Abstract: To use seawater as the raw material in the reef foundation reinforcement based on microbial induced calcite precipitation (MICP), seawater concentration test and MICP sand reinforcement test with concentrated seawater as calcium source solution were carried out. In this work, the influence of bacterial fixation mode, bacterial injection batch, the urea concentration in cement solution and the injection velocity of cement solution on the reinforcement effect were studied. The research results showed that the maximum concentration of seawater is three times the original concentration under the condition of no precipitation of calcium ion, and the content of calcium ion is about 0.033 mol/L. The amount of urea added should