While water is known to significantly reduce the strength of rocks, there remains a paucity of data on water-weakening of gypsum. Here, we quantify water-weakening in a natural gypsum facies from Monferrato (Italy) by performing experiments on nominally dry, oil-saturated, and water-saturated samples. Uniaxial and conventional triaxial experiments revealed significant water-weakening in Monferrato gypsum as well as a strong strain-rate dependence of uniaxial compressive strength. Moreover, uniaxial creep tests showed significant time-dependent deformation in samples saturated with sulphate over-saturated water, but not in dry and oil-saturated samples. The creep phenomenology is similar to that observed in other rock types and is consistent with stress-corrosion microcracking, which is supported by our microstructural observations. However, we systematically recorded more inelastic strain in samples deformed at low strain-rates suggesting that additional mechanisms were also active. Comparing our new data on short-term strength with published results for other rock types, we conclude that, when saturated with water in equilibrium with the rock, weakening in gypsum is not notably higher than in other rocks and is partially due to a reduction of fracture toughness in the presence of water.

虽然已知水会显着降低岩石的强度，但仍然缺乏关于石膏水弱化的数据。在这里，我们通过对名义上干燥的、油饱和的和水饱和的样品进行实验来量化来自 Monferrato（意大利）的天然石膏相中的水弱化。单轴和常规三轴实验揭示了 Monferrato 石膏中的显着水弱化以及单轴抗压强度的强烈应变率依赖性。此外，单轴蠕变试验表明，在硫酸盐过饱和水饱和的样品中，随时间变化的变形显着，而在干燥和油饱和样品中则没有。蠕变现象类似于在其他岩石类型中观察到的现象，并且与我们的微观结构观察结果支持的应力腐蚀微裂纹一致。然而，我们系统地记录了在低应变率下变形的样品中更多的非弹性应变，这表明其他机制也很活跃。将我们关于短期强度的新数据与其他岩石类型的已发表结果进行比较，我们得出结论，当与岩石平衡的水饱和时，石膏的弱化程度并不明显高于其他岩石，部分原因是存在水时的断裂韧性。