Experimental study of the water weakening of carbonate rocks

Carbonate rocks, such as chalks and calcarenites, are very often subject to damage processes responsible of the progressive degradation of their mechanical properties. In particular the water weakening of such rocks can cause the collapse of cliffs and underground cavities, with dangerous consequences for the anthropic environment. In this paper the results of an experimental campaign, intended to both clarify and quantify the mechanical consequences of water weakening, are illustrated. Results of standard laboratory experiments (Uniaxial Compression, Oedometric Compression and Indirect Tensile tests) and non-standard experimental tests (weathering under oedometric and unconfined conditions) are presented. Suitable physical and geotechnical indices are also introduced and different time scales to describe the physical/chemical reactions induced by the water saturation of the material are taken into consideration. The main results can be summarized as: i) a short-term marked and instantaneous reduction in strength, when water fills the pores of the rock, ii) a long-term dissolution of the material causing further damage and iii) a progressive chemically induced reduction in the grain size.