No abstract is provided for this article.
No abstract is provided for this article.
France comprises 10,000 km of river levees. Those levees show highly variable performances caused by the various types of design and construction, age, environment, loadings, and maintenance and repair works performed on them. Available information on levees also varies in quality and most often proves to be incomplete, uncertain, or imprecise. Based on this, a method for providing a quantitative evaluation of levee performance is suggested. Such a method, based on a multicriteria decision-making model and subjective probabilities, takes all available pieces of information into account—design, construction, visual inspections, and geophysical and geotechnical investigations—and reckons them with the level of uncertainty of the available data. This method provides decision-making support in identifying the least efficient sections and setting up investigation and maintenance programs.
Face aux enjeux de la décarbonation de la production d’énergie, de la résilience des territoires face aux impacts du changement climatique, et de la préservation de la biodiversité, il est essentiel d’explorer les solutions d’aménagements de réservoirs susceptibles de répondre à ces sujets. Les centrales photovoltaïques flottantes sur retenues de barrages répondent à cet objectif [7]. La France dispose d’un potentiel d’installation de centrales photovoltaïques flottantes important, et de nombreux projets émergent. Ces projets apparaissent, pour nombre d’entre eux, loin des standards de sécurité attendus vis-à-vis de la sécurité des barrages. Devant cette situation, le CFBR a créé un groupe de travail visant à produire des recommandations techniques pour les projets d’installation de centrales photovoltaïques flottantes sur les retenues de barrage, de manière à améliorer la qualité des projets tout en garantissant la sécurité des barrages. Cet article rend compte de la première phase de travail de ce groupe qui a établi une enquête de retour d’expérience des projets en cours et des manques pour la profession des centrales photovoltaïques flottantes et des barrages.
: A computational methodology dedicated to embankment dam performance assessment has been designed and implemented. The model's inputs are the whole set of available information and data: visual observations, monitoring measurements, calculated data, and documents related to design and construction processes. First, a formal grid is proposed to structure the inputs. It is composed of six fields: name, definition, scale, references as anchorage points on the scale, and spatial and temporal characteristics. Structured inputs are called indicators. Second, an indicator aggregation method is proposed that allows obtaining not only the dam performance but also the assessment of its design and construction practices. The methodology is illustrated mainly with the internal erosion mechanism through the embankment, but results concerning other failure modes are also provided. An application of the method for monitoring dams through time is given.
The aim is of this study to find a relevant criterion to detect and map tree roots in the surrounding soil. In each following ex- periments, we studied properties of propagation, espacially velocity and attenuation of amplitude, as parameters to discriminate the root from the soil. Our work has been initiated on laboratory experiment with an ultrasonic transmission device to highlight relative differences between samples of soil and roots. Measurements were repeated on different root samples (species, dimension, decomposition time) to cover the diversity encountered on dikes. Then an intermediate state device reproducing in-situ conditions in laboratory was performed at the soil surface in two plastic tank containers: one control of bare soil and another containing a root sample burried in homogeneous soil. We shown with laboratory experiments that information provided by the velocity term seems relevant to localize roots in the soil for healthy root samples. Same conclusion was derived from tanks study where significant variations of velocity were observed due to root presence.
. The experience feedback on a crisis that hit a city is frequently used as a "recollection" tool. However, it may not be held in itself as a tool for analyzing a city's performance. The city, considered as a complex system, was modeled using a functional analysis method. Based on such modeling, two risk analysis methods (Failure Mode and Effect Analysis and Event Tree Method) were deployed and adjusted. Lastly, a qualitative reasoning model had been used for get the scenario modeling of the urban crisis. Such functional model was deployed on a case study.
This paper presents a robust observer based on redundancy computing EMF on 2-axis rotor oriented reference frame. Driving sensorless synchronous machine is presented in 3 steps. The first is a stalling phase to avoid wrong rotation whatever the initial rotor position is. The second step is a calibration phase, to estimate accurately the electrical parameters of the drive. So using the 2 first step, finally we control the sensorless drive by estimating EMF, velocity and position which are quite close to reality only by voltages and currents measurements.
