The following are summaries of papers published in other parts of ICE Proceedings during 2007 that readers of Municipal Engineer may find of interest. Summaries of all papers in ICE journals are freely available and fully searchable at the ‘journals online’ section of the ICE website. See www.ice.org.uk/journals for details.
Garyllis River Footbridge—harmonising engineering and architectural features
A. D. Toumazis
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 160, No. 1, March, 1–7, doi: 10.1680/bren.2007.160.1.1
This paper describes the design development of a low-cost pedestrian and cycle bridge recently constructed across Garyllis River in Limassol, Cyprus. Three identical trusses provide the basic span crossing, and the top and bottom geometrical shape of each truss is parabolic. The slabs spanning the curved top members of the trusses form the pedestrian crossing while the beams extending as cantilevers on either side of the curved bottom members provide support for the two cycle paths. The central truss is vertical while the tops of the two side trusses are inclined inwards. This configuration produces a gently curved cycle path and a narrowing and then widening central footpath. It also causes the cycle paths to have an inward slope and the footpath to have an outward slope, thus improving the feeling of safety.
Probability-based bridge assessment
A. O’Connor and I. Enevoldsen
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 160, No. 3, September, 129–137, doi: 10.1680/bren.2007.160.3.129
This paper describes the application of the newly developed Danish guideline for probability-based assessment of bridges to a beam and slab bridge that was built in 1935 and is located outside Copenhagen. The guideline, published by the Danish Roads Directorate in 2004, reflects a commitment to consider probability-based assessment for all bridge structures that have failed a deterministic assessment. For the structure analysed, modelling of the critical limit states is presented as are the statistical techniques employed in modelling the loads and resistances. The overall aim of the analysis was to achieve a higher load rating for the structure than that resulting from a traditional deterministic analysis. Ultimately the cost benefits to bridge owners/managers of performing a probabilistic assessment are apparent from the results, which provide a higher load rating for the bridge than were achieved through deterministic assessment. Although the guideline is intended to be applied in probability-based assessment of Danish bridges it is anticipated that it could equally be applied in other countries.
The real service life of road bridges
H.-Å. Mattsson and H. Sundquist
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 160, No. 4, December, 173–179, doi: 10.1680/bren.2007.160.4.173
Bridges form an important part of a nation’s road system and require large capital investment. The number of bridges in a nation’s bridge stock is seldom constant from one year to another as new bridges are built and old structures are demolished. This paper, based on a case study of 1170 bridges demolished in Sweden during a 15-year period (1990–2005), describes the real life span for various types of road bridges. The major reasons for demolition of bridges are addressed and survival analysis for different types of road bridges is introduced.
Site-specific traffic load modelling for bridge assessment
A. O’Connor and E. M. Eichinger
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 160, No. 4, December, 185–194, doi: 10.1680/bren.2007.160.4.185
Assessment of highway bridge structures requires accurate prediction of the load effects that a structure may be expected to resist during its required remaining life. Generally, these load effects are determined from codified models more appropriate to design than assessment. This approach is very conservative for existing structures as it fails to fully recognise the reduced level of uncertainty associated with evaluation of (a) the loads to which an existing structure is subjected and (b) the resistance that an existing structure provides. This paper proposes a more rational approach to load effect prediction for existing structures. In the approach the actual traffic loading to which a structure is subjected is measured on site and is employed in simulation to determine site-specific characteristic load effects. The methodology proposed is dependent upon the availability of unbiased site-specific traffic statistics. This paper presents the results of an experiment performed in Vienna and describes the use of weigh-in-motion (WIM) statistics in the prediction of site-specific characteristic load effects—that is, values with specified probability of exceedance during the required lifetime of the structure, against which the structure may be assessed. The advantage of the approach is demonstrated through reductions in the load effect values. The implication for bridge assessment is reduced rehabilitation costs and the avoidance of unnecessary replacement of serviceable highway structures.
Delivering value in public sector construction
J. Stonehouse
Proceedings of the Institution of Civil Engineers, Civil Engineering, 160, No. 1, February, 13, doi: 10.1680/cien.2007.160.1.13
The UK Government currently spends around £33 billion each year on civil engineering and building works. Jennifer Stonehouse of the Office of Government Commerce reports on the first year of the Public Sector Construction Clients Forum, which was created to ensure the public gets value for money.
From securing to procuring our future
Q. Leiper and C. Pepper
Proceedings of the Institution of Civil Engineers, Civil Engineering, 160, No. 1, February, 14, doi: 10.1680/cien.2007.160.1.14
Last summer the Sustainable Procurement Task Force challenged the UK Government to apply the principles of its sustainable development policy to its own procurement. Quentin Leiper and Chrissie Pepper of ICE say there is a real opportunity here for civil engineers to demonstrate leadership.
Managing the inner world of infrastructure
M. Abbott
Proceedings of the Institution of Civil Engineers, Civil Engineering, 160, No. 1, February, 26–32, doi: 10.1680/cien.2007.160.1.26
Stakeholder participation in major infrastructure projects is a multi-faceted and controversial topic. This paper introduces some of the more immediate issues and attempts to show that experience in so-called first-world projects is equally relevant in the third world. It suggests that every project exists in an ‘outer’ physical world and an ‘inner’ world of the collective minds of stakeholders, and that the creation of a communications environment in which the two worlds can begin to align is essential to success. This is now increasingly possible thanks to the internet and mobile telephony and, as demonstrated by experiences on the £6 billion Denmark–Sweden fixed link, it can lead to an almost utopian working environment of complete trust and absolute integrity.
