Apr 17
John Armstrong, Georgios Rempelos, Jingfu Wei, John Preston, Simon Blainey, John Easton and Clive Roberts,
WIT Transactions on Built Environment, 199, 127 – 138.
(doi:10.2495/CR200121). (In Press) In Press date: 17 April 2020
Work undertaken on the socio-economic assessment of the installation of under-sleeper pads (USPs) on a busy commuter railway route in Britain, as part of the Track to the Future (T2F) project, was presented at COMPRAIL 2018. This was followed by an expanded, comparative analysis of the same route, comparing the noise-reduction and other costs and benefits of USPs, rail dampers and noise barriers, published in the International Journal of Transport Development and Integration. Such analyses provide useful information and decision-making assistance to infrastructure managers, funders and other stakeholders, but typically require the repeated development of bespoke models of study locations, interventions and effects. The “one-off” nature of these models increases the time and costs required for such studies, and makes it more difficult to compare similar schemes in different locations, or different types of intervention in a single location. There is, therefore, a need for an improved, more generalised and standardised, transferable, replicable and comparison-enabling approach to the socioeconomic assessment of such interventions. Ongoing work on the T2F project entails the development and use of standardised templates to describe the input costs and expected impacts of different infrastructure, rolling stock or operational interventions. These form the inputs to, and part of the development for, T2F of an improved, generalised, ontology-based assessment framework, which is being developed using the West Coastway railway line between Portsmouth and Brighton on England’s south coast as an initial case study. This paper describes the context and rationale for the development of the assessment framework, its components and the methodology being adopted.
Keywords
railways, maintenance, renewals, enhancements, interventions, environmental impact, economic assessment, assessment template, ontologies
Mar 17
Behavioral guidance systems are commonly used in freshwater fish conservation. The biological relevance of sound to fish and recorded responses to human-generated noise supports the viability of the use of acoustics as an effective stimulus in such technologies. Relatively little information exists on the long-term responses and recovery of fish to repeated acoustic exposures. In a controlled laboratory study, the response and tolerance of Eurasian minnow (Phoxinus phoxinus) shoals to tonal signals (150 Hz of 1 s pulse duration) differing only in temporal characteristics (“continuous,” “slow,” “intermediate,” or “fast” pulse repetition rate) were investigated. In comparison to independent control groups, fish increased their mean group swimming speed, decreased inter-individual distance, and became more aligned in response to the onset of all four acoustic treatments. The magnitude of response, and time taken to develop a tolerance to a treatment differed according to pulse repetition rate. Groups were found to have the greatest and longest lasting response to tone sequences tested in this study when they were pulsed at an intermediate rate of 0.2 s−1. This study illustrates the importance of understanding the response of fish to acoustic signals, and will assist toward the development of longer-term effective acoustic guidance systems.
Schematic of experimental flume setup including the experimental area in which fish were exposed to acoustic stimuli. Hydrophone positions are shown for acoustic mapping at three water depths (7 cm; 13.5 cm; 20 cm), with “X” indicating the position at which sound pressure levels (RMS) (dB re 1 μPa) were standardized.
Mar 10
Diego Panici, Gustavo De Almeida
Published: 10 Mar 2020
Journal of Fluid Mechanics, vol. 886, A19.
https://doi.org/10.1017/jfm.2019.1048
This paper proposes a theoretical model to describe previous laboratory observations of the dynamics of debris accumulations around bridge piers of cylindrical shape. The model is based on the assumption that the observed dynamics is mainly governed by dynamic changes of the point of application of the drag force exerted on the solid body formed by debris accumulated around the pier. A phase plane analysis of the resulting non-linear system of ODEs shows that the model captures the main patterns observed in previous laboratory experiments, including an oscillatory motion and the removal of debris from the pier by the flow. The model provides a theoretical basis for the analysis of the conditions required for debris jams to remain stable over long periods of exposure to impinging flow. Namely, the model indicates that stability of debris accumulations primarily depends on geometrical asymmetry and on the length of the extension downstream of the pier. The former induces the torque required to rotate the jam about the pier, while the latter produces a stabilising effect after the body rotates.
Mar 10
Mar 10
Panici, D. & De Almeida, G.,
Published on 10 Mar 2020,
In : Journal of Fluid Mechanics. 886, 21 p., A19.
This paper proposes a theoretical model to describe previous laboratory observations of the dynamics of debris accumulations around bridge piers of cylindrical shape. The model is based on the assumption that the observed dynamics is mainly governed by dynamic changes of the point of application of the drag force exerted on the solid body formed by debris accumulated around the pier. A phase plane analysis of the resulting non-linear system of ODEs shows that the model captures the main patterns observed in previous laboratory experiments, including an oscillatory motion and the removal of debris from the pier by the flow. The model provides a theoretical basis for the analysis of the conditions required for debris jams to remain stable over long periods of exposure to impinging flow. Namely, the model indicates that stability of debris accumulations primarily depends on geometrical asymmetry and on the length of the extension downstream of the pier. The former induces the torque required to rotate the jam about the pier, while the latter produces a stabilising effect after the body rotates.
