The CRC for Rail Innovation recognises the importance of investing in the future of collaborative research.

To date, the CRC has awarded 77 CRC Research Scholarships to PhD and Masters Candidates across our seven partner universities to enable post graduate students to carry out further research in topics that span all of our themes. Many of the student topics are aligned to our CRC projects.

To gain an appreciation of the breadth of this research, click on the names below to learn more.


Andrew George - Theoretical and numerical investigation on traction forces for high adhesion locomotives.

Masters Candidate - Central Queensland University

For several years high-adhesion locomotives have been available and in use across the world. These use AC drive systems and advanced slip control systems to produce 50% more traction force than older DC-drive locomotives for the same engine power. Unfortunately Australian rail operators are holding back on adopting high-adhesion locomotives due to a lack of understanding of the effects of locomotive traction force on track infrastructure. This is especially a concern where it is essential to minimise the need for maintenance on lines where track access is difficult or expensive, such as suburban lines.

This thesis is concerned with modelling locomotive traction forces using simulation. The focus will be on Australian railways and Australian versions of high adhesion AC locomotives. Several parameters such as locomotive type, train configurations and track geometry and surface conditions are considered. After completing a literature review to become familiar with the state-of-the-art a more detailed methodology has now been developed to realistically simulate locomotive wheel-rail forces under traction. In short coupler forces generated using longitudinal train simulation software will be fed into a more detailed multi-body locomotive model to generate wheel-rail contact forces. Traction control will be simulated in a separate program to the multi-body locomotive model, with the two communicating via a co-simulation system during analysis.

The key outputs from this research will be:

  • An improved understanding of how wheel-rail contact forces are affected by locomotive traction. This will allow rail operators to make more informed decisions about track maintenance and renewal.

  • The development of an advanced locomotive traction simulation methodology that includes wheel-rail contact and variable friction modelling. Most traction research completed so far has been more limited.

  • An acceptance procedure for validating multi-body locomotive models. Standards exist worldwide that govern the dynamic behaviour of real-world locomotives, but no equivalents for virtual locomotive models have been found.

Aligned to project Locomotive Adhesion

Chandrahas Rathod - Microstructural characterisation of insulated rail joints.

PhD Candidate - University of Wollongong

Insulated Rail joints (IRJs) are an integral part of the signalling system. IRJs are periodically replaced due to accumulated damage at the railhead like metal flow and rolling contact fatigue (RCF). The main goal of the project is to develop a railhead at the vicinity of IRJs by employing laser surface depositing technique using high hardness and higher yield stress material, which prevents RCF and reduce extent of railend metal flow. This new IRJ design could lead to great extent in reducing maintenance costs and replacement of IRJs.

Aligned to project Insulated Rail Joints

Dr Ali Ghandeharioon - Analytical and numerical study of soil disturbance associated with the installation of mandrel-driven prefabricated vertical drains

PhD Thesis Abstract - University of Wollongong

Prefabricated vertical drains (PVDs) combined with preloading have gained in popularity among the most effective ground improvement techniques available to mitigate the unacceptable differential settlements caused by the heterogeneity and high compressibility of soft soil deposits. In this thesis the installation of mandrel-driven PVDs and associated disturbance in cohesive soils ere studied by conducting analytical investigations, laboratory experiments, and numerical modelling. The pattern of disturbed regions surrounding the mandrels and the distribution of stresses in soils obtained from the analytical and numerical predictions agreed with the results of the laboratory tests. A number of case histories taken from Malaysia, Australia and Thailand were also analysed to evaluate the associated soil disturbance during installation of prefabricated vertical drains.

An analytical study of mandrel penetration and the resulting disturbance in soft saturated clays was carried out with a new elliptical cavity expansion theory (CET). This research postulated that installing PVDs in the field with commonly used mandrels would create elliptical CET was developed using modified Cam clay parameters for undrained analysis with a formulation based on polar coordinates that accounts for the rate of mandrel penetration and the time for predicting internal pressure in the cavity, corresponding stresses and excess pore pressure in the soil while driving the mandrel. The pattern of distribution calculated for the excess pore pressure was verified using data available in the literature. A more realistic elliptical smear zone based on the elliptical CET was introduced while the disturbed soil surrounding the mandrel was characterised by the plastic shear strain normalised by the rigidity index.

A number of large-scale laboratory tests that incorporated the field conditions and effects of confining pressures were performed. A consolidometer specifically designed for the purpose, and a machine capable of driving mandrels at realistic rates were used in these experiments. The variations of pore water pressure during installation of a mandrel-driven PVD and withdrawal of the mandrel monitored by fast response pore pressure transducers connected to a digital data logger. The extent of smear zone in the large-scale consolidometer was determined using the results of moisture content tests on samples, which in relation to the installed PVD were cored along different polar axes from various locations. The smear zone was then analysed to establish a relationship between its size and the in-situ effective stresses.