Intelligent travel: planning for the revolution
W. Stewart
Proceedings of the Institution of Civil Engineers, Civil Engineering, 160, No. 1, February, 39–42, doi: 10.1680/cien.2007.160.1.39
This paper describes the 50-year view by the UK Government’s Foresight programme of the future of intelligent transport infrastructure, its implications and its social context. By 2055, it is envisaged that intelligence and pervasive information will be built in to everyday life, encompassing needs to communicate and travel. People will better understand the resource implications as well as the direct costs of their lifestyles—and perhaps they will actually travel less. However, given the slow speed at which infrastructure systems adapt, the research concluded that civil engineers need to start planning now for the inevitable travel revolution. The paper is based on the author’s 2006 Unwin lecture, delivered to the Institution of Civil Engineers and Institution of Mechanical Engineers on 6 April 2006, prepared with Phil Blythe of Newcastle University.
Solving the puzzle of Britain’s underground assets
J. Brayshaw
Proceedings of the Institution of Civil Engineers, Civil Engineering, 160, No. 2, May, 52, doi: 10.1680/cien.2007.160.2.52
The UK’s National Underground Asset Group was launched two years ago to coordinate and share data on the country’s vast and inconsistently charted network of buried services. ICE’s representative on the Group, James Brayshaw of Ordnance Survey, provides an update.
A clearer vision for pedestrian guardrails
D. Stewart
Proceedings of the Institution of Civil Engineers, Civil Engineering, 160, No. 3, August, 131–136, doi: 10.1680/cien.2007.160.3.131
Pedestrian guardrails have been used increasingly on Britain’s streets since the 1930s, but their value is now being questioned by planners in the light of the new trend of reducing street furniture. This paper disputes claims that guardrail removal enhances safety by presenting evidence of the large reductions in casualties after erection of guardrails, particularly those that do not block visibility. Chronic lack of research is highlighted, with particular reference to visibility and its inadequate treatment in design standards. Deterrence of diagonal crossing is identified as a prime reason why guardrails are so successful in preventing pedestrian accidents, which clarifies how they can be used most effectively. Recent work to improve the design of guardrails is also outlined.
Atlantis: a new joined-up world for flood and water engineers
J. Brayshaw and K. Murray
Proceedings of the Institution of Civil Engineers, Civil Engineering, 160, No. 4 November, 149 doi: 10.1680/cien.2007.160.4.149
Civil engineers designing flood defence and water-quality schemes in Britain could soon benefit significantly from a nationwide data-interoperability initiative called Atlantis.
Mechanical properties of cement-bound recycled pavements
M. Katsakou and S. Kolias
Proceedings of the Institution of Civil Engineers, Construction Materials, 160, No. 4, November, 171–179, doi: 10.1680/coma.2007.160.4.171
Tensile (uniaxial and flexural) and compressive (uniaxial cube and equivalent cube) tests were carried out on mixtures of crushed aggregates and milled bituminous materials with proportions by mass 100/0, 75/25, 50/50, 25/75, 0/100, respectively. All mixtures were bound with 3 or 5% by mass (b.m.) cement and 5·2% b.m. water. Strength and modulus of elasticity were determined for one-day- and 60-day-old specimens. It was found that this type of recycled materials forms a generation of new materials with different and enhanced properties in comparison with ordinary cement-bound granular materials. Both strength and modulus of elasticity decreased as the proportion of milled bituminous material in the mix increased. However, the rate of decrease of the tensile strength was lower than that of the corresponding compressive strength and similarly the rate of decrease of the modulus of elasticity was lower than that of the corresponding strength. For each mix proportion a different relationship existed between compressive strength and tensile strength and between tensile strength and the corresponding modulus of elasticity.
Using X-ray computed tomography to study paving materials
K. Gopalakrishnan, H. Ceylan and F. Inanc
Proceedings of the Institution of Civil Engineers, Construction Materials, 160, No. 1, February, 15–23, doi: 10.1680/coma.2007.160.1.15
X-ray computed tomography, a non-destructive three-dimensional imaging tool, has been very helpful in medical diagnosis since the first commercial tomographs were constructed in 1973. In recent years it has gained increasing applications in civil engineering materials research. Several investigators have illustrated the use of computed tomography scans for the non-destructive evaluation of soils and have shown promising applications in characterisation, modelling and computational simulation to optimise asphalt concrete mix design, predict performance and conduct investigative forensic studies. This paper provides a detailed review of X-ray computed tomography applications in characterizing asphalt concrete and also describes preliminary studies conducted at the Center for Nondestructive Evaluation (CNDE) at Iowa State University for characterizing asphalt and concrete materials using X-ray microcomputed tomography or micro-computed tomography. Researchers are currently using the advanced imaging facilities available at the CNDE to develop a deeper understanding of the pavement internal structure, to develop and optimise the various parameters that describe the internal structure and to relate them to the performance of pavements in a scientific way. This will provide the foundations for building more durable and long-lasting transportation infrastructure systems.
