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Articles 31 - 60 of 124
Full-Text Articles in Science and Technology Studies
Optimum Allocation Of Sample To Strata And Stages With Simple Additional Constraints, Robert Clark, David Steel
Optimum Allocation Of Sample To Strata And Stages With Simple Additional Constraints, Robert Clark, David Steel
Robert Clark
The optimum allocation of a sample to strata and stages in a stratified two-stage design for a simple cost function is well known. In practice there may be reasons to impose simple additional constraints. It is shown how the theory for optimum allocation can be generalized to account for such constraints. A simple way of assessing the effect that each constraint has on the efficiency of the sample design is developed. This general approach allows several additional constraints that are used in practice to be applied. Data from the 1996 redesign of the Australian Monthly Labour Force Survey are used …
Sample Design Using Imperfect Design Data, Robert Clark
Sample Design Using Imperfect Design Data, Robert Clark
Robert Clark
A well-designed sampling plan can greatly enhance the information that can be produced from a survey. Once a broad sample design is identified, specific design parameters such as sample sizes and selection probabilities need to be chosen. This is typically achieved using an optimal sample design, which minimizes the variance of a key statistic or statistics, expressed as a function of design parameters and population characteristics, subject to a cost constraint. In practice, only imprecise estimates of population characteristics are available, but the effects of this variability are usually ignored. A general approach to sample allocation allowing for imprecise design …
Developing The Design Of A Continuous National Health Survey For New Zealand, Robert Clark, Robert Templeton, Anne Mcnicholas
Developing The Design Of A Continuous National Health Survey For New Zealand, Robert Clark, Robert Templeton, Anne Mcnicholas
Robert Clark
Background A continuously operating survey can yield advantages in survey management, field operations, and the provision of timely information for policymakers and researchers. We describe the key features of the sample design of the New Zealand (NZ) Health Survey, which has been conducted on a continuous basis since mid-2011, and compare to a number of other national population health surveys. Methods A number of strategies to improve the NZ Health Survey are described: implementation of a targeted dual-frame sample design for better Maori, Pacific, and Asian statistics; movement from periodic to continuous operation; use of core questions with rotating topic …
An Outlier Robust Block Bootstrap For Small Area Estimation, Payam Mokhtarian, Ray Chambers
An Outlier Robust Block Bootstrap For Small Area Estimation, Payam Mokhtarian, Ray Chambers
Payam Mokhtarian
Small area inference based on mixed models, i.e. models that contain both fixed and random effects, are the industry standard for this field, allowing between area heterogeneity to be represented by random area effects. Use of the linear mixed model is ubiquitous in this context, with maximum likelihood, or its close relative, REML, the standard method for estimating the parameters of this model. These parameter estimates, and in particular the resulting predicted values of the random area effects, are then used to construct empirical best linear unbiased predictors (EBLUPs) of the unknown small area means. It is now well known …
Bayesian Nonparametric Reliability Analysis For A Railway System At Component Level, Payam Mokhtarian, Mohammad-Reza Namazi-Rad, Tin Kin Ho, Thomas Suesse
Bayesian Nonparametric Reliability Analysis For A Railway System At Component Level, Payam Mokhtarian, Mohammad-Reza Namazi-Rad, Tin Kin Ho, Thomas Suesse
Payam Mokhtarian
Railway system is a typical large-scale complex system with interconnected sub-systems which contain numerous components. System reliability is retained through appropriate maintenance measures and cost-effective asset management requires accurate estimation of reliability at the lowest level. However, real-life reliability data at component level of a railway system is not always available in practice, let alone complete. The component lifetime distributions from the manufacturers are often obscured and complicated by the actual usage and working environments. Reliability analysis thus calls for a suitable methodology to estimate a component lifetime under the conditions of a lack of failure data and unknown and/or …
