Abstract: Disintegration of mudstone is important in geotechnical engineering of southwest China. By indoor disintegration resistance test, disintegration features of mudstone are described in detail from three aspects, including morphological changes of disintegration products, disintegration resistance index and particle size analysis. On the basis of disintegration resistance index, disintegration intensity is divided into three levels: strong disintegration, middle disintegration and weak disintegration, and the disintegration mechanism is also classified into three types: swell disintegration after absorbing water, disintegration under wedging pressure and disintegration under mixed factors. Results show that as standard cycle times of disintegration increase, disintegration resistance index of mudstone decreases in negative exponential distribution. Furthermore, strong disintegration mudstone belongs to the mechanism of swell disintegration after absorbing water, weak disintegration mudstone and middle disintegration mudstone belong to that of disintegration under wedging pressure and disintegration under mixed factors, respectively. Finally, disintegration intensity is obviously relevant to the particle size and disintegration mechanism of disintegration product. Particle size of strong or weak disintegration product has a polarization trend, yet that of middle disintegration product is mainly middle-size.

Key words: mudstone, disintegration resistance, disintegration resistance index, disintegration mechanism, particle size analysis