Abstract: This article aims to study the micromechanism of hydration instability of rock-anchorage agent structure. Based on the SEM test and nanoindentation test of anchored mudstone specimen, the evolution of micromechanical properties of rock-anchorage agent structure under different moisture contents was analyzed. The results show that the structural integrity of rock-anchorage agent structure is good under dry conditions, and the interface is a bonding area with a certain width. With increasing the moisture content, dissolution holes and cracks occur in the structure, the range of bonding area is reduced. As a result, the rock-anchorage agent structure debonding failure appears at saturated moisture content. At low moisture content, the indentation data is discrete due to the difference in mechanical properties among the components, and at high moisture content, the cementation ability of each component deteriorates, the overall mechanical properties of the structure decrease, and the data dispersion becomes small. The aggravation of hydration-induced damage makes the cementation structure of mudstone failed and leads to macroscopic damage, while the anchorage agent will fill the micropores generated at the interface under hydration so that the mechanical properties of the interface will be improved relative to the rock part. Therefore, the attenuation range of the microscopic parameters of the interface is smaller than that of the mudstone part.

Key words: mudstone, rock-anchorage agent structure, hydration instability, micromechanical characteristics, nanoindentation