A General Framework For Infrastructure System Reliability Modelling And Analysis, Payam Mokhtarian, Mohammad-Reza Namazi-Rad, Tin Kin Ho, Mahmoud Efatmaneshnik
A General Framework For Infrastructure System Reliability Modelling And Analysis, Payam Mokhtarian, Mohammad-Reza Namazi-Rad, Tin Kin Ho, Mahmoud Efatmaneshnik
Payam Mokhtarian
An infrastructure system is inherently complex, with layers of both explicitly defined and hidden or subtle interfaces with other infrastructure systems and human users. High availability is desired, which implies stringent requirements on reliability and safety. Reliability analysis typically starts at component or sub-system level and aggregates through the system functional hierarchy. Because of the system complexity, incorporating occurrences of all possible interactions and scenarios is not always practical and failure data is often limited. Moreover, there are unobserved events among the sub-systems distributing either randomly or with temporal trend. To facilitate reliability analysis amid the complex environment and uncertain …
A Probabilistic Predictive Model For Residential Mobility In Australia, Mohammad-Reza Namazi-Rad, Nagesh Shukla, Albert Munoz, Payam Mokhtarian, Jun Ma
A Probabilistic Predictive Model For Residential Mobility In Australia, Mohammad-Reza Namazi-Rad, Nagesh Shukla, Albert Munoz, Payam Mokhtarian, Jun Ma
Payam Mokhtarian
Household relocation modelling is an integral part of the planning process as residential movements influence the demand for community facilities and services. Department of Families, Housing, Community Services and Indigenous Affairs (FaHCSIA) created the Household, Income and Labour Dynamics in Australia (HILDA) program to collect reliable longitudinal data on family and household dynamics. Socio-demographic information (such as general health situation and well-being, lifestyle changes, residential mobility, income and welfare dynamics, and labour market dynamics) is collected from the sampled individuals and households. The data shows that approximately 17% of Australian households and 13% of couple families in the HILDA sample …
Performance And Prediction Of Marine Clay Treated With Vacuum And Surcharge Consolidation At Port Of Brisbane, Buddhima Indraratna, A S. Balasubramaniam, Harry Poulos, Cholachat Rujikiatkamjorn, Jayantha Ameratunga
Performance And Prediction Of Marine Clay Treated With Vacuum And Surcharge Consolidation At Port Of Brisbane, Buddhima Indraratna, A S. Balasubramaniam, Harry Poulos, Cholachat Rujikiatkamjorn, Jayantha Ameratunga
Cholachat Rujikiatkamjorn
During the past decade, the application of vacuum preloading for stabilising soft coastal clay and other low-lying estuarine soils has become popular in Australia. The cost-effectiveness isa major factor in most projects in view of the significantly reduced time for achieving high degree of consolidation. Due to an increase in trade activities at the Port of Brisbane, new facilities on Fisherman Islands at the mouth of the Brisbane River will be constructed on the new outer area (235 ha) adjacent to the existing port facilities via land reclamation. A vacuum assited surcharge load and conventional surcharge scheme in conjunction with …
Conceptual Model Describing Smear Zone Caused By Mandrel Action, Cholachat Rujikiatkamjorn, Made Ardana, Buddhima Indraratna, S Leroueil
Conceptual Model Describing Smear Zone Caused By Mandrel Action, Cholachat Rujikiatkamjorn, Made Ardana, Buddhima Indraratna, S Leroueil
Cholachat Rujikiatkamjorn
In this study the characteristics and extent of the smear zone are investigated using a large, undisturbed sample. The aim of using such a sample is to capture the realistic characteristics of the smear zone in relation to the in situ soil structure during the installation of prefabricated vertical drains (PVDs) using a mandrel. The extent of the smear zone for Bulli clay (New South Wales, Australia) is determined on the basis of normalised permeability (k(h)/k(hu)) and the reduction in the water content upon consolidation. The permeability and compressibility of the soil are investigated to determine the extent to which …