The installation of a mandrel w simulated numerically using a commercial finite element software package, ABAQUS. The finite element models included coupled analyses with a large-strain formulation. Coulomb’s law of friction and the penalty method were incorporated into the numerical technique. It was shown that the soil surrounding the mandrel moved radially and downwards as the mandrel was installed. The variations of pore water pressure at different locations during the installation of a mandrel-driven PVD and withdrawal of the mandrel were illustrated. There was an agreement between the pore pressures measured in the laboratory and the finite element predictions. The extent of smear zone was studies according to a numerical simulation of the mandrel installation.

The analytical formulation incorporating the elliptical CET presented in this thesis was applied to case histories from the Muar clay region in Malaysia and the Sunshine Motorway in Australia. The ratio of plastic shear strain to the rigidity index was found useful for estimating the extent of the smear zone in the field because in practical situations the basic soil parameters may be used without sophisticated large-scale testing.

Moreover, the numerical model of mandrel installations was specifically developed to study a case history from the Second Bangkok International Airport in Thailand. The variations of pore pressure while installing a vertical drain and withdrawing the mandrel were obtained. The plastic shear strain was evaluated to identify different aspects of disturbance in the soil elements. The results of this analysis indicated that the model developed can be applied to field conditions.

Ghandeharioon, A (2010) Analytical and numerical study of soil disturbance associated with the installation of mandrel-driven prefabricated vertical drains (Doctoral dissertation, University of Wollongong) Retrieved from Trove.

Dr Dominic Trani - Application of constriction size based filtration criteria for railway subballast under cyclic conditions

PhD Thesis Abstract - University of Wollongong

In rail track environments, the loading system is cyclic unlike the steady seepage force the usually occurs in embankment dams. The mechanisms of filtration, interface behaviour, and time dependant changes of the drainage and filtration properties occurring within the filter medium require further research to improve the design guidelines. A novel cyclic process simulation filtration apparatus was designed and commissioned at the University of Wollongong, and a standard test procedure was established. The test apparatus was designed to simulate heavy haul train operations. The key parameters that influence the change in porosity and pore water pressure within the sub ballast layer under cyclic conditions in rail track environments were identified.

Crushed basaltic road base was used as the filter subballast. The slurry form of the base soil, which is a low plasticity and highly erodible silty clay, was pumped form the bottom of the filter to simulate clay pumping and hydraulic erosion. Grading characteristics such as the uniformity coefficient and the mass of fines, and the external loading factors such as the maximum compressive load and slurry loading rate, were found to be the main factors that influence the mechanical characteristics and seepage hydraulics of subballasts under cyclic conditions.

The evidence gathered from laboratory testing suggests that the subballast selection criteria adopted by the railway industry, which are based on mathematical and empirical models generated from static load conditions in embankment dams, does not address the filtration mechanism of subballasts under cyclic conditions. Apart from being a commonly used buffer for the ballast layer against subgrade attrition, subballast is primarily designed to act as a stress dissipation layer (capping layer) and its function as a filter is often regarded as a lesser priority. With more emphasis on the stress reductions function, well graded subballast containing larger particles provides a better skeletal resistance against applied stresses. However, well graded subballasts containing relatively coarse grains (20% fine sand, 30 % fine gravel) are too porous to effectively capture the fines within its voids. Laboratory findings suggested that uniformly graded subballasts with not more than 30% fine sands (particles range of 0.15 to 0.425 mm) has an enhances filtering capacity. Due to the lack of mechanical resistance against axial deformation, the application of cyclic stress to uniformly graded subballasts reduces porosity and enables the filter to trap migrating fines more effectively. Moreover, this intrusion of fines changes the PSD of the subballast which reduces its porosity and further inhibits drainage.

A multi-layer mathematical approach was used to predict the time dependent permeability of this filter, with (a) a reduction in porosity as a function of compression under cyclic loading, and (b) the amount of fines trapped within the filter voids, being the two main aspects of this proposed model. Laboratory test results conducted on a novel cyclic loading permeameter were used to validate the proposed model. The set of equations that forms an integral part of the proposed model is then presented as compact visual guidelines anticipated to provide a more practical tool for railway practitioners.

Trani, L D (2009) Application of constriction size based filtration criteria for railway subballast under cyclic conditions (Doctoral dissertation, University of Wollongong, 2009). Retrieved from Trove

Aligned to project Ballast Design

Dr Nayoma Tennakoon - Geotechnical Study of Engineering Behaviour of Fouled Ballast.

