The wide range of gypsum facies observed all over the world and the strong heterogeneity that may be present even within a single facies often cause an inhomogeneous mechanical response that, if neglected, may be particularly dangerous in the framework of underground excavations. In addition, gypsum is particularly sensible to the presence of water. The high relative humidity conditions often registered in underground gypsum quarries may imply an additional worsening of mechanical properties. In the present study, the strength and the creep response of a natural gypsum rock facies are investigated, considering the influence of material heterogeneity and relative humidity conditions. The heterogeneity of the material, quantified with MIP and SEM analyses, is observed to strongly affect the mechanical response. To this intrinsic mechanical variability, the influence of an external parameter as the relative humidity is observed to generate an additional reduction of material strength and to increase the creep strain rate in the long-term tests. The effect of all these elements in the underground quarry framework is discussed and a constitutive model of these experimental results is provided.

全世界观察到的石膏相广泛，即使在单个相中也可能存在强烈的异质性，通常会引起不均匀的机械响应，如果忽略这些响应，则在地下挖掘的框架中可能特别危险。另外，石膏对水的存在特别敏感。通常在地下石膏采石场中记录到的较高的相对湿度条件可能意味着机械性能的进一步恶化。在本研究中，考虑了材料异质性和相对湿度条件的影响，研究了天然石膏岩相的强度和蠕变响应。观察到材料的异质性（通过MIP和SEM分析量化）对机械响应有很大影响。对于这种固有的机械可变性，在长期测试中，观察到外部参数作为相对湿度的影响会导致材料强度进一步降低，并增加蠕变应变率。讨论了所有这些元素在地下采石场中的作用，并提供了这些实验结果的本构模型。