Behaviour Of Clay-Fouled Ballast Under Drained Triaxial Testing, Buddhima Indraratna, Nayoma C. Tennakoon, Sanjay Shrawan Nimbalkar, Cholachat Rujikiatkamjorn
Behaviour Of Clay-Fouled Ballast Under Drained Triaxial Testing, Buddhima Indraratna, Nayoma C. Tennakoon, Sanjay Shrawan Nimbalkar, Cholachat Rujikiatkamjorn
Cholachat Rujikiatkamjorn
Contamination or fouling of rail ballast with external fines, including slurried and pumped subgrade material (e.g. clay and silt), is one of the primary reasons for track deterioration. Fouling causes differential settlement of the track, and also decreases the load-bearing capacity, owing to the reduction in the friction angle of the granular assembly. In certain circumstances, fouled ballast needs to be cleaned or replaced to maintain the desired track stiffness, load-bearing capacity and track alignment, all of which influence safety. This paper presents and discusses the results of a series of large-scale triaxial tests conducted on latite basalt, a rail …
Analytical Solutions For Filtration Process Based On Constriction Size Concept, Vo Trong Nguyen, Cholachat Rujikiatkamjorn, Buddhima Indraratna
Analytical Solutions For Filtration Process Based On Constriction Size Concept, Vo Trong Nguyen, Cholachat Rujikiatkamjorn, Buddhima Indraratna
Cholachat Rujikiatkamjorn
An analytical model is proposed to describe the filtration process applicable to a base soil-filter system. The Navier-Stokes equations for porous media are used to capture the hydrodynamic behavior, whereas, numerically, a new algorithm is proposed to solve the Navier-Stokes equation in a nonlinear form. The various mixtures of base soil particles eroded and water flow within the system are computed using the workenergy principle incorporating the constriction size of the filter.The model can assess the filtration process through the flowrate and the accumulation and redistribution of fine particles within the filter. By discretizing the base soil and filter domains …
Current State Of The Art In Vacuum Preloading For Stabilising Soft Soil, Cholachat Rujikiatkamjorn, Buddhima Indraratna
Current State Of The Art In Vacuum Preloading For Stabilising Soft Soil, Cholachat Rujikiatkamjorn, Buddhima Indraratna
Cholachat Rujikiatkamjorn
In this paper the analytical solutions for radial consolidation that include time dependent surcharge loading and vacuum pressure are proposed, whilst also considering the impact of the parabolic variation of permeability in the smear zone. The use of the spectral method for multilayered soil consolidation is introduced and verified. The Elliptical Cavity Expansion Theory is used to predict the extent of soil disturbance (smear zone) caused by the installation of mandrel driven vertical drains. The predicted smear zone is then compared to the data obtained from large-scale radial consolidation tests. Furthermore, the advantages and limitations of applying a vacuum through …
Ground Improvement At The Port Of Brisbane, Australia Using Vertical Drains And Vacuum Assisted Preloading, Buddhima Indraratna, Cholachat Rujikiatkamjorn, A S. Balasubramaniam
Ground Improvement At The Port Of Brisbane, Australia Using Vertical Drains And Vacuum Assisted Preloading, Buddhima Indraratna, Cholachat Rujikiatkamjorn, A S. Balasubramaniam
Cholachat Rujikiatkamjorn
Soft clays in coastal areas have low shear strength and high compressibility. Thus construction activities for infrastructure developments in these deposits often pose geotechnical problems due to large time dependent settlements and lateral movements. Ground improvement techniques are adopted to reduce the water content of the soft clays by preloading techniques with vertical drains. Depending on the magnitude of the surcharge used substantial immediate settlement with lateral movements can takes place during preloading. This in tum causes stability problems in the loaded areas. The use of vacuum assisted preloading has now become a popular method in Australia where substantial loads …
