Next, different intelligent approaches of machine learning (ML) were employed to provide cost-effective and accurate speedy tools. Among eight machine learning algorithms and advanced ensemble models, comparative study revealed the efficiency of gradient boosting model with coefficients of determinations of up to 98.5% for the prediction of UCS. Feature importance analysis suggested the duration of treatment and the cement content as the main contributing factors to the UCS. Highly accurate and efficient EPR-based models with coefficients of determination of higher than 99% were also proposed for the prediction of shear strength and shear stress parameters.
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2023 |
Aminpour M, Alaie R, Khosravi S, Kardani N, Moridpour S, Nazem M, 'Slope stability machine learning predictions on spatially variable random fields with and without factor of safety calculations', Computers and Geotechnics, 153 (2023) [C1] Random field Monte Carlo (MC) reliability analysis is a robust stochastic method to determine the probability of failure. This method, however, requires a large number of numerica... [more] Random field Monte Carlo (MC) reliability analysis is a robust stochastic method to determine the probability of failure. This method, however, requires a large number of numerical simulations demanding high computational costs. This paper explores the efficiency of machine learning (ML) models and Artificial Neural Networks used as surrogate models trained on a limited number of random field slope stability simulations in predicting the results of large datasets. The paper explores the efficiency of the predictions on the probability of failure using databases with and without factor of safety (FOS) computations. An extensive range of soil heterogeneity and anisotropy is examined on unstratified and layered slopes. On datasets requiring only the examination of failure or non-failure class of slopes (without FOSs), the performance of ML classification of the random field slope stability results generally reduces with higher anisotropy and heterogeneity of the soil. However, using the probability summation method proposed here, ML prediction of the probability of failure is shown to be highly accurate for the whole range of soil heterogeneity and anisotropy. The errors in the predicted probability of failure using 5% of MC data is only 0.46% in average for the prediction of the remaining unseen 95% of data. Offering such accuracies, the approach accelerates the computations for about 100 folds. The models also proved similarly efficient in predicting FOSs for stratified random field anisotropic heterogenous slopes.
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2023 |
Aminpour M, Alaie R, Kardani N, Moridpour S, Nazem M, 'Highly efficient reliability analysis of anisotropic heterogeneous slopes: machine learning-aided Monte Carlo method', Acta Geotechnica, 18 3367-3389 (2023) [C1] Machine learning (ML) algorithms are increasingly used as surrogate models to increase the efficiency of stochastic reliability analyses in geotechnical engineering. This paper pr... [more] Machine learning (ML) algorithms are increasingly used as surrogate models to increase the efficiency of stochastic reliability analyses in geotechnical engineering. This paper presents a highly efficient ML-aided reliability technique that is able to accurately predict the results of a Monte Carlo (MC) reliability study and yet performs 500 times faster. A complete MC reliability analysis on anisotropic heterogeneous slopes consisting of 120,000 simulated samples is conducted in parallel to the proposed ML-aided stochastic technique. Comparing the results of the complete MC study and the proposed ML-aided technique, the expected errors of the proposed method are realistically examined. Circumventing the time-consuming computation of factors of safety for the training datasets, the proposed technique is more efficient than previous methods. Different ML models, including random forest, support vector machine and artificial neural networks, are presented, optimised and compared. The effects of the size and type of training and testing datasets are discussed. The expected errors of the ML predicted probability of failure are characterised by different levels of soil heterogeneity and anisotropy. Using only 1% of MC samples to train ML surrogate models, the proposed technique can accurately predict the probability of failure with mean errors limited to 0.7%. The proposed technique reduces the computational time required for our study from 306¿days to only 14¿h, providing 500 times higher efficiency.
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2022 |
Wang Y, Smith J, Nazem M, 'Effect of Various Rainfall Conditions on the Roadside Stabilisation of Slopes in Gippsland', INTERNATIONAL JOURNAL OF CIVIL ENGINEERING, 21 173-192 (2022) [C1]
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2022 |
Kardani N, Bardhan A, Samui P, Nazem M, Zhou A, Armaghani DJ, 'A novel technique based on the improved firefly algorithm coupled with extreme learning machine (ELM-IFF) for predicting the thermal conductivity of soil', Engineering with Computers, 38 3321-3340 (2022) [C1] Thermal conductivity is a specific thermal property of soil which controls the exchange of thermal energy. If predicted accurately, the thermal conductivity of soil has a signific... [more] Thermal conductivity is a specific thermal property of soil which controls the exchange of thermal energy. If predicted accurately, the thermal conductivity of soil has a significant effect on geothermal applications. Since the thermal conductivity is influenced by multiple variables including soil type and mineralogy, dry density, and water content, its precise prediction becomes a challenging problem. In this study, novel computational approaches including hybridisation of two metaheuristic optimisation algorithms, i.e. firefly algorithm (FF) and improved firefly algorithm (IFF), with conventional machine learning techniques including extreme learning machine (ELM), adaptive neuro-fuzzy interface system (ANFIS) and artificial neural network (ANN), are proposed to predict the thermal conductivity of unsaturated soils. FF and IFF are used to optimise the internal parameters of the ELM, ANFIS and ANN. These six hybrid models are applied to the dataset of 257 soil cases considering six influential variables for predicting the thermal conductivity of unsaturated soils. Several performance parameters are used to verify the predictive performance and generalisation capability of the developed hybrid models. The obtained results from the computational process confirmed that ELM-IFF attained the best predictive performance with a coefficient of determination = 0.9615, variance account for = 96.06%, root mean square error = 0.0428, and mean absolute error = 0.0316 on the testing dataset (validation phase). The results of the models are also visualised and analysed through different approaches using Taylor diagrams, regression error characteristic curves and area under curve scores, rank analysis and a novel method called accuracy matrix. It was found that all the proposed hybrid models have a great ability to be considered as alternatives for empirical relevant models. The developed ELM-IFF model can be employed in the initial stages of any engineering projects for fast determination of thermal conductivity.
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2022 |
Kardani N, Zhou A, Lin X, Nazem M, 'Experimental Study and Machine Learning Aided Modelling of the Mechanical Behaviour of Rammed Earth', Geotechnical and Geological Engineering, 40 5007-5027 (2022) [C1] Rammed earth is a sustainable building technique for constructing foundations, floors, and walls using natural raw materials such as earth, chalk, lime, with stabilizers like ceme... [more] Rammed earth is a sustainable building technique for constructing foundations, floors, and walls using natural raw materials such as earth, chalk, lime, with stabilizers like cements. As the proportion of various materials changes, the mechanical properties of rammed earth materials are also varying correspondingly. A series of experimental studies are first conducted to evaluate the effects of different proportions of raw materials including clay, sand, cement, and water under various loading rates on the strength/deformation properties (peak strength, qf; residual strength, qres; initial modulus, Emax; secant modulus at 50% peak strength, E50) and stress¿strain relationships (s1~ e1) of rammed earth. A soft computing method (extreme gradient boosting machine, XGBoost) is then developed to model peak strength, residual strength, initial modulus, secant modulus and entire stress¿strain relationships obtained from the experimental studies. Three performance metrics including the root mean squared error, variance accounted for and R-squared value (R2) are used to measure the performance of the applied model. Comparisons between simulations and experiments show that the developed XGBoost algorithm is a promising alternative in modelling key mechanical properties and entire stress¿strain relationships for rammed earth. For stress¿strain relationships calculated R-squared value for the training set is 0.978 and that for the testing dataset is 0.908. The key factor that most significantly affects the peak strength, residual strength, initial modulus, secant modulus and entire stress¿strain relationships for rammed earth can be identified by using the developed soft computing method.
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2022 |
Kardani N, Aminpour M, Nouman Amjad Raja M, Kumar G, Bardhan A, Nazem M, 'Prediction of the resilient modulus of compacted subgrade soils using ensemble machine learning methods', Transportation Geotechnics, 36 (2022) [C1] The accurate estimation of resilient modulus (MR) of compacted subgrade soil is imperative for the safe and sustainable design of flexible pavement systems. The aim of this study ... [more] The accurate estimation of resilient modulus (MR) of compacted subgrade soil is imperative for the safe and sustainable design of flexible pavement systems. The aim of this study is to explore the potential of ensemble machine learning techniques for predicting the MR of pavement subgrade soil. For this, 2813 data points from twelve compacted subgrade soils were collected which consists of the following inputs parameters: dry unit weight, weighted plasticity index, deviator stress, confining stress, number of freeze¿thaw cycles, and moisture content. Four commonly used machine learning (ML) methods, namely, gradient boosting regression (GBR), decision tree regression (DTR), K nearest neighbour regression (KNR), and random forest regression (RFR) were developed and implemented for forecasting the MR value. Thereafter, several ensemble ML techniques including voting ensemble (VO-ENSM), voting ensemble with RF as a meta-model (VO-ENSM (RF)), stacking ensemble (ST-ENSM) and bagging ensemble (BG-ENSM) were utilised to amalgamate the outputs from the developed standalone ML models. Additionally, a multiple linear regression model was also developed as a baseline. The predictive veracity, reliability and trustworthiness of the developed ensemble models were corroborated using rigorous statistical testing, ranking technique, and uncertainty analysis. The results as obtained have shown that the BG-ENSM outperformed its counterparts in predicting the MR of subgrade soil. Hence, it can be a part of portfolio of predicting tools utilised by the practitioners in evaluating the strength of the pavement subgrade soil. Finally, the sensitivity analysis was performed to assess the strength of input variables on the MR.