PhD Thesis Abstract - University of Wollongong

Railways are among the fastest and most economic transport modes in Australia, and the improvements in track performance are the direct results of the increase in the volume of rail traffic, as well as the need for reducing the cost of rail maintenance. Ballast is the uniformly graded coarse aggregate placed underneath the sleepers whose main purpose is to facilitate rapid drainage and provide structural support for the heavy loads exerted by the passage of trains.

When the ballast voids are wholly or partially filled with the intrusion of fine materials, particle breakage and pumping of soft subgrade soil, the track can be considered as being ‘fouled’. In Queensland, on the average, 20% decrease in load carrying capacity is due to ballast fouling. The reduced void space in ballast significantly affects its hydraulic conductivity by reducing the drainage capacity of the track. In order to ensure acceptable track performance and longevity, it is pertinent to maintain rapid drainage conditions within the ballasted bed. However, fouling reduces the drainage capacity of the ballast, excess pore water pressure can be generated under the passage of fast moving trains (cyclic load), which further compromises track resiliency while contributing to increased maintenance costs. In addition, fouling causes differential settlement of the track and also decreases it load bearing capacity due to the reduction in internal friction of the granular assembly.

The design aspects and maintenance cost of ballasted tracks can be significantly reduced if an accurate estimation of different types of fouling material and associated degradation mechanisms can be properly quantified. To maintain the required track geometry with fouled ballast, frequent maintenance activities should be carried out. However, the decision for practicing engineers of where and when to perform the maintenance operations due to lack of adequate information of fouled ballast condition is often difficult to make. Therefore, it is important to understand both the mechanical and hydro-mechanical characteristics of fouled ballast for different proportions of fouling, because, this will significantly assist towards optimising the time frame for maintenance while effectively minimising the maintenance costs.

A series of large scale hydraulic conductivity tests with specimen size of 500 x 500 mm high, were conducted with different proportions of fouling to study the relationship between the extent of fouling and hydraulic conductivity. Since the hydraulic conductivity obtained from laboratory experiments were one-dimensional given that tow-dimensional flow conditions may prevail in reality, a numerical analysis was conducted using SeepW (2007a) to quantify the drainage capacity of ballast under different degrees of fouling. Subsequently, a quantitative classification for drainage in relation to the degree of fouling, which is very useful tool for practical engineers, is presented in this thesis. The analysis showed that both the location and extent of fouling played an important role when assessing the overall drainage capacity of track. Based on the research outcomes, ballast cleaning using the undercutting method is recommended when the Void Contaminant Index (VCI) of the top 100mm of the ballast layer exceeds 50%. When the shoulder ballast is fouled by more than 50% VCI, then it should be either cleaned or replaced to maintain acceptable drainage. This is because, if shoulder ballast is fouled to a high level (VCI > 50&) the ‘poor drainage’ of the track can occur even if the other ballast layers are relatively clean.
In order to establish the relationship between the extent of fouling and the associated strength-deformation properties, a series of large scale (300 mm diameter by 600 mm height) monotonic triaxial tests were carried out for different levels of fouling for confining pressures in the range of 10-60 kPa. Based on the laboratory findings, a novel empirical relationship between the peak deviator stress and VCI has been proposed to assist the practitioner in their preliminary track condition assessment. At a significantly high level of fouling (VCI> 50%), a considerable drop in shear strength can affect the stability and load carrying capacity of the track.

A series of large scale cyclic drained triaxial tests has been conducted to investigate the effects of fouling on settlement and ballast degradation, along with a number of loading cycles, simulating realistic field loading conditions. The experimental investigation showed that an increase in fouling always increases the permanent axial strain at a given number of cycles, while an increase in fouling lowered the compressive strain at final N> 500,00 cycles. This suggests that at excessive level of fouling the dilation of the ballast layer is initiated as the number of load cycles increases. Not surprisingly, the corresponding magnitude of resilient strain was shown to decrease with an increasing degree of fouling. Apart from the detrimental effects discussed earlier, fouling leads to a reduction in particle breakage.

A constitutive model for clay fouled ballast is formulated using bounding surface framework under monotonic lading and drained condition. The model is validated with the large scale triaxial experiments carries out in this research.

Tennakoon, N (2010) Geotechnical study of engineering behaviour of fouled ballast (Doctoral Dissertation, University of Wollongong, 2010) Retrieved from Trove.

Aligned to project Ballast Design

Dr Ngoc Trung Ngo - Performance of geotextile stabilized fouled ballast in rail tracks.