Dem Simulation Of The Behaviour Of Geogrid Stabilised Ballast Fouled With Coal, Ngoc Trung Ngo, Buddhima Indraratna, Cholachat Rujikiatkamjorn
Dem Simulation Of The Behaviour Of Geogrid Stabilised Ballast Fouled With Coal, Ngoc Trung Ngo, Buddhima Indraratna, Cholachat Rujikiatkamjorn
Cholachat Rujikiatkamjorn
Geogrids are commonly used in railway construction for reinforcement and stabilisation. When railway ballast becomes fouled due to ballast breakage, infiltration of coal fines, dust and subgrade soil pumping, the reinforcement effect of geogrids decreases significantly. This paper presents results obtained from Discrete Element Method (DEM) to study the interface behaviour of coal-fouled ballast reinforced by geogrid subjected to direct shear testing. In this study, irregularly-shaped aggregates (ballast) were modelled by clumping together 10-20 spheres in appropriate sizes and positions. The geogrid was modelled by bonding a large number of small spheres together to form the desired grid geometry and …
Compaction Of Coal Wash As Reclamation Fill, Buddhima Indraratna, Cholachat Rujikiatkamjorn, Gabriele Chiaro
Compaction Of Coal Wash As Reclamation Fill, Buddhima Indraratna, Cholachat Rujikiatkamjorn, Gabriele Chiaro
Cholachat Rujikiatkamjorn
In this paper, detailed laboratory investigations were conducted on coal wash produced at coal mine, Wollongong, New South Wales, Australia. Geotechnical tests were conducted to determine the particle size distribution, compaction characteristics, shear resistance and collapse potential. The compaction tests were conducted under dry and submerged condition to examine the compactability and the strength of the coal wash. The laboratory tests show that compacted coal wash has good potential as effective fill for embankments, and land reclamation. Although coal wash is compacted under submerged condition, increased level of compaction has minimal effect.
Behavior Of Fresh And Fouled Railway Ballast Subjected To Direct Shear Testing: Discrete Element Simulation, B Indraratna, N T Ngo, C Rujikiatkamjorn, J S. Vinod
Behavior Of Fresh And Fouled Railway Ballast Subjected To Direct Shear Testing: Discrete Element Simulation, B Indraratna, N T Ngo, C Rujikiatkamjorn, J S. Vinod
Cholachat Rujikiatkamjorn
This paper presents the three-dimensional discrete element method (DEM) that was used to study the shear behaviour of fresh and coal fouled ballast in direct shear testing. The volumetric changes and stress-strain behaviour of fresh and fouled ballast were simulated and compared with the experimental results. 'Clump logic' in Particle Flow Code (PFC3D) incorporated in a MATLAB Code was used to simulate irregular shaped particles in which groups of ten to twenty spherical balls were clumped together in appropriate sizes to simulate ballast particles. Fouled ballast with various Void Contaminant Index (VCI), ranging from 20%VCI to 70%VCI, were modelled by …
Numerical Solution Of Stone Column Improved Soft Soil Considering Arching, Clogging And Smear Effects, Buddhima Indraratna, Sudip Basack, Cholachat Rujikiatkamjorn
Numerical Solution Of Stone Column Improved Soft Soil Considering Arching, Clogging And Smear Effects, Buddhima Indraratna, Sudip Basack, Cholachat Rujikiatkamjorn
Cholachat Rujikiatkamjorn
Improvement of soft clay deposits by the installation of stone columns is one of the most popular techniques followed worldwide. The stone columns not only act as reinforcingmaterial increasing the overall strength and stiffness of the compressible soft soil, but they also promote consolidation through effective drainage. The analytical and numerical solutions available for ascertaining the response of column-reinforced soil have been developed on the basis of the equal strain hypothesis. For typical surcharge (embankment) loading, the free strain analysis appears to give more realistic results comparable to field data. The paper presents a novel numericalmodel (finite-differencemethod) to analyze the …
Laboratory Study Of Small-Strain Behavior Of A Compacted Silty Sand, Ana Heitor, Buddhima Indraratna, Cholachat Rujikiatkamjorn
Laboratory Study Of Small-Strain Behavior Of A Compacted Silty Sand, Ana Heitor, Buddhima Indraratna, Cholachat Rujikiatkamjorn
Cholachat Rujikiatkamjorn