Feb 28
Georgios Rempelos, Prof Jonathan Preston and Dr Simon Blainey
1361-9209
Scopus rating (2019): CiteScore 7.7 SJR 1.662 SNIP 2.05
10.1016/j.trd.2020.102285
This paper provides an assessment of the lifecycle Greenhouse Gas (GHG) emissions associated with the four most common sleeper (railroad tie or cross-tie in North America) types present in the UK rail network. It estimates the embodied material, process and transport emissions linked with the lifecycle activities of construction, relay/renewal and end-of-life of these variants at low and high traffic tonnage. The analysis suggests that at low traffic loads, the softwood sleepers perform the best over the whole simulated-period. At high traffic loads, the concrete sleepers outperform all other variants in terms of lifecycle CO2e emissions, followed by hardwood, softwood and steel. Regardless of the scenario examined, the steel sleepers perform the worst due to the carbon intensive nature of their manufacturing process. This performance gap is amplified at high traffic loads, as their service life is excessively compromised. The analysis reveals that the end-of-life pathway of timber is a critical determinant of its footprint. Results suggest that the impact of disposing of these sleepers results in their footprint being magnified. Nevertheless, if a minimum of 50% follows the combustion pathway with subsequent heat recuperation, then a GHG reduction potential of between 11% and 18% of their footprint is feasible. From a whole-lifecycle cost lens, for higher tonnage routes, the choice of concrete sleepers results in considerable financial savings. If the infrastructure manager was to install sleepers with stiff under sleeper pads (USPs), it may achieve additional economic and GHG savings, with potential for increasing the latter using recycled carbon-neutral USPs.
Feb 25
Fluvial habitat connectivity is essential for the transfer of energy, materials and organisms along rivers. In-river barriers (such as dams and weirs) disrupt the river continuum, causing numerous populations of fish to decline as movement between critical habitats is impeded. Gauging weirs, present worldwide, act as barriers to the upstream movement of some fish due to the unfavourable hydraulic conditions created on the downstream face. Regulations, such as the Water Framework Directive (European Commission, 2010) along with others internationally, requires that these barriers be retrofitted or removed so that fluvial connectivity is increased and habitat connectivity restored. There is a need to develop simple low-cost solutions to enhance multi-species fish passage, while not impacting the ability of these structures to gauge flow or increasing their potential to accumulate debris. In this thesis a staggered array of Cylindrical Bristle Clusters (CBCs) were developed as a novel solution to aid fish passage over gauging weirs. The simplicity and modularity of the design helps improve cost effectiveness and ease of installation. Experiments investigated the use of an array CBCs, mounted on the downstream face of Crump weirs, to improve upstream passage of multiple species of fish while maintaining gauging accuracy. Results showed that the passage efficiency of a Crump weir was increased for roach and chub when retrofitted with CBCs. Swim path analysis indicated fish utilised low velocity zones in the wake of clusters to facilitate passage. Fish exhibited a range of sinuous swimming behaviours while manoeuvring through the CBC array to ascend the weir, the most common of which was zigzagging between two lines of clusters. Time taken to pass the weir and length of the swim path were greatest under the highest cluster density, where manoeuvrability was most constrained. Debris accumulation was minimal during the test period. Passage efficiency, the number of fish that passed as a percentage of those that attempted to do so, was a function of cluster diameter and spacing; efficiency was highest (> 80 %) when the ratio of lateral cluster spacing (centre to centre) (Sc) to diameter was less than 5. Cluster array configurations with the lowest wake overlap (D = 0.03 m, Sd = 0.15 m) produced the highest array drag. Maximum velocity reduction can be obtained when wake overlap is minimised, where low velocity areas no longer extend from one cluster to the next. However, wake overlap has a significant influence on fish passage where increasing the proportion of linking low velocity area is more beneficial for fish. Therefore, a compromise is required between increasing velocity reduction potential and improving fish pass utilisation where increased wake width and overlap are potentially best. Consequently, optimal conditions for fish passage can be obtained through tailoring array layout so that the area of low velocity and spacing between the clusters is maximised whilst increasing the overall flow resistance created by the pass. This body of research highlights the potential for a staggered array of CBCs to improve the upstream passage of multiple species of fish at gauging weirs, common barriers to fish migration, without affecting the accuracy of flow gauging. Placement of clusters close to the weir crest without compromising gauging accuracy is a key benefit of this design for regulatory agencies, ecological engineers, and the operators and managers of river infrastructure tasked with mitigating habitat fragmentation for fish while maintaining the provision of services.
Feb 25
Collaborative Research in Fisheries pp 249-262
Malta has managed a Fisheries Management Zone (FMZ), which extends to 25 NM from the baseline of the Maltese Islands, since 1971. The key aim of the Malta FMZ is to protect the fisheries resources of Malta’s marine area and the ecosystems on which they depend. While bottom trawling is limited in terms of the number of vessels, it is one of the major contributors to landings. As of the start of the GAP project (April 2011), 12 bottom trawlers were licensed to trawl within the FMZ. The study was originally the initiative of fishers, motivated by the need to have data that could be used as a basis to advise on the management of the trawling fleet working within the FMZ. Throughout the sampling design stage, the methodology was discussed between fishers and scientists with the aim of using fishers’ knowledge to determine sampling locations while at the same time obtaining sound results. A 13-month study was conducted, using modified versions of “mazara” type nets traditionally used by Maltese bottom trawlers. The nets had two square mesh cod-ends with mesh sizes of 40 mm and 20 mm. Data were collected on seven target species and three non-target species which will be used to address data gaps with respect to nursery and spawning areas of local populations of targeted stocks. This chapter provides an initial discussion on the potential contribution of the information collected to provide management advice for Malta’s trawl fisheries management plan, the main focus of which is the control of fishing effort.
Co-management Mediterranean Stock assessment Fishers’ knowledge Malta