Integrity of ductile iron pipe installed by horizontal drilling
S. T. Ariaratnam Bonds and D. W. Crabtree
Proceedings of the Institution of Civil Engineers, Construction Materials, 160, No. 2, May, 75–80, doi: 10.1680/coma.2007.160.2.75
The introduction of restrained joint ductile iron is rapidly gaining acceptance as an alternative pipe material for municipal engineering applications using horizontal directional drilling. The boltless restrained connection offers flexibility, ease of assembly, and positive restraint against endwise axial separation due to pulling during trenchless installations. This paper discusses the results of a field testing programme to evaluate the performance of restrained joint ductile iron pipe installed by horizontal directional drilling. The main area of concern is the potential corrosive effects on the pipe from the bentonite-based drilling fluid used in the installation. The research involved assessment of the installation durability and effectiveness of two combinations of externally applied, loose wrapped, polyethylene encasement to provide a protective barrier. Observations found that employing 0.02 mm linear low-density polyethylene encasement provided excellent protection to the ductile iron pipe against corrosion from drilling fluid and soils with low resistivities.
Greywater recycling: treatment options and applications
M. Pidou, F. A. Memon, T. Stephenson, B. Jefferson and P. Jeffrey
Proceedings of the Institution of Civil Engineers, Engineering Sustainability, 160, No. 3, September, 119–131, doi: 10.1680/ensu.2007.160.3.119
Wastewater is an immense resource that could find significant applications in regions of water scarcity. Greywater has particular advantages in that it is a large source with a low organic content. Through critical analysis of data from existing greywater recycling applications, this paper presents a review of existing technologies and applications by collating a disparate information base and comparing/contrasting the strengths and weaknesses of different approaches. Simple technologies and sand filters have been shown to have a limited effect on greywater; membranes are reported to provide good solids removal but cannot efficiently tackle the organic fraction. Alternatively, biological and extensive schemes achieve a good general treatment of greywater with particularly effective removal of organics. The best overall performances were observed within schemes that combine different types of methods to ensure effective treatment of all the fractions.
Thermal waste treatment for sustainable energy
C. Ryu, V. N. Sharif and J. Swithenbank
Proceedings of the Institution of Civil Engineers, Engineering Sustainability, 160, No. 3, September, 133–140, doi: 10.1680/ensu.2007.160.3.133
Waste disposal, energy production and pollution minimisation are key problems that must be addressed for sustainable cities of the future. In a world with finite resources witnessing a population explosion, much effort is being made to change the way in which developed societies consume energy and materials and dispose of waste. This paper reviews the current UK practices of segregation and treatment of municipal solid waste (MSW) with focus on advanced thermal treatment technologies. MSW is segregated either at source or at dedicated facilities across the country. The residues of waste segregation can be thermally treated for energy recovery. Direct incineration of unsorted waste is currently the main route practiced by the energy from waste (EfW) industry. Typical MSW incinerators can burn wastes with a wide range of calorific values without any waste pre-processing. However, these incineration systems have low energy efficiency and suffer from unfavourable public opinion. Consequently, gas clean-up technologies associated with waste incinerators have been developed further, especially for dioxin removal and fly ash treatment. The two main alternatives to incineration are gasification of pre-processed waste and production of solid recovered fuel (SRF) from mechanical and biological treatment (MBT). Both processes have potentially higher energy efficiencies than incineration and more flexibility in the use of primary products. Further technology developments with regulatory drivers are required to compete with incineration. Another route available for EfW is pyrolysis, producing cheap and storable fuel products. Pyrolysis is suitable only for specific types of waste material. Pyrolysis of waste wood can produce a good-quality char that can be readily burned in coal-fired power plants or other higher energy efficiency thermal systems.
Speed and reloading effects on pavement rutting
L. Korkiala-Tannttu
Proceedings of the Institution of Civil Engineers, Geotechnical Engineering, 160, No. 3, July, 123–127, doi: 10.1680/geng.2007.160.3.123
This paper concentrates on two factors that affect the permanent deformation (rutting) of unbound pavement layers. These factors are the loading speed and stress history. The loading speed has a simultaneous two-way effect: the permanent response of the unbound material itself, and the change in the stress state depending on the resilient properties of the upper-bound layers. The modelled examples show that the dominating factor in the speed effect is the change in stress state due to the change in the resilient properties of the bound layers, whereas the speed effects on the unbound material itself have a smaller role. In addition, the effect of loading speed depends greatly on the temperature, varying from 10–15% at 10°C to 20–25% at 25°C. The measured effects can be estimated reasonably well with modelling. Unloading–reloading cycles at various load levels have little effect on the permanent deformation. The effect is usually so small that it can be neglected in calculations, but the preloading history itself has a clear effect on the permanent deformation.