PhD Thesis Abstract - University of Wollongong

The railway track network plays an essential role of the transportation infrastructure worldwide. During operations, the ballast becomes contaminated or fouled due to the infiltration of fines from the surface, mud pumping up from the subgrade, and ballast degradation under repeated train loading. In Queensland and New South Wales, Australia, ballast degradation and infiltration of fine particles such as coal and soft subgrade fills the voids in the ballast layer, which restricts drainage, and results in uneven track settlement and high maintenance costs to clean the ballast.

Geosynthetics have been increasingly used in railroads to provide reinforcement and confinement pressure to the layer of ballast. However, the interaction mechanism and behaviour of the geosynthetics and ballast at their interface are not well understood, particularly when the ballast is severely fouled. This is due to the steady accumulation of fine particles that clog the apertures of the geosynthetics, which dramatically reduced its beneficial effects and also causes track instability associated with substantial deformation.

This research aims to study how the interface between ballast and geogrid copes with fouling by coal fines. The shear stress-displacement behaviour of fresh and fouled ballast, and ballast reinforced with geogrids was investigated through a series of large-scale direct shear tests where the levels of fouling ranged from 0% to 95% Void Contamination Index (VCI), and at relatively low normal stresses varying from 15 KPa to 75 KPa. The results indicated that inclusion of geogrids increases the shear strength and apparent angle of shearing resistance, while only slightly reducing the vertical displacement of the composite geogrid-ballast system. However, when the ballast was fouled by coal fines, the benefits of geogrid reinforcement decreased in proportion to the increasing level of fouling. A conceptual normalised shear strength model was proposed to predict this decrease in the peak shear stress and peak angle of shearing resistance caused by coal fines at a given normal stress.

A novel Track Process Simulation Apparatus (TPSA) was used to simulate realistic rail track conditions subjected to cyclic loading and the VOID Contamination Index (VCI) was used to evaluate the level of ballast fouling. The inclusion of geogrid at the interface between the layer of ballast and sub-ballast provides additional internal confinement and particle interlocking via the geogrid apertures, which reduces deformation. A threshold value of VCI=40% has been proposed to assist practitioners in conducting track maintenance. If the level of fouling exceeds this threshold the geogrid reinforcement significantly decreases its effectiveness, and the fouled ballast exhibits pronounced dilation. Based on the experimental results, an equation incorporating VCI was proposed to predict the deformation of fresh and fouled ballast. This equation improves track design and assists in making appropriate and timely decisions on track maintenance.

The Discrete Element Method (DEM) was used to study the shear behaviour of fresh and 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. Fouled ballast with various Void Contaminant Index (VCI), ranging from 20%VCI to 70%VCI, were modelled by injecting a specified number of miniature spherical particles into the voids of fresh ballast. The DEM simulation highlights the fact that the peak shear stress of the ballast assembly decreases and the dilation of fouled ballast increases with an increasing of VCI. Furthermore, the distribution of contact force chains and particle displacement vectors clearly explains the formation of a shear band and the evolution of volumetric change during shearing. An acceptable agreement was found between the DEM simulation and laboratory data.

Ngo, N T (2010) Performance of geogrids stabilised fouled ballast in rail tracks (Doctoral Dissertation, University of Wollongong, 2010) Retrieved from Trove.

Dr Sakdirat Kaewunruen - Experimental and numerical studies for evaluating dynamic behaviour of prestressed concrete sleepers subject to severe impact loading

PhD Thesis Abstract - University of Wollongong.

Rail operators are consistently demanding higher axle loads to compete effectively with other modes of transport, particularly for heavy haul freight of minerals. However, high axle loads can only be achieved by ensuring that the existing rail infrastructure can cope with the greater static and dynamic loads associated with the wheel-rail interactions. Premature cracking of prestressed concrete sleepers is often the result of high-intensity dynamic loading caused by wheel or rail irregularities. The high-magnitude wheel loads produced by a small percentage of ‘bad’ wheels or rail head surface defects are crudely accounted for ain the Australian Standard AS 1085.14 by a single load amplification factor. In addition, there is a widespread perception within the railway engineering community that the carrying capacity of the existing track infrastructure is not fully utilised, and concrete sleepers possess significant amounts of untapped reserve strength. This can be attributed to the current design philosophy for concrete sleepers, outlined in AS 1085.14. This is based on the assessment of permissible stresses resulting from quasi-static wheel loads and essentially the static response of concrete sleepers, making it unduly conservative and very costly for the railway organisations. This thesis addresses the identified deficiencies of the current design method through an in-depth analysis of the dynamic response of concrete sleepers under realistic loading conditions and proposes a more rational de3sign procedure.

