A micro-scale inspired chemo-mechanical model of bonded geomaterials

Abstract

a b s t r a c tChemical processes influence the mechanical properties of geomaterials, resulting in either strengthening or weakening effects, the latter being particularly critical for long-term safety assessment in civil and energy engineering. Coupling of chemical and mechanical processes in cemented soils and rocks is investigated starting form a micro-structural chemo-mechanical model. The model consists of an assembly of grains and bonds undergoing dissolution or precipitation of mineral mass, affecting geometrical characteristics of the assembly. The principal such characteristics are the evolution of specific surface area and of bond cross-sectional area at the micro-scale, and of porosity at the macro-scale, which become key variables linking the micro-scale and macro-scale mechanisms. This framework has the advantage of avoiding unphysical situations, such as the occurrence of mineral precipitation with no pore space available or the occurrence of dissolution with no cementing material left. The evolution of important micromechanical quantities, such as the number of active bonds and their cross section is tracked. At the macro-scale, a reactive chemo-plasticity model is combined with a model for bonded geomaterials. The resulting micro-to macro-scale transition, schematically applicable to both materials with reactive grains and bonds and materials with only reacting bonds, is validated against the available experimental evidence, concerning calcarenite with both reactive bonds and grains made of the same mineral. The model is thus shown to provide a flexible framework for a consistent interpretation of experimental loading paths, and can be readily extended to more complex circumstances.

A 3D Numerical Approach to Assess the Temporal Evolution of Settlement Damage to Buildings on Cavities Subject to Weathering

“…Despite considerable progress made in recent years in the study of the interactions between the soil (or rock) mass and the environment (including hydraulic, thermal and chemical coupling phenomena) (Alonso et al 1990;Cekerevac and Laloui 2004;Della Vecchia and Romero 2013;Gajo et al 2015;Gens 2010;Hueckel and Borsetto 1990;Jommi 2000; Uchaipichat and Khalili 2009), the application of advanced models to perform 3D numerical simulations to address such question is rare. In particular, chemo-hydro-mechanical (CHM)-coupled advanced numerical simulations are usually performed for 2D idealized problems to show the robustness of integration schemes or to simulate laboratory-scale boundary value problems (Fernandez-Merodo et al 2007;Tamagnini et al 2002;Tamagnini and Ciantia 2016).…”

Chemo-mechanical modeling of artificially and naturally bonded soils

“…As such two cases imply a different overall behavior both at the micro-and at the macro-scale, bespoke modelling is required to address each situation. While in Gajo et al [26] a model was presented focused on the chemo-mechanical behavior of materials with both chemically reacting grain and bond minerals, this work further develops Gajo et al's [26] framework, building up on the cross-scale relationships and making it suitable to capture the chemo-mechanical behavior of bonded geomaterials with only reactive bond minerals and chemically inert grains.…”

“…Published experimental data on the loss/gain of strength of geomaterials due to chemo-mechanical effects are not particularly abundant. An account of the phenomenological and modeling background relevant to materials with both reactive grains and bonds, such as calcarenite, was given in [26] (see Section 2 therein), whereas here we review the published work on materials with chemically inert grains, but reactive bonds.…”

Micro-feature-motivated numerical analysis of the coupled bio-chemo-hydro-mechanical behaviour in MICP

“…To incorporate the microstructural properties in the defined specific reaction surface the geometric method (GM) [44] is used, by which all solid grains are idealised as spheres with identical average diameter, and all calcite bonds are assumed to be cylindrical with identical average length and radius. According to the study in [20,21], two different types of reaction surface in large and small porosity configurations are considered (Fig. 2).…”