Small-strain behavior is a key indicator for assessing the performance of compacted fills. Compaction conditions, i.e., initial moisture content and applied energy, govern compaction effectiveness and thus, the structure and matric suction of compacted soil. This paper presents an experimental study of the small-strain behavior of compacted silty sand prepared with different compaction conditions. Specimens with varying initial moisture contents and compaction energies were tested with bender elements to determine the small-strain shear modulus (G0), while the post-compaction matric suction was measured using the filter paper method and tensiometer. The experimental data suggest a pronounced relationship between G0 and the …
Effects Of Geosynthetic Reinforcement On Performance Of Ballasted Rail Track, Pongpipat Anantanasakul, Buddhima Indraratna, Sanjay S. Nimbalkar, Tim Neville
Effects Of Geosynthetic Reinforcement On Performance Of Ballasted Rail Track, Pongpipat Anantanasakul, Buddhima Indraratna, Sanjay S. Nimbalkar, Tim Neville
Buddhima Indraratna
The 'field' performance of different geosynthetics to reinforce ballasted rail tracks was investigated. An extensive monitoring program was undertaken on fully instrumented track sections constructed near Singleton, New South Wales. Four types of geosynthetics were installed at the ballast-subballast interface of track sections located on subgrades with three distinctly different values of stiffness. It was found that geogrids could decrease vertical settlements of the ballast layer with obvious benefits of improved track stability and decreased maintenance cost. It was also found that the effectiveness of reinforcing geogrids increased when the subgrade stiffness decreased. Keywords: Geosynthetic, Reinforcement, Rail track, Ballast.
Coupled Hydro-Geochemical Modelling Of A Permeable Reactive Barrier For Treating Acidic Groundwater, Buddhima Indraratna, Punyama Pathirage, Kerry Rowe, Laura Banasiak
Coupled Hydro-Geochemical Modelling Of A Permeable Reactive Barrier For Treating Acidic Groundwater, Buddhima Indraratna, Punyama Pathirage, Kerry Rowe, Laura Banasiak
Buddhima Indraratna
This study focuses on coupling geochemistry with geo-hydraulics to enable time-dependent modelling of the remediation of acidic groundwater using an alkaline permeable reactive barrier (PRB). Chemical clogging due to secondary mineral precipitates reduces the porosity and hydraulic conductivity of the reactive medium. The governing equations are incorporated into commercial numerical codes, MODFLOW and RT3D. An original algorithm was developed for RT3D to simulate geochemical reactions occurring in the PRB. The results and the model predictions are in agreement, confirming that the hydraulic conductivity reduction due to mineral precipitation occurs at the start of permeation and continues until halfway through the …
Performance And Prediction Of Marine Clay Treated With Vacuum And Surcharge Consolidation At Port Of Brisbane, Buddhima Indraratna, A S. Balasubramaniam, Harry Poulos, Cholachat Rujikiatkamjorn, Jayantha Ameratunga
Performance And Prediction Of Marine Clay Treated With Vacuum And Surcharge Consolidation At Port Of Brisbane, Buddhima Indraratna, A S. Balasubramaniam, Harry Poulos, Cholachat Rujikiatkamjorn, Jayantha Ameratunga
Buddhima Indraratna
During the past decade, the application of vacuum preloading for stabilising soft coastal clay and other low-lying estuarine soils has become popular in Australia. The cost-effectiveness isa major factor in most projects in view of the significantly reduced time for achieving high degree of consolidation. Due to an increase in trade activities at the Port of Brisbane, new facilities on Fisherman Islands at the mouth of the Brisbane River will be constructed on the new outer area (235 ha) adjacent to the existing port facilities via land reclamation. A vacuum assited surcharge load and conventional surcharge scheme in conjunction with …
Conceptual Model Describing Smear Zone Caused By Mandrel Action, Cholachat Rujikiatkamjorn, Made Ardana, Buddhima Indraratna, S Leroueil
Conceptual Model Describing Smear Zone Caused By Mandrel Action, Cholachat Rujikiatkamjorn, Made Ardana, Buddhima Indraratna, S Leroueil
Buddhima Indraratna
