Geotechnique | 2019
Chemo-mechanical coupling constitutive model for chalk considering chalk–fluid physicochemical interaction
Abstract
Chalk shows a pronounced water-weakening effect, which can be attributed to the microscopic physicochemical interactions between the pore fluid and the chalk matrix. In this paper a conceptual elastoplastic model is developed for describing the chemo-mechanical behaviour of chalk based on the framework of the modified Cam Clay model. Central to the model is the concept of intergranular stresses, introduced as the substitute for Terzaghi s effective stress to describe the chalk behaviour. In this context, the microscopic physicochemical interactions are characterised by introducing a macroscopic surface force potential. The composition and significance of pore water pressure are analysed, and the intergranular stress tensor is explicitly defined. To address the hardening effect of the microscopic physicochemical interactions, the preconsolidation pressure function is modified by introducing the intrinsic intergranular pressure as an additional hardening variable that accounts solely for the chalk–fluid int...