To explore the effects of acid environment on the disintegration characteristics of purple parent rocks

the similarity principle and the correlation fractal dimension calculation formula were used to investigate the fractal dimension features of purple mudstone disintegration of the Suining group (J3S)

the Saximiao group (J2S) and the Penglaizhen group(J3P) under different pH conditions. Therefore

24 times of static disintegration tests were carried out for these rock samples. The results showed that the pH played an important role in the disintegration of purple mudstone. The lower the pH value was

the stronger the disintegration was. The fractal dimension of J3S and J2S under different pH approached to 3 after 24 test cycles

and the lower the pH

the fewer cycles to obtain the stable fractal dimension

while that of J3P didn’t reach the stable fractal dimension. Fractal dimension had no significant differences among different acid treatments in the preliminary stage (p＞0.05)

but had significant differences (p＜0.05) in the middle-later period. Furthermore

the differences of the fractal dimension under different acid treatments of each mudstone group varied with the disintegration stage. The disintegration rate of purple rock increased with increasing acidity

resulting from that most of the mineral composition of purple rock could not dissolve in water but chemical reaction in acid solutions and produced soluble salts.