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.