Two-component Mixture Model Research Articles

Continuum model for natural slopes in slow movement

A two-component mixture model is proposed to describe the slow motion of natural slopes, which may creep and slide along their basal surface under the effect of gravity. The field equations comprise the balance laws of mass and momentum and constitutive relations for the partial stresses of the fluid and the solid as well as the seepage force. The fluid is modelled as an incompressible perfect liquid and the soil as a viscous isotropic body in which the stress may also depend on the porosity. The seepage force is described by Darcy's law. Explicit constitutive formulas are presented. The kinematic and dynamic boundary conditions for the fixed basal surface and the movable free and phreatic surfaces are stated. The shallowness of the moving mass permits reduction and simplication of the governing equations describing the initial boundary value problem. This makes it possible to separate the determination of the stress and velocity distributions from the evolution of the movable surfaces. Examples are given which highlight the roles of the phenomenological parameters in the constitutive relations. Finally, computational results for a real landslide (La Frasse, Switzerland) are compared with field data, demonstrating the usefulness of the proposed theoretical model and approximations. L'articie propose un modéle á deux composantes pour déire le mouvement lent des pentes naturelles qui peuvent fluer et glisser le long de leur surface de base sous l'effet de la gravité. Les équations de base comprennent les lois d'équilibre de la masse et du moment et des relations constitutives pour les contraintes partielles du fluide et dusolide aussi bien que la force de filtration. Le fluide est modeléisé comme un liquide parfait incompressible et le sol comme un corps isotrope visqueux dans lequel la contrainte peut aussi dépendre de la porositié. La force de filtration est décrite par la loi de Darcy. Des formules constitutives explicites et les conditions limites cinématiques et dynamiques pour la surface de base fixe et les surfaces libres et phréatiques mobiles sont présentées. La faible de profondeut de la masse en mouvement permet laréduction et lasimplification des equations principales qui décrivent le problème de lavaleur limite initiale. De cette faqon il est possible de distinguer les distributions de contrainte et de vitesses de I' olution des surfaces mobiles. Des exemples sont donnés qui illustrent les rôles joués par les paramètres phénoménologiques dans les relations constitutives. Finalement, une comparaison des réultats calculés pour un glissement de terrain réel (la Frasse, en Suisse) avec des don de chantier données de chantier démontre I'utilitb du modéle théorique et des approximations proposées.

Spontaneous Raman spectroscopy of shocked H 2O

We have developed a new Raman spectroscopic system for recording spontaneous Raman spectra from shocked matter at high pressure and temperature during shock passage. This system has been applied to the study of the OH-stretch band of water shocked to pressures between 7.5 and 25.7 GPa. The spectra indicate that strong intermolecular hydrogen-bonding persists to 12 GPa and decreases in strength at higher pressures. A two-component mixture model fits the data well under shock conditions.

TRANSIENT THERMAL STRESSES IN A CHEMICALLY HARDENING MATERIAL CAST WITHIN AN ELASTIC CYLINDRICAL MOLD

Abstract A method is formulated for determining the transient thermal stresses that evolve during the molding process within a material hardening as the result of an exothermic chemical reaction. The formulation is applied to the restricted case in which the shear-to-bulk-modulus ratio for the fully hardened material is small, and where the material is cast in the form of an infinitely long solid cylinder in a thermally thin elastic mold. The heat-generation rate and temperature variation are derived from a first-order chemical reaction. The solidification of the material is described by a transformation from an initial liquidlike state to an elastic solid, with thermoelastic constitutive rate equations during the hardening process based upon a two-component mixture model whose composition is related to the degree of reaction. Graphs for transient stresses and residual stress distributions are shown in terms of dimensionless variables, with hardening rate related to thermochemical constants, and with the ...