In order to shift the conventional methodology to a more rational design method that involves more realistic dynamic response of concrete sleepers ad performance-based design methodology, a significant research effort within the framework of the C00erative Research Centre (CRC) for Railway Engineering and Technologies has been carried out to perform comprehensive studies of the loading conditions, the dynamic response, and the dynamic resistance of prestressed concrete sleepers. The collaborative research between the University of Wollongong (UoW) and Queensland University of Technology (QUT) has addressed such important issues as the spectrum and amplitudes of dynamic forces applied to the railway track, evaluation of the reserve capacity of typical pre3stressed concrete sleepers designed to the current code AS 1085.14, and the development of a new limit states design concept.

The comprehensive literature review highlighted the extremely limited research work that previously had been done in this field of research. In order to enhance an understanding of the dynamic performance of railway tracks, the first part of this thesis investigates the dynamic characteristics of the global railway track and its individual components with particular reference to rail pads and prestressed concrete (PC) sleepers. The experimental techniques for extracting dynamic properties of track components, developed in the laboratory, have been successfully applied in flied trials. Moreover, this thesis provides an intensive review aimed at predicting wheel impact loads due to the wheel/rail irregularities at different return periods (based on the field data from wheel impact detectors).

The experimental and numerical investigations into the dynamic behaviour of prestressed concrete sleepers subjected to severe impact loading are then presented. The impact tests were carried out using the prestressed concrete sleepers manufactured in Australia. A track test bed was simulated in the laboratory and calibrated against the frequency response functions obtained for rail tracks. A series of incremental impact loading tests for the prestressed concrete sleepers was performed, ranging from a typical design load to a severe wheel load. The cumulative impact damage and crack propagation in concrete sleepers were identified. The effects of track environment together with the relationship between the bending moment of prestressed concrete sleepers and the applied impact force are also presented.

The later part of the this thesis identifies the responses of prestressed concrete sleepers in railway track structures under both single and repeated impact loads associated with different probabilities of occurrence. The residual capacities of the damaged prestressed concrete sleepers are studied in order to clarify the notion about the reserve strength of the concrete sleepers. The numerical investigations of the static and impact behaviours of railway prestressed concrete sleepers under static and dynamic loads were also undertaken to supplement the experimental findings in this thesis.

A proposal for the reliability-based design concepts and rationales associated with the development of limit states design procedures for the conversion of AS 1085.14 to a limit states design format is one of the key outcomes of this thesis. The new limit states design concepts and procedures for railway prestressed concrete sleepers are presented as the design guidelines for the railway engineers. The new methodology is aimed not only to save the material resources to achieve financial gains, but also to reduce the amount of cement production which would otherwise emit carbon dioxide as a contributing factor towards global warming.

Kaewunruen, S (2007) Experimental and numerical studies for evaluating dynamic behaviour of prestressed concrete sleepers subject to severe impact loading (Doctoral Dissertation, University of Wollongong, 2007) Retrieved from Trove.

Engr MD Mojibul Sajjad - Top of Lubrication and Friction Management

Masters Candidate - Central Queensland University

Isuru Udara Wickramasinghe - The effect of lubrication and loading on surface damage in the wheel/rail contact.

PhD candidate - Queensland University of Technology

The purpose of this work is to study the effect of variable loading conditions and lubrication on wheel/rail wear so that the load carrying capacity of railways can be optimised. A twin-disk rolling contact fatigue test rig is used to correlate rates and modes of wear with the number of contact cycles. The materials used in the tests conform to the specifications currently employed in the Australian rail industry. Both rail and wheel disks have been cast using the standard rail and wheel material compositions and have been hardened in accordance with the industry standard. Finite element models of the wheel/rail contact have been devised to correlate and understand the relationship of varying load conditions and material/lubricant properties with experimentally observed wear phenomena.

Aligned to project Rail Grinding Best Practices

Khaja Karimullah Syed - Composite soil-structure interaction applied to rail tracks under cyclic loading.

PhD Candidate - University of Wollongong

This research aims at establishing the role of geogrid-reinforcement on the settlement and breakage of rail ballast under high-speed train loading. The influence of geogrid aperture size and its location within the track on the effectiveness of geogrid in restraining the lateral flow of ballast will be captured. For this purpose, a novel laboratory apparatus to measure the lateral spread of ballast has been developed at the University of Wollongong. The results of this study will benefit the rail industry in the form of reduced maintenance costs through enhanced track longevity.

Khoa Duy Vo - Stress analysis of wheel/rail adhesion.

