为了研究隧道施工过程中水对石膏岩的软化作用规律，以三叠系下统嘉陵江组地层中的石膏岩为研究对象，进行了不同时间的淡水浸泡软化试验研究，对石膏岩单轴抗压强度、抗剪强度、弹性模量以及泊松比随浸泡时间的变化规律进行分析。研究发现：随着浸泡时间的增长，石膏岩的单轴抗压强度、抗剪强度和弹性模量呈负指数下降趋势，而泊松比在一定条件下呈线性增加趋势；在损伤力学基础上，推导出了基于时间因素的石膏岩软化损伤演化方程，揭示了脆性系数与软化损伤变量之间的关系，建立了石膏岩在不同淡水浸泡时间下的软化深度模型，可用于判别穿越石膏层隧道开挖过程中围岩在地下水作用下的软化区域。

To investigate the performance of gypsum rock softened by water in the tunneling, gypsum rocks from Lower Triassic Jialing River Group were immersed by fresh water within different times for softening tests. The variations of uniaxial compressive strength, shear strength, elastic modulus and Poisson’s ratio of gypsum rocks with increasing immersion time were analyzed. The study indicated that, with the increase of the immersion time, the uniaxial compressive strength, shear strength and elastic modulus of gypsum rock exhibited a decline trend as a negative exponent, while Poisson’s ratio presented a linear increase trend under certain conditions. On the basis of damage mechanics, a softening damage evolution equation was deduced by considering time effect of gypsum rock. The relationship between the brittleness coefficient and softening-damage variable was revealed, and the softening-depth model at different immersion time was established. This study can be used to identify the softening area of surrounding rock caused by groundwater in the tunneling through gypsum layer.