Abstract: Through the sludge solidification technology, the municipal sludge is transformed into a new type of municipal sludge solidified soil. In order to study the engineering properties of the sludge solidified soil, the unconfined strength test, shrinkage test, leaching toxicity test and microstructure test are carried out on the new type of municipal sewage sludge solidified soil. The test results show that the unconfined compressive strength of urban sludge solidified soil increases with the aging period, and basically stable after 28 days. The linear shrinkage of new city sludge solidified soil increases with age, and 28 days later tend to a stable value; compared with city sludge solidified soil after digestion, the leaching toxicity of city sludge solidification in soil decreased, the leaching amount of heavy metals are in line with the requirements of national standard. The peak of calcium hydroxide in the urban sludge after lime digestion diffraction peak is very high; but with the increase of curing age, the diffraction peak of calcium hydroxide in the city sludge solidified soil decreased; the diffraction peak of calcium carbonate increased. Microstructure studies show that there is a large number of fibrous material associated with soil particles and agglomerates of particles of city sludge solidified soil in SEM images, interactive spatial structure of soil skeleton fiber, which improves the strength of the soil.

Key words: municipal sludge solidified soil, shrinkage characteristics, leaching toxicity, micromechanism