Static equilibrium bays in coast protection
S. P. Herrington, B. Li and S. Brooks
Proceedings of the Institution of Civil Engineers, Maritime Engineering, 160, No. 2, June, 47–55, doi: 10.1680/maen.2007.160.2.47
As part of the 2004 Hythe to Folkestone Harbour coast protection scheme, two static equilibrium bays were formed using rock headland structures and shingle imported as part of the beach renourishment phase of the scheme. The development of this element of the scheme and the appraisal process that led to these bay forms being chosen as the most appropriate form of coast protection are discussed. The performance of the bays has been continually monitored since their construction and the measured plan-shape of each bay has been compared with the theoretical predictions. This has shown that there is good agreement between the crenular plan forms predicted by the mathematical models and the theoretical methods, which are founded on the log-spiral curve that has been shown to represent the crenular plan form of naturally formed bays. Observations based on the survey data collected over the 20 months since the completion of the scheme have shown that the measured plan form is in relatively good agreement with the theoretical predictions. The bays do, however, exhibit distinct yet small differences from the theoretical form, but nevertheless are approaching an equilibrium state
Integrating environmental issues in estuary flood plans
T. Matthewson
Proceedings of the Institution of Civil Engineers, Maritime Engineering, 160, No. 3, September, 105–111, doi: 10.1680/maen.2007.160.3.105
The Humber Estuary is designated at national and international levels on account of its importance for the conservation, among other things, of estuarine habitats and the wildlife these support. The estuary and its floodplain also contain major industry and ports, and important historic buildings, settlements, landscapes and archaeological sites. Since the mid-1990s the Environment Agency has been developing a strategy for managing the Humber Estuary’s flood defences for the next 100 years, culminating in the publication in August 2005 of works proposed for the first five years of this period. Environmental considerations have been integrated into the decision making throughout this development process, from high-level strategy planning through to detailed selection of options at specific locations. This has been achieved by a series of ‘tiered’ environmental appraisals, with the type and level of analysis reflecting the stage of flood risk management. The flood risk management planning has been especially effective at integrating wildlife conservation within its development; indeed the impact on important natural habitats has been a major driver for the selection of the preferred approach. In future projects of this scale, a similar focus may be required on other aspects of the environment to ensure all aspects of sustainability are addressed.
Implementation and implications of Water Framework Directive
J. Brooke, Consultant, Peterborough, UK
Proceedings of the Institution of Civil Engineers, Maritime Engineering, 160, No. 4, December, 139–141, doi: 10.1680/maen.2007.160.4.139
The European Union (EU) Water Framework Directive (WFD), which was transposed into law in most member states in 2003, introduces a new, integrated regime of protection, improvement and management to all water bodies. These include rivers and canals, coastal and estuarine waters and, in some countries, large marine areas. The WFD also aims to prevent further deterioration in water status and to reduce or phase out pollution from certain named ‘priority and priority hazardous substances’ (these are being identified as part of the process of agreeing a separate ‘daughter Directive’ to the WFD). Another key objective of the WFD is to ensure that water bodies reach ‘good status’ by the end of 2015. Reaching good status requires not only chemical but also new ecological targets to be met. Implementation of this ambitious Directive is continuing apace in both the UK and at EU level. Stakeholder participation is a key element of the provisions of the Directive and the navigation sector is ensuring that it gets involved in this process at all levels. This briefing note provides a short overview of these activities.
Modelling faecal bacteria pathways in receiving waters
I. Schnauder, B. Bockelmann-Evans and B. Lin
Proceedings of the Institution of Civil Engineers, Maritime Engineering, 160, No.4, December, 143-153, doi: 10.1680/maen.2007.160.4.143
The two-dimensional finite-volume model ‘Hemat’ was refined to model the pathways, fate and decay factors of faecal indicator organisms for an integrated river and coastal basin water system. The numerical model was developed, calibrated and tested by modelling faecal indicator organism inputs from river sources. A comprehensive field data set was available including intensive offshore survey data collected during a two-week period; these were used as a time series for the verification of the hydrodynamic model. River discharges and water quality data were used as boundary and initial conditions for the model. The impact of alternative land-use management strategies on the water quality of the receiving estuarine and coastal waters was investigated by modelling a series of 14 scenarios. Generally, the model results show that the faecal indicator organism input from point sources of sewage effluent dominated during dry weather and base flow conditions. On the other hand, riverine sources (such as diffuse catchment sources) significantly dominated the concentrations in the bay both during and after rainfall events. Finally, it was found that a reduction in land used for animal husbandry can considerably reduce the critical peak concentration occurring after heavy rainfall events.
Realignment in low-lying coastal areas: UK experiences
N. I. Pontee
Proceedings of the Institution of Civil Engineers, Maritime Engineering, 160, No.4, December, 155-166, doi: 10.1680/maen.2007.160.4.155
The present paper reviews the context of realignment in the UK from both a coastal process and policy context, and explains the approaches that can be adopted to implement realignment. A number of case studies are then presented covering both estuarine managed realignment schemes involving the removal of flood embankments; and natural barriers beaches where realignment is likely. The paper demonstrates that while realignment leads to more natural coasts, such approaches are not without their disadvantages. The breaching of coastal defences, be they natural or man- made, has environmental, social and economic implications. Although policies involving realignment might be the most sustainable solutions in theory, this does not mean that they will be immediately embraced by the public, when they have come to expect continued flood protection. It is suggested that the promulgation of policies involving realignment requires a number of elements including increasing public awareness of coastal change, floodproofing properties, providing temporary defence measures, restricting the development of new properties and considering governmental compensation for affected home owners.
How infrastructure procurement can enhance social development
J. Hawkins and J. Wells
Proceedings of the Institution of Civil Engineers, Management, Procurement and Law, 160, No. 1, February, 33–38, doi: 10.1680/mpal.2007.160.1.33
This paper reports the findings of a study by Engineers Against Poverty and the Institution of Civil Engineers into the factors in infrastructure procurement that are currently inhibiting the achievement of social development objectives. The paper explores the impact/performance of the asset and the service it delivers (the product), and the opportunities during the project’s construction and operation (the process). The study adopted a very broad definition of ‘procurement’ to embrace all stages from project identification to the final monitoring, enforcement and evaluation. Methods included reviews of procurement documentation and practice in four case-study countries (India, Indonesia, Kenya and Nigeria), round-table discussions and in-depth interviews with stakeholders. This yielded a long list of inhibiting factors but also some encouraging efforts at reform. The paper concludes that procurement procedures and contract agreement have the potential to promote social objectives. However, the objectives should be clearly identified in the project design; the budget and procurement strategy have to be appropriate; and implementation must be monitored and enforced.
