Lambing and mortality rate in Ouled-Djellal sheeps in Tebessa region-Algeria

The aim of this work is to study lamb births and mortalities in Algerian sheep Ouled Djellal breed distributed in different zones of Tébessa region, which is divided according to bioclimatic stage, staff in livestock and area agricultural vocation, into four distinct zones: northern (A, B), middle (C) and southern zone (D). During two years 2015-2016, birth numbers (BN) and mortality rates (MR) of 355 sheep flocks were recorded using a questionnaire. Concerning BN the total number was 21244 lambs representing a mean 59±31 per flock. No significant differences between the birth means of C and D (75±28 vs 83±30) were registered. Birth mean was significantly higher (P<0,05) in B (40±17) than A (29±10), when comparison with C and D, the births of A and B were highly significantly (P<0,001). According to (BN) the studied region were classified into 3 zone groups: (a) with high lambing rate (C, D); (b) with medium lambing rate (B); (c) with low lambing (A). In regard to mortality rates, the total rate was 24±6%. The (MR) in A (27±5%) was significantly higher (P<0,05) as compared to other zones (B) 24±4%, (C) 23±7% and (D) 22±4%. However, no significant differences between B, C and D were revealed. According to the results of (MR) the studied region was classified into two groups: (a) with low MR (C, D), (b) with high MR (A, B). Our result showed that zones influence the (BN) and (MR) in Tébessa region, and southern zones especially D seems the appropriate to practice breeding of Ouled Djellal breed

Investigating instability in granular materials by means of a microstructural model

International audienceUnder certain loading conditions, instability in loose sand can develop at a shear stress level much lower than the critical state failure line. To analyse these types of problems, we adopt the micromechanical approach developed earlier for the modelling of granular material behaviour. The stress-strain relationship for a granular assembly is determined by integrating the behaviour of the inter-particle contacts in all orientations. The constitutive model is applied to simulate undrained triaxial and constant-q tests on loose sand. Numerical simulations are compared to experimental results in order to evaluate the model's ability to predict the different modes of instability of the granular assembly. With the model we have also analysed instability at inter-particle level to observe how it is connected to instability at the assembly level.Dans certaines conditions de chargement, des ruptures par instabilité peuvent prendre naissance dans les sables lâches pour des niveaux de contraintes très nettement inférieurs à ceux correspondant à la plasticité parfaite. Pour analyser ce type de problèmes, nous adoptons une approche d'homogénéisation développée précédemment pour la modélisation du comportement des matériaux granulaires. La relation contrainte-déformation macroscopique est obtenue en intégrant le comportement défini au niveau du contact inter-granulaire. Le modèle est utilisé pour simuler des essais non drainés et des essais à déviateur constant sur un sable lâche. Les résultats de la simulation à l'échelle macroscopique sont comparés à des résultats expérimentaux de façon à apprécier la capacité du modèle à prédire la naissance de l'instabilité sur ces chemins particuliers. Une analyse à l'échelle des différents plans de contact inter-granulaire a également été entreprise afin de relier les conditions d'instabilité aux différentes échelles

On the attraction power of critical state in granular materials

202303 bcfcAccepted ManuscriptOthersChina Scholarship Council (CSC); BRGM (French geological Survey)Publishe