Chemo-mechanical weathering of calcarenites: Experiments and theory

Calcarenite is a very common natural soft rock strongly affected by weathering processes that markedly reduce its mechanical properties with time. Cliffs and underground cavities formed in calcarenites are frequently affected by intense erosion phenomena and unexpected collapses. These latter are usually the final 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. In general, test results mainly put in evidence: a) a marked and instantaneous reduction in strength and stiffness when macro-pores are filled with water, b) a slow successive reduction in strength and stiffness occurring in a very long period of time; c) a more pronounced weakening of the material in case of wetting and drying cycles. In the present work we will discuss i) some experimental results used to identify the physics of the processes taking place at the micro-scale and ii) we will describe the main features of a multiscale strain hardening-chemical softening elasto-plastic constitutive model recently conceived by the authors to simulate the hydro-chemo-mechanical process.