A time-dependent anisotropic model for argillaceous rocks: application to an underground excavation in Callovo-Oxfordian claystone

The paper presents a constitutive model for argillaceous rocks, developed within the framework of elastoplasticity, that includes a number of features that are relevant for a satisfactory description of their hydromechanical behaviour: anisotropy of strength and stiffness, behaviour nonlinearity and occurrence of plastic strains prior to peak strength, significant softening after peak, time-dependent creep deformations and permeability increase due to damage. Both saturated and unsaturated conditions are envisaged. The constitutive model is then applied to the simulation of triaxial and creep tests on Callovo-Oxfordian (COx) claystone. Although the main objective has been the simulation of the COx claystone behaviour, the model can be readily used for other argillaceous materials. The constitutive model developed is then applied, via a suitable coupled hydromechanical formulation, to the analysis of the excavation of a drift in the Meuse/Haute-Marne Underground Research Laboratory. The pattern of observed pore water pressures and displacements, as well as the shape and extent of the damaged zone, are generally satisfactorily reproduced. The relevance and importance of rock anisotropy and of the development of a damaged zone around the excavations are clearly demonstrated.Peer ReviewedPostprint (author's final draft

The roots of regional trade in the Americas 1870 to 1950

The oft-mentioned failure of the economic integration of South America contrasts with the North American, European and East Asian experiences. While low levels of development, geographical and historical explanations are at the root of our understanding of South America's scarce regional trade integration, due to data limitations such explanations have been little analyzed quantitatively in the long run before the Second World War. We use for the first time a new database on bilateral trade for 11 countries of the region between 1870 and 1950. Our results confirm the conventional view of the existence of a historical handicap of regional trade in the Americas, especially during the commodity boom of the Atlantic globalization prior to the First World War

Las competencias del docente de maestría en universidades colombianas : apreciaciones de alumnos y profesores

Este artículo muestra los resultados de investigación sobre la visión competencial docente desde la óptica de sus protagonistas: enseñantes y aprendices. El diseño del estudio es descriptivo ex post facto desde la metodología empírico-analítica, compuesta por métodos cuantitativos, a partir de instrumentos como los cuestionarios y fuentes vinculadas con programas de maestría (docentes y alumnos). Su objetivo es analizar la apreciación de los informantes respecto al perfil docente actual y sus necesidades competenciales requeridas, todo desde la tarea docente e investigadora. Los resultados evidencian diferencias significativas que arrojan un conjunto de necesidades para la formación docente. Finalmente se exponen algunas reflexiones para una mejora de la formación de formadores en el contexto analizadoThis article shows the results of research on the teaching competency view from the perspective of its protagonists: teachers and apprentices. The study design is descriptive ex post facto from the empirical-analytical methodology, composed of quantitative methods, from instruments such as questionnaires and sources linked to master's programs (teachers and students). Its objective is to analyze the informants' appreciation of the current teaching profile and their required competency needs, all from the teaching and research task. The results prove significant differences that show a set of needs for teacher training. Finally, some reflections are presented for an improvement of the formation of trainers in the analyzed contex