Effect of composite erosion on the durability of microbial solidified construction waste soil

The construction waste soil is faced with the threat of freeze-thaw-wind erosion in cold and arid areas. In order to solve the durability problem of solidified construction waste soil by microbial induced calcium carbonate precipitation (MICP) technology, the strength attenuation law and micro-damage mechanism of solidified construction waste soil under combined erosion conditions were systematically studied by freeze-thaw-indoor wind tunnel test and microstructure test. The results show that with the increase of the number of composite erosion, the integrity of the apparent morphology of the sample decreases, the surface strength and the thickness of the solidified layer decrease, and the wind erosion mass loss increases gradually. However, after 9 freeze-thaw cycles, the cumulative wind erosion mass loss rate is only 0.117%, which is much lower than 8.12% of the undisturbed soil sample. The surface strength decreases by 8.29%, and the strength loss under composite erosion is 19.62%, indicating that it still has high wind erosion dust resistance and composite erosion resistance durability. The smaller the void ratio of the construction waste soil and the more the curing times, the better the curing improvement effect and the stronger the durability of the composite erosion resistance. Microscopic analysis showed that with the increase of freeze-thaw cycles, the porosity of the shallow surface layer of the sample increased, the integrity decreased, the adhesion between soil particles decreased, and the influence on the crystal morphology of calcium carbonate was small, still dominated by calcite, containing a small amount of vaterite and aragonite. Three-dimensional structure analysis further showed that the content of calcium carbonate in the surface layer increased significantly after microbial solidification, and gradually decreased with the increase of radial infiltration depth. The porosity distribution was just the opposite, and the porosity increased significantly along the radial direction.