Water-sensitive strata are widely distributed in the crust and have the characteristics of hydration weakening, hydration loosening, hydration spalling, hydration swelling or hydration dissolution. They are mainly clays, clayey strata (such as mudstone, shale, phyllite, slate, etc.), soluble rocks (sulfate rocks, carbonate rocks), and some other special rock masses.

A large number of engineering practices have shown that water-sensitive formations are a challenging problem that affects the stability of underground engineering such as tunnel engineering and mine engineering, while reducing service life and reliability. For example, the Qiguding Tunnel of China Meida Expressway encountered carbonized mudstone that resembled the characteristics of “dark chocolate”, which was easy to hydrate and weather when it was exposed to water, and the self-stabilization ability of the surrounding rock after excavation was poor, which brought great difficulties to the construction. The Niagara Tunnel project in Canada encountered limestone, sandstone, siltstone, shale and mudstone, and the large volume of overbreak was the leading factor contributing to delays in the project. The Liuhai Mine in Longkou Mining Area encountered coal-measure soft rocks, and under the interaction of engineering stress and rock layer expansion, the integrity of the rock mass was destroyed, the porosity and permeability were increased, the water absorption capacity of the rock mass and the surface area exposed to the air were improved, which provided conditions for the expansion and weakening of fracture water in the later stage. The rheology of the rock mass caused large deformation of roadway for a long time.

This Special Issue aims to collect the latest research results on the stability of underground engineering in water-sensitive strata. We welcome original research and review articles that provide insight into the role of water in water-sensitive minerals, rock masses, support structures, and new ideas, materials, methods, and devices to mitigate or solve this problem.

Potential topics include but are not limited to the following:

• Macroscopic and microscopic characteristics of hydration of water-sensitive minerals
• Role of water on the physical and chemical characteristics of water-sensitive rock masses
• Rheology characteristics and self-healing effect of water-sensitive rock masses
• Grouting materials and methods for improving water-sensitive rock masses
• Anchoring materials and methods for improving water-sensitive rock masses
• Instability mechanism of underground engineering in water-sensitive strata
• Coupling effect of water and other physical fields of underground engineering in water-sensitive strata
• Excavation methods for underground engineering in water-sensitive strata
• Supporting methods for underground engineering in water-sensitive strata
• Numerical modelling for underground engineering in water-sensitive strata
• Monitoring and early warning method of underground engineering in water-sensitive strata