The Public Contracts Regulations 2006
R. Williams
Proceedings of the Institution of Civil Engineers, Management, Procurement and Law, 160, No. 2, May, 45–49, doi: 10.1680/mpal.2007.160.2.45
The procurement of work, goods and services by public authorities is subject to a new EU Directive and new implementing Regulations in the UK. The aim of the new laws is to bring the legislative framework into line with practical developments in procurement and new European case law. The changes are also intended to simplify the law for lawyers and construction professionals alike. Have the new Regulations achieved these aims? This briefing suggests that the answer is a qualified yes, and explains some of the most important changes brought about by the new laws.
The psychology of managing project cost
T. Aikens
Proceedings of the Institution of Civil Engineers, Management, Procurement and Law, 160, No. 2, May, 51–53, doi: 10.1680/mpal.2007.160.2.51
Managing cost is an integral part of any engineering project. The impact of overspending can be significant in both private and public sectors. Despite better cost management systems and training, major projects are still suffering large cost overruns. In this article, the author examines the impact of how we think and the project environment on how we manage cost. From the early profit motive, or budget ceiling, to the delivery pressure during construction, managers are often pushed either to reduce budgets or spend unwisely. Contracts such as rates-based design can encourage the wrong behaviours and increase cost dramatically. There is no single answer. We need to consider how our thoughts affect our behaviour and look at the bigger picture of the overall (business) project beyond a shortterm cost issue. Communication is how we convey are thoughts, so needless to say it is vital to effective cost management.
Lateral position of traffic negotiating horizontal bends
B. Gunay and D. Woodward
Proceedings of the Institution of Civil Engineers, Transport, 160, No. 1, February, 1–11, doi: 10.1680/tran.2007.160.1.11
The lateral position of vehicles at horizontal curves and roundabout circles has been studied, and it has been observed that drivers tend to straighten their travel path as much as possible when negotiating these bends in a corner-cutting fashion. In addition to skid resistance loss, this behaviour results in the early scuffing and removal of road markings. Preliminary data were collected in Northern Ireland at eight different sites over 15 lanes in total. It was found that the expected geometrical location of the wheel path is not the same as the actual observed location at certain sections of highways. On horizontal curves, the most travelled wheel path is shifted towards the convex side of the curve, and this shift increases with decreasing radius, such as at roundabouts, where it reaches a maximum displacement. This shift was about 140 cm in the outer circles of roundabouts and about 60 cm in the inner circles. For horizontal curves the figure was in the region of 30–40 cm.
Traffic-flow impact of toll booths on M50 motorway, Dublin
M. Rogers and S. Darcy
Proceedings of the Institution of Civil Engineers, Transport, 160, No. 1, February, 13–17, doi: 10.1680/tran.2007.160.1.13
The M50 was opened to traffic in 1990. In the intervening years the daily volumes have increased dramatically, and are predicted to exceed 90 000 by 2006. In recent times the motorway has been repeatedly congested, both during weekdays and at weekends. There is at present a perception among motorists, reinforced by political and media comment, that existing delays and congestion along the M50 are caused primarily by the operation of the toll booths at the West-Link toll bridge, located at the centre point of Dublin’s M50 C-Ring motorway. This paper examines the validity of this assertion, and highlights other capacity constraints within the link that may provide more plausible and technically robust explanations for the delays experienced by motorists in the vicinity of the toll plaza.
Improving a gypsum sand roadbed soil by increased compaction
S. S. Razouki and A. N. Ibrahim
Proceedings of the Institution of Civil Engineers, Transport, 160, No. 1, February, 27–31, doi: 10.1680/tran.2007.160.1.21
A silty sand of the SM group according to the Unified Soil Classification System and of the A-1-b group according to the American Association of State Highway and Transportation Officials (AASHTO) soil classification system, with about 28% gypsum content, was tested in the laboratory for California Bearing Ratio (CBR) under four different compaction efforts. Twenty-four pairs of CBR soil samples were completed at the optimum moisture content derived from a modified AASHTO compaction test. To achieve different compaction efforts, four groups, each of six pairs of samples, were compacted using 10, 30, 50 and 70 blows per layer respectively. The individual pairs in each group were then soaked for different periods of time—4, 7, 15, 30, 60 and 120 days—while subject to a surcharge load of 40 lbf (178 N). The CBR test results show the significant effect of compaction effort on CBR value. An increase in soaking period causes a significant decrease in the CBR for each degree of compaction effort. Samples made under low compaction efforts are affected more by soaking than those made under high compaction efforts.
