Speaker
Prof. Pierre-Yves HICHER
Professor of the Research Institute in Civil and Mechanical Engineering
Ecole Centrale de Nantes, France
Abstract
Instability of granular material is an important topic in geotechnical engineering because it may lead to catastrophic events such as the collapse of earth structures. There are two aspects in the study of instability, namely, material instability (also known as intrinsic/constitutive instability) and geometrical instability. The phenomenon of localisation formation in a specimen of finite size can be studied as a boundary value problem for which initial inhomogeneities, as well as boundary conditions, play an important role. However, it has been shown that the occurrence of localisation can be predicted at a constitutive level. More recently, several authors have demonstrated that other modes of instability can occur within granular materials and demonstrated that any non-associated elastoplastic model could exhibit domains of instability inside the plastic limit. Experimental evidences support these theoretical approaches. For example, in loose sand under undrained conditions, an instable condition can be obtained at a low shear stress level and subsequently, the strength is reduced to almost zero, corresponding to a material state known as static liquefaction. In this talk, we present a study of material instability based on laboratory testing and field cases. The analysis of these examples demonstrates the major role played by the material initial density as well as the loading conditions.
Biography
Professor Pierre-Yves Hicher is currently a Professor of exceptional rank at the Research Institute in Civil and Mechanical Engineering, Ecole Centrale de Nantes, France. Professor Hicher worked in Ecole Centrale de Paris from 1974 to 1993. During this period, he received PhD degree at Ecole Centrale de Paris in 1979, and then promoted to assistant professor in 1981 and associate professor in 1983. He joined Ecole Centrale de Nantes as a full Professor in 1996.
Professor Hicher is the President of the Scientific Council of Ecole Centrale de Nantes. He is a member of the Executive Council of the PGCE (Civil Engineering and Eco-construction Network), Chairman of the Granular Materials Committee of ASCE, Associate Editor of the Journal of Engineering Mechanics (ASCE), Member of the editorial board of the European Journal of Environmental and Civil Engineering, Expert for the Ministry of High Education and Research (AERES, ANR, PES). He is the reviewer for a number of international journals, including J. Eng. Mechanics ASCE, Eur. J. of Mechanics, Int. J. Num. Anal. Methods in Geomechanics, Geotechnique, ASTM Geotechnical Testing J., Canadian Geot. J., Computers and Geotchnics, European Journal of Environmental and Civil Engineering, Granular Matter and J Aerospace Eng. Professor Hicher has published more than 60 international journal papers and 8 books. He has supervised 38 PhD students in the fields of soil mechanics, foundation engineering, granular materials, constitutive modelling and numerical modeling.