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Development of experimental methodology of investigating the relative and interactive effects of physicochemical properties of permeating fluids on incipient motion of granular particles
Get PDFParticle mobilization is a fundamental aspect in the process of soil erosion and has been known to affect the stability of critical infrastructures such as levees and dams. In the field, fluids permeating through earthen dams or levees may exhibit a range of physicochemical characteristics that may affect the incipient motion of soils. This paper presents an experimental methodology that can be used to evaluate the relative and interactive effects of a fluid’s physicochemical properties on the incipient motion of a granular particle under laminar flow condition. The results obtained from the present research demonstrated the ability of the experimental setup and methodology in studying the effect physicochemical properties (such as viscosity, pH and ionic strength) of fluids on incipient motion of granular particles under laminar flow condition
Dealing with data – Innovation in the monitoring, operation and maintenance of reservoir assets
No full textOwners of large reservoirs often have to comply with statutory monitoring and maintenance regimes as well as the day-to-day operation and maintenance (O&M) of the dam, pipework, valves and appurtenant structures. These requirements can generate a large amount of data which is important for many different people involved in the smooth running of the asset, and which needs to be accessed in different formats, locations, and times, for different purposes. The consequences of ‘missing’ important data can range from something as simple as a broken access gate, to something as serious as a catastrophic dam breach. This paper describes research into advanced data interaction techniques such as Augmented Reality and Near Field Communication, and how these were applied to existing data in a reservoir O&M manual for a reservoir in the UK, in order to develop the ‘Reservoir App’ – a smarter way of generating, accessing and using reservoir data
Methods and tools to support real time risk-based flood forecasting - a UK pilot application
No full textFlood managers have traditionally used probabilistic models to assess potential flood risk for strategic planning and non-operational applications. Computational restrictions on data volumes and simulation times have meant that information on the risk of flooding has not been available for operational flood forecasting purposes. In practice, however, the operational flood manager has probabilistic questions to answer, which are not completely supported by the outputs of traditional, deterministic flood forecasting systems. In a collaborative approach, HR Wallingford and Deltares have developed methods, tools and techniques to extend existing flood forecasting systems with elements of strategic flood risk analysis, including probabilistic failure analysis, two dimensional flood spreading simulation and the analysis of flood impacts and consequences. This paper presents the results of the application of these new operational flood risk management tools to a pilot catchment in the UK. It discusses the problems of performing probabilistic flood risk assessment in real time and how these have been addressed in this study. It also describes the challenges of the communication of risk to operational flood managers and to the general public, and how these new methods and tools can provide risk-based supporting evidence to assist with this process
Continuous grid monitoring to optimize sedimentation management
Get PDFFluves and GTC monitor since November 2015 continuously a sediment trap with dimensions 200 x 20 meters managed by the Flemish Environmental Agency (VMM) in Belgium. The continuous follow-up of sedimentation of the trap provides insights on temporal and spatial evolution of trapping efficiency. VMM will use the insights to optimize operational dredging decisions and for optimizing the design of future traps. The installed measuring system is based on distributed temperature sensing with a fiber optic cable of more than 2 km. A digital terrain model (DTM) of the sediment trap is transmitted to the client on a hourly to daily basis. Results after winter floods from November 2015 till February 2016 show a significant spatial variation in sedimentation through the sedimentation trap. Also, zones with different temporal evolution of filling of the trap could be observed. The technique shows great potential for detailed spatial and temporal observation of sedimentation processes in large areas, as well as the ability to detect thin sedimentation layers
Relationships of underwater sound pressure and particle velocity in a shipbuilding dock
Get PDFUnderwater sound is characterized: 1. directional particle motion; 2. scalar pressure waves.
Theoretically these are related and it is possible to
estimate the particle velocity through measurements
of pressure (e.g. Filiciotto et al. 2016, Nedelec 2016).
However, this relationship assumes that sound
propagates as a plane wave; an assumption that is not
met in shelf seas or shallow water regions, where a
wide range of fish and invertebrate species have been
shown to respond to both sound pressure and particle
velocity (e.g. Radford et al. 2012).
