Gurmel S. Ghataora

A comparison of railway track foundation design methods

Abstract One of the primary functions of the layers that make up the trackbed in a conventional railway track system is to distribute wheel/rail contact forces so that the stresses in the subgrade are of an acceptable level. To ensure that the trackbed layers perform this task adequately, there are a number of design procedures that may be used to calculate an appropriate thickness of the layers. This paper describes and compares five such design procedures from the USA, UK, Europe, and Japan. The comparisons show that the design procedures give large differences in the calculated layer thicknesses which are due to the design methodologies used in each procedure. Consequently, to enable an appropriate design procedure to be adopted for a given set of conditions, it is necessary to have a thorough knowledge of the methodologies employed together with their inherent assumptions.

EVALUATION OF RAILWAY TRACKBED AND FORMATION: A CASE STUDY

To determine the causes of poor track geometry, a trackbed investigation should comprise a full assessment of ballast, sub-ballast and formation condition. If information about any of these layers is omitted, the true cause of poor formation sites cannot be ascertained satisfactorily and consequently appropriate ground improvement schemes may not be implemented. This has been observed in the UK rail network with examples of a lack of detailed site investigation and subsequent expensive remedial work being carried out without eliminating the initial cause of the problem. This paper summarises the trackbed investigation performed at a site requiring high maintenance, suspected as being caused by poor formation. The paper concludes with an analysis of ground conditions and possible choice of remedial schemes.

Effect of Fiber Inclusions on Flexural Strength of Soils Treated with Nontraditional Additives

AbstractThe effect of randomly oriented discrete synthetic fiber inclusions on the properties of soils treated with proprietary liquid chemical stabilization additives was evaluated in a laboratory-based investigation. Mercia mudstone, Oxford clay, and limestone quarry fines were stabilized with a proprietary polymer and reinforced with discrete fibers. The findings were compared with untreated and reinforced specimens, which served as the control. Test results showed that the inclusion of randomly oriented discrete synthetic fibers had no significant effect on the compaction characteristics of the soils examined. However, it did result in significant improvements in the toughness of all soils examined and load retention after peak strength for Mercia mudstone and Oxford clay. Polymer/sulphonated oil-stabilized and fiber-reinforced Mercia mudstone and Oxford clay specimens were found to be highly susceptible to moisture, while polymer-stabilized and reinforced limestone quarry fines specimens demonstrated...

Sewage sludge ash characteristics and potential for use in bricks, tiles and glass ceramics

The characteristics of sewage sludge ash (SSA) and its use in ceramic applications pertaining to bricks, tiles and glass ceramics have been assessed using the globally published literature in the English medium. It is shown that SSA possesses similar chemical characteristics to established ceramic materials and under heat treatment achieves the targeted densification, strength increases and absorption reductions. In brick and tile applications, technical requirements relating to strength, absorption and durability are achievable, with merely manageable performance reductions with SSA as a partial clay replacement. Fluxing properties of SSA facilitate lower firing temperatures during ceramics production, although reductions in mix plasticity leads to higher forming water requirements. SSA glass ceramics attained strengths in excess of natural materials such as granite and marble and displayed strong durability properties. The thermal treatment and nature of ceramic products also effectively restricted heavy metal leaching to low levels. Case studies, predominantly in bricks applications, reinforce confidence in the material with suitable technical performances achieved in practical conditions.

Assessment of the Performance of Trial Trenches Backfilled with Cementitious Materials

Longitudinal and transverse trial trenches backfilled with unbound graded granular material. Lytag:cement and PFA:sand:cement were monitored over a period of one year. Permanent deformation, elastic deflection and ease of break-out of backfill were used to assess the performance of the trenches. Granular backfill exhibited settlement of 2 and 5mm for the transverse and longitudinal trenches respectively. The corresponding settlement for cementitious backfill was 1 and 2mm. For all types of backfill materials, longitudinal trenches showed greater settlement than the corresponding transverse trenches. Settlement of the trenches took place mainly in the first two months after construction and the rate of settlement became insignificant after that period. Field trials showed that cementitious materials performed better than granular backfill both in terms of permanent deformation and less elastic deflection. Falling weight deflectometer tests were conducted to estimate the elastic modulus of the backfill. It was found that after about one year the deduced elastic modulus of granular backfill became similar to that of the surrounding soil. The deduced elastic modulus of the two cementitious backfille became higher than for the control section, but poor bond between fill and trench wall may have limited the deduced value for Lytag cement mix. One metre length of each transverse trench was excavated to assess ease of break-out. Whilst the granular backfill was the quickest to excavate, Lytagxement backfill was favoured by the operatives as it could be broken out and handled as easy as the granular backfill. The initial cost of PFA:sand:cement was very close to the granular backfill whereas Lytagxement was 12–28% more expensive. If long-term performance is considered, cementitious backfill may be more economical even though the initial cost is higher.

