Disintegration Characteristics and Mechanisms of Carbonaceous Mudstone Subjected to Load and Cyclic Drying–Wetting

Carbonaceous mudstone is a common embankment material with the characteristics of water softening and water disintegration, which often causes the instability of embankments. This paper presents an experimental work on the disintegration characteristics and mechanisms of carbonaceous mudstone under the combined action of load and cyclic drying–wetting. Disintegration tests were conducted by a novel instrument. Afterward, the evolution of disintegration parameters [i.e., coefficient of uniformity ($C_{\mathrm{u}}$), coefficient of curvature ($C_{\mathrm{c}}$), disintegration rate (DRE), disintegration ratio ($Dr$), and fractal dimension ($D$)] during the disintegration process was studied. Finally, the gray relational theory was used to evaluate the impact of disintegration characteristics on the degree of stability of carbonaceous mudstone. The results show that the large particles decrease in number and the small particles increase in number with increasing drying–wetting cycles. Moreover, the DREs of carbonaceous mudstone are very high with final values larger than 10% in all cases. Generally, the larger the load is, the higher the DRE is, while the lower the $Dr$ is. The $D$ increases with the increase of load and number of cycles. The results of gray relation analysis show that the variation in the $Dr$ is the best parameter for characterizing the disintegration of carbonaceous mudstone. The $Dr$ of carbonaceous mudstone decreases with increasing number of drying–wetting cycles under different loads, which can provide a useful reference for the stability analysis and engineering practice of carbonaceous mudstone embankments.