Cam-Clay plasticity, Part VIII: A constitutive framework for porous materials with evolving internal structure

Abstract

Natural geomaterials often exhibit pore size distributions with two dominant porosity scales. Examples include fractured rocks where the dominant porosities are those of the fractures and rock matrix, and aggregated soils where the dominant porosities are those of the micropores and macropores. We develop a constitutive framework for this type of materials that covers both steady-state and transient fluid flow responses. The framework relies on a thermodynamically consistent effective stress previously developed for porous media with two dominant porosity scales. We show that this effective stress is equivalent to the weighted sum of the individual effective stresses in the micropores and macropores, with the weighting done according to the pore fractions. This partitioning of the effective stress into two single-porosity effective stresses allows fluid pressure dissipation at the macropores and micropores to be considered separately, with important implications for individual characterization of the hardening responses at the two pore scales. Experimental data suggest that the constitutive framework captures the laboratory responses of aggregated soils more accurately than other models previously reported in the literature. Numerical simulations of boundary-value problems reveal the capability of the framework to capture the effect of secondary compression as the micropores discharge fluids into the macropores.

A new simplified Hypothesis B method for calculating consolidation settlements of double soil layers exhibiting creep

“…Cosenza and Korošak presented a heuristic approach that adopts two additional parameters of fractional order and fractional viscosity factor, to consider the ‘secondary consolidation’ of clayey soil as a result of pore water pressure diffusion from micro‐ to macro‐pores. Borja and Choo developed a framework of soil constitutive model to consider the pore water pressure dissipation in the macro‐ and micro‐scale, and used this model to simulate the ‘secondary compression’ in one‐dimensional (1D) consolidation, which agrees well with the experimental data. The double porosity theory provides the basis for understanding the soil consolidation behavior.…”

Responses of chemically active and naturally fractured shale under time‐dependent mechanical loading and ionic solution exposure

“…Equation is corresponding to the equation 15 by Borja and Koliji, equation 51 by Borja and Choo, and equation 2.70 by Coussy …”

“…There are also mechanical models available for elastoplastic transversely isotropic materials . Nonlinear frameworks for similar topics can be also found, for example in previous studies …”

Study of the 1‐D consolidation behavior of two‐layered soft soils: Parametric studies using a rheological model with viscoplastic body

“…Hicher carried out a set of indoor tests to analyze and quantify the viscous properties of the EVP clay. Borja and Choo considered the macro‐ and micro‐scales and simulated the “secondary compression” during 1‐D consolidation. Yin and Feng and Feng and Yin proposed a simplified Hypothesis B method to calculate the consolidation settlement for both single and double soil layers exhibiting creep.…”