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2022 |
Wang Y, Nazem M, Smith JV, 'Effect of Dimension Variables on the Behaviour of Slopes Stabilised by an Integrated Method Combining Gabion-Faced Geogrid-Reinforced Retaining Wall with Embedded Piles', International Journal of Geosynthetics and Ground Engineering, 8 (2022) [C1] Severe slope instability exists in the area of South Gippsland in Victoria state located in south-east Australia. An integrated slope-stabilisation method, which includes a pile-r... [more] Severe slope instability exists in the area of South Gippsland in Victoria state located in south-east Australia. An integrated slope-stabilisation method, which includes a pile-retaining structure installed at toe of the gabion-faced geogrid-reinforced retaining wall, has widely been used in this district. A continuous steel rail wall embedded in the concrete pile then provides lateral support to the retaining wall. The effectiveness of the integrated method is first illustrated by comparing the slope stability evaluated by strength reduction method and behaviours of the slope obtained by elastoplastic analysis. A series of parametric studies are then performed to investigate effects of facing inclinations, embedded geogrid length, and vertical spacing of geogrid layers on the stability and behaviour of the slope and the behaviour of the pile under various uniform surcharge load conditions. The numerical results indicate that additional contribution from piles can increase the stability of the slope up to 42.9 %. The dimensional variables of gabion-faced geogrid-reinforced retaining wall also impose significant impact on the behaviour of slopes and piles, and the effect of each variable has also been quantitatively evaluated and qualitatively described. The effect of the geogrid amount on behaviours of slopes and piles has also been investigated through the comparison between two slope configurations with maximum and minimum geogrid amount. The results from the parametric studies can then be used as a design reference for the future applications of this integrated slope-stabilisation method.
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2022 |
Kardani N, Bardhan A, Roy B, Samui P, Nazem M, Armaghani DJ, Zhou A, 'A novel improved Harris Hawks optimization algorithm coupled with ELM for predicting permeability of tight carbonates', Engineering with Computers, 38 4323-4346 (2022) [C1] Tight carbonate reservoirs appear to be heterogeneous due to the patchy production of various digenetic properties. Consequently, the permeability calculation of tight rocks is co... [more] Tight carbonate reservoirs appear to be heterogeneous due to the patchy production of various digenetic properties. Consequently, the permeability calculation of tight rocks is costly, and only a finite number of core plugs in any single reservoir can be estimated. Hence, in the present study, a novel hybrid model constructed by combination of the improved version of the Harris Hawks optimisation (HHO), i.e., IHHO, and extreme learning machine (ELM) is proposed to predict the permeability of tight carbonates using limited number of input variables. The proposed IHHO employs a mutation mechanism to avoid trapping in local optima by increasing the search capabilities. Subsequently, ELM-IHHO, a novel metaheuristic ELM-based algorithm, was developed to predict the permeability of tight carbonates. Experimental results show that the proposed ELM-IHHO attained the most accurate prediction with R2 = 0.9254 and RMSE = 0.0619 in the testing phase. The result of the proposed model is significantly better than those obtained from other ELM-based hybrid models developed with particle swarm optimisation, genetic algorithm, and slime mould algorithm. The results also illustrate that the proposed ELM-IHHO model outperforms the other benchmark model, such as back-propagation neural nets, support vector regression, random forest, and group method of data handling in predicting the permeability of tight carbonates.
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2022 |
Kardani N, Bardhan A, Gupta S, Samui P, Nazem M, Zhang Y, Zhou A, 'Predicting permeability of tight carbonates using a hybrid machine learning approach of modified equilibrium optimizer and extreme learning machine', Acta Geotechnica, 17 1239-1255 (2022) [C1] It is a problematic task to perform petro-physical property prediction of carbonate reservoir rocks in most cases, specifically for permeability prediction since a carbonate rock ... [more] It is a problematic task to perform petro-physical property prediction of carbonate reservoir rocks in most cases, specifically for permeability prediction since a carbonate rock most commonly contains grains of heterogeneous size distributions. Consequently, the permeability calculation of tight rocks in laboratories is costly and very time-consuming. Therefore, this study aims to tackle this issue by developing novel hybrid models based on combination of the modified version of the equilibrium optimizer (EO), i.e., MEO, and two conventional machine learning algorithms, namely extreme learning machine (ELM) and artificial neural network (ANN). The MEO employs a mutation mechanism in order to avoid trapping in local optima of EO by increasing the search capabilities. In this study, ELM-MEO and ANN-MEO, novel metaheuristic ELM-based and ANN-based algorithms, were constructed to predict the permeability of tight carbonates. In addition, ANN, ELM, RF, RVM and MARS combined with particle swarm optimization and genetic programming algorithm have a better insight into the performances for preferably predicting the permeability carbonates. The results illustrate that the proposed ELM-MEO model with R2 = 0.9323, RMSE = 0.0612 and MAE = 0.0442 in training stage and R2 = 0.8743, RMSE = 0.0806 and MAE = 0.0660 in testing stage, outperformed other ELM-based and ANN-based metaheuristic models in predicting the permeability of tight carbonates at all levels.
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2022 |
Kardani N, Bardhan A, Samui P, Nazem M, Asteris PG, Zhou A, 'Predicting the thermal conductivity of soils using integrated approach of ANN and PSO with adaptive and time-varying acceleration coefficients', International Journal of Thermal Sciences, 173 (2022) [C1] This study aims to propose hybrid adaptive neuro swarm intelligence (HANSI) techniques for predicting the thermal conductivity of unsaturated soils. The novel contribution is made... [more] This study aims to propose hybrid adaptive neuro swarm intelligence (HANSI) techniques for predicting the thermal conductivity of unsaturated soils. The novel contribution is made by integrating artificial neural networks (ANNs) and particle swarm optimisation (PSO) with adaptive and time-varying acceleration coefficients. Two HANSI techniques, namely ANN-IPSO (ANN optimised with improved PSO) and ANN-APSO (ANN optimised with adaptive PSO) were constructed. To train and validate the proposed models, a dataset of 257 measurements of the thermal conductivity of soils featuring 6 influencing factors was used. The proposed ANN-APSO model has the best prediction performance in both the training and testing stages, according to the results. Also, during the validation phase, the suggested ANN-APSO model attained the most accurate prediction with Adj. R2 = 0.9265, R2 = 0.9442, and RMSE = 0.0515. These results are significantly better than those obtained from other hybrid ANN models constructed with standard PSO, IPSO, new self-organizing hierarchical PSO, modified new self-organizing hierarchical PSO, genetic algorithm, biogeography-based optimisation, and firefly algorithm. Based on the experimental results, the newly constructed HANSI models, especially ANN-APSO can be considered as an alternate solution for predicting real-time engineering problems, including the thermal conductivity of unsaturated soils.
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2021 |
Kardani N, Zhou A, Nazem M, Lin X, 'Modelling of municipal solid waste gasification using an optimised ensemble soft computing model', Fuel, 289 (2021) [C1] Modelling and simulation of municipal solid waste (MSW) gasification process is a complex and computationally expensive task due to the porous structure of MSW and the nonlinear r... [more] Modelling and simulation of municipal solid waste (MSW) gasification process is a complex and computationally expensive task due to the porous structure of MSW and the nonlinear relations amongst various parameters. In this study, to model the MSW gasification in fluidised bed gasifier, an optimised ensemble model (OEM) is established based on five advanced soft computing models, including decision tree (DT), extreme gradient boosting (XGB), random forest (RF), multilayer perceptron (MLP) and support vector regression (SVR). The particle swarm optimisation (PSO) algorithm is employed to optimise the five models. The proposed optimised ensemble model is then implemented to predict the gasification characteristics including heating value of gas (LHV), heating value of gasification products (LHVp) and the syngas yield in the process of MSW gasification. The simulation results reveal that the proposed ensemble model is a promising alternative in modelling the nonlinear complex thermochemical processes, such as MSW gasification. Furthermore, through the analysis of the importance of influential variables, the temperature is found to be the most important variable in the modelling of MSW gasification.
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2021 |
Kardani N, Zhou A, Nazem M, Shen SL, 'Improved prediction of slope stability using a hybrid stacking ensemble method based on finite element analysis and field data', Journal of Rock Mechanics and Geotechnical Engineering, 13 188-201 (2021) [C1] Slope failures lead to catastrophic consequences in numerous countries and thus the stability assessment for slopes is of high interest in geotechnical and geological engineering ... [more] Slope failures lead to catastrophic consequences in numerous countries and thus the stability assessment for slopes is of high interest in geotechnical and geological engineering researches. A hybrid stacking ensemble approach is proposed in this study for enhancing the prediction of slope stability. In the hybrid stacking ensemble approach, we used an artificial bee colony (ABC) algorithm to find out the best combination of base classifiers (level 0) and determined a suitable meta-classifier (level 1) from a pool of 11 individual optimized machine learning (OML) algorithms. Finite element analysis (FEA) was conducted in order to form the synthetic database for the training stage (150 cases) of the proposed model while 107 real field slope cases were used for the testing stage. The results by the hybrid stacking ensemble approach were then compared with that obtained by the 11 individual OML methods using confusion matrix, F1-score, and area under the curve, i.e. AUC-score. The comparisons showed that a significant improvement in the prediction ability of slope stability has been achieved by the hybrid stacking ensemble (AUC = 90.4%), which is 7% higher than the best of the 11 individual OML methods (AUC = 82.9%). Then, a further comparison was undertaken between the hybrid stacking ensemble method and basic ensemble classifier on slope stability prediction. The results showed a prominent performance of the hybrid stacking ensemble method over the basic ensemble method. Finally, the importance of the variables for slope stability was studied using linear vector quantization (LVQ) method.
