Abstract: Under desiccation conditions, the argillaceous cement of red bed mudstone will crack due to the change of water content, and the cracks will develop further and finally lead to the disintegration of red mudstone. At present, the research on the disintegration mechanism of red mudstone is mostly qualitative description, lack of quantitative analysis method. Therefore, the quantitative study of the occurrence and propagation of the red mudstone argillaceous cement cracking is of great significance to the further theoretical study of the red mudstone disintegration. Based on linear elastic fracture mechanics and unsaturated soil mechanics, a formula that considering water content change was developed to calculate crack depth and spacing of argillaceous cement in red mudstone, and the sensitivity of the formula parameters was analyzed. CT test data were used to calibrate the PFC2D numerical model, and based on the numerical test results of desiccation cracking, the formulas of fracture depth and spacing were compared and verified. The proposed formula can well predict the crack depth and spacing of the red layer argillaceous cement, and the crack depth increases rapidly at first and then slowly with the decrease of water content. The research results are helpful to deepen the quantitative theoretical analysis of red mudstone disintegration and provide reference for predicting the degree of red mudstone cracking in engineering.

Key words: argillaceous cement of red bed mudstone, desiccation cracking, fracture mechanics, crack depth, crack spacing