Variational Continuum Multiphase Poroelasticity

This book collects the theoretical derivation of a recently presented general variational macroscopic continuum theory of multiphase poroelasticity (VMTPM), together with its applications to consolidation and stress partitioning problems of interest in several applicative engineering contexts, such as in geomechanics and biomechanics. The theory is derived based on a purely-variational deduction, rooted in the least-Action principle, by considering a minimal set of kinematic descriptors. The treatment herein considered keeps a specific focus on the derivation of most general medium-independent governing equations. It is shown that VMTPM recovers paradigms of consolidated use in multiphase poroelasticity such as Terzaghi's stress partitioning principle and Biot's equations for wave propagation. In particular, the variational treatment permits the derivation of a general medium-independent stress partitioning law, and the proposed variational theory predicts that the external stress, the fluid pressure, and the stress tensor work-associated with the macroscopic strain of the solid phase are partitioned according to a relation which, from a formal point of view, turns out to be strictly compliant with Terzaghi's law, irrespective of the microstructural and constitutive features of a given medium. Moreover, it is shown that some experimental observations on saturated sandstones, generally considered as proof of deviations from Terzaghi's law, are ordinarily predicted by VMTPM. As a peculiar prediction of VMTPM, the book shows that the phenomenon of compression-induced liquefaction experimentally observed in cohesionless mixtures can be obtained as a natural implication of this theory by a purely rational deduction. A characterization of the phenomenon of crack closure in fractured media is also inferred in terms of macroscopic strain and stress paths. Altogether the results reported in this monograph exemplify the capability of VMTPM to describe and predict a large class of linear and nonlinear mechanical behaviors observed in two-phase saturated materials.

This volume is devoted to an actual topic which is the focus world-wide of various research groups. It contains contributions describing the material behavior on different scales, new existence and uniqueness theorems, the formulation of constitutive equations for advanced materials. The main emphasis of the contributions is directed on the following items - Modelling and simulation of natural and artificial materials with significant microstructure, - Generalized continua as a result of multi-scale models, - Multi-field actions on materials resulting in generalized material models, - Theories including higher gradients, and - Comparison with discrete modelling approaches

This book presents a collection of contributions on the advanced mechanics of materials and mechanics of structures approaches, written in honor of Professor Kienzler. It covers various topics related to constitutive models for advanced materials, recent developments in mechanics of configuration forces, as well as new approaches to the efficient modeling and analysis of engineering structures.

The book presents the proceedings of the XXV National Congress of the Italian Association of Theoretical and Applied Mechanics (Palermo, September 2022). The topics cover theoretical, computational, experimental and technical-applicative aspects. Chapters: Fluid Mechanics, Solid Mechanics, Structural Mechanics, Mechanics of Machine, Computational Mechanics, Biomechanics, Masonry Modelling and Analysis, Dynamical Systems in Civil and Mechanical Structures, Control and Experimental Dynamics, Mechanical Modelling of Metamaterials and Periodic Structures, Novel Stochastic Dynamics, Signal Processing Techniques for Civil Engineering Applications, Vibration-based Monitoring and Dynamic Identification of Historic Constructions, Modeling and Analysis of Nanocomposites and Small-Scale Structures, Gradient Flows in Mechanics and Continuum Physics, Multibody Systems Vibration Analysis, Mechanics of Renewable Energy Systems, Mathematical Modeling and Experimental Techniques for Quantification and Prediction of Fluid Dynamic Noise, and Advanced Process Mechanics. Keywords: Fluid Mechanics, Solid Mechanics, Structural Mechanics, Mechanics of Machine, Computational Mechanics, Biomechanics, Masonry Modelling and Analysis, Dynamical Systems in Civil and Mechanical Structures, Control and Experimental Dynamics, Mechanical Modelling of Metamaterials and Periodic Structures, Novel Stochastic Dynamics, Signal Processing Techniques for Civil Engineering Applications, Vibration-based Monitoring and Dynamic Identification of Historic Constructions, Modeling and Analysis of Nanocomposites and Small-Scale Structures, Gradient Flows in Mechanics and Continuum Physics, Multibody Systems Vibration Analysis, Mechanics of Renewable Energy Systems, Mathematical Modeling and Experimental Techniques for Quantification and Prediction of Fluid Dynamic Noise, and Advanced Process Mechanics.

The book reviews the two features of the variational approach: its use as a universal tool to describe physical phenomena and as a source for qualitative and quantitative methods of studying particular problems. Berdichevsky’s work differs from other books on the subject in focusing mostly on the physical origin of variational principles as well as establishing their interrelations. For example, the Gibbs principles appear as a consequence of the Einstein formula for thermodynamic fluctuations rather than as the first principles of the theory of thermodynamic equilibrium. Mathematical issues are considered as long as they shed light on the physical outcomes and/or provide a useful technique for the direct study of variational problems. In addition, a thorough account of variational principles discovered in various branches of continuum mechanics is given. This book, the second volume, describes how the variational approach can be applied to constructing models of continuum media, such as the theory of elastic plates; shells and beams; shallow water theory; heterogeneous mixtures; granular materials; and turbulence. It goes on to apply the variational approach to asymptotical analysis of problems with small parameters, such as the derivation of the theory of elastic plates, shells and beams from three-dimensional elasticity theory; and the basics of homogenization theory. A theory of stochastic variational problems is considered in detail too, along with applications to the homogenization of continua with random microstructures.

It clarifies many physical concepts (such as particulate viscosity and solids pressure) and introduces the new dependent variable - the volume fraction of the dispersed phase. Exercises are provided for further study, and lead into applications not covered in the text itself

F. dell'Isola, L. Placidi: Variational principles are a powerful tool also for formulating field theories. - F. dell'Isola, P. Seppecher, A. Madeo: Beyond Euler-Cauchy Continua. The structure of contact actions in N-th gradient generalized continua: a generalization of the Cauchy tetrahedron argument. - B. Bourdin, G.A. Francfort: Fracture. - S. Gavrilyuk: Multiphase flow modeling via Hamilton's principle. - V. L. Berdichevsky: Introduction to stochastic variational problems. - A. Carcaterra: New concepts in damping generation and control: theoretical formulation and industrial applications. - F. dell'Isola, P. Seppecher, A. Madeo: Fluid shock wave generation at solid-material discontinuity surfaces in porous media. Variational methods give an efficient and elegant way to formulate and solve mathematical problems that are of interest to scientists and engineers. In this book three fundamental aspects of the variational formulation of mechanics will be presented: physical, mathematical and applicative ones. The first aspect concerns the investigation of the nature of real physical problems with the aim of finding the best variational formulation suitable to those problems. The second aspect is the study of the well-posedeness of those mathematical problems which need to be solved in order to draw previsions from the formulated models. And the third aspect is related to the direct application of variational analysis to solve real engineering problems.