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2021 |
Wang Y, Smith JV, Nazem M, 'Optimisation of a Slope-Stabilisation System Combining Gabion-Faced Geogrid-Reinforced Retaining Wall with Embedded Piles', KSCE Journal of Civil Engineering, 25 4535-4551 (2021) [C1] Slope instability is a common geotechnical issue in South Gippsland, Victoria, Australia. The network of rural roads constructed and maintained by the local authority are greatly ... [more] Slope instability is a common geotechnical issue in South Gippsland, Victoria, Australia. The network of rural roads constructed and maintained by the local authority are greatly affected by the instability. An integrated slope-stabilisation system that combines two well-developed slope stabilisation methods has been used widely in this district. These two methods are gabion-faced geogrid-reinforced retaining wall and pile retaining structures. These two methods are connected by a steel rail that is welded at the top of the piles to buttress the lowest row of the gabion basket wall. In order to reflect the site conditions accurately, a three-dimensional non-linear finite element approach is adopted in this study. The elastic-perfectly plastic constitutive model with the Mohr-Coulomb yield criterion is used to describe the behaviour of the soil and the gabion basket. With the assistance of the shear strength reduction technique, the effectiveness of the integrated system is demonstrated through the comparison of the representative indicators of the slope stability among various slope configurations. A series of parametric studies related to the ratio of the embedded length of geogrid to the height of the slope, the ratio of the embedded length of the pile to the thickness of the unstable soil layer, and the ratio of the spacing to the diameter of the pile have also been conducted for the purpose of optimising this slope stabilisation infrastructure. The results from the parametric studies indicate that the optimised and improved integrated infrastructure can stabilise the road and slope economically without the loss of the safety margin.
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2021 |
Ghorbani J, Nazem M, Kodikara J, Wriggers P, 'Finite element solution for static and dynamic interactions of cylindrical rigid objects and unsaturated granular soils', Computer Methods in Applied Mechanics and Engineering, 384 (2021) [C1] By employing a mortar-type contact algorithm, we develop a theoretical and numerical framework for elastoplastic interaction of unsaturated granular soils with a rigid cylindrical... [more] By employing a mortar-type contact algorithm, we develop a theoretical and numerical framework for elastoplastic interaction of unsaturated granular soils with a rigid cylindrical object in both static and dynamic analyses. The elastoplastic response is modelled with a constitutive model based on the effective stress concept for unsaturated soils. The constitutive model offers the ability to simulate the effect of stress-induced anisotropy on the plastic response. Several numerical examples are provided for verification purposes and sensitivity analysis, demonstrating the capabilities of the presented framework.
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2021 |
Falamarzi A, Moridpour S, Nazem M, 'A time-based track quality index: Melbourne tram case study', International Journal of Rail Transportation, 9 23-38 (2021) [C1] Track quality indices can be used as an indicator of rail condition concerning the risk of damage or failure. Previous studies have mainly focused on conventional rail track quali... [more] Track quality indices can be used as an indicator of rail condition concerning the risk of damage or failure. Previous studies have mainly focused on conventional rail track quality indices and light rail tracks have not been addressed properly. In order to fill this gap, this research aims to develop a track quality index which is usable for both conventional and tram rail tracks. In this research dataset of the Melbourne tram network is used. In this research, based on the statistical analysis, track geometry parameters which are statistically significant in the development of the proposed index for the Melbourne tram network are determined. For the evaluation, the predictability performance of the index proposed in this paper is compared with the three major indices in the literature. According to the results of the case study evaluation, the current values of the proposed index has reasonable correlations with its previous values.
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2021 |
Kardani N, Zhou A, Shen SL, Nazem M, 'Estimating unconfined compressive strength of unsaturated cemented soils using alternative evolutionary approaches', Transportation Geotechnics, 29 (2021) [C1] The use of cement as a curing agent has been widely adopted in soft soil engineering to increase the strength of soft soil. The cemented soil is gradually exposed to the air and i... [more] The use of cement as a curing agent has been widely adopted in soft soil engineering to increase the strength of soft soil. The cemented soil is gradually exposed to the air and in a natural environment becomes unsaturated. Unconfined compressive strength (UCS) of the unsaturated cemented soils is a key parameter for assessing their strength behaviour. UCS determination of unsaturated cemented soils by using laboratory methods is a complex, time-consuming, and expensive procedure due to the difficulty in suction control. This study aims to model the UCS of unsaturated cemented Wenzhou clay, i.e., capture the nonlinear relations between UCS and its influential variables including cement content (%), dry density (g/cm3) and suction (MPa) for the first time by using machine learning approach. Toward this aim, three advanced computational frameworks are developed based on hybrid evolutionary approaches in which evolutionary optimisation algorithms including genetic algorithm (GA), particle swarm optimisation (PSO) and imperialist competitive algorithm (ICA) are hybridised with artificial neural network (ANN). Results show that developed models have a great ability to mimic the nonlinear relationships between UCS and its influential variables and PSO-ANN presents the best performance among three models on the training dataset with R2=0.9888, RMSE=0.129 and VAF=97.742, and testing dataset with R2=0.9412, RMSE=0.237 and VAF=90.414. To facilitate engineering application, an engineering database for Wenzhou soft clay at different cement ratios (up to 11%), suctions (up to 300 MPa) and dry densities (1¿1.5 g/cm3) is built by using the developed PSO-ANN model.
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2021 |
Nazem M, Moavenian MH, 'Alternative remeshing techniques for large deformation analysis of geotechnical problems', Computers and Geotechnics, 138 (2021) [C1]
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2021 |
Ghorbani J, Airey DW, Carter JP, Nazem M, 'Unsaturated soil dynamics: Finite element solution including stress-induced anisotropy', COMPUTERS AND GEOTECHNICS, 133 (2021) [C1]
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2020 |
Kardani N, Zhou A, Nazem M, Shen SL, 'Estimation of Bearing Capacity of Piles in Cohesionless Soil Using Optimised Machine Learning Approaches', Geotechnical and Geological Engineering, 38 2271-2291 (2020) [C1] Accurate estimation of the bearing capacity of piles requires complex modelling techniques which are not justified by timeframe, budget, or scope of the projects. In this study, s... [more] Accurate estimation of the bearing capacity of piles requires complex modelling techniques which are not justified by timeframe, budget, or scope of the projects. In this study, six advanced machine learning algorithms including decision tree, k-nearest neighbour, multilayer perceptron artificial neural network, random forest, support vector regressor and extremely gradient boosting are employed to model the bearing capacity of piles in cohesionless soil, and the particle swarm optimisation algorithm is used to optimate the hyper-parameters of machine learning algorithms. A dataset comprising of 59 cases is employed and the R-squared value, root mean square error and variance accounted for are used as performance metrics to compare the performance of optimised machine learning methods. The comparison reveals that the optimised machine learning methods have great potential to estimate bearing capacity of piles and the particle swarm optimisation algorithm is efficient in the hyper-parameter tuning. The results show that R-squared values of six optimised machine learning approaches on the testing set vary from 0.731 to 0.9615. Also, the optimised extremely gradient boosting (R-squared value = 0.9615) shows the best performance compared with other algorithms. Furthermore, the relative importance of influential variable is investigated, which shows that effective stress is the most influential variable for bearing capacity of piles with an importance score of 30.9%. In addition, the results by the optimised machine learning method are compared to the ß-method which is a popular empirical method. It is revealed the prominent performance of optimised machine learning approaches.
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2020 |
Ghorbani J, Nazem M, Carter JP, 'Dynamic Compaction of Clays: Numerical Study Based on the Mechanics of Unsaturated Soils', International Journal of Geomechanics, 20 04020195-1-04020195-13 (2020) [C1]
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2020 |
Zhang Y, Zhou A, Nazem M, Carter J, 'Fully coupled global equations for hydro-mechanical analysis of unsaturated soils', COMPUTATIONAL MECHANICS, 67 107-125 (2020) [C1]
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2019 |
Salmi EF, Karakus M, Nazem M, 'Assessing the effects of rock mass gradual deterioration on the long-term stability of abandoned mine workings and the mechanisms of post-mining subsidence A case study of Castle Fields mine', Tunnelling and Underground Space Technology, 88 169-185 (2019) [C1]
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2019 |
Zhang Y, Zhou A, Nazem M, Carter J, 'Finite element implementation of a fully coupled hydro-mechanical model and unsaturated soil analysis under hydraulic and mechanical loads', Computers and Geotechnics, 110 222-241 (2019) [C1]
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2018 |
Ghorbani J, Nazem M, Carter JP, Sloan SW, 'A stress integration scheme for elasto-plastic response of unsaturated soils subjected to large deformations', COMPUTERS AND GEOTECHNICS, 94 231-246 (2018) [C1]
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2017 |
Salmi EF, Nazem M, Karakus M, 'The effect of rock mass gradual deterioration on the mechanism of post mining subsidence over shallow abandoned coal mines', INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 91 59-71 (2017) [C1]
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2017 |
Salmi EF, Nazem M, Karakus M, 'Numerical analysis of a large landslide induced by coal mining subsidence', ENGINEERING GEOLOGY, 217 141-152 (2017) [C1]
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2017 |
Kardani O, Nazem M, Kardani M, Sloan S, 'On the application of the maximum entropy meshfree method for elastoplastic geotechnical analysis', COMPUTERS AND GEOTECHNICS, 84 68-77 (2017) [C1]
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2017 |
Khishvand M, Nazem M, Sloan SW, Carter JP, 'Application of the third medium method for frictionless contact problems in geomechanics', COMPUTERS AND GEOTECHNICS, 85 117-125 (2017) [C1]
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2017 |
Fathi Salmi E, Nazem M, Giacomini A, 'A Numerical Investigation of Sinkhole Subsidence Development over Shallow Excavations in Tectonised Weak Rocks: The Dolaei Tunnel s Excavation Case', Geotechnical and Geological Engineering, 35 1685-1716 (2017) [C1]
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2016 |
Sabetamal H, Carter JP, Nazem M, Sloan SW, 'Coupled analysis of dynamically penetrating anchors', Computers and Geotechnics, 77 26-44 (2016) [C1] The development of a numerical procedure for the finite element analysis of anchors dynamically penetrating into saturated soils is outlined, highlighting its unique features and ... [more] The development of a numerical procedure for the finite element analysis of anchors dynamically penetrating into saturated soils is outlined, highlighting its unique features and capabilities. The mechanical behaviour of saturated porous media is predicted using mixture theory. An algorithm is developed for frictional contact in terms of effective normal stress. The contact formulation is based on a mortar segment-to-segment scheme, which considers the interpolation functions of the contact elements to be of order N, thus overcoming a numerical deficiency of the so-called node-to-segment (NTS) contact algorithm. The nonlinear behaviour of the solid constituent is captured by the Modified Cam Clay soil model. The soil constitutive model is also adapted so as to incorporate the dependence of clay strength on strain rate. An appropriate energy-absorbing boundary is used to eliminate possible wave reflections from the artificial mesh boundaries. To illustrate the use of the proposed computational scheme, simulations of dynamically penetrating anchors are conducted. Results are presented and discussed for the installation phase followed by 'setup', i.e., pore pressure dissipation and soil consolidation. The results, in particular, reveal the effects of strain rate on the generation of excess pore pressure, bearing resistance and frictional forces. The setup analyses also illustrate the pattern in which pore pressures are dissipated within the soil domain after installation. Hole closure behind a dynamic projectile is also illustrated by an example.
