Abstract: In the humid and rainy coastal areas of Fujian, the granite residual soil is easy to disintegrate in water, resulting in geological hazards such as landslides, which has a great impact on the slope stability and the road engineering. Therefore, it is necessary to pay close attention to its disintegration characteristics and the occurrence mechanism. In this paper, a granite residual soil in Sanming City, Fujian Province is taken as the research object, and a series of the disintegration test devices are designed. The disintegration tests of the granite residual soil samples under three conditions of the undisturbed soil, the remolded compaction and the cement improvement are performed. The disintegration failure mechanism of the residual soil is explored from the perspective of the soil structure and the composition. The results show that the disintegration process of the granite residual soil samples can be divided into three stages: the surface disintegration stage, the structural failure disintegration stage and the cement dissolution disintegration stage. The disintegration phenomenon of the undisturbed soil sample is obvious, and the disintegration rate is the fastest, followed by the compacted sample, and finally improved sample. The variation of the disintegration rate of the granite residual soil with time is mainly that the disintegration rate of the soil increases first, reaches the peak, and then decreases. The compaction and the cement curing agent can improve the disintegration resistance of the granite residual soil, and the complete disintegration time can be extended to 3~8 times of undisturbed soil. The disintegration failure of the granite residual soil is mainly affected by soil structure, the composition, and the saturation. The combination of the three factors makes the granite residual soil have the characteristics of easy disintegration in water. The research results reveal the disintegration characteristics and the disintegration mechanism of the granite residual soil, which can provide a theoretical basis for the treatment of the granite residual soil in related projects.

Key words: Slope Engineering, Granite Residual Soil, Disintegration Rate, Disintegration Mechanism