In this study the characteristics and extent of the smear zone are investigated using a large, undisturbed sample. The aim of using such a sample is to capture the realistic characteristics of the smear zone in relation to the in situ soil structure during the installation of prefabricated vertical drains (PVDs) using a mandrel. The extent of the smear zone for Bulli clay (New South Wales, Australia) is determined on the basis of normalised permeability (k(h)/k(hu)) and the reduction in the water content upon consolidation. The permeability and compressibility of the soil are investigated to determine the extent to which …
Rail Track Infrastructure For Enhanced Speed - Analysis Design And Construction Challenges, Buddhima Indraratna, Sanjay Shrawan Nimbalkar, Jayan Sylaja J S Vinod
Rail Track Infrastructure For Enhanced Speed - Analysis Design And Construction Challenges, Buddhima Indraratna, Sanjay Shrawan Nimbalkar, Jayan Sylaja J S Vinod
Buddhima Indraratna
Rail is one of the largest transportation modes offering freight and passenger traffic in rapidly developing nations, including India. Conscious efforts to improve productivity, modernization and technology upgrading have led to an impressive growth in railways. Large-scale physical modeling, sophisticated numerical modeling and full-scale field monitoring often provide significant knowledge to better understand track performance and to extend the current state-of-the-art in design. A series of large-scale laboratory tests were conducted to establish relationships between (i) ballast breakage and train speed, (ii) ballast fouling and strength and (iii) interface strength and geogrids. Comprehensive field trials were carried out on instrumented …
Performance Assessment Of Reinforced Ballasted Rail Track, Buddhima Indraratna, Sanjay Nimbalkar, Tim Neville
Performance Assessment Of Reinforced Ballasted Rail Track, Buddhima Indraratna, Sanjay Nimbalkar, Tim Neville
Buddhima Indraratna
In coastal Australia, high population density and increased traffic volumes have promoted rapid expansion of urban transportation infrastructure including railways. Coastal soft clays pose significant construction challenges. Therefore, the search for innovative ground improvement techniques imperative for more resilient and sustainable transport infrastructure has become an obvious priority in research and development. Use of artificial inclusions such as polymeric geosynthetics and energy-absorbing shock mats is described in this paper as a suitable alternative for reducing unacceptable track degradation and for ensuring sustainable track alignment. An extensive monitoring programme was undertaken on fully instrumented track sections constructed near Singleton, New South …
Behaviour Of Clay-Fouled Ballast Under Drained Triaxial Testing, Buddhima Indraratna, Nayoma C. Tennakoon, Sanjay Shrawan Nimbalkar, Cholachat Rujikiatkamjorn
Behaviour Of Clay-Fouled Ballast Under Drained Triaxial Testing, Buddhima Indraratna, Nayoma C. Tennakoon, Sanjay Shrawan Nimbalkar, Cholachat Rujikiatkamjorn
Buddhima Indraratna
Contamination or fouling of rail ballast with external fines, including slurried and pumped subgrade material (e.g. clay and silt), is one of the primary reasons for track deterioration. Fouling causes differential settlement of the track, and also decreases the load-bearing capacity, owing to the reduction in the friction angle of the granular assembly. In certain circumstances, fouled ballast needs to be cleaned or replaced to maintain the desired track stiffness, load-bearing capacity and track alignment, all of which influence safety. This paper presents and discusses the results of a series of large-scale triaxial tests conducted on latite basalt, a rail …
From Theory To Practice In Rail Geotechnology, B Indraratna, Sanjay Nimbalkar, N Tennakoon, Q D. Sun
From Theory To Practice In Rail Geotechnology, B Indraratna, Sanjay Nimbalkar, N Tennakoon, Q D. Sun
Buddhima Indraratna
