Disintegration behavior and mechanism of carbonaceous mudstone under acidic corrosion and wetting-drying cycles

摘要

The disintegration of carbonaceous mudstone under the recurring action of acid rain increases the risk of geohazard occurrence.In this paper, a series of disintegration tests were conducted at pH values of 1, 3, 5, and 7 to investigate the disintegrationbehavior and disintegration mechanism of carbonaceous mudstone under acidic corrosion and wetting-drying cycles.The disintegration process can be divided into three stages (e.g., water absorption saturation, fracture expansion, and surfaceexfoliation). With the increase of wetting-drying cycles, the particle size of carbonaceous mudstone gradually decreases,and the particle size gradation curve of carbonaceous mudstone after disintegration is S-shaped, which is consistent withWeibull function distribution. A smaller value of the Weibull model parameter λ (the scale parameter) results in a smalleraverage particle size of the carbonaceous mudstone disintegration products, and the value of k (the shape parameter) revealsthe degree of drastic change in the grain gradation of carbonaceous mudstone k and λ together reflect the rate of carbonaceousmudstone disintegration. A smaller decrease in the disintegration ratio and decreasing rate is observed with an increase inthe number of wetting-drying cycles. The disintegration ratios of carbonaceous mudstone under the four pH conditions fromlargest to smallest are pH = 7 > pH = 5 > pH = 3 > pH = 1. The disintegration of carbonaceous mudstone is mainly causedby hydration-swelling, adsorption-fracturing, and dissolution-erosion. The presence of acid promotes the dissolution-erosionof carbonate in carbonaceous mudstones, which in turn accelerates the hydration-swelling and adsorption-fracturing as wellas the disintegration ratio of carbonaceous mudstones.