Abstract:Disintegrate of mudstone is conducting under the frequent rainfall-drying interactions in nature, which causing a series of geological disasters. In order to further study the disintegration characteristics of mudstone, a self-designed test device was used to simulate the actual environment of rainfall in the natural environment, and four different lumpiness samples were prepared for the mudstone in the Weinan area of Jiangxi Province. Experimental study on indoor disintegration under cyclic action was carried out. The results show that, The relationships between percentage of each group and cycle number of mudstone disintegration show three trends. That is, as the cycle numbers increases, the percentage of different particle groups decreases, increases first and then decreases, and increases. Moreover, In the curve of the percentage of each particle group, there is a significant peak in the curve under different cycles. The curve basically shows increasing to the peak first, then decreasing. Before the peak, as the cycle numbers increases, the position of the curve gradually moves downward; and after the peak, as the cycle numbers increases, the position of the curve gradually moves upward. In addition, the relationship between the cumulative percentage of particle group and particle size after the disintegration of the larger mudstone shows the “S” shape, while the shale with smaller block size is hyperbolic after disintegration. As the dry and wet cycle numbers increase, the relationship curve between cumulative percentage of each group of mudstone disintegration gradually moves toward the smaller particle size; the gap between the curves decreases continuously, and finally attain basic stable. This indicates that the disintegration rate of the mudstone is gradually reduced and finally stabilizes. Besides, based on the optimized gradation equation, the relative slake durability index is derived and the correctness of the model is verified. As the sample lumpiness increases, its slake durability index and relative slake durability index all decrease.