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Variation of small strain stiffness for piping-influenced Toyoura sand
Get PDFLandslides triggered by piping are frequently reported during stormy periods. Despite large amount of model tests related with internal erosion, there is little research on the mechanical properties of disturbed soil by means of element experiment. In this paper, an attempt was made to create artificial piping by dissolving water soluble material (glucose) in sand. Chains of voids were generated when water was infiltrated and drained out through the specimen. Small torsional cyclic loadings were conducted on the hollow cylindrical specimens in order to obtain the small strain stiffness of the soil before/after piping erosion. According to the results, reduction of shear modulus was found in specimen with internal pipes after water infiltration, and piping-induced anisotropy was found to be obvious
Asset Management Planning – providing the evidence to support robust and risk-based investment decisions
No full textOver the last decade the UK’s joint Flood and Coastal Erosion Risk Management Research and Development programme has been developing methods to support a move to a risk-based approach to flood defence asset management. Looking to ensure investment is less ‘find and fix’ and made to those assets where the biggest risk reduction can be made for the money available. In addition, providing the capability to articulate the benefits of investing in these assets quantitatively and transparently. This paper describes how the Asset Performance Tools (APT) project [1] is delivering practical methods, prototype tools and supporting guidance which, together with related initiatives such as the Environment Agency’s Creating Asset Management Capacity (CAMC) strategic programme [2] and the ‘State of the Nation’ (SoN) [3] supportive datasets, will enable a risk-based, ‘predict and protect’ approach to asset management. A key advance is the ability to bring in local knowledge to make national generic datasets locally relevant. The paper also highlights existing outputs that can already be used to support a more proactive approach to asset management. It will summarise the ongoing work which will further develop and fine tune performance assessment and investment decision processes within an integrated conceptual framework aligned with ISO55000, deliverable via CAMC and whose concepts can be used by all risk management authorities
Tangible and Intangible Flood damage evaluation
No full textFlooding and flash floods that cause significant economic and social damage have been widely studied in the last few decades. The European Commission Flood Directive 2007/60 Flood Risk Management Plans require the assessment of potential damage to give an appreciation of the magnitude of the consequences of a flood event and so help stakeholders to use a cost benefit approach to planning flood mitigation measures. This paper evaluates the direct tangible flood damage applying the JRC water depth-damage functions for the European territory to estimate the potential economic damage. Intangible damage is evaluated with the Life Safety Model (LSM) to study the dynamic interactions among people, vehicles, buildings and the flood wave. LSM assesses potential flood damage and allows the development of a Flood Evacuation Plan in case of an emergency, underlining the evacuation routes adopted by people and vehicles. This enables emergency managers to avoid evacuation bottleneck problems and identify areas of potential high mortality. The impact of changes such as road network improvements, the location of safe havens and timing of flood warnings can be assessed in terms of potential loss of life. The developed methodology has been applied on the Sardinian Flood Risk Management Plan pilot basin, the Coghinas river lowland basin
The risk analysis of levee systems: a comparison of international best practices
No full textA risk analysis of a levee system estimates the overall level of flood risk associated with the levee system, according to a series of loading conditions, the levee performance and the vulnerability to flooding of assets in the protected area. This process, which requires the identification and examination of all the components that determine the risk of flooding in a system, includes different steps. Among these steps, ‘levee system failure analysis’, ‘flood consequences analysis’ and ‘risk attribution’ have benefitted from the most important advances of recent research projects. This paper presents a critical analysis of the latest methods to conduct levee system failure analysis, flood consequences analysis and risk attribution. It shows how these methods can contribute to improving the efficiency of the risk analysis process and therefore the design and management of levee systems
Time-dependent reliability analysis of flood defence assets using generic fragility curve
No full textFlood defence assets such as earth embankments comprise the vital part of linear flood defences in many countries including the UK and protect inland from flooding. The risks of flooding are likely to increase in the future due to increasing pressure on land use, increasing rainfall events and rising sea level caused by climate change also affect aging flood defence assets. Therefore, it is important that the flood defence assets are maintained at a high level of safety and serviceability. The high costs associated with preserving these deteriorating flood defence assets and the limited funds available for their maintenance require the development of systematic approaches to ensure the sustainable flood-risk management system. The integration of realistic deterioration measurement and reliabilitybased performance assessment techniques has tremendous potential for structural safety and economic feasibility of flood defence assets. Therefore, the need for reliability-based performance assessment is evident. However, investigations on time-dependent reliability analysis of flood defence assets are limited. This paper presents a novel approach for time-dependent reliability analysis of flood defence assets. In the analysis, time-dependent fragility curve is developed by using the state-based stochastic deterioration model. The applicability of the proposed approach is then demonstrated with a case study
