Civil Engineering

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. q (M. Brough). 1 A track condition index based upon standard deviations of track geometry.

This paper presents a numerical method to predict soil-geotextile interface friction parameters. A strain softening model was used to simulate the relationship between shear stress and horizontal displacement at the soil-geotextile interface. Pullout tests were performed on two types of geotextile, with different tensile stiffnesses, embedded in a granular soil. For each geotextile, pull-out tests were performed at confining pressures of 20, 50, 100, and 200 kPa. It was found that, unless breakage of the geotextile occurs, the peak pull-out force occurs after a small displacement of the free end of the geotextile. At the peak pull-out force, the maximum shear stress occurs near the free end of the geotextile while the shear stress at the loaded end is at or near a residual value. The use of an average interface friction angle overestimates pull-out resistance. The numerical technique developed in this paper provides more accurate values for soil-geotextile interface friction parameters.

Railway track subgrade failure induced by climate related softening, may lead to unplanned maintenance costs and consequential and costly train delays. The softening process can be due to the presence of water in the upper parts of the track foundation due to inadequate drainage system or poorly maintained railway track drainage. In order to better make use of scarce resources and plan railway track and associated drainage maintenance rationally it would be helpful to better understand and quantify the relationships between the causes of poor subgrade and the railway track drainage system. The understanding of railway track drainage associated failure can be further used to infer engineering knowledge into railway performance models and associated risk analysis methodologies.To this end, this paper describes the development of a fault tree analysis approach which considers the failure mode(s) for railway track subgrade.The fault chart has been developed in two stages, in the first stage, failure mechanisms are diagnosed utilizing a cause-effect diagram, and in the second stage a fault tree analysis (FTA) is performed.

Investigations and research into the recent use of rubber particles in concrete has been well documented. However, information on the rubber particle sizes or their distributions within concrete which may also influence the concrete properties is still limited. In this study, three groups of singly-sized rubber particle samples (3 mm, 0.5 mm and 0.3 mm) and one sample of continuous size grading (prepared by blending the three singly-sized samples to form the same particle distribution curve of sand) were used to replace 20% of the natural fine aggregate by volume. The reference concrete containing 100% sand was also prepared to

Stiffness of the railway subgrade is a signi®cant 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.

Link to publication on Research at Birmingham portal General rights Unless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or the copyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposes permitted by law. • Users may freely distribute the URL that is used to identify this publication. • Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of private study or non-commercial research. • User may use extracts from the document in line with the concept of 'fair dealing' under the Copyright, Designs and Patents Act 1988 (?) • Users may not further distribute the material nor use it for the purposes of commercial gain. Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Link to publication on Research at Birmingham portal General rights Unless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or the copyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposes permitted by law. • Users may freely distribute the URL that is used to identify this publication. • Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of private study or non-commercial research. • User may use extracts from the document in line with the concept of 'fair dealing' under the Copyright, Designs and Patents Act 1988 (?) • Users may not further distribute the material nor use it for the purposes of commercial gain. Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Although research has found that using rubber in concrete will enhance its resilience and reduce its density, the significant loss of strength owing to lack of bonding has remained unresolved. This study considers how to minimise the loss of strength of concrete with used rubber tyre crumb aggregates and investigates the improvement of water permeability resistance that may consequentially develop. A surface of rubber crumb was modified by soaking in the saturated sodium hydroxide solution or silane coupling agent (SCA) before using. Up to 20% of natural fine aggregate was volumetrically replaced with treated rubber crumb. Experimental results show higher compressive and flexural strengths, Young's modulus and water permeability resistance from the samples with SCA-treated rubber than with as-received or sodium-hydroxide-treated rubber. X-ray diffraction pattern analyses indicate almost no change in crystalline phase for the rubber surface modification. Microscopic inspections s...

Fundamental differences exist with respect to soil types formed under temperate and tropical climatic conditions. Their use for road pavement designs will require methods which take into account their behaviour in these distinct climate zones. Road pavement design with the respective soil material will therefore require different approaches. The adoption of temperatebased empirical pavement design systems for tropical pavement design parameters is inappropriate because the underlying assumptions do not reflect tropical conditions. At the other extreme of pavement design is the mechanistic approach. A hybrid method is the mechanistic-empirical (ME) method where empirical models are used to fill in the gaps between the mechanics and the performance of the pavement. This paper presents a rational approach in the application of ME pavement design principles to evolve a design framework which takes into account tropical conditions using Ghana as a case study.

Sewage Sludge Ash (SSA) use in concrete related applications is assessed through systematic review involving analysis and evaluation of the global literature found published since 1983. The material characteristics indicate potential for various applications: in small dosages as raw feed in Portland cement production, as fine and filler aggregates, or in ground form as cement component, with manageable effects on performance. Using manufactured SSA aggregate, concrete strength suitable for structural applications and lightweight properties comparable to Leca are attainable. SSA can be used in bulk, in controlled low strength materials (CLSM), aerated and foamed concretes. Reported case studies give encouraging signals.

