Abstract

Triassic anhydrite and gypsum rocks are widespread in the Southern Alps. Two case studies from Lombardy are presented. The former is characterised by a thick lens of gypsum and anhydrite covered by dolostones and with many underground cavities generating subsidence. Indiscriminate urbanization led to build in risky areas. At the second site, gypsum and anhydrite were quarried with a room and pillar technique. At present, lower levels are completely flooded and groundwater flowing contributes to dissolution of pillars. Uniaxial, triaxial and splitting tensile tests have been performed on intact cores of anhydrite and gypsum. The effect of anisotropy on UCS was investigated. Samples have been degraded under a constant water flux and specimen have been measured, weighted and tested for UCS at regular intervals. The compressive strength of degraded samples is reduced dramatically in the earlier stages of degradation. X-ray diffraction and SEM/EDS analyses, both on intact and degraded samples show that the outer border of anhydrite cores transforms to gypsum during the water flux.

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