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2016 |
Ghorbani J, Nazem M, Carter JP, 'Numerical modelling of multiphase flow in unsaturated deforming porous media', Computers and Geotechnics, 71 195-206 (2016) [C1] The aim of this paper is to address a number of significant challenges in the analysis of multiphase unsaturated soils when subjected to both static and dynamic loading. These cha... [more] The aim of this paper is to address a number of significant challenges in the analysis of multiphase unsaturated soils when subjected to both static and dynamic loading. These challenges include the non-linear behaviour of the solid skeleton of the soil as well as the means by which the unsaturated nature of the multi-phase soil is dealt with. A review of some fundamental issues in partially saturated soils as well as the governing equations are presented and then the application of the generalised-. a algorithm for time integration of the global equations of motion for unsaturated soils is demonstrated. Solutions to these equations obtained by the finite element method are validated by recently presented analytical solutions. A description of the selected constitutive model and its integration is also presented, together with a strategy to verify the numerical implementation. Finally, solutions for the classic problem of static loading of a rigid footing resting on a partially saturated (three-phase) soil and a fully saturated (two-phase) soil are presented.
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2016 |
Sabetamal H, Nazem M, Sloan SW, Carter JP, 'Frictionless contact formulation for dynamic analysis of nonlinear saturated porous media based on the mortar method', International Journal for Numerical and Analytical Methods in Geomechanics, 40 25-61 (2016) [C1] A finite element algorithm for frictionless contact problems in a two-phase saturated porous medium, considering finite deformation and inertia effects, has been formulated and im... [more] A finite element algorithm for frictionless contact problems in a two-phase saturated porous medium, considering finite deformation and inertia effects, has been formulated and implemented in a finite element programme. The mechanical behaviour of the saturated porous medium is predicted using mixture theory, which models the dynamic advection of fluids through a fully saturated porous solid matrix. The resulting mixed formulation predicts all field variables including the solid displacement, pore fluid pressure and Darcy velocity of the pore fluid. The contact constraints arising from the requirement for continuity of the contact traction, as well as the fluid flow across the contact interface, are enforced using a penalty approach that is regularised with an augmented Lagrangian method. The contact formulation is based on a mortar segment-to-segment scheme that allows the interpolation functions of the contact elements to be of order N. The main thrust of this paper is therefore how to deal with contact interfaces in problems that involve both dynamics and consolidation and possibly large deformations of porous media. The numerical algorithm is first verified using several illustrative examples. This algorithm is then employed to solve a pipe-seabed interaction problem, involving large deformations and dynamic effects, and the results of the analysis are also compared with those obtained using a node-to-segment contact algorithm. The results of this study indicate that the proposed method is able to solve the highly nonlinear problem of dynamic soil-structure interaction when coupled with pore water pressures and Darcy velocity.
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2016 |
Nazem M, Kardani M, Bienen B, Cassidy M, 'A stable Maximum-Entropy Meshless method for analysis of porous media', COMPUTERS AND GEOTECHNICS, 80 248-260 (2016) [C1]
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2016 |
Moavenian MH, Nazem M, Carter JP, Randolph MF, 'Numerical analysis of penetrometers free-falling into soil with shear strength increasing linearly with depth', Computers and Geotechnics, 72 57-66 (2016) [C1] Dynamic penetrometers have been used for offshore oil and gas industry applications such as pipeline feasibility studies and anchoring systems, and military applications including... [more] Dynamic penetrometers have been used for offshore oil and gas industry applications such as pipeline feasibility studies and anchoring systems, and military applications including naval mine countermeasures and terminal ballistic studies. The main challenge of using dynamic penetrometers is the interpretation of their test results in order to deduce the mechanical properties of the penetrated soil via empirical or theoretical relations. Recently, a robust numerical method based on the Arbitrary Lagrangian-Eulerian (ALE) technique has been developed for analysing dynamic penetration problems and used to investigate a smooth penetrometer free falling into a uniform layer of clayey soil. Numerical as well as experimental results indicate that the penetration characteristics, including the impact energy, total time, and total depth of penetration, depend on the mechanical properties of the soil including its stiffness and strength parameters as well as the geometry of the penetrometer and its initial impact energy. In this study, the ALE method is employed to study the effect of shear strength increasing with depth (a common condition of seabed deposits) on the penetration characteristics of a free falling penetrometer. Conducting more than two thousand numerical simulations has shown that there is an approximate quadratic relation between the final embedment depth of a FFP penetrating into a non-uniform clay soil and the combined kinetic energy on contact with the soil and subsequent loss in potential energy of the penetrometer.
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2015 |
Kardani M, Nazem M, Carter JP, 'Application of high-order elements for coupled analysis in geomechanics', COUPLED PROBLEMS 2015 - Proceedings of the 6th International Conference on Coupled Problems in Science and Engineering, 1209-1217 (2015) [C1] In this paper high-order triangular elements are implemented in the framework of the Arbitrary Lagrangian-Eulerian method for the analysis of large strain consolidation problems i... [more] In this paper high-order triangular elements are implemented in the framework of the Arbitrary Lagrangian-Eulerian method for the analysis of large strain consolidation problems in geomechanics. The theory of consolidation, as well as details of the high-order elements, including cubic (10-noded), quartic (15-noded), quantic (21-noded) and sextic (28- noded) elements are discussed. The accuracy and the efficiency of high-order elements in the analysis of consolidation problems are demonstrated conducting a small deformation analysis of the soil under a strip footing as well as a large deformation analysis of a vertical cut subjected to a surcharge loading. Based on the numerical results, it is shown that high-order elements not only improve the accuracy of solution but can also significantly decrease the required computational time. It is also demonstrated that assuming identical order for displacement shape functions and the pore water pressure shape functions does not affect the stability of the time-marching analysis of consolidation nor the accuracy of the numerical predictions.
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2015 |
Wang D, Bienen B, Nazem M, Tian Y, Zheng J, Pucker T, Randolph MF, 'Large deformation finite element analyses in geotechnical engineering', Computers and Geotechnics, 65 104-114 (2015) [C1] Geotechnical applications often involve large displacements of structural elements, such as penetrometers or footings, in soil. Three numerical analysis approaches capable of acco... [more] Geotechnical applications often involve large displacements of structural elements, such as penetrometers or footings, in soil. Three numerical analysis approaches capable of accounting for large deformations are investigated here: the implicit remeshing and interpolation technique by small strain (RITSS), an efficient Arbitrary Lagrangian-Eulerian (EALE) implicit method and the Coupled Eulerian-Lagrangian (CEL) approach available as part of commercial software. The theoretical basis and implementation of the methods are discussed before their relative performance is evaluated through four benchmark cases covering static, dynamic and coupled problems in geotechnical engineering. Available established analytical and numerical results are also provided for comparison purpose. The advantages and limitation of the different approaches are highlighted. The RITSS and EALE predict comparable results in all cases, demonstrating the robustness of both in-house codes. Employing implicit integration scheme, RITSS and EALE have stable convergence although their computational efficiency may be low for high-speed problems. The CEL is commercially available, but user expertise on element size, critical step time and critical velocity for quasi-static analysis is required. Additionally, mesh-independency is not satisfactorily achieved in the CEL analysis for the dynamic case.
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2015 |
Carter JP, Sabetamal H, Nazem M, Sloan SW, 'One-dimensional test problems for dynamic consolidation', ACTA GEOTECHNICA, 10 173-178 (2015) [C1]
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2015 |
Kardani M, Nazem M, Carter JP, Abbo AJ, 'Efficiency of high-order elements in large-deformation problems of geomechanics', International Journal of Geomechanics, 15 (2015) [C1] This paper investigates the application of high-order elements within the framework of the arbitrary Lagrangian-Eulerian method for the analysis of elastoplastic problems involvin... [more] This paper investigates the application of high-order elements within the framework of the arbitrary Lagrangian-Eulerian method for the analysis of elastoplastic problems involving large deformations. The governing equations of the method as well as its important aspects such as the nodal stress recovery and the remapping of state variables are discussed. The efficiency and accuracy of 6-, 10-, 15-, and 21-noded triangular elements are compared for the analysis of two geotechnical engineering problems, namely, the behavior of an undrained layer of soil under a strip footing subjected to large deformations and the soil behavior in a biaxial test. The use of high-order elements is shown to increase the accuracy of the numerical results and to significantly decrease the computational time required to achieve a specific level of accuracy. For problems considered in this study, the 21-noded elements outperform other triangular elements.
