Experimental methodology for chemo-mechanical weathering of calcarenites

Calcarenite is a soft rock strongly affected by weathering processes that markedly reduce the mechanical rock properties with time. As a consequence, cliffs and underground cavities formed in calcaernites are frequently affected by intense erosion and instabilities. The field and laboratory experimental results mainly show three peculiarities of calcarenite mechanical behavior: a) a marked and instantaneous reduction in strength, up to 60% of the dry initial value, when water fills the pores of the rock; b) a slow reduction in strength after saturation; c) progressive weakening of the material during wetting and drying cycles. In the present work we concentrate on the long term effect of water on calcarenite. In this context, an experimental procedure necessary for the calibration of a strain hardening-chemical softening elasto-plastic constitutive model is presented. Suitably designed tests under controlled "weathering" conditions were performed in order to define the critical variables that can physically explain the variety of phenomena occurring in the material.