Laboratory study on the effects of hydraulic and granulometric parameters on the response of granular soil to internal erosion

Erosion is a major environmental problem to agricultural land as well as to civil engineering infrastructures. Rainwater infiltration into granular soils can lead to the migration of fine particles by suffusion. This experimental study is conducted to evaluate the susceptibility to erosion of cohesionless soils. The soil under investigation was collected from the coastal region of Mostaganem (West of Algeria) where erosion has recently caused several damages. To assess soil instability to erosion, two approaches have been proposed in the literature: the geometric approach and the hydraulic approach. Few studies have examined the combination of the two methods. The objective of our study is the combination of the two approaches by determining the critical hydraulic load responsible for triggering erosion as a function of soil characteristics. An experimental parametric study was conducted to determine the influence of initial amount of fines, hydraulic gradient and axial stress on the initiation and evolution of suffusion. A combination of the interactions between these parameters allowed us to express the critical hydraulic gradient and to identify the hydraulic behavior of the soil according to the studied parameters. This approach can better estimate the erodibility of cohesionless soils. It can be used in future development studies at this site to reduce the risk of erosion

Explicit Mapping of Acoustic Regimes For Wind Instruments

This paper proposes a methodology to map the various acoustic regimes of wind instruments. The maps can be generated in a multi-dimensional space consisting of design, control parameters, and initial conditions. The bound- aries of the maps are obtained explicitly in terms of the parameters using a support vector machine (SVM) classifier as well as a dedicated adaptive sam- pling scheme. The approach is demonstrated on a simplified clarinet model for which several maps are generated based on different criteria. Examples of computation of the probability of occurrence of a specific acoustic regime are also provided. In addition, the approach is demonstrated on a design optimization example for optimal intonation

Multi-level A Priori Hyper-Reduction of mechanical models involving internal variables

International audienceThis paper concerns the adaptation of reduced-order models during simulations of series of elastoviscoplastic problems. In continuation with previous works, this paper aimed at extending the A Priori Hyper-Reduction method (APHR method) for nonlinear thermal problems to nonlinear mechanical problems involving internal variables. This method is an a priori approach because full incremental responses of detailed models are not forecasted in order to build reduced-order models. The recent extension of the Hyper-Reduction method to reduction of mechanical models involving internal variables makes possible the reduction of degrees of freedom and the reduction of integration points. A multi-level formulation is introduced to focus on the capability of the method to perform efficient parallel computations to adapt reduced-order models

Hyper-reduction framework for model calibration in plasticity-induced fatigue

International audienceBackground:Many mechanical experiments in plasticity-induced fatigue are prepared by the recourse to finite element simulations. Usual simulation outputs, like local stress estimations or lifetime predictions, are useful to choose boundary conditions and the shape of a specimen. In practice, many other numerical data are also generated by these simulations. But unfortunately, these data are ignored, although they can facilitate the calibration procedure. The focus of this paper is to illustrate a new simulation protocol for finite-element model calibration. By the recourse to hyper-reduction of mechanical models, more data science is involved in the proposed protocol, in order to solve less nonlinear mechanical equations during the calibration of mechanical parameters. Usually, the location of the crack initiation is very sensitive to the heterogeneities in the material. The proposed protocol is versatile enough in order to focus the hyper-reduced predictions where the first crack is initiated during the fatigue test.Methods:In this paper, we restrict our attention to elastoplasticity or elastoviscoplasticity without damage nor crack propagation. We propose to take advantage of the duration of both the experiment design and the experimental protocol, to collect numerical data aiming to reduce the computational complexity of the calibration procedure. Until experimental data are available, we have time to prepare the calibration by substituting numerical data to nonlinear equations. This substitution is performed by the recourse to the hyper-reduction method (Ryckelynck in J Comput Phys 202(1):346–366, 2005, Int J Numer Method Eng 77(1):75–89, 2009). An hyper-reduced order model involves a reduced basis for the displacement approximation, a reduced basis for stress predictions and a reduced integration domain for the setting of reduced governing equations. The reduced integration domain incorporates a zone of interest that covers the location of the crack initiation. This zone of interest is updated according to experimental observations performed during the fatigue test.Results:Bending experiments have been performed to study the influence of a grain boundary on AM1 superalloy oligocyclic fatigue at high temperature. The proposed hyper-reduction framework is shown to be relevant for the modeling of these experiments. To account for the microstructure generated by a real industrial casting process, the specimen has been machined in a turbine blade. The model calibration aims to identify the loading condition applied on the specimen in order to estimate the stress at the point where the first crack is initiated, before the crack propagation. The model parameters are related to the load distribution on the specimen. The calibration speed-up obtained by hyper-reduction is almost 1000, including the update of the reduced integration domain focused on the experimental location of the crack initiation. The related electric-energy saving is 99.9 %

SVM CLASSIFICATION OF QUASI-PERIODIC REGIMES OF SINGLE REED INSTRUMENTS

International audienceSingle-reed instruments can produce multiphonic sounds when they generate quasi-periodic oscillation regimes. An approach to map the periodic and quasi-periodic regimes of a wind instrument is presented. The mapping is performed using an SVM classifier trained using the output of a simplified single-reed instrument model. The SVM classifier is iteratively refined using an adaptive sampling scheme referred to as Explicit Design Space Decomposition. This method provides the explicit boundaries separating quasi-periodic and periodic regimes and highlights the influence of key parameters involved in the production of multiphonic sounds

