The deterioration of the mechanical properties of gypsum due to water–rock reactions has attracted extensive attention in the areas of structural geology and civil engineering, and accurately predicting variations in the mechanical behavior of gypsum under different engineering conditions presents a challenging yet intriguing endeavor. In our study, we conducted experimental investigations of the influence of water–rock reactions on the mechanical behavior and mechanisms of gypsum-bearing mudstone. Subsequently, we constructed a mechanical damage model to predict the behavior under varying dissolution times. During the water–rock reaction, water dissolves substances along crystal interfaces and mineral joint surfaces, changing the way particles contact each other, weakening the contact strength, creating intergranular solubility pores, and causing an increase in porosity, all of which lead to a decrease in the mechanical strength of gypsum–containing rocks. The experimental results showed that the maximum decrease in peak strength and cohesion of the samples with the increase in porosity was 69.68% and 79.02% after the water–rock reaction, respectively, and the internal friction angle showed a small fluctuation change with increasing porosity. The maximum increase in elastic modulus and peak strength with increase in confining pressure was 34.21% and 37.10%, respectively. In addition, for samples with different shapes and spatial locations of weak zones due to water–rock reactions, there is no clear relationship between the change of elastic modulus and the porosity of the samples. By constraining the peak strength and peak deformation, the established gypsum-bearing mudstone constitutive model was accurate and flexible. Comparing the established damage constitutive model with measurements, we found that the developed damage constitutive model is compatible with the measured data during the damage evolution process of water–rock reactions over long periods and can play a predictive role. This study has laid an important foundation for research on the evolution of gypsum mechanical properties and model construction under water–rock reactions.

由于水-岩反应而引起的石膏力学性能的恶化引起了结构地质学和土木工程领域的广泛关注，准确预测不同工程条件下石膏力学行为的变化是一项具有挑战性但又令人着迷的努力。在我们的研究中，我们进行了水岩反应对含石膏泥岩力学行为和机制影响的实验研究。随后，我们构建了机械损伤模型来预测不同溶解时间下的行为。在水岩反应过程中，水沿着晶体界面和矿物节理面溶解物质，改变了颗粒相互接触的方式，削弱了接触强度，形成粒间溶孔，导致孔隙度增加，导致孔隙度降低。含石膏岩石的机械强度。实验结果表明，水岩反应后样品的峰值强度和黏聚力随孔隙度的增加最大下降分别为69.68%和79.02%，内摩擦角随孔隙度的增加呈现较小的波动变化。随着围压的增加，弹性模量和峰值强度的最大增加分别为34.21%和37.10%。此外，对于不同形状和水岩反应弱区空间位置的样品，弹性模量的变化与样品的孔隙率之间没有明确的关系。通过约束峰值强度和峰值变形，建立的含膏泥岩本构模型准确、灵活。将建立的损伤本构模型与实测数据进行比较，发现所建立的损伤本构模型与长周期水岩反应损伤演化过程中的实测数据相符，能够起到预测作用。该研究为水岩反应下石膏力学性能演化及模型构建研究奠定了重要基础。