GT soil firming agent is a kind of new material that modifies and reinforces soil. Its main raw materials are industry waste materials of high calcium ash and desulfurated gypsum; and its minor constituents are quicklime

cement

plaster

sulfuric acid aluminum

alunite

etc. It is synthesized with ingredient method of full powder

by removing free water of desulfurated gypsum using counteraction way of quicklime. The improved soils were made by adding lime and GT soil firming agent with given proportion

and then were cured and submerged underwater. Compaction tests

direct shear tests

compression tests and permeability tests were carried out. The tests indicate that the engineering properties of GT soil firming agent improved soil

such as compaction effect

shearing strength

compressibility and resistance to permeability

are better than lime-improved soil. Improving mechanism of GT soil firming agent is studied further more. The results can be for reference to further study and engineering application.