Travel patterns of three distinct driver age groups in Greece
I. Spyropoulou, E. Papadimitriou, G. Yannis and J. Golias
Proceedings of the Institution of Civil Engineers, Transport, 160, No.3, August, 117–124, doi: 10.1680/tran.2007.160.3.117
Within this research the travel patterns of passenger car drivers are investigated in relation to their age, as recorded from a national travel survey conducted in Greece. For the needs of this research drivers are classified into three mutually exclusive age groups: young (18–24), adult (25–64) and elderly (65p). The mobility of these three driver groups—expressed in terms of average annual distance driven—is then investigated with respect to parameters involving driver characteristics (experience, gender), vehicle characteristics (engine size) and the nature of the trip (time of trip and road type). Several patterns are analysed, and the dependence of the various travel patterns on driver age is tested through analysis of variance (ANOVA), mainly by the use of the Welch test. The results show that driver experience is not an influencing factor for driver mobility, whereas driver gender and vehicle characteristics, such as engine size, are. Furthermore, the results illustrate dependences between driver age and driving at night and during the weekends, highlighting the relationship between driver age and trip purpose. The distribution of mobility across the different road types does not reveal any interactions with driver age; however, specific trends are detected when distance driven is also segregated into weekday and weekend categories, indicating a relationship between driver age and mobility in relation to type of day.
Identification of potential highways maintenance schemes
T. J. Brownlee, S. Finnie and D. Wightman
Proceedings of the Institution of Civil Engineers, Transport, 160, No.3, August, 139–146, doi: 10.1680/tran.2007.160.3.139
This paper presents a methodology for identifying potential pavement maintenance schemes from machine survey data. Highways authorities make maintenance decisions based on a number of factors; condition data is a common starting point. However, there are currently no universally accepted techniques for ranking subsections by condition, based on the comparison of data from multiple condition assessment surveys. The methodology presented in this paper utilises condition data that have been captured from standard machine-based condition assessment surveys—specifically TRACS (traffic-speed road assessment condition survey), deflectograph and SCRIM (sideways force coefficient routine investigation machine). The resultant data are analysed using a multi-criteria analysis (MCA) technique known as TOPSIS (the technique for order preference by similarity to the ideal solution). This technique is capable of investigating a number of alternative solutions. The road subsections within the data set are prioritised in terms of their condition relative to each other. The road subsections exhibiting the worst condition can then be highlighted and, according to their geographical proximity, potential schemes can be identified.
Comparison of noise impacts from urban transport
M. Frost and S. Ison
Proceedings of the Institution of Civil Engineers, Transport, 160, No.4, November, 165–172, doi: 10.1680/tran.2007.160.4.165
When new transport schemes are considered, a key issue is the potential impact of noise. The reaction of people to noise however is both personal and subjective. Whereas all types of new urban transport scheme have noise evaluations, little work has been undertaken to date to compare the noise generated by the different modes of transport namely, a tram, car, bus and guided bus. The lack of such evaluations has implications for scheme perception when new modes are introduced, and such comparisons frequently form part of the public debate when systems are proposed. This paper outlines the assessment of noise and its measurement, reviews the limited published comparisons between modes and presents the results of an extensive series of noise measurements of in-service trams, buses and cars, (taken mainly within the Greater Nottingham area). The measurements have been made across a range of similar operational circumstances to allow comparison between the relative noise of particular modes. The paper concludes that from measurement across operational circumstances there should be little perceived difference in noise from buses and trams, but that proportionately cars can generate significant emissions.
Biodegradable municipal solid waste: biotreatment options
C. J. Banks and E. I. Stentiford
Proceedings of the Institution of Civil Engineers, Waste and Resource Management, 160, No. 1, February, 11–18, doi: 10.1680/warm.2007.160.1.11
The context under which the UK Government plans to divert biodegradable municipal solid waste from landfill described and the role that bioprocessing may play is presented. The concepts developed from different types anaerobic processes and the differing possible process configurations are considered. The most commonly used options are then appraised on the basis of technical engineering operation and microbiological functionality. Some practical examples of system types are given, although these are not based on case studies. The long history of waste composting (aerobic bioprocessing) has meant that there are a large number of process systems on offer. The fundamentals behind the different types of process are considered, focusing on their overall aim of achieving sanitisation and stabilisation. The interrelationships between the key factors of particle size, aeration, nutrients and moisture content are considered together with how each of the generic systems seeks to manage them.
The South Shropshire biowaste digester, UK
M. Chesshire
Proceedings of the Institution of Civil Engineers, Waste and Resource Management, 160, No. 1, February, 19–26, doi: 10.1680/warm.2007.160.1.19
The South Shropshire biowaste digester is designed to recycle 5000 t per year of source-segregated household kitchen waste and green garden waste. This waste, collected at the kerbside, is transformed into renewable electricity and biofertiliser. It is one of nine full-scale projects funded by the UK Department for Environment, Food and Rural Affairs (Defra) to demonstrate technologies that enable biodegradable municipal waste to be diverted from landfill. Previous research, over a period of eight years leading to the biowaste digester, concentrated on the anaerobic digestion of food waste, which is able to contribute to the positive reduction in the emission of greenhouse gases in a number of different ways. As a renewable energy technology, anaerobic digestion is unusual in that the overall net reduction in the emission of carbon dioxide is greater than simply the carbon dioxide emissions from the fossil fuels that it displaces; however, apart from its application on sewage works and in landfill sites, the process is not yet widely applied in the UK. The project met the necessary permitting requirements and construction started in June 2005. The first biowaste was processed in March 2006 and the plant is operating at 50% of its design throughput. The first year of operation has shown that the quality of the biowaste is very different from that anticipated, in particular with a low capture of food waste. This issue is being addressed in order that the project can demonstrate the effective role that anaerobic digestion can play in the UK’s future waste management strategy.
