SLAKING CHARACTERISTICS OF SILTY MUDSTONE UNDER ACID RAIN ACTION BASED ON FRACTAL DIMENSION

Slaking process of claystone is vulnerable to environmental condition. The acid rain can significantly affect the process. The corresponding mechanism remains to be studied. Traditionally, the slaking characteristic of claystone is evaluated by second cycle slake durability index which is determined by the mass of the residual particles larger than 2 mm only. Such evaluation fails to reflect the characteristics of the overall particle size distribution. This paper takes the Panzhihua landslide as an example. The site is located in the typical acid rain area. The silty mudstone samples located on the sliding surface are processed. Then a series of slaking experiments are carried out by the use of solutions with different pH values. Based on the fractal theory, the fractal dimension is introduced to quantitatively describe the slaking characteristics of silty mudstone. The correlations between fractal dimension with acid rain duration and acidity of rainfall are established, respectively. The substantial cause for the slaking characteristic differences due to different rainfall acidity is determined through analyzing the solution chemical composition. The results highlight that the fractal theory can better reflect the acid rain slaking characteristics of silty mudstone. The higher the fractal dimension is, the higher the slaking degree. The logarithmic positive correlation exists between the fractal dimension and the duration of acid rain, the final fractal dimension and the acidity of rainfall. The reason for the slaking characteristics difference under various rainfall acidities lies in the different degrees of dolomite and calcite dissolutions. Conclusions of this paper can be taken as references for engineering property evaluation of rock mass in acid rain area.