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2014 |
Sabetamal H, Nazem M, Carter JP, Sloan SW, 'Large deformation dynamic analysis of saturated porous media with applications to penetration problems', COMPUTERS AND GEOTECHNICS, 55 117-131 (2014) [C1]
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2014 |
O'Loughlin CD, Nazem M, Chow SH, Randolph MF, Gaudin C, White DJ, 'Dynamic embedment of projectiles in clay', Australian Geomechanics Journal, 49 133-145 (2014) [C1] This paper provides an overview of the work of the Australian Research Council-funded Centre for Geotechnical Science and Engineering on free falling projectiles that have applica... [more] This paper provides an overview of the work of the Australian Research Council-funded Centre for Geotechnical Science and Engineering on free falling projectiles that have applications as seabed characterisation tools and as anchoring systems for floating facilities. These projectiles are released in water and dynamically embed into the seabed through the kinetic energy they gain during freefall. The high penetration velocity, which can be up to 25 m/s at impact with the seabed, induces shear strain rates in the soil that are up to eight orders of magnitude higher than in a typical laboratory test. The difficulty in quantifying the soil strength at these very high strain rates, together with hydrodynamic aspects including pressure drag and potential water entrainment along the projectile-soil interface, complicates assessment of the penetration response. A large database of centrifuge and field data has been collated by the Centre and is used in this paper to quantify embedment potential and to examine the merit of a simple analytical framework that captures the dynamic response of free-falling projectiles. Aspects of the dynamic embedment process that cannot be predicted by the analytical framework, including potential hole closure during installation and pore pressure generation are investigated in finite element analyses that model the dynamic penetration of projectiles in soil. Example results from these analyses are provided.
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2014 |
Kardani M, Nazem M, Carter JP, Abbo AJ, 'Large strain coupled analysis of geotechnical problems using high-order elements', Australian Geomechanics Journal, 49 167-174 (2014) [C1] In this paper high-order triangular elements are implemented in the framework of the Arbitrary Lagrangian-Eulerian method for the analysis of large strain coupled consolidation pr... [more] In this paper high-order triangular elements are implemented in the framework of the Arbitrary Lagrangian-Eulerian method for the analysis of large strain coupled consolidation problems in geomechanics. The theory of coupled consolidation, as well as details of the high-order elements, including quadratic (6-noded), cubic (10-noded), quartic (15-noded) and quantic (21-noded) elements, are discussed. The accuracy and the efficiency of high-order elements in the analysis of undrained problems are presented by solving two classical geomechanics problems. These include the bearing capacity of soil under a footing and the large deformation analysis of a vertical cut subjected to a surcharge loading. Based on the numerical results, it is shown that high-order elements not only improve the accuracy of the solution, but can also significantly decrease the required computational time.
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2014 |
Sharafisafa M, Nazem M, 'Application of the distinct element method and the extended finite element method in modelling cracks and coalescence in brittle materials', Computational Materials Science, 91 102-121 (2014) [C1] In this paper we study the performance of the discrete element method (DEM) and the extended finite element method (XFEM) modelling the crack initiation, propagation and coalescen... [more] In this paper we study the performance of the discrete element method (DEM) and the extended finite element method (XFEM) modelling the crack initiation, propagation and coalescence in fractured rock masses. Firstly, the crack propagation in a rock sample with single closed and open flaws and subjected to an uniaxial compression is simulated by the DEM and XFEM. The results obtained by the two methods are then compared with the experimental results reported by Park and Bobet (2009). Under an uniaxial compression load, two types of cracks are observed including the tensile or wing cracks, and the shear or secondary cracks. The results obtained by the DEM are in good agreement with the experimental results, viz., both wing and shear cracks are accurately modelled. The XFEM, on the other hand, can predict the tensile (wing) cracks, but fails to model the shear cracks. In second part of this study we consider the analysis of fracture propagation and coalescence in rock masses containing two open or closed flaws. The results predicted by the DEM and XFEM are then compared with experimental test results. Coalescence is produced by the linkage of two flaws and a combination of wing and secondary cracks. In the crack propagation and coalescence problem, the DEM is able to predict all cracks involved in rock fracturing, such as the wing and secondary cracks, as well as the crack linkage between two adjacent flaws and their subsequent coalescence. However, the XFEM results only represent the wing cracks, and the method fails to predict the shear cracks. Finally, the effect of filling materials in open flaws on the crack propagation is investigated. The results indicate that the initiation and propagation of cracks and their coalescence in a material containing open flaws significantly change when the flaws are filled with a weak material. © 2014 Elsevier B.V. All rights reserved.
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2013 |
Kardani M, Nazem M, Sheng D, Carter JP, 'Large deformation analysis of geomechanics problems by a combined rh-adaptive finite element method', COMPUTERS AND GEOTECHNICS, 49 90-99 (2013) [C1]
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2012 |
Nazem M, Carter JP, Airey DW, Chow SH, 'Dynamic analysis of a smooth penetrometer free-falling into uniform clay', Geotechnique, 62 893-905 (2012) [C1]
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2012 |
Kardani M, Nazem M, Abbo AJ, Sheng D, Sloan SW, 'Refined h-adaptive finite element procedure for large deformation geotechnical problems', Computational Mechanics, 49 21-33 (2012) [C1]
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2012 |
Nazem M, Kardani M, Carter JP, Sheng D, 'A comparative study of error assessment techniques for dynamic contact problems of geomechanics', Computers and Geotechnics, 40 62-73 (2012) [C1]
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2009 |
Nazem M, Carter JP, Sheng D, Sloan SW, 'Alternative stress-integration schemes for large-deformation problems of solid mechanics', Finite Elements in Analysis and Design, 45 934-943 (2009) [C1]
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2009 |
Sheng D, Nazem M, Carter JP, 'Some computational aspects for solving deep penetration problems in geomechanics', Computational Mechanics, 44 549-561 (2009) [C1]
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2009 |
Nazem M, Carter JP, Airey DW, 'Arbitrary Lagrangian-Eulerian method for dynamic analysis of geotechnical problems', Computers and Geotechnics, 36 549-557 (2009) [C1]
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2009 |
Nazem M, Rahmani I, Rezaee-Pajand M, 'Nonlinear FE analysis of reinforced concrete structures using a tresca-type yield surface', Scientia Iranica Transaction A-Civil Engineering, 16 512-519 (2009) [C1]
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2008 |
Nazem M, Sheng D, Carter JP, Sloan SW, 'Arbitrary Lagrangian-Eulerian method for large-strain consolidation problems', International Journal for Numerical and Analytical Methods in Geomechanics, 32 1023-1050 (2008) [C1]
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2007 |
Krabbenhoft K, Damkilde L, Nazem M, 'An implicit mixed enthalpy-temperature method for phase-change problems', Heat and Mass Transfer, 43 233-241 (2007) [C1]
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2006 |
Nazem M, Sheng D, Carter JP, 'Stress integration and mesh refinement for large deformation in geomechanics', International Journal for Numerical Methods in Engineering, 65 1002-1027 (2006) [C1]
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2003 |
Rezaiee-Pajand M, Nazem M, 'Elasto-plastic analysis of three-dimensional structures', Engineering Computations, 20 274-295 (2003) [C1]
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Conference (43 outputs)
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2021 |
Zhang Y, Nazem M, Zhou A, Carter J, 'Numerical Modelling of Dynamic Compaction of Soils', Challenges and Innovations in Geomechanics Proceedings of the 16th International Conference of IACMAG, Virtual (2021) [E1]
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2021 |
Zhang Y, Zhou A, Nazem M, Carter J, 'Numerical Analysis of Shallow Foundations Considering Hydraulic Hysteresis and Deformation Dependent Soil-Water Retention', Challenges and Innovations in Geomechanics Proceedings of the 16th International Conference of IACMAG, online (2021) [E1]
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2019 |
Nazem M, Cassidy M, 'Merits of the maximum entropy meshless method for coupled analysis of offshore problems', 8th International Conference on Computational Methods in Marine Engineering, MARINE 2019 (2019) Despite the recent advances in meshless analysis methods, their application in tackling offshore geotechnical problems is relatively limited. In meshless methods the problem domai... [more] Despite the recent advances in meshless analysis methods, their application in tackling offshore geotechnical problems is relatively limited. In meshless methods the problem domain is discretised by a set of nodes and, unlike the traditional finite element method, the connectivity between the elements and nodes does not exist. This means that the meshless methods may outperform the finite element method in problems including excessively large deformations, discontinuities or strain localisation. On the other hand, the shape functions in meshless methods are not usually simple polynomial functions which are explicitly evaluated at an arbitrary point. These functions are commonly obtained by solving a complex and relatively time-consuming optimisation problem, significantly affecting the overall computational time. This issue may become even more serious when the shape functions need to be updated during each time step of the analysis. In this study, we attempt to address the efficiency and performance of one of the recently developed meshless methods for solving offshore problems where the solid displacements are coupled with the pore fluid pressures. This method is based on the principle of Maximum-Entropy [1], and its performance is presented by comparing its results with those obtained by the finite element method. This is achieved by studying the consolidation and bearing capacity of soil under an offshore foundation, using various nodal discretisations and boundary conditions. The results indicate that, for the problems considered in this study, the Maximum Entropy Meshless method (1) can provide a stable solution regardless of the domain discretisation density, and (2) outperforms the finite element method by reducing the computational time but achieving the same accuracy. |
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2018 |
Falamarzi A, Moridpour S, Nazem M, Cheraghi S, 'Development of random forests regression model to predict track degradation index: Melbourne case study', ATRF 2018 - Australasian Transport Research Forum 2018, Proceedings (2018) © 2018 ATRF, Commonwealth of Australia. All rights reserved. In rail infrastructure maintenance management systems, Track Degradation Index (TDI) is considered as a representative... [more] © 2018 ATRF, Commonwealth of Australia. All rights reserved. In rail infrastructure maintenance management systems, Track Degradation Index (TDI) is considered as a representative of quality of rail tracks. This index is usually developed based on the deviation rate or standard deviation of track geometry parameters. In this regard, prediction of future TDI is an important task as it can be employed to determine when and where maintenance and renewal activities must be deployed. In this study, a track geometry data set from Melbourne tram network has been used as the case study and gauge deviation parameter is selected as the main parameter to develop TDI. For prediction of the future TDI, Random Forests (RF) model as a Machine Learning (ML) model is used to predict the future TDI of the data set. Since TDI is a continuous variable, Random Forests Regression (RFR) model is applied. In this study, RF model has added two algorithms to the basic Decision Trees (DT) model including bagging and random subspace method. These algorithms can reduce the overfitting problem and over-focus on special features. Based on the results of this study, adjusted R2 value of the proposed prediction model is 0.93, which demonstrates that the model has the satisfying performance in predicting the TDI.