Objectives: This work compares direct measurements of sound
pressure level (SPL) and particle velocity generated by
experimental pile driving
Assessing the risks associated with internal erosion phenomena in aging embankment dams: a New Zealand perspective
Get PDFEarth embankment dams form a vital part of New Zealand’s hydropower, agricultural, and water supply infrastructure. The challenges faced in the management of aging embankment dams are compounded by factors specific to New Zealand, including large variability in soil types and the highly tectonic environment in which the dams are located. Internal erosion, triggered by both seismic and non-seismic events, is considered one of the primary risks to New Zealand embankment dams. Spurred by the recent Canterbury Earthquake Sequence, hydropower asset owners in New Zealand have expressed a need for improved guidance for the evaluation of embankments (1) following significant earthquake ground motions, and (2) from a whole-life perspective. This study considers the applicability of existing empirical methods to assess the potential for internal erosion in the New Zealand context. Two distinct mechanisms of internal erosion are considered: (1) internal instability, and (2) filter incompatibility. Four existing empirical geometric methods were used to assess the potential for internal instability in 19 widely-graded New Zealand soils. One existing method was found to be mathematically ineffectual with respect to the widely-graded soils considered in this study and all methods lack reliable verification using volcanic soils. Existing screening methods suggest that a number of glacial, alluvial, and volcanic materials used in construction of New Zealand’s large earth dams may be susceptible to some degree of internal instability phenomena, irrespective of seismic hazard. Secondly, a case-study concerning a common type of widely-graded base-filter soil interface demonstrates ambiguous analysis results arising from overlap in No Erosion and Excessive Erosion thresholds. Uncertainties in interpretation could be resolved by the future development of statistical guidelines for filter assessment. With regard to both internal instability and filter incompatibility mechanisms, the applicability of existing empirical analysis techniques to New Zealand soils appears limited due to a lack verification for the diverse geological range of fill soils encountered. In addition, existing stability thresholds have not been verified for long-term or seismic loading conditions inherent in the New Zealand context. This study highlights significant shortcomings in the applicability of existing screening methods used to assess the potential for internal erosion in New Zealand soils
A case of severe channel-morphology change due to human influences in the Touqian River, Taiwan
Get PDFOne reach that locates in the midstream of the Touqian River in northern Taiwan was subjected to various human disturbances; the channel morphology in the reach changed severely as a result. This case study looks into the role of human disturbance on channel evolution by exploring the chronological change in channel morphology due to human influences in the studied reach. The major human influences in this reach include gravel mining, bridge construction and its protection works, and weir construction. Channel morphology downstream the bridge was transformed from an alluvial channel to a bedrock channel since the installation of a massive protection work. Later on, the bridge and its protection work were broken in recent years. After their failure, the reach started to take re-deposition and has returned to an alluvial channel. Chronological data including aerial photographs, cross-section surveys and hydrological data were compiled and analyzed. Also, field geology was conducted to characterize the distribution of bedrock outcrop and the erosion processes in the studied reach. According to the study results, the maximum depth of bedrock incision exceeds 15 meters. Main influences can be attributed to various human activities and the low resistance of young sedimentary rocks to erosion. The case study, as a fine example, demonstrates the processes of channel-morphology change due to human disturbances
Laboratory experiments on scour around flat circular buckets for high waves and strong current at Wido Windfarm, Westsouth Sea, Korea
Get PDFLaboratory experiment on scour around three circular suction bucket foundations was carried out at Kookmin University basin, 0.8 m wide, 1 m deep, and 23 m long. The buckets form the foundations of wind power towers of Korea Westsouth Sea Windfarm. Bed material at the site is sand, and finer sand was chosen for laboratory modelling test. The strongest current of 1.03 m/s, the maximum significant wave height of 5.3 m, and the maximum wave height of 8.1 m were undistortedly scaled down by 1/70 in length. Measured scour depths are all under 0.6 times the bucket diameter. Experimental results for currents have been compared with a numerical model STEP, and its modified version STEP-K. Both models over predict the scour depths around the buckets, and also predict earlier evolution of the scour compared to the laboratory measurements
Dikes reinforced by deep mixing techniques - Long term properties
Get PDFThe deep Soil-Mixing technique consists in mixing a hydraulic binder into the soil mechanically in order to improve its properties. As far as dikes are concerned, two methods are available. The dry method which is one of these, consists in making a 1 m pre-trenched zone where cement powder is spread and the mixing tool mixes the soil and the cement with water down to a depth of 9 m from the top of the dyke. For the study of erodibility with laboratory tests, a hole erosion test apparatus is used in order to characterize the internal erosion of soils. Samples created in the laboratory as well as cored samples have been tested to get some ranges of soil-mixed responses
Applying emulators for improved flood risk analysis
No full textFlood risk analysis often involves the integration of multivariate probability distributions over a domain defined by a consequence function. Often, solutions of this risk integral involves Monte-Carlo sampling techniques, whereby 1000’s of potential flood events are generated. It is necessary to evaluate the consequence of flooding for each sampled event. A significant computational time is required in running flood related physical process models, making it computationally impractical to evaluate flood risk using this approach. To overcome the computational challenges, this paper focusses on the Gaussian Process Emulator (GPE) meta-modelling approach. Traditionally, a “look-up table” method is used when a large number of simulations from a numerical model are required. This approach typically involves simulating conditions defined across a regular matrix, and then linearly interpolating intermediate conditions. In this paper we compare a traditional “look-up table” approach to the GPE and analyse their performance in approximating SWAN wave transformation model. In both cases, selecting an appropriate training design set is important and is taken into consideration in the analysis. The analysis shows that the GPE approach requires significantly fewer SWAN runs to obtain similar (or better) accuracies, enabling a substantial reduction in computation time, hence aiding the practicality of Monte-Carlo sampling techniques in advanced flood risk modelling