In recent times the increase in axle loads and train speeds have posed serious geotechnical issues with ballasted railway tracks, both in Australia and the world. The large deformations and degradation of ballast under cyclic and impact loads, and the low bearing capacity of compacted ballast and impaired drainage often exacerbate track maintenance. In recent times in Australia, geosynthetics have been trialed in ballasted tracks constructed on soft and saturated formations to help improve stability and longevity. Comprehensive field studies on instrumented tracks at Bulli (near Wollongong) and Singleton (near Newcastle) supported by RailCorp and ARTC, were carried out to …
Current State Of The Art In Vacuum Preloading For Stabilising Soft Soil, Cholachat Rujikiatkamjorn, Buddhima Indraratna
Current State Of The Art In Vacuum Preloading For Stabilising Soft Soil, Cholachat Rujikiatkamjorn, Buddhima Indraratna
Buddhima Indraratna
In this paper the analytical solutions for radial consolidation that include time dependent surcharge loading and vacuum pressure are proposed, whilst also considering the impact of the parabolic variation of permeability in the smear zone. The use of the spectral method for multilayered soil consolidation is introduced and verified. The Elliptical Cavity Expansion Theory is used to predict the extent of soil disturbance (smear zone) caused by the installation of mandrel driven vertical drains. The predicted smear zone is then compared to the data obtained from large-scale radial consolidation tests. Furthermore, the advantages and limitations of applying a vacuum through …
Ground Improvement At The Port Of Brisbane, Australia Using Vertical Drains And Vacuum Assisted Preloading, Buddhima Indraratna, Cholachat Rujikiatkamjorn, A S. Balasubramaniam
Ground Improvement At The Port Of Brisbane, Australia Using Vertical Drains And Vacuum Assisted Preloading, Buddhima Indraratna, Cholachat Rujikiatkamjorn, A S. Balasubramaniam
Buddhima Indraratna
Soft clays in coastal areas have low shear strength and high compressibility. Thus construction activities for infrastructure developments in these deposits often pose geotechnical problems due to large time dependent settlements and lateral movements. Ground improvement techniques are adopted to reduce the water content of the soft clays by preloading techniques with vertical drains. Depending on the magnitude of the surcharge used substantial immediate settlement with lateral movements can takes place during preloading. This in tum causes stability problems in the loaded areas. The use of vacuum assisted preloading has now become a popular method in Australia where substantial loads …
Dem Simulation Of The Behaviour Of Geogrid Stabilised Ballast Fouled With Coal, Ngoc Trung Ngo, Buddhima Indraratna, Cholachat Rujikiatkamjorn
Dem Simulation Of The Behaviour Of Geogrid Stabilised Ballast Fouled With Coal, Ngoc Trung Ngo, Buddhima Indraratna, Cholachat Rujikiatkamjorn
Buddhima Indraratna
Geogrids are commonly used in railway construction for reinforcement and stabilisation. When railway ballast becomes fouled due to ballast breakage, infiltration of coal fines, dust and subgrade soil pumping, the reinforcement effect of geogrids decreases significantly. This paper presents results obtained from Discrete Element Method (DEM) to study the interface behaviour of coal-fouled ballast reinforced by geogrid subjected to direct shear testing. In this study, irregularly-shaped aggregates (ballast) were modelled by clumping together 10-20 spheres in appropriate sizes and positions. The geogrid was modelled by bonding a large number of small spheres together to form the desired grid geometry and …
Compaction Of Coal Wash As Reclamation Fill, Buddhima Indraratna, Cholachat Rujikiatkamjorn, Gabriele Chiaro
Compaction Of Coal Wash As Reclamation Fill, Buddhima Indraratna, Cholachat Rujikiatkamjorn, Gabriele Chiaro
Buddhima Indraratna
In this paper, detailed laboratory investigations were conducted on coal wash produced at coal mine, Wollongong, New South Wales, Australia. Geotechnical tests were conducted to determine the particle size distribution, compaction characteristics, shear resistance and collapse potential. The compaction tests were conducted under dry and submerged condition to examine the compactability and the strength of the coal wash. The laboratory tests show that compacted coal wash has good potential as effective fill for embankments, and land reclamation. Although coal wash is compacted under submerged condition, increased level of compaction has minimal effect.