Maurice A. Biot's paper "Mechanics of Deformation and Acoustic Propagation in Porous Media" presents a unified treatment of the mechanics of deformation and acoustic propagation in porous media. The paper builds on Biot's earlier theory of deformation of porous media, which is derived from general principles of nonequilibrium thermodynamics. The fluid-solid medium is treated as a complex physical-chemical system with relaxation and viscoelastic properties. The paper discusses specific relaxation models and emphasizes the general applicability of a correspondence principle. The theory of acoustic propagation is extended to include anisotropic media, solid dissipation, and other relaxation effects. The paper also considers sources of dissipation other than fluid viscosity. The paper begins with an introduction that outlines the purpose of the paper, which is to reformulate the linear mechanics of fluid-saturated porous media in a more systematic and general context. The paper discusses the importance of viscoelasticity in consolidation problems of clay and the role of thermodynamic operators in explaining special aspects of the consolidation problem that do not agree with the elastic theory. The paper then presents the strain energy of a porous elastic medium, deriving the stress-strain relations for an isotropic medium. The paper discusses the linear stress-strain relations, deriving the quadratic form for the strain energy and the stress-strain relations for a linear material. The paper also discusses the thermodynamic foundation of Darcy's law, deriving the dissipation function and the Onsager relations. The paper then discusses the thermodynamics of viscoelastic behavior, emphasizing the correspondence principle and its applications to various areas. The paper also discusses the physical significance of the operators, illustrating their flexibility and generality with examples. The paper concludes with a discussion of the physical significance of the operators and their applications to various phenomena, including creep laws and the interaction of elasticity of the solid and fluid viscosity around areas of grain contact.Maurice A. Biot's paper "Mechanics of Deformation and Acoustic Propagation in Porous Media" presents a unified treatment of the mechanics of deformation and acoustic propagation in porous media. The paper builds on Biot's earlier theory of deformation of porous media, which is derived from general principles of nonequilibrium thermodynamics. The fluid-solid medium is treated as a complex physical-chemical system with relaxation and viscoelastic properties. The paper discusses specific relaxation models and emphasizes the general applicability of a correspondence principle. The theory of acoustic propagation is extended to include anisotropic media, solid dissipation, and other relaxation effects. The paper also considers sources of dissipation other than fluid viscosity. The paper begins with an introduction that outlines the purpose of the paper, which is to reformulate the linear mechanics of fluid-saturated porous media in a more systematic and general context. The paper discusses the importance of viscoelasticity in consolidation problems of clay and the role of thermodynamic operators in explaining special aspects of the consolidation problem that do not agree with the elastic theory. The paper then presents the strain energy of a porous elastic medium, deriving the stress-strain relations for an isotropic medium. The paper discusses the linear stress-strain relations, deriving the quadratic form for the strain energy and the stress-strain relations for a linear material. The paper also discusses the thermodynamic foundation of Darcy's law, deriving the dissipation function and the Onsager relations. The paper then discusses the thermodynamics of viscoelastic behavior, emphasizing the correspondence principle and its applications to various areas. The paper also discusses the physical significance of the operators, illustrating their flexibility and generality with examples. The paper concludes with a discussion of the physical significance of the operators and their applications to various phenomena, including creep laws and the interaction of elasticity of the solid and fluid viscosity around areas of grain contact.