Production of Recycled Plastic Aggregates and Its Utilization in Concrete

AbstractPlastic represents an environmental issue, as only 7% of it is recycled. The plastic remaining is either burned, disposed of in an uncontrolled manner, or landfilled. Thus, to reduce the qu...

Use of cyclic penetration test to estimate the stiffness of railway subgrade

Stiffness of the railway subgrade is a significant factor in maintaining good track quality. The aim of the research was to develop a quick and accurate method for measuring the stiffness of railway subgrade. After a review of the stress regime in subgrade and existing measurement methods, this paper describes a novel cyclic penetration test based the California bearing ratio (CBR) test mould for assessing subgrade soil stiffness. The test reproduces stress conditions in a soil similar to those of the railway subgrade. The results show a close relationship between permanent deformation and CBR values. Based on results of the cyclic penetration tests, plastic deformation was predicted and there was good agreement between the predicted and the measured subgrade settlements.

RESILIENT GEOTECHNICAL INFRASTRUCTURE ASSET MANAGEMENT

The concept of sustainability and resilience has gained significant importance in the recent years in the infrastructure engineering industry. Key challenges currently faced by the infrastructure industry worldwide include obsolescence, growing demands, climate change, increased vulnerability, demand for multi-functionality and growing interdependencies between different asset types. With the recent changes in the economic, social and environmental scenarios, there is an increasing pressure to develop robust, flexible and multifunctional asset management solutions that not only suit the needs of present but also ensure that they are safe, secure and resilient to what the future may hold. Ultimately all infrastructure assets interact with the ground and their integrity relies substantially on the performance of geotechnical assets. Hence, making geotechnical asset management a critical starting point in future-proofing the infrastructure network. The paper highlights the need to devise resilient asset management solutions. The paper focuses on two transport modes namely highways and railways and aims to present an asset management framework, which will test the resiliency of current geotechnical solutions to the plausible conditions of the future. The proposed asset management framework will enable strategic decision makers to evaluate the resilience potential of proposed geotechnical asset management solutions in the light of future conditions with varying socio-economic and environmental patterns.

An investigation of the suitability of the construction of an old railway embankment for a new freight route

Abstract In Europe there is increasing political, environmental and economic pressure for more freight to be carried by rail. Consequently, initiatives are underway to recommission redundant and under-utilised railway infrastructure. There are a number of technical and environmental issues which must be addressed in order to reuse such lines, including designing a suitable track substructure which can carry the proposed freight at design speeds and loads which far exceed those originally intended. To investigate the feasibility of utilising such infrastructure, research was conducted on a heritage line at East Leake, UK. The research consisted of measuring the performance of the existing track, field and laboratory trials to determine the engineering properties of embankment materials and the development of an analytical methodology to establish a suitable structural design for a conventional ballasted railway track. The preliminary analysis demonstrated that a thickness of 0·44 m of granular material placed on the embankment would be sufficient to prevent structural failure of the embankment for freight trains with a wheel load of 125 kN travelling at up to 125 km h−1 for a period of 60 years. The thickness of granular material is similar to that currently used on similar lines in the UK.

Movement of Water Through Ballast and Subballast for Dual-Line Railway Track

The purpose of effective track design is to ensure that load from trains can be safely supported by subgrade soils, which are likely to be affected by water. Because it is almost impossible to prevent water from entering the ballasted track and therefore affecting the underlying layers, it is vitally important that water can drain away rapidly. The study undertaken shows how water moves through a dual-railway track, which is either symmetrical about the centerline or superelevated with a continuous slope of the subgrade across both tracks. The study shows that water may be retained in the track nearest the drain for more than a week with possible consequential impact on increased deformation and therefore the need for more maintenance. It also shows that a high permeability composite may be included near the base of the subballast to effect significant improvement in track drainage.