Abstract: Granite residual soil is prone to soften and disintegrate in contact with water.The effects of compactness and number of dry-wet cycles on the disintegration characteristics and disintegration indexes of granite residual soil were examined via disintegration test under dry-wet cycles.Results demonstrated that the smaller degree of compaction and the more times of dry-wet cycles,the faster the disintegration and the shorter the time required for the sample to completely disintegrate.The functional relations of average disintegration rate against number of dry-wet cycles and degree of compaction were fitted.The microstructure change of granite residual soil under dry-wet cycle was obtained by scanning electron microscope test.The micro-mechanism of disintegration was explained:with the number of dry-wet cycles increased,the lamellar structure of flake particles was destroyed,the agglomeration of particles was weakened,the plane porosity increased,and the structure tended to loose,which accelerated the disintegration of granite residual soil.

Key words: granite residual soil, dry-wet cycle, degree of compaction, disintegration, scanning electron microscope