PhD Candidate - University of Wollongong

The complicated phenomenon of the wheel rolling on the rail is a combination of many important factors such as the train speed, the wheel loading, the adhesion in contact patch, and the reaction of the track components. Railway researchers always try to optimize the properties of train system. The appearance of the new generation AC traction locomotive has brought to the Australian Railway many advantages. The greatest benefit gained from using AC traction is the higher level of adhesion can be achieved. Although the performances of high adhesion locomotive have been improved, the interrogate referring to rail damage and the join of sleeper-rail in some high adhesion conditions is still being raised. Hence the stress distribution of the contact patch associated with high adhesion for a variety of wheel rail profiles and forcesneed to be studied very carefully. In this research, the data from the field test integrated with Finite Element Method (FEM) will be utilized to examine the complex wheel-rail contact phenomenon. According to the result obtained from the simulation, the estimation and maintenance methods of the railway system will be forthcoming to maximize the using longevity of the train and to minimize the railway accidents.

Mehran Aflatooni - Synthetic Rating System for railway bridge management.

PhD Candidate - Queensland University of Technology

Currently bridges are being rated individually based on the structural condition of their elements. In this research a method for rating a network of bridges by taking into account the most crucial factors and critical elements will be developed for more effective management of railway bridges. A comprehensive literature review about the subject has been carried out and a practical research plan is being established. The outcomes will be used to conduct timely preventive and corrective actions within a restricted budget to improve the safety and functionality of the railway bridges.

Aligned to project Life Cycle Management of Bridges

Mohammad Mahdi Biabani - Improvement of sub-ballast performance with geocell.

PhD Candidate - University of Technology

Traditional rail tracks, although providing a rigid platform, have a higher maintenance cost than non-ballasted slab tracks. However, by providing a confinement system such as geocell, there is an opportunity to increase the performance of both ballast and sub-ballast such as

  • an increase in the laid bearing capacity of the sub-ballast giving the opportunity to increase the number of cycles

  • leading to a stiffer bed for the ballast which could lead to a reduction in the thickness of the ballast

  • allowing more recycled ballast to be used in the sub-ballast layer and thus reducing the cost of both construction and maintenance.

Mohammadali Farjoo - An investigation on rail squat prediction due to rolling contact fatigue

PhD Candidate - University of Queensland

Rolling Contact Fatigue (RCF) is one of the common types of damage which takes place in rolling contact problems. A rail squat is a specific RCF problem that appears on a rail. The crack usually seems to be formed from a surface flaw and grows to almost 5 mm below the running surface. It appears on a rail surface as a type of ‘bruise’ damage, caused by plastic deformation above the crack, which can easily be found visually. A squat grows almost parallel to the rail surface in the direction of travel, but often turns in the opposite direction as well. In Australia, a major western railway company spends more than 50% of its annual re-railing budget on replacing squat damaged rail.

This thesis investigates those parameters that affect initiation and propagation of squats. A wheel-rail contact force is assumed to move over the rail surface. While this contact load moves over a crack, the equivalent stress intensity factor (SIF) at the crack tip changes. First the model is compared with simplifies analytical contact solutions and it is shown that the assumptions introduce substantial errors due to the complexity of rail and wheel geometry in the squat region. Then a simplified numerical model of a rail crack is used to check the influence of boundary conditions on the crack growth rate. This model is validated with another independent numerical model [1].

A 3D finite element (FE) model of a piece of a rail is created and associated boundary conditions and loading forces are applied. It is found that due

Aligned to project Rail Squats

Muditha Pallewattha - Improvement of Soil Stability along Rail Corridors through Native Vegetation - Bio Engineering

PhD Candidate - University of Wollongong

Current demand of the infrastructure facilities along metropolitan areas has been lead to construct earth structures, major highways and railways on soft soils. In relation to above facts civil engineering is in a more challenging situation to discover more cost effective, reliable and sustainable methods for ground improvement. In that case green corridor concept or ground improvement using native vegetation can be considered as a more effective method. Even though this is considered as a new idea, the use of vegetation in hill slopes to prevent erosion and to give some stability had been started in centuries back without proper engineering quantification. Trees are capable of increasing the matric suction of the soil subgrade underneath the substructure via root water uptake, in conjunction with the tree canopy evapo-transpiration. At the same time, these trees are capable of providing significant mechanical reinforcement through the anchoring effect provided by the root network plus the additional cohesive increment due to hair roots generating osmotic suction.