Modélisation algorithmique par réduction de modèle et maîtrise des événements recurrents inhérents aux problèmes d'optimisation

National audienceNous proposons de traiter efficacement, par une méthode de réduction de modèle, une suite de simulations dans le cadre de l'optimisation de structures. Lorsqu'une base est construite pour représenter les évènements significatifs contenus dans l'ensemble des simulations, les évènements récurrents masquent les évènements spécifiques à chaque simulation. Le processus d'adaptation du modèle d'ordre réduit et l'efficacité du processus d'optimisation peuvent s'en trouver affectés. Nous proposerons un nouvel algorithme d'adaptation permettant d'atténuer l'effet de ces évènements récurrents

A Minimal Model of a Single-Reed Instrument Producing Quasi-Periodic Sounds

International audienceSingle-reed instruments can produce multiphonic sounds when they generate quasi-periodic oscillations. The aim of this article is to identify a minimal model of a single reed-instrument producing quasi-periodic oscillations. To better understand the influence of model parameters on the production of quasi-periodic regimes, the mapping between parameters and quasi-periodic regimes is explicitly identified using a support vector machine (SVM) classifier. SVMs enable the construction of boundaries between quasi-periodic and periodic regimes that are explicitly defined in terms of the parameters. Results and conclusions obtained from the numerical model are compared to published experiments related to the the production of quasi-periodic oscillations with an alto saxophone. This qualitative comparison highlights the influence of key parameters on the production of multiphonic sounds

Silting of foum el gherza reservoir

The Foum El Gherza Reservoir fails to satisfy the irrigation of 300,000 palms of Sidi Okba and Seriana due to advanced siltation. Based on data from bathymetric surveys conducted by the National Agency for Dams, the siltation rate was estimated at 0.9 million m3/year. With a total capacity of 47 million of m3, the Foum El Gherza dam is silted up with more than 65 million m3. In this case, the life of the dam will not exceed 11 years of operation. The total silting of the reservoir will occur in 2023. Desilting the dam proves an emergency to save the palms of Seriana and Sidi Okba

Etude expérimentale de l’effet du processus électro-osmotique dans un sol fin salin de la région de Mostaganem

In civil engineering, electro-osmosis is a technique used as a means of dehydration, treatment of fine soils for the improvement and remediation. It is also used in agriculture for the desalinization of soils. In this study, the effect of electro-osmosis on the properties of a fine soil of the Ain Nouissy-Mostaganem region under a difference of electric potential was analyzed. The objective is to study the behavior of the water flow and the modification of some parameters, such as the electrical conductivity, the pH and the Atterberg limits during and after the electrokinetic process. These parameters make it possible to understand and control the performance of this technique with respect to the treatment under consideration. Soil heating during this process was approached through the surface temperature, indicating a loss of relative energy when the voltage gradient exceeds an optimal value.En génie civil, l'électro-osmose est une technique utilisée comme moyen de déshydratation et de traitement des sols fins pour l’amélioration et la dépollution. Elle est aussi utilisée en agriculture pour la désalinisation des sols. Dans cette étude, l'effet de l’électro-osmose sur les propriétés d'un sol fin de la région d’Ain Nouissy-Mostaganem sous une différence de potentiel électrique a été analysée. L’objectif est d’étudier le comportement de l’écoulement hydrique et la modification de certains paramètres, tels que la conductivité électrique, le pH et les limites d’Atterberg durant et après le processus électrocinétique. Ces paramètres permettent de comprendre et de contrôler la performance de cette technique vis-à-vis du traitement considéré. Le chauffage du sol durant ce processus a été abordé à travers la température de surface, indiquant une perte d’énergie relative lorsque le gradient de tension dépasse une valeur optimale.En génie civil, l'électro-osmose est une technique utilisée comme moyen de déshydratation et de traitement des sols fins pour l’amélioration et la dépollution. Elle est aussi utilisée en agriculture pour la désalinisation des sols. Dans cette étude, l'effet de l’électro-osmose sur les propriétés d'un sol fin de la région d’Ain Nouissy-Mostaganem sous une différence de potentiel électrique a été analysée. L’objectif est d’étudier le comportement de l’écoulement hydrique et la modification de certains paramètres, tels que la conductivité électrique, le pH et les limites d’Atterberg durant et après le processus électrocinétique. Ces paramètres permettent de comprendre et de contrôler la performance de cette technique vis-à-vis du traitement considéré. Le chauffage du sol durant ce processus a été abordé à travers la température de surface, indiquant une perte d’énergie relative lorsque le gradient de tension dépasse une valeur optimale

The Cenomanian-Turonian of the Saharan Atlas (Algeria)

International audienceThrough the correlation of a ten of sections from platform to basin we suggest that the Cenomanian-Turonian Boundary Event and the deposition of black shales are at least in part linked to morphologic changes due to shallow-water carbonate production during a rise in relative sea-level, at first slow, faster later