Influences of wetting-drying cycles on expansive soils improved with disintegrated sandstone with different particle size groups

Based on the project of diverting water from Yangtze River to Huaihe River, the long-term effect of the improved expansive soils with disintegrated sandstone waste from river excavation is studied. The results show that: (1) The disintegrated sandstone improves the compactness and strength characteristics of the expansive soils. The improved expansive soils have the best compactness when the particle size of the disintegrated sandstone is less than 2 mm. The direct shear index of the physically improved soils is positively correlated with the particle size of the sandstone. The direct shear index of the compositely improved soils is mainly controlled by the improvement of cement, and the influences of particle size of the sandstone is not obvious. (2) The disintegrated sandstone can inhibit the cracking of the improved expansive soils during wetting-drying cycles. When the particle size of the sandstone is larger than 10 mm, there will be crack concentration in the surrounding soils. The crack rate of the compositely improved soils is significantly lower than that of the cement-improved soils, and has no significant correlation with the particle size of the sandstone. (3) The disintegrated sandstone has the effect of delaying the cohesion attenuation of the improved soils in the process of wetting-drying cycles, and the effect is affected by the particle size of the sandstone. The particle size of sandstone shall not be greater than 10 mm in the physically improved soils and 5 mm in the compositely improved soils. (4) The microscopic evolution characteristics of the disintegrated sandstone affect the macroscopic crack development and strength attenuation of the improved soils.