报告摘要
Granular materials are now known to be an illustration of complex materials as they display emergent macroscopic properties when loaded. An initially homogenous response can bifurcate into a heterogeneous one with the appearance of a rich variety of structured kinematical patterns. The shear banding that ensues illustrates a symmetry-breaking transition with multiple choices of macroscopic behaviours, a common feature of dynamical complex systems. Even though the phenomenon has been studied for decades, this regime transition remains mostly mysterious in geomaterials, with no convincing arguments that could link it to the underlying microscopic mechanisms. The lecture investigates this issue by invoking the extremal entropy production theorems to seek any connection with the second-order work theory in the mechanics of failure. A general equation linking the derivatives of the entropy of a mechanical system to the second-order work is thus inferred, which leads to a thermodynamic interpretation of bifurcations in the failure behaviour of granular materials under a given loading. This is verified through discrete element simulations that highlight the fundamental role played by the elastic energy stored within a granular material before a bifurcation occurs, which also corresponds to a minimization of the entropy production. The analysis suggests a new interpretation of the intriguing shear banding phenomenon as a bifurcation with the emergence of ordered dissipative structures germane to nonequilibrium thermodynamics of open systems.
主讲人简介
Dr. François NICOT is currently Professor at University Savoie Mont-Blanc. He received his Engineer and Ph.D. degrees in civil engineering in 1995 and 1999, respectively, at Centrale School of Lyon (France). As a world-renowned researcher in soil mechanics, his activities deal with geomechanics, with a special focus on micromechanics of granular materials and multiscale failure modelling. Application fields span from constitutive modelling of geomaterials to gravity-driven natural hazards analysis, including slope engineering issues. He has published more than 200 articles, including 130 papers in international journals together with more than 20 collective books. He is co-director of the International Research Network GeoMech (Multi-Physics and Multi-scale Couplings in Geo-environmental Mechanics), gathering more than 25 academic institutions over the world. He is currently Editor-in-Chief of the European Journal of Environmental and Civil Engineering (Taylor & Francis Publ.) and Associate Editor of Granular Matter (Springer Publ.) and Water Sciences and Engineering (Hohai Univ.)
协办单位：浙江省力学学会岩土力学与工程专业委员会、浙江省岩土力学与工程学会本构理论与数值分析专业委员会、浙江大学岩土工程计算中心