Describing failure in geomaterials using second-order work approach

查看全文 作　　者：Franois [1]Nicot;Félix [2]Darve 机构地区：[1]Institut de Recherche en Sciences et Technologies de l'Environnement et de l'Agriculture(IRSTEA), Erosion Torrentielle Neige et Avalanches (ETNA)Geomechanics Group,Grenoble 38402, France;[2]Université Joseph Fourier (UJF)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Sols,Solides, Structures et Risques,Grenoble 38041, France 出　　处：《Water Science and Engineering》索引2015年第8卷第2期,共7页 基　　金：the French Research Network Me Ge (Multiscale and Multiphysics Couplings in Geo-environmental Mechanics GDR CNRS 3176/2340, 2008e2015) for having supported this work 摘　　要：Geomaterials are known to be non-associated materials. Granular soils therefore exhibit a variety of failure modes, with diffuse or localized kinematical patterns. In fact, the notion of failure itself can be confusing with regard to granular soils, because it is not associated with an obvious phenomenology. In this study, we built a proper framework, using the second-order work theory, to describe some failure modes in geomaterials based on energy conservation. The occurrence of failure is defined by an abrupt increase in kinetic energy. The increase in kinetic energy from an equilibrium state, under incremental loading, is shown to be equal to the difference between the external second-order work,involving the external loading parameters, and the internal second-order work, involving the constitutive properties of the material. When a stress limit state is reached, a certain stress component passes through a maximum value and then may decrease. Under such a condition, if a certain additional external loading is applied, the system fails, sharply increasing the strain rate. The internal stress is no longer able to balance the external stress, leading to a dynamic response of the specimen. As an illustration, the theoretical framework was applied to the well-known undrained triaxial test for loose soils. The influence of the loading control mode was clearly highlighted. It is shown that the plastic limit theory appears to be a particular case of this more general second-order work theory. When the plastic limit condition is met, the internal second-order work is nil. A class of incremental external loadings causes the kinetic energy to increase dramatically, leading to the sudden collapse of the specimen, as observed in laboratory. 关 键 词：岩土材料 失效模式 二阶 不排水三轴试验 增量加载 平衡状态 负载参数 运动学特征