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2017 |
Falamarzi A, Moridpour S, Nazem M, Hesami R, 'Rail degradation predication: Melbourne tram system case study', ATRF 2017 - Australasian Transport Research Forum 2017, Proceedings (2017) Nowadays, tram as an accessible and convenient mode of public transport is implemented and used in different cities. Due to high frequency of accelerations and decelerations along... [more] Nowadays, tram as an accessible and convenient mode of public transport is implemented and used in different cities. Due to high frequency of accelerations and decelerations along their routes and sharing the route with other vehicles, the rate of degradation of tram tracks (light rail) is different from the degradation rate of train tracks (heavy rail). In this paper, track gauge deviation as an indicator of irregularities on the rail-wheel contact surface is used for developing the track degradation model. Data set used in this study includes the curve sections of Melbourne tram network and divided into repaired and unrepaired segments. For data analysis more than 13 km of curved tracks are examined. Annual tonnage, previous gauge deviation and track structural properties like track surface, rail support, rail profile and gauge deviation are considered as the influencing variables on the future gauge deviation. Two different models including a regression model and an Artificial Neural Networks (ANN) model have been developed for predicting tram track gauge deviation. According to the results, the performances of the regression models are not very different from the ANN models. The determination coefficients of the selected models are approximately 0.8 and higher.
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2017 |
Falamarzi A, Moridpour S, Nazem M, Hesami R, 'Rail degradation predication: Melbourne tram system case study', ATRF 2017 - Australasian Transport Research Forum 2017, Proceedings (2017) © 2017 ATRF, Commonwealth of Australia. All rights reserved. Nowadays, tram as an accessible and convenient mode of public transport is implemented and used in different cities. D... [more] © 2017 ATRF, Commonwealth of Australia. All rights reserved. Nowadays, tram as an accessible and convenient mode of public transport is implemented and used in different cities. Due to high frequency of accelerations and decelerations along their routes and sharing the route with other vehicles, the rate of degradation of tram tracks (light rail) is different from the degradation rate of train tracks (heavy rail). In this paper, track gauge deviation as an indicator of irregularities on the rail-wheel contact surface is used for developing the track degradation model. Data set used in this study includes the curve sections of Melbourne tram network and divided into repaired and unrepaired segments. For data analysis more than 13 km of curved tracks are examined. Annual tonnage, previous gauge deviation and track structural properties like track surface, rail support, rail profile and gauge deviation are considered as the influencing variables on the future gauge deviation. Two different models including a regression model and an Artificial Neural Networks (ANN) model have been developed for predicting tram track gauge deviation. According to the results, the performances of the regression models are not very different from the ANN models. The determination coefficients of the selected models are approximately 0.8 and higher.
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2017 |
Falamarzi A, Moridpour S, Nazem M, Hesami R, 'Rail degradation predication: Melbourne tram system case study', ATRF 2017 - Australasian Transport Research Forum 2017, Proceedings (2017) © 2017 ATRF, Commonwealth of Australia. All rights reserved. Nowadays, tram as an accessible and convenient mode of public transport is implemented and used in different cities. D... [more] © 2017 ATRF, Commonwealth of Australia. All rights reserved. Nowadays, tram as an accessible and convenient mode of public transport is implemented and used in different cities. Due to high frequency of accelerations and decelerations along their routes and sharing the route with other vehicles, the rate of degradation of tram tracks (light rail) is different from the degradation rate of train tracks (heavy rail). In this paper, track gauge deviation as an indicator of irregularities on the rail-wheel contact surface is used for developing the track degradation model. Data set used in this study includes the curve sections of Melbourne tram network and divided into repaired and unrepaired segments. For data analysis more than 13 km of curved tracks are examined. Annual tonnage, previous gauge deviation and track structural properties like track surface, rail support, rail profile and gauge deviation are considered as the influencing variables on the future gauge deviation. Two different models including a regression model and an Artificial Neural Networks (ANN) model have been developed for predicting tram track gauge deviation. According to the results, the performances of the regression models are not very different from the ANN models. The determination coefficients of the selected models are approximately 0.8 and higher.
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2016 |
Sabetamal H, Carter JP, Nazem M, Sloan SW, 'Numerical study of the effects of strain rate on the behaviour of dynamically penetrating anchors in clay', Proceedings of the International Conference on Computational Methods, Berkeley, CA, USA (2016) [E1]
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2016 |
Khishvand M, Nazem M, 'On Application of the Third Medium Contact Method in Analysis of Geotechnical Problems', Applied Mechanics and Materials, Brisbane, QLD, Australia (2016) [E1]
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2015 |
Zakrzewski N, Nazem M, 'The maximum-entropy meshless method for dynamic and coupled analysis of offshore geotechnical problems', Frontiers in Offshore Geotechnics III - 3rd International Symposium on Frontiers in Offshore Geotechnics, ISFOG 2015 (2015) [E1] There exist many problems in the offshore geotechnical setting which necessitate a dynamic analysis or a consolidation analysis. In recent years literature on this topic has been ... [more] There exist many problems in the offshore geotechnical setting which necessitate a dynamic analysis or a consolidation analysis. In recent years literature on this topic has been dominated by the application of Finite Element Methods to solving such problems and addressing the inherent shortcomings associated with their use. These issues include, but are not limited to, the occurrence of mesh distortion in problems involving large deformations and the inability to adequately capture discontinuities. The intrinsic nature of meshfree methods, however, makes them a more appropriate means of solving offshore geotechnical problems. This study presents a robust Maximum-Entropy Meshless method for nonlinear analysis of offshore problems in which the effect of time-dependent behaviour cannot be ignored. The Generalised-a time integration scheme and the Backward-Euler method are respectively employed for dynamic analysis and coupled analysis of such problems. The applicability of this meshless method is presented by studying the undrained soil behaviour under a circular footing subjected to dynamic loading as well as static loading.
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2015 |
Ghorbani J, Nazem M, Carter JP, 'Application of the generalised-a method in dynamic analysis of partially saturated media', Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014 (2015) [E1] The main aim of this study is to apply a robust time integration technique for simulating the behaviour of unsaturated soils subjected to dynamic loads. The governing equations of... [more] The main aim of this study is to apply a robust time integration technique for simulating the behaviour of unsaturated soils subjected to dynamic loads. The governing equations of the three soil phases and their interactions are derived based on the mass conservation law, linear momentum balance and energy conservation of each phase in an isothermal environment. In addition, a number of experimental equations are employed to represent the hydraulic conductivity and the drainage characteristics of the soil, such as the suction-saturation relationship and the dependency of the hydraulic conductivity on suction. The global system of equations is then solved by using an implicit time-stepping algorithm based on the Generalised-a integration scheme. The accuracy of the numerical model and the finite element code is verified by comparing the numerical results with results obtained by an analytical solution. © 2015 Taylor & Francis Group, London.
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2015 |
Sabetamal H, Nazem M, Sloan SW, Carter JP, 'Numerical modelling of offshore pipe-seabed interaction problems', Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014 (2015) [E1] This study outlines the development of a computational scheme which accounts for large deformation dynamic behaviour of saturated porous media and models soil-structure interactio... [more] This study outlines the development of a computational scheme which accounts for large deformation dynamic behaviour of saturated porous media and models soil-structure interaction using a high-order frictional contact algorithm. The numerical scheme is employed to analyse a dynamic coupled problem of pipeline-seabed interaction in two steps, including the simulation of the dynamic embedment process as well as the subsequent consolidation stage. The analysis considers a frictional interface between the pipe and the soil which is normally ignored in most analyses due to numerical difficulties. The nonlinear behaviour of the solid constituent is captured by the Modified Cam Clay soil model, allowing the incorporation of shear-induced pore water pressures during the embedment process. The results of this study indicate that the proposed method is able to solve the highly nonlinear problem of dynamic soil-pipe interaction coupled with pore water pressures and Darcy velocity. The results also show that a dynamic approach is necessary for coupled problems of pipe-seabed interaction involving very fast loading. © 2015 Taylor & Francis Group, London.
