Modelling the multiscale behaviour of claystone: deformation, rupture, and hydro-mechanical phenomena around underground galleries

Abstract

In the context of underground exploitation, the behaviour of rocks near galleries and tunnels conditions their stability. Underground drilling generates deformations, damage, fracturing, and significant modification of flow characteristics in the surrounding rock. However, the influence of small-scale characteristics and behaviour on the rock deformations and damage at engineering scale remains a complex issue. Consequently, the multiscale behaviour of a clay rock is modelled starting from the large scale of the excavation damaged zone around galleries and then enriching the approach by considering microstructural characteristics from the scale of mineral inclusions. Lastly, a double-scale numerical framework is considered. It allows to relate small- to large-scale rock behaviour in terms of deformations and material rupture. In fact, the development of damage and cracking at microscale allows to predict large-scale fracturing. The developed method focuses on a claystone in the particular context of long-term management of high-level nuclear wastes by deep geological repository. The results highlight the possibilities of double-scale computing in the prediction of the behaviour of underground engineering structures.

Large‐scale failure prediction of clay rock from small‐scale damage mechanisms of the rock medium using multiscale modelling

“…Among the computational homogenisation approaches, finite element methods (FEM) are often used at larger scale combined with various numerical approaches at smaller scale. 12,15,[23][24][25] From a constitutive point of view, multiscale methods allow a scale transition (based on the notion of scale separation) for which the homogenised small-scale response (e.g. mesoscopic) serves as an implicit constitutive law at larger scale (e.g.…”