Slaking of mudstone in acid rain area is significantly stronger than that in non-acid rain area

and the slaking mechanism needs to be studied. Based on the formation and development characteristics of hydro-chemical coupled damage under acid rain

this paper took a landslide at Panzhihua city airport as an example

which is in a typical acid rain area. Silty mudstone rock samples located in the sliding zone were selected and processed. After that

a series of slaking experiments was comparatively carried out under different pH conditions. In order to explore the micro-mechanism of acid rain-aggravated slaking behavior of silty mudstone

we adopted a series of analytical methods

including analyzing cation composition changes in different pH slaking fluids

observing micro-structure change of samples before and after acid rain treatment as well as analyzing slaking failure modes of silty mudstone. Finally

an index named specific surface area increment index was introduced to reflect the impacts of acid rain-induced chemical damage on slaking behavior of silty mudstone. The results highlight that: the acid rain-induced chemical damage in silty mudstone was mainly caused by the dissolution of specific minerals

which provided extra paths for the slaking of silty mudstone. With the decrease of pH value of slaking fluid

the acid rain-induced chemical damage of silty mudstone increased

the slaking paths increased

the slaking failure mode changed

and the slaking residues were broken into finer fragments. The specific surface area increment index could well capture the fragmentation degree of slaking residuals. The more breaking the slaking residuals

the higher the specific surface area increment index

and the greater the slaking degree of silty mudstone. Conclusions of this paper provide theoretical reference for the evaluation of geotechnical engineering properties and reinforcement design in acid rain areas.