Abstract: This study aims to improve the cementation effect of microbially induced carbonate precipitation (MICP) technology on calcareous sand in the marine environment. On the basis of previous studies, the multi-gradient artificial domestication and culture test of Sporosarcina pasteurii in the artificial seawater environment was carried out. Combined with the mechanical test and microstructural analysis of MICP-cemented calcareous sand column, the domestication effect of Sporosarcina pasteurii was evaluated. The results showed that: (1) The bacterial concentration after five-gradient domestication in the seawater environment can reach more than 97% of that in the freshwater environment, and after interaction with cementing fluid, the carbonate production was increased to a certain extent compared with that in the freshwater environment. (2) The domesticated Sporosarcina pasteurii had a strong temperature adaptability, and it had a good MICP performance at 10 ℃ to 30 ℃. (3) Both carbonate production and unconfined compressive strength of calcareous sand columns cemented in the seawater environment were higher than those before domestication, especially for the bacteria after five-gradient domestication. The bacteria after domestication became smaller, thus the carbonate crystals (calcium carbonate and magnesium carbonate) generated in the seawater environment became smaller and denser. They can better fill the pores between calcareous sand particles and cement the adjacent calcareous sand particles, indicating that the Sporosarcina pasteurii after domestication had an excellent MICP performance. The relevant ideas and methods can provide reference for the research and application of MICP technology in the reinforcement of calcareous sand foundation in the seawater environment.

Key words: cementation in seawater environment, gradient domestication, calcareous sand, Sporosarcina pasteurii, microbially induced carbonate precipitation (MICP)