An innovative in-vessel tunnel composting system
A. L. Webb
Proceedings of the Institution of Civil Engineers, Waste and Resource Management, 160, No. 1, February, 27–31, doi: 10.1680/warm.2007.160.1.27
The batch tunnel composting demonstrator project under construction at St Ives, Cambridgeshire, UK, is one of a number of similar projects funded by the UK Department for Environment, Food and Rural Affairs as part of the New Technologies Demonstrator Programme (NTDP). The St Ives project includes the design, build and assessment of a new in-vessel composting plant and its demonstration to local authorities to highlight the central role of composting in efforts to divert biodegradable municipal waste (BMW) from landfill. Current statistics show that several million tonnes of BMW are landfilled each year in the UK, much of which could instead be composted. Assuming all current composting facilities are working at full capacity, over 100 new plants capable of processing 100 000 t per annum would be required to compost this volume of waste. The NTDP aims to present the technical, environmental and economic viability of new techniques to divert BMW from landfill and encourage the construction of further processing facilities. The new St Ives composting plant will be equipped with an innovative system to heat the walls and floors of the tunnel in order to ensure the entire composting mass reaches the temperatures specified by the 2005 Animal By-Product Regulations (ABPR) and reduce the risk of cold spots. The project will assess the effectiveness of this heating system.
Rotary in-vessel advanced aerobic composting
N. Box
Proceedings of the Institution of Civil Engineers, Waste and Resource Management, 160, No. 1, February, 33–38, doi: 10.1680/warm.2007.160.1.33
This paper describes the adaptation and development of a rotary in-vessel advanced composting system for sourceseparated garden and kitchen waste, food industry waste and other biodegradable municipal waste (BMW) as part of the UK Department for Environment, Food and Rural Affairs (Defra) New Technologies Demonstrator Programme. Over the life of the project, the plant aims to convert 10 000 t of BMW into high-grade fertiliser to be supplied to the agricultural market. Investigation and development work carried out in connection with an end market for the product is also summarised.
England’s waste strategy: waste or resource management?
I. Avery
Proceedings of the Institution of Civil Engineers, Waste and Resource Management, 160, No. 2, May, 45–48, doi: 10.1680/warm.2007.160.2.45
In January 2006 the Institution of Civil Engineers (ICE), in conjunction with the Institution of Mechanical Engineers (IMechE), published The Case for a Resource Management Strategy, proposing that the national waste management strategy be repositioned as a resource management strategy, making up one element of a wider sustainable consumption and production agenda. The ensuing debate and stakeholder interest established support for England to adopt a material resource economy and a follow-up report How to Deliver a Resource Management Strategy was published in March 2007. This briefing outlines the blueprint set out in that document, summarises the government’s response and assesses the extent to which the government’s response reflects the resource management approach.
Landfill stability and integrity: the UK design approach
G. Fowmes, N. Dixon and D. R. V. Jones
Proceedings of the Institution of Civil Engineers, Waste and Resource Management, 160, No. 2, May, 51–61, doi: 10.1680/warm.2007.160.2.51
This paper highlights the design considerations, in terms of stability and integrity, for EC Landfill Directive compliant sites. The paper details a design chart based on research and development reports produced for the Environment Agency (England and Wales) intended to guide designers and highlight areas for consideration in each of six aspects of landfill construction: subgrade, basal lining system, shallow-slope lining system, steep-slope lining system, waste slopes and capping lining systems. The paper is not intended to offer design methodologies in terms of which calculation methods should be adopted, but to provide designers with a framework in which to apply engineering skill and judgement and to highlight challenges.
Aerobic digestion of municipal solid waste in Durham, UK
M. Johnson
Proceedings of the Institution of Civil Engineers, Waste and Resource Management, 160, No. 3, August, 93–96, doi: 10.1680/warm.2007.160.3.93
An in-vessel aerobic digestion plant has been in operation at the Thornley waste transfer station in County Durham, UK, since January 2002. Until recently the plant consisted of two aerobic digestion towers with a total capacity in excess of 30 000 t per annum; it processes unsegregated municipal solid waste (MSW) resulting in a diversion rate of over 70% of its input weight from landfill. This type of process is commonly referred to as mechanical and biological treatment (MBT) and is attracting significant interest from local authorities as an alternative to mass burn incineration and landfill disposal. In contrast to some other MBT systems, this system is configured to optimise conditions for maximum degradation of the biodegradable components of MSW commonly referred to as biodegradable municipal waste (BMW). While the current plant has been in operation for 4.5 years, assistance was sought from the UK Department for Environment, Food and Rural Affairs under the New Technologies Demonstrator Programme to support additional research and development with the aim of enhancing the process.
Pyrolysis of biodegradable wastes using microwaves
J. P. Robinson, S. W. Kingman, C. E. Snape and H. Shang
Proceedings of the Institution of Civil Engineers, Waste and Resource Management, 160, No. 3, August, 97–103, doi: 10.1680/warm.2007.160.3.97
The pyrolysis of biodegradable wastes using microwaves was studied as a potential technology to divert waste streams from landfill by converting the biomass into a high-value char, with a potential market as a co-firing media in pulverised fuel power stations. It is demonstrated that pyrolysis can be achieved using inherent moisture as the microwave absorbing phase and that complete char formation can be attained. The efficiency of the process is dependent on the microwave cavity used and it was found that microwave pyrolysis is governed primarily by the rate at which energy is supplied to the waste material. When the heating rate is maximised, the calorific value of the produced pyrolysis gases is greater than the total microwave energy required, meaning that the process is potentially selfsustaining. The dielectric properties of other waste materials are presented and these are used to identify the prevalent design criteria for translating the pyrolysis process to pilot scale.