Much of the previous research carried out to quantify the mechanical strength generated by tree roots has been mainly based on empiricism. In many cases, empirical relations have been developed for given tree species grown under known soil conditions. The extrapolation of such empirical relations from one tree-soil system to another can be misleading. Root based suction of a tree improves the shear strength and accelerates the pore water pressure dissipation. In addition it may alter the potential failure conditions of the soil-root system from a saturated to an unsaturated domain. Therefore, the root based suction and the mechanical properties of the root network is to be analysed within a coupled multiphase framework.

Niroshan Walgama Wellalage Karunarathna - Development of risk prediction methodology for rail bridges based on deterioration

PhD Candidate – University of Wollongong

There are over 10 thousands rail bridges in Australia that were made of different materials and constructed at different years. Managing thousands of bridges has become a real challenge for rail bridge engineers without having a systematic approach for decision making. Developing deterioration models is essential in order to implement a comprehensive Bridge Management System (BMS) in Australia. Thus, this research is aimed towards to develop best suitable deterioration models for Australian rail bridges. Firstly, existing methods for bridge condition prediction modelling are reviewed and weaknesses and limitations of those methods will be identified. Secondly, available data on Australian railway bridges will be collected from relevant rail bridge authorities. Finally, advanced method such as Markov Chain Monte Carlo (MCMC) methods and Artificial Neural Network (ANN) approaches are expected to employ in order to overcome the limitations of existing bridge deterioration modelling techniques.

Aligned to project Life Cycle Management of Bridges

Shah Sanjar Nafis Ahmad - Ensuring track safety and reducing unnecessary train speed restrictions in hot weather by the application of a unified track stability management tool

Masters dissertation - Central Queensland University

The risk of track buckling has been considered as a significant safety and operational hazard in railway companies. The cost due to inadequate management of track can be divided into maintenance and operation section. The maintenance cost involves repairing track buckling, inspecting and re-stressing track to the desired state to reduce the risk of track buckling. On the other hand, the consequence of derailments as a result of track buckling in front of trains or under the trains has led the railway companies to decide on speed restrictions whenever high compressive stress resulting from high rail temperature is suspected, which not only incurs loss in terms of fine but also has negative effect on customers’ perception on railway safety. Considering the high cost involved to make the track operational after any derailment there is always a notion to implement a speed restriction policy on the conservative side considering the uncertainty of track resistance, stress free temperature (SFT) and rail temperature due to lacking of quantified values.

In case of unavailability of measured data on track resistance, SFT and rail temperature, railway companies utilise a routine and on event management program to maintain the stability of track. In Australia, the railway companies are segmented in to different states and currently, there is no common standard in regards to track stability has been accepted by all the railway companies.
In this thesis, prctice3s/procedures adopted by different railways to manage track stability have been collated and a gap analysis has been undertaken to help improve track stability. The analysis revealed that track stability management differs markedly/noticeably between railway companies, and that there is a need for a unified tool to determine the requirements of different preventive maintenance programs. The collated information on the recent theories and practices on the stability of continuous welded rail would help the railway companies to develop a common standard on track stability management.

Considering the cost involved in train delays a special attention has been given to determine the appropriate speed restrictions setting. Current practices involve application of speed restrictions based on air temperature without considering the variations of stress free temperature (SFT). The uncertainly in predicting rail temperature correctly based on air temperature and the lack of data on lateral track strength have made railway companies depend on conservative approximations of maximum rail temperature that leads to unnecessary speed restrictions and delays in train operations. In a field test carried out on the Queensland Rail heavy haul Blackwater system, rail creep, effect on rail temperature of the compass orientation of rail and variation of SFT on straight and curved track have been quantified using strain gauges, thermocouples, rails stress monitors (RSMs) and total station surveying equipment.

Accordingly, from the results of the gap analysis and an understanding of recent developments in the theory of track buckling, a tool to better manage track stability is presented. The tool allows track stability to be managed by determining priority based track locations to re-stress based on an adequate margin of safety against buckling risk of continuous welded rail. The tool offers guidance on inspections and speed restrictions based on a knowledge of track strength, rail stress and predicted rail temperatures.

Finally, the developed track stability management (TSM) tool can help to reduce the train delays by providing adequate information on track strength, rail stress and the time period of maximum temperature of rail on a specific compass orientation. The thesis shows that, combining information on track strength, rail stress, inspection data, weather information and train operating condit5ions creates a unique decision-making tool to maximise safety and minimise delays when operating trains.

Nafis Ahmas, S S (2011) Ensuring track safety and reducing unnecessary train speed restrictions in hot weather by the application of a unified track stability management tool (Masters Dissertation, Central Queensland University, 2011) Retrieved from Trove.