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2015 |
Ghorbani J, Nazem M, Carter JP, 'Numerical study of dynamic soil compaction at different degrees of saturation', Proceedings of the International Offshore and Polar Engineering Conference (2015) [E1] Dynamic compaction is known as one of the most cost-effective soil improvement techniques. In this method the soil at the ground surface or at a relatively deep depth is compacted... [more] Dynamic compaction is known as one of the most cost-effective soil improvement techniques. In this method the soil at the ground surface or at a relatively deep depth is compacted by repeatedly dropping heavy weights on the ground. Since its introduction, dynamic compaction has exhibited its versatility and simplicity of use in different types of civil engineering projects, including building structures, container terminals, highways, airports, dockyards, and harbours. However, despite the abundance of experimental data and field observation reports, few numerical approaches have been established in the literature to effectively deal with soil behaviour under dynamic compaction. This is mainly due to the dependence of soil dynamic response on variations in the moisture content. Therefore, to achieve a comprehensive understanding of dynamic compaction the soil should be modelled as a three-phase porous medium. The presence of a non-wetting and a wetting phase, together with the existence of inertia forces in each phase, makes the solution of the coupled dynamic system computationally demanding. Moreover, large deformations often take place during dynamic compaction; hence the infinitesimal strain theory cannot be employed for higher impact loads. In this paper a finite element approach is introduced to numerically simulate the problem of dynamic compaction under the framework of unsaturated soil mechanics. The governing equations are derived based upon the overall momentum balance of the mixture, the mass balance of the liquid phase, and the mass balance of the gas phase. Phase changes and chemical reactions are not considered. Among other important parameters, the effect of the degree of saturation on the soil response will be addressed.
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2015 |
Nazem M, Carter JP, Sloan SW, 'Aspects of numerical simulation of torpedo anchor installation', Proceedings of the International Offshore and Polar Engineering Conference (2015) [E1] The dynamic penetration of anchors into the seabed is an important problem in offshore geomechanics and one of the most challenging for geotechnical analysts. Complications due to... [more] The dynamic penetration of anchors into the seabed is an important problem in offshore geomechanics and one of the most challenging for geotechnical analysts. Complications due to the nonlinear material response of the soil, the large deformations caused by the insertion of the object, and the changing boundary conditions at the contact between the soil and the anchors must be taken into account. Moreover, the presence of a pore fluid, and the pressure that it may exert, requires a fully coupled displacement-pore pressure analysis. Recent work has facilitated the modelling of the dynamic penetration of objects into soil. The finite element method is one of the most commonly used techniques for tackling problems of soil penetration because the resulting solutions satisfy the equation of dynamic equilibrium and the method can incorporate sophisticated soil models as well as complex boundary conditions. This study discusses a number of challenging aspects of the numerical simulation of dynamically embedded anchors, particularly torpedo anchors, and presents a robust analysis strategy for such problems. This technique is based on the Arbitrary Lagrangian-Eulerian method and rigorously incorporates displacements, velocities, and accelerations of the solid phase along with the pore pressure and velocities of the fluid phase.
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2015 |
Fathi Salmi E, Nazem M, Giacomini A, 'A practical method to control the formation of Sinkhole subsidence - The dolaei road tunnel case study', 13th ISRM International Congress of Rock Mechanics (2015) Numerical simulation of collapse of tunnels in weak rocks is one of the challenging problems in rock mechanics. Collapse can impose technical and financial difficulties during the... [more] Numerical simulation of collapse of tunnels in weak rocks is one of the challenging problems in rock mechanics. Collapse can impose technical and financial difficulties during the construction of underground excavations. This phenomenon, particularly in shallow excavations, may lead to propagation of a caved zone toward the surface and formation of chimney subsidence. Chimney subsidence has numerous catastrophic consequences such as the adverse environmental impacts and damage to surface structures in vicinity of excavations. Due to the importance of subsidence in civil engineering, the main goal of this study is to propose an appropriate method for preventing the formation of subsidence in shallow tunnels in weak rocks. The Dolaei road tunnel is investigated as a case study, where a large chimney subsidence has occurred. The geology of the area and the geostructural characteristics of the rock mass surrounding the tunnel are briefly reviewed in this paper. Two-dimensional as well as three-dimensional numerical simulations are conducted to study the tunnel stability. Moreover, the effects of staged excavation and pre-supporting method on controlling the ground movements are studied. Outcomes of this study indicate that employing forepoling and staged excavation can be a practical remedy to control the ground movements and prevent the formation of chimney subsidence.
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2014 |
Nazem M, Carter JP, Kardani M, 'Analysis of soil penetration problems by High-order elements', Applied Mechanics and Materials (2014) [E1] This paper addresses the application of high-order elements in the analysis of soil penetration problems, particularly those involving inertia forces and large deformations. Among... [more] This paper addresses the application of high-order elements in the analysis of soil penetration problems, particularly those involving inertia forces and large deformations. Among others, 15-node triangular elements are formulated within an Arbitrary Lagrangian-Eulerian finite element method. Preliminary studies indicate that high-order elements can significantly decrease the analysis time without significant loss of accuracy. © (2014) Trans Tech Publications, Switzerland.
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2013 |
Carter JP, Nazem M, Airey DW, 'Analysis of Dynamic Loading and Penetration of Soils - Application to site investigation and ground improvement', International Conference on Geotechnical Engineering, ICGE 12, Hammamet, Tunisia (2013) [E2]
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2013 |
Sabetamal H, Nazem M, Carter JP, 'Numerical analysis of torpedo anchors', Computational Geomechanics, COMGEO III - Proceedings of the 3nd International Symposium on Computational Geomechanics (2013) This paper presents the development of a numerical framework based on the finite element method and its application in the analysis of torpedo anchors. The procedure is based on a... [more] This paper presents the development of a numerical framework based on the finite element method and its application in the analysis of torpedo anchors. The procedure is based on a mixture theory for the dynamic behaviour of saturated porous media. The nonlinear behaviour of the solid phase of soil is represented by the Modified Cam Clay material model and the interface between the soil and the structure is modelled by a mortar segment-to-segment frictional contact method. An Arbitrary Lagrangian-Eulerian (ALE) method is adopted to avoid mesh distortion throughout the numerical simulation. The generalised-a method is utilised to integrate the governing equations of motion in the time domain. Results obtained from the installation phase of a torpedo anchor reveal that the anchor decelerates at a constant rate during most of its penetration. Analysis results show a typical distribution of excess pore-water pressure during free falling installation, having higher magnitudes at the face and lower magnitudes along the shaft. The computational results for the setup phase indicate that for soil elements located within a radial distance of approximately one diameter from the centreline of the torpedo, 90% of consolidation takes place in a few days after installation, depending on the value of soil permeability.
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2013 |
Fathi Salmi E, Nazem M, Giacomini A, 'Analytical and numerical studies on the mechanism of mining subsidence', Computational Geomechanics, COMGEO III - Proceedings of the 3nd International Symposium on Computational Geomechanics (2013) Ground subsidence due to mining is a very complicated geomechanics phenomenon, particularly in the longwall mining method. Due to the adverse consequences of subsidence on surface... [more] Ground subsidence due to mining is a very complicated geomechanics phenomenon, particularly in the longwall mining method. Due to the adverse consequences of subsidence on surface structures, facilities, and environment, subsidence prediction has attracted interest in geotechnical engineering over the past few decades. Previous research has indicated that the thickness and inclination of seam, depth of working panel, and ground characteristics are the main factors which should be considered in estimating the subsidence. Methods for predicting the subsidence are: empirical, analytical and/or numerical. The geotechnical characteristics of ground affect the caving, collapse, and bulking of goaf and the extent of the cavity toward the surface. The main aim of this paper is to investigate the mechanism of ground surface subsidence based on analytical and numerical simulations. Analytical solutions are based on the theory of elasticity. The Distinct Element Method, which can simulate jointed and stratified rock mass, is used for numerical modelling of subsidence due to mining. In this paper, numerical and analytical results are obtained for two different cases of isotropic and transverse isotropic (layered) strata. Outcomes of this study indicate that the weak planes and stratification not only play a significant role in geotechnical behavior of the rock mass, but they affect the mechanism of ground movement. Results also show that considering the real structure and properties of ground will lead to more accurate estimation of measured subsidence in the field.