Anaerobic digestion of verge cuttings for transport fuel: closing the energy cycle
A. Salter, M. Delafield, S. Heaven and Z. Gunton
Proceedings of the Institution of Civil Engineers, Waste and Resource Management, 160, No. 3, August, 105–112, doi: 10.1680/warm.2007.160.3.105
Roadside verges need to be cut for both safety and ecological reasons. This requires energy, currently acquired from fossil fuels with associated release of CO2. Leaving the cuttings in place has a detrimental effect on plant species richness; removal leads to increased biodiversity but produces green waste for disposal. This paper describes a model to determine the energy efficiency and surplus energy yield from the use of verge cuttings as a feedstock for anaerobic digestion. The model is scaleable and could be used by national and local authorities to find ways of reducing fossil fuel consumption. Although based on UK data, the same principles can be applied anywhere with roadside verges or similar sources of green cuttings. The model uses results from trials in Powys, Wales to determine the feasibility of collection and the potential methane yield of the cuttings. The results indicate that verge material can be collected in a manner that is both CO2 neutral and produces more energy than that required for cutting, transporting and processing. The nature of the fuel produced means the process is self-sustaining—biogas can be used to fuel vehicles required for cutting and transport and to provide heat and electricity for the anaerobic digestion process.
Peak residential water demand
C. Tricarico, G. de Marinis, R. Gargano and A. Leopardi
Proceedings of the Institution of Civil Engineers, Water Management, 160, No. 2, June, 115–121, doi: 10.1680/wama.2007.160.2.115
Residential water consumption has been analysed by monitoring a water distribution system in a small town of about 1200 inhabitants, Piedimonte San Germano, in southern Italy. The design of a water distribution system is usually undertaken with reference to the maximum water required by customers—one of the most onerous operating conditions to which an hydraulic network is exposed. The aim of the present work has been to contribute to the characterisation of the peak water demand through statistical inferences on a large data sample collected from the system under consideration. Specifically, the data have been analysed for the effect of resampling the raw data with respect to time interval on the estimate of peak demand factor. Formulae are suggested to estimate the maximum flow demand for small towns, in relation to the number of users. In addition, statistical inferences have shown that the stochastic, maximum flow demand is described by the log-normal and Gumbel models. With reference to small residential areas, the parameters of such statistical distributions have been estimated. These have shown that the coefficient of variation (CV) of the peak water demand is a function of the number of users. Although these results are only directly applicable to the specific context from which they have been obtained, the comparison with the sparse data available in the technical literature leads to the belief that the proposed relationships could be extended to other small residential areas.
Influence of El Niño on rainfall in Guyana and Uganda
R. Wardlaw, D. Jaigopaul and Z. Rahaman
Proceedings of the Institution of Civil Engineers, Water Management, 160, No. 3, September, 135–143, doi: 10.1680/wama.2007.160.3.135
El Niño/southern oscillation (ENSO) activity is known to affect weather patterns in many parts of the world. This paper develops an approach to identifying signals and incorporating associated impacts on hydrological risk into water resources planning and management. The paper builds on earlier research reported in the climatology literature, and brings this to the engineering domain. An evaluation of seasonal rainfall in Guyana clearly demonstrates that distinct rainfall distributions are associated with La Niña and El Niño events. Forecasts of these events are made by a number of organisations at lead times of up to eight months. If these are coupled with the precipitation analysis presented in this paper, an objective hydrological risk assessment can be made. The methodology applied in Guyana has been repeated with data on net basin supply to Lake Victoria. There is a clear indication of a link between ENSO activity and net basin supply to Lake Victoria.
Prioritising sewerage maintenance on serviceability criteria
S. Arthur and H. Crow
Proceedings of the Institution of Civil Engineers, Water Management, 160, No. 3, September, 189–194, doi: 10.1680/wama.2007.160.3.189
In the UK and elsewhere, there has been a concerted move away from primarily assessing sewer system capacity to focus on ‘serviceability’ as a key performance indicator in sewerage provision. Increasingly, water regulators are recognising that a prime concern of customers is avoiding flooding of their property, as environmental improvements can often be intangible. However, regulators insist that environmental factors are also given strenuous attention. Based on these considerations, it is evident that sewerage providers will increasingly consider undertaking proactive maintenance on sub-critical and non-critical sewers in order to reduce the risk of customers experiencing reduced levels of serviceability. This paper documents the development of a methodology to manage capital maintenance expenditure within the context of ‘serviceability’ to customers, the public and the environment. The methodology has been applied alongside Infoworks-CS software to determine critical points in a small coastal catchment in Edinburgh, Scotland. The paper also discusses how these results are linked to customer complaints held in a geographic information system (GIS) database, and how the approach developed was able to recommend which assets should be proactively maintained to minimise the risk of serviceability loss. For the catchment considered, key serviceability performance indicators were found to be combined sewer overflow (CSO) spills, flooding in residential areas, flooding in commercial zones and disruption to traffic.