Aligned to project Track Stability Management

Shiran Galpathage - Improvement of shear strength of soft grounds using native tree root suction and root reinforcements

PhD Candidate - University of Wollongong

Aligned to project Ballast Design

Siva Naidoo Lingamanaik - Residual stresses in railway wheels.

PHD Candidate - Monash University

My research work involves the study of residual stresses in recently developed low carbon bainitic-martensitic (LCBM) steel for rail wheels which have shown to offer similar to superior properties compared to conventional pearlitic rail wheels. Alternate quenching conditions have been designed using the Finite Element method for LCBM rail wheels and beneficial compressive residual stresses have been developed in the rim of the LCBM rail wheels, making it possible to produce LCBM rail wheels. The cooling rates assumed in the FE model have been verified against full size experimental quenching of LCBM rail wheels. The project has now reached the stage of producing LCBM rail wheels for service trials.

Aligned to project New Wheel Steels

Ye Tian - Locomotive adhesion control and corrugation detection

PhD Candidate – University of Queensland

This research considers locomotive adhesion/creep control. The idea is to control/limit the creep on the contact patch between the wheel and the rail track. In this way the traction force can be controlled to a desirable level, usually to the maximum tractive force available. The difficulty lies in the nonlinearity of the creep-tractive force characteristic and uncertainty of contact conditions. Without proper control, the creep will increase significantly so that the tractive force will drop while the contact damage to the rail tracks and wheels will increase dramatically.
The research benefits the industry in two main ways:

1. Proper controlled creep can provide maximum tractive force during operation, thus improve the operation efficiency;

2. It can also reduce the cost spent on rail track maintenance, which is up to millions of dollars per year.

Aligned to project Locomotive Adhesion

Ying Min Wu - Development of Rail Temperature Prediction Model and Software

Masters dissertation - Central Queensland University

The railway track buckling occurs all over the world due to inadequate rail stress adjustment, which is greatly influenced by the variation in weather induced rail temperature and the rigidity of the track structure. Climate change and the ever increase in extreme changes in temperatures have made buckling an ever more prevalent problem in the railway industry.

The ultimate goal of any research in the area of track stability management is to comprehensively manage rail buckling and the subsequent procedures that follow after buckling. The first step to have a clear understanding of how the temperature change of the rail track is influenced by the environmental conditions. The second step is to have an accurate prediction of what the environmental conditions will be in the next day so that management procedure can be put into place.

This study aims to develop a model and software that is capable of predicting rail temperature 24 hours in advance that is as accurate for use in the rail buckling management. Two distinct and separate mathematical manipulations are performed to achieve this goal.

One method used weather forecasts from the Australian Bureau of Meteorology (BoM) and forecasts the weather for the location that the rail is situated. This involves using 3-dimensional cubic interpolation that is the weather parameters are interpolated in 2-dimensions geographically and then 1-dimensionally through time. An interactive software is written in MATLAB to convert the BoM raw data into a rail temperature forecast for this study. The result is a 15-minute forecast for every 3.06 km. The second method used multivariate linear regression, to predict the rail temperatures 24 to 48 hours in advance.
To validate the rail temperature predications, 3 months field test spanning June, July and August 2010, is conducted on Queensland Rail’s (QR) coal network, this involved erecting an automated weather station (AWS) and adhering temperature sensors on to a section of track. The guidelines of World Meteorological Organization’s (WMO) were followed for implementation of the AWS on site (WMO 2008). The AWS model WXT520 , produced by Vaisala (Vaisala 2009) was used in this study which an off the shelf product that is similar to what some rail companies are already using for continues monitoring of critical sites.
The temperature sensors (surface thermocouples) and an off the shelf product Salient system’s rail-stress modules are used to measure rail surface temperatures on both rails of the ii track (Salient Systems Inc 2009). The sensors were attached to the surface of the rail track to directly measure temperature change of the rail profile throughout the diurnal cycle.
Statistical correlations between the different measured points of the rail profile are evaluated in relation to the diurnal cycle to assess the accuracy of current rail temperature measuring practices.

Statistical evaluation of how well the BoM predictions compare with weather parameters at the field experimentation site are performed, so too is a statistical evaluation of the accuracy of the rail temperature model developed. The prediction model is compared with the existing empirical methods as found in the literature review and an assessment of track conditions.

This is a flag ship study in Australia; the main purpose of this study is to prove in a test case scenario that a rail temperature forecast without use of weather instrumentation is possible and the accuracy of the prediction is as good if not better than the instrumentation calculation.

Wu, Y M (2011) Development of Rail Temperature Prediction Model and Software (Doctoral Dissertation, Central Queensland University, 2011) Retrieved from Trove.

Aligned to project Track Stability Management