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2013 | Kardani M, Nazem M, Abbo AJ, 'H-adaptive finite element analysis of consolidation problems in geomechanics', Computational Plasticity XII: Fundamentals and Applications - Proceedings of the 12th International Conference on Computational Plasticity - Fundamentals and Applications, COMPLAS 2013, Barcelona, Spain (2013) [E2] | ||||||||||
2013 |
Sabetamal H, Nazem M, Carter JP, 'Numerical analysis of torpedo anchors', ComGeo III, Computational Geomechanics, Krakow, Poland (2013) [E2]
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2013 |
Nazem M, Kardani M, Carter JP, Sloan SW, 'On the application of high-order elements in large deformation problems of geomechanics', ComGeo III, Computational Geomechanics, Krakow, Poland (2013) [E2]
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2013 |
Moavenian M, Nazem M, Carter JP, 'Numerical analysis of a penetrometer free-falling into a non-uniform soil layer', ComGeo III, Computational Geomechanics, Krakow, Poland (2013) [E2]
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2013 |
Carter JP, Nazem M, 'Analysis of dynamic penetration of soils', From Materials to Structures: Advancement Through Innovation - Proceedings of the 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM 2012, Sydney (2013) [E1]
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2012 |
Sabetamal H, Nazem M, Sloan SW, Carter JP, 'Finite element simulation of dynamic pile penetration into a saturated porous medium', 6th European Congress on Computational Methods in Applied Sciences and Engineering, ECCOMAS 2012, Vienna, Austria (2012) [E2]
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2011 |
Nazem M, Carter JP, 'Numerical investigation of dynamic penetration factors for a free falling penetrometer', Computer Methods for Geomechanics: Frontiers and New Applications. Volume 2, Melbourne, VIC (2011) [E1]
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2011 |
Nazem M, Kardani M, Carter JP, Sheng D, 'Application of h-adaptive fe method for dynamic analysis of geotechnical problems', COMGEO II - Proceedings of the 2nd International Symposium on Computational Geomechanics, Cavtat, Croatia (2011) [E1]
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2011 |
Sabetamal H, Nazem M, Sloan SW, Carter JP, 'Numerical simulation of dynamic pore fluid-solid interaction in fully saturated non-linear porous media', COMPLAS XI: 11th International Conference on Computational Plasticity, Barcelona, Spain (2011) [E2]
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2011 | Kardani M, Nazem M, Sheng D, 'Application of h-adaptive FE method for analysis of contact problems in geomechanics', Program and abstracts: 2nd International Conference on Computational Contact Mechanics, Hanover, Germany (2011) [E3] | ||||||||||
2010 |
Nazem M, Carter JP, Airey DW, 'Arbitrary Lagrangian-Eulerian method for nonlinear problems of geomechanics', IOP Conf. Series: Materials Science and Engineering, Sydney, NSW (2010) [E1]
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2010 | Kardani M, Nazem M, Abbo AJ, Sheng D, 'A study of adaptive finite element methods in solving large deformation problems in geomechanics', Proceedings of the IV European Conference on Computational Mechanics, Palais des Congres, France (2010) [E3] | ||||||||||
2010 |
Carter JP, Nazem M, 'Analysis of dynamic penetration of objects into soil layers', Numerical Methods in Geotechnical Engineering, Trondheim, Norway (2010) [E1]
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2010 |
Carter JP, Nazem M, Airey DW, Chow SH, 'Dynamic analysis of free-falling penetrometers in soil deposits', Proceedings of the GeoFlorida 2010 Conference, West Palm Beach, Florida (2010) [E2]
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2010 | Kardani M, Nazem M, Abbo AJ, Sheng D, 'A comparative study of h-adaptive and r-adaptive finite element methods in geomechanics', Proceedings of the Joint 9th World Congress on Computational Mechanics and 4th Asian Pacific Congress on Computational Mechanics, Sydney, NSW (2010) [E3] | ||||||||||
2008 |
Nazem M, Carter JP, 'Stress-integration algorithms for geomechanics problems involving large deformations', WCCM8, ECCOMAS 2008, Venice, Italy (2008) [E3]
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2008 |
Nazem M, Carter JP, 'Dynamic analysis of geotechnical problems by arbitrary Lagrangian-Eulerian method', Proceedings of the 12th International Conference of International Association for Computer Methods and Advances in Geomechanics (IACMAG), Goa, India (2008) [E1]
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2007 | Nazem M, Sheng D, Abbo AJ, 'Alternative stress integration schemes in large deformation problems of geomechanics', Numerical Models in Geomechanics: Proceedings of the Tenth International Symposium on Numerical Models in Geomechanics (NUMOG X), Rhodes, Greece (2007) [E1] | ||||||||||
2005 | Nazem M, Sheng D, 'Arbitrary Lagrangian-Eulerian Method For Consolidation Problems In Geomechanics', Proceedings of the Eighth International Conference on Computational Plasticity - Computational Plasticity: Fundamentals and Applications (COMPLAS VIII), Barcelona, Spain (2005) [E3] | ||||||||||
2004 |
Nazem M, Sheng D, 'Alternative Solution Methods For Large Deformations In Geomechanics', Proceedings of the 9th Symposium on Numerical Models in Geomechanics, Ottawa, Canada (2004) [E1]
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2003 | Sheng D, Nazem M, 'Numerical Analysis Of Footings On Unsaturated Soils', Proceedings Of The 2nd Asian Conference On Unsaturated Soils (UNSAT-ASIA 2003), Osaka, Japan (2003) [E1] | ||||||||||
Show 40 more conferences |
Grants and Funding
Summary
Number of grants | 6 |
---|---|
Total funding | $1,799,829 |
Click on a grant title below to expand the full details for that specific grant.
20161 grants / $221,950
Unsaturated Soil Dynamics$221,950
Funding body: ARC (Australian Research Council)
Funding body | ARC (Australian Research Council) |
---|---|
Project Team | Doctor Majid Nazem, Emeritus Professor John Carter |
Scheme | Discovery Projects |
Role | Investigator |
Funding Start | 2016 |
Funding Finish | 2018 |
GNo | G1600415 |
Type Of Funding | Aust Competitive - Commonwealth |
Category | 1CS |
UON | Y |
20151 grants / $93,244
Unsaturated Soil Dynamics$93,244
Funding body: ARC (Australian Research Council)
Funding body | ARC (Australian Research Council) |
---|---|
Project Team | Doctor Majid Nazem, Emeritus Professor John Carter |
Scheme | Discovery Projects |
Role | Lead |
Funding Start | 2015 |
Funding Finish | 2018 |
GNo | G1400130 |
Type Of Funding | Aust Competitive - Commonwealth |
Category | 1CS |
UON | Y |
20112 grants / $1,152,691
Dynamic soil structure interaction$722,691
Funding body: ARC (Australian Research Council)
Funding body | ARC (Australian Research Council) |
---|---|
Project Team | Emeritus Professor John Carter, Doctor Majid Nazem, Associate Professor Andrew Abbo |
Scheme | Discovery Projects |
Role | Investigator |
Funding Start | 2011 |
Funding Finish | 2014 |
GNo | G1000200 |
Type Of Funding | Aust Competitive - Commonwealth |
Category | 1CS |
UON | Y |
Geomechanics of multiple seam mining interactions$430,000
Funding body: ARC (Australian Research Council)
Funding body | ARC (Australian Research Council) |
---|---|
Project Team | Doctor Majid Nazem, Dr Richard Merifield |
Scheme | Discovery Projects |
Role | Lead |
Funding Start | 2011 |
Funding Finish | 2013 |
GNo | G1000138 |
Type Of Funding | Aust Competitive - Commonwealth |
Category | 1CS |
UON | Y |
20091 grants / $330,244
2007 Research Fellowship - PRCGMM$330,244
Funding body: University of Newcastle
Funding body | University of Newcastle |
---|---|
Project Team | Doctor Majid Nazem |
Scheme | Research Fellowship |
Role | Lead |
Funding Start | 2009 |
Funding Finish | 2012 |
GNo | G0189727 |
Type Of Funding | Internal |
Category | INTE |
UON | Y |
20081 grants / $1,700
IACMAG 12, Goa, India, 1/10/2008 - 6/10/2008$1,700
Funding body: University of Newcastle
Funding body | University of Newcastle |
---|---|
Project Team | Doctor Majid Nazem |
Scheme | Travel Grant |
Role | Lead |
Funding Start | 2008 |
Funding Finish | 2008 |
GNo | G0189280 |
Type Of Funding | Internal |
Category | INTE |
UON | Y |
Research Supervision
Number of supervisions
Past Supervision
Year | Level of Study | Research Title | Program | Supervisor Type |
---|---|---|---|---|
2019 | PhD | Numerical Investigations for Hydraulic Fracturing in Geo-Materials | PhD (Civil Eng), College of Engineering, Science and Environment, The University of Newcastle | Co-Supervisor |
2018 | PhD | Application of the Third Medium Contact Method in Geomechanics | PhD (Civil Eng), College of Engineering, Science and Environment, The University of Newcastle | Principal Supervisor |
2017 | PhD | Mesh Optimisation Methods for Large Deformation Analysis of Geomechanics Problems | PhD (Civil Eng), College of Engineering, Science and Environment, The University of Newcastle | Principal Supervisor |
2016 | PhD | A Numerical Investigation of the Mechanisms of Post-Mining Subsidence | PhD (Civil Eng), College of Engineering, Science and Environment, The University of Newcastle | Principal Supervisor |
2016 | PhD | Numerical Simulation of Dynamic Compaction Within the Framework of Unsaturated Porous Media | PhD (Civil Eng), College of Engineering, Science and Environment, The University of Newcastle | Principal Supervisor |
2015 | PhD | Finite Element Algorithms for Dynamic Analysis of Geotechnical Problems | PhD (Civil Eng), College of Engineering, Science and Environment, The University of Newcastle | Principal Supervisor |
2014 | PhD | Applications of Large Deformation Finite Element Method to Geotechnical Problems with Contact | PhD (Civil Eng), College of Engineering, Science and Environment, The University of Newcastle | Co-Supervisor |
News
News • 21 Nov 2014
ARC Discovery Project funding success
Dr Majidreza Nazem and Professor John Carter have been awarded more than $583,000 in ARC Discovery Project funding commencing in 2015 for their research project Unsaturated Soil Dynamics.
Dr Majid Nazem
Position
Honorary Associate Professor
School of Engineering
College of Engineering, Science and Environment
Focus area
Civil Engineering
Contact Details
majidreza.nazem@newcastle.edu.au | |
Phone | (02) 4921 6048 |
Fax | (02) 4921 6991 |
Office
Room | 217 |
---|---|
Building | EA |
Location | Callaghan University Drive Callaghan, NSW 2308 Australia |