A multiscale approach for evaluating the failure condition of calcarenite structures subject to environmental loads

Soft and highly porous rocks such as calcarenites are very common in the entire Mediterranean region. Due to their porous calcareous structure these rocks are quite prone to water induced weathering mechanisms. Cliffs and underground cavities formed of calcarenites are frequently affected by intense erosion phenomena, weathering processes and unexpected collapses. These latter are usually the long-term result of a very complex hydro-chemo mechanical process taking place at the micro-scale which can be detected and analyzed by means of field and laboratory experimental test campaigns. Experimental tests results show a marked and instantaneous reduction in strength and stiffness for these porous rocks when macro-pores are filled with water and a slow successive reduction in strength and stiffness occurring in the long-term due to dissolution processes. To cope with deterministic assessment of the stability of natural and anthropic caves micro and macro experimental test were performed to identify the physics of the processes taking place at both the micro-scale and the macro-scale. A multiscale constitutive model following the framework of strain-hardening plasticity was formulated incorporating the hydro-chemo mechanical occurring at the microscale. The elasto-plastic constitutive model was implemented into the GeHoMadrid Finite Element code including the reactive transport of chemical species in a porous system. Small scale laboratory boundary value problems will be used to validate the coupled numerical code. Finally 2D FEM academic examples in calcarenite formation will be addressed: in the first, a failure mechanism triggered in the short term by a water infiltration from ground level is simulated; in the second a cliff instability occurring in a long term dissolution process is tackled. © 2015 Taylor & Francis Group.