Detecting scour and liquefaction using OBS sensors
Get PDFThis work examined the performance of Optical Back-Scatter (OBS) sensors for detecting sediment movement around a model subsea structure. Three types of tests were conducted using a circular cylinder model equipped with 16 OBS sensors. The sensor recorded a dramatic reduction in back scatter when it became unburied (due to sediment movement) and was exposed to clear water. Based on this feature, the sensors were used to investigate the scour processes around a model pile, and the spanwise scour rate of a partially buried model pipeline. The test results agree well with existing knowledge. When the sensors were fully buried in sand, it was also observed that the sensor readings fluctuate noticeably when sand particles move local to the sensors. Based on this feature, the OBS sensors were used to detect sediment movement induced by seabed liquefaction. Through the tests presented in this paper, it has been demonstrated that the sensor can be used as a new device to detect local scour and liquefaction in laboratory tests
Estimation of scour for bridges in Illinois
Get PDFScour development around bridge piers is one of the main reasons for bridge failure. This paper presents the comparison of ultimate pier and contraction scour depth for cohesive soils at nine bridge sites in Illinois. Results obtained from common prediction methods such as SRICOS, Hydraulic Engineering Circular No. 18 (HEC 18), Florida Department of Transportation (FDOT) and reduction factor method were compared. All bridge piers have round nose shape except one. SRICOS and FDOT method predicted the lowest and highest ultimate depths of scour, respectively. Measured scour depth for real time obtained from the field was also compared with the ones predicted by SRICOS and modified HEC – 18 methods. In this case, SRICOS method and modified HEC – 18 predictions were in reasonable agreement with each other, however, they both were conservative
Prototype measuring of erosion and currents under the keel of a sailing ship in a canal
Get PDFA full scale experiment with a deep loaded push-tow barge combination was carried out in the Juliana Canal to determine the stability of a canal bed against future ship-induced loads. The resulting under keel currents and the subsequent bed erosion were monitored and analyzed. Clearly, the results showed that in the future the canal bed will be instable. The observed bed lowering could be estimated with a time/dependent scour prediction formula. The results of the observed flow velocities under the ship´s keel were comparable with measured flow velocities in small-scale experiments
Oil spill risk assessments for coastal zone protection In the Arabian Gulf
No full textIntroduction. Oil spills can be disastrous in terms of their ecological, social and economic effects on the coastal zone. In the Arabian Gulf, oil has the potential for accidental release into the marine environment across a range of operations, including coastal developments (ports, terminals, etc.), as well as offshore activities (oil and gas exploration, shipping, etc.). Accurate predictions of the fate and behaviour of spilled oil are therefore important and usually require the use of computational models. Simulations rely on a range of model predictions – including detailed hydrodynamic and meteorological fields – as well as adequate representation of the properties and physics of the spilled oil.
Oil spill model assessment procedures. The authors have recently carried out research to establish best practice procedures for the assessment of the fate of spilled oil and its impact in coastal and offshore regions (Henno et al., 2015). An integrated framework for oil spill assessment was developed, using both established modelling tools and enhanced Lagrangian models. The study brought together expertise in coastal processes, metocean studies, the maritime industry and marine ecology. The procedure was demonstrated and validated using data for a real spill incident in coastal waters.
Coastal zone protection in the Arabian Gulf. The Arabian Gulf is an area of rapid industrial development. Over the last decade in particular, there have been significant expansions in ports, refineries and other coastal facilities across the region. As a relatively enclosed basin, water exchange occurs over long periods, with estimated residence times of 2-5 years (Elshorbagy et al, 2006). This means that pollutants and spills in coastal waters can have both local and regional effects, potentially over long time-scales. Therefore it is important that planning studies and pollution risk assessments for each new coastal development do not occur in isolation. Regional level pollution and oil spill assessments are one way to inform Coastal Zone Management (CZM) plans, protecting the environment from the potential harmful effects of spills.
Modelling to support management plans. To support CZM and planning for new coastal developments, the authors applied their validated spill assessment procedure to sites in the Arabian Gulf. The study used a combination of calibrated hydrodynamic models, validated oil spill models, and state-of-the-art parallel computing capabilities. Model simulations demonstrate the potential fate of spills from a range of industrial sites, and their transport over the wider Gulf by tidal- and wind-driven currents. These can be readily refined and extended to inform Environmental Impact Assessments (EIAs), risk assessments and Coastal Zone Management (CZM) plans for new developments. The outputs include the likelihood of shoreline or sensitive receiver impact, and minimum transport times for oil to reach designated sites. Sensitive coastal areas can then be protected from potential spills through suitable management and spill response plans