Biot の弾性係数と有効応力の概念 Elastic coefficients in the Biot theory and concept of the effective stress
Elastic coefficients in the Biot theory (Biot coefficients) for fluid-saturated porous media are expressed by conventional elastic coefficients and porosity. Practical applicability of this theory is established by it. Derivation of Biot coefficients is generally performed by the deformation analysis in which the total stress is resolved into two components: the effective stress and the fluid (hydrostatic) stress. Use of this pair of stress components has been developed as powerful tools in soil mechanics, where soils are assumed to be the granular media whose solid parts consist of grains with point-contact. It is a problem to be considered whether the same premise underlies the expressions of Biot coefficients or not. In this point of view, we discuss the concept of this pair of stress components, and we remark that it is used in two different aspects as follows: The first aspect is evaluation of the shear resistance resulting from solid friction. In this case the effective stress is regarded as the key factor controlling the solid friction. The second aspect is utility for the deformation analysis. By converting the total stress into the above pair of components we can evaluate dilatation of the solid material and the skeleton separately. The first aspect needs the premise of granular media, but the second aspect is free from such restriction. The utility in the second aspect is demonstrated by actual evaluation of Biot coefficients. In this evaluation, we particularly assume propagation of the longitudinal plane wave as the situation of stress field. This situation is directly connected to geophysical application. Expressions of Biot coefficients as the result agree with those derived by other authors based on the situation of hydrostatic compression.
- 物理探査 = BUTSURI-TANSA Geophysical Exploration
物理探査 = BUTSURI-TANSA Geophysical Exploration 58(6), 631-642, 2005-12-01
The Society of Exploration Geophysicists of Japan