One of the legacies of the coal mining industry is the existence of numerous colliery spoil mounds. Run-off waters from some of these mounds result in oxidation of sulphur compounds causing pH to drop to perhaps as low as 2.5. At this pH, mobility for metals increases and it results in destruction of both flora and fauna. In order to reduce acidity, a number of solutions have been investigated with varying degree of success. A recent study to reduce acidity in spoil run-off water included the use of Basic Oxygen Steel slag. Its slow release of lime resulted in longer term remediation compared with other techniques. In addition to this, steel slag contains elements which are essential for plant growth and can be regarded as a weak fertiliser. This was substantiated in two field trials, which had the aim of not only remediating acidity from two different types of colliery spoils, but also to develop a composition that supports grass growth. The objectives were achieved at both sites a...

Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

This study presents an analysis of a 30 000 strong data matrix derived from 227 studies originating from 35 countries since 1968. Similar to the fly ash effect, the carbonation of concrete increases with the incorporation of ground granulated blast-furnace slag (GGBS), but the rate increases as GGBS content is increased. This effect is greater for concrete designed on an equal water/cement (w/c) basis to the corresponding Portland cement (PC) concrete than on an equal strength basis. The Eurocode 2 specification for XC3 carbonation exposure in terms of the characteristic cube strength of concrete (or its w/c ratio) may need to be increased (or decreased) with the addition of GGBS. Other influencing factors, including GGBS fineness, total cement content and curing, were also investigated. In some cases, the carbonation of in-service GGBS concrete has been estimated to exceed the specified cover before 50 years of service life. Measures to minimise the carbonation of GGBS concrete are...

The deformation behaviour of cement-bentonite (CB) materials used in low-permeability cut-off walls is critical to the performance of these barriers on site. While a number of investigations have focused on the deformation behaviour of CB materials, it is suggested that insufficient knowledge has been generated to allow for the determination of the behaviour of a CB wall on site with confidence. This paper reviews the deformation behaviour of other cemented particulate systems commonly encountered in civil engineering, concrete, rock, clays and cemented soils, and compares it with CB response to determine if the greater research effort associated with these materials could be used to improve understanding of CB. It is concluded that a direct comparison of physical behaviour between these materials is problematic due to the differences observed. Furthermore, formation of microcracks before the peak strength in cemented materials (rocks, etc.) is an area that does not appear to have b...

Link to publication on Research at Birmingham portal General rights Unless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or the copyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposes permitted by law. • Users may freely distribute the URL that is used to identify this publication. • Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of private study or non-commercial research. • User may use extracts from the document in line with the concept of 'fair dealing' under the Copyright, Designs and Patents Act 1988 (?) • Users may not further distribute the material nor use it for the purposes of commercial gain. Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Extraction of resources in remote locations can require temporary haul roads to transport extremely large, slow-moving, indivisible loads (e.g., plant, oil–gas production modules, and reactors, weighing in excess of 1000 t) without interruptions. Poor subgrade soils may experience larger cyclic strains and greater cyclic degradation under these conditions than under conventional roads, yet the short engineering life precludes many foundation-strengthening options due to cost. As there is little research into this unique situation, this paper synthesizes research from a broad range of applications to discuss implications on expected soil response. Reference is made to critical state theory and discrete element method (DEM) modelling to develop fundamental concepts considering particle-scale interactions. Cyclic failure is proposed to be a kinematically unstable process, triggered by shear banding on the Hvorslev surface, tensile liquefaction or fabric-governed meta-stable liquefactio...

Plastic represents an environmental issue, as only 7% of it is recycled. The plastic remaining 9 is either burned, disposed of in an uncontrolled manner or landfilled. Thus, in order to 10 reduce the quantity of plastic which is disposed of, there is a need to increase the amount of 11 the material which enters various product streams. This includes its use in the construction 12 industry, and more particularly in concrete, which utilises very large quantities of aggregate. 13 A novel aggregate (RPA) comprising recycled plastic was developed. The aggregate 14 produced was lightweight, with a density ranging from 510 to 750k kg/m 3 and absorption of from 2.7 to 9.81%. Other properties were comparable to aggregates of similar densities. Various composition RPA was used in concrete and the resulting properties of both fresh and cured concrete were measured. For a given w/c ratio, it was possible to achieve slump of between 40 and 220 mm and fresh density of between 1827 and 2055 kg/m 3. Further, 28-day strengths of between 14 and 18 MPa were achieved. Flexural strength was also measured. SEM analysis was undertaken to view the structure of the aggregate and the interface between the RPA and the cement matrix.

Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

This paper presents analysis and evaluation of experimental results of chloride ingress and chloride-induced corrosion resistance of concrete made with Portland limestone cement (PLC). The results were mined from 169 globally published studies from 32 countries since 1989, yielding a matrix of 20 500 data points. This study showed that chloride ingress in concrete increases with increasing limestone (LS) content, within the range permitted in BS EN 197-1:2011. However, this effect is less for PLC concrete mixes designed for strength equal to corresponding Portland cement (PC) concrete mixes than those designed on an equal water/cement (w/c) basis. The results also showed that Eurocode 2 specifications for chloride exposure, in terms of characteristic cube strength of concrete or w/c ratio, may need to be reviewed for the use of LS with PC. This study also investigated other influencing factors such as cement content, LS fineness, the method of producing PLC, aggregate volume content...