No abstract is provided for this article.
Accident statistics for embankment dams show that internal erosion is a major cause of incidents involving these structures. However, internal erosion is a complex process and remains difficult to assess probabilistically. This technical note presents a probabilistic analysis of internal erosion for an existing embankment dam. The spatial variability of soil properties is modeled using random field theory and incorporated into a finite element seepage analysis. The probabilistic results yield spatial distributions of the means and variances of key hydraulic parameters, such as flow velocity and hydraulic gradient. By applying initiation criteria for three internal erosion mechanisms—backward erosion, suffusion, and contact erosion—the safety of the dam is assessed through the initiation probability ( P f ), derived from the probability distribution of the factor of safety (FoS) for each mechanism. This approach is used to evaluate the probability of internal erosion initiation across different zones of the dam. The results can then be used for risk analysis studies for embankment dams by assessing potential failure scenarios due to internal erosion. • Spatial variability of hydraulic properties modeled via random fields. • Coupled finite element seepage analysis with geostatistical inputs. • Initiation probability estimated for three internal erosion mechanisms. • Real-case application enhances dam safety risk assessment.
Modelling concrete shear strength is the main difficulty in probabilistic reliability analysis of gravity dam structural safety. The main reason arises from the lack of test data on the parameters. This paper proposes a procedure for probability modelling of Roller Compacted Concrete (RCC) gravity dam shear strength based on all tests performed during dam construction and all available data. The procedure embraces several methods: statistical analysis of RCC density, analysis of scatter at different spatial scales, data unification, and a physical formulation of the RCC intrinsic curve. A case study demonstrates the applicability of the procedure on an existing RCC gravity dam. The probability distributions obtained are incorporated into the formulation of the shear strength limit state using a first order reliability method and Monte Carlo simulations.
Levees are large alignment works on which only imperfect information are usually available. In this particular context, a probability-based model is suggested for evaluating the levee performance, taking into account imperfect data in a probabilistic format. Such a model will implement subjective probabilities that have been elicited by expert assessment to evaluate all criteria and uncertainties thereof. Based on a deterministic model of multicriteria aggregation and using Monte Carlo simulations, this will ultimately help build probability distributions for the performance indicator and for each levee section. The benefit of this model is to determine how much an evaluation may be trusted and to help decide which technical actions should be taken to improve a levee section performance. Résumé: Les digues sont des ouvrages à grands linéaires pour lesquels on ne dispose généralement que d’informations imparfaites. Dans ce contexte, on propose un modèle probabiliste d’évaluation de la performance des digues permettant la prise en compte des données imparfaites sous format probabiliste. Ce modèle met en œuvre des probabilités subjectives élicitées par jugement expert pour l’évaluation des critères et de leurs incertitudes. Sur la base d’un modèle déterministe d’agrégation multicritère et au moyen de simulations de Monte Carlo, il permet au final de construire des distributions de probabilité pour l’indicateur de performance et pour chaque tronçon de digue. Ce modèle présente les avantages d’apprécier la confiance qui peut être accordée à une évaluation et de guider le choix des actions techniques pour améliorer la performance d’un tronçon de digue.
In this study, we assessed induced polarization as potential non-destructive method for root detection in dike embankments. We used both laboratory and field experiment to describe the electrical signal with a focus on soil water content. Our objective was to determine in which hydric state of the soil, and related electrical properties, roots could be accurately discriminated. We hypothesized that preferential water zone absorption near the roots could, in some conditions, contribute to locate them. During the laboratory experiments, we compared the response of containers filled with the same homogeneous silty clay bare material, and without (A) or with freshly cut root (B) at different levels of soil water content. Resistivity and phase variations with soil water content indicated that it was preferable to work in dry conditions since the contrast was higher. Interactions and overlapping between polarization effects of both root and soil made it difficult to interpret first chargeability maps. This led us to study temporal-spatial variations by considering the dynamics of water absorption during a field experiment. High resolution time lapses images showed a correlation between root location and complex resistivity anomalies. Although these first results have to be confirmed by further measurements, induced polarization seems to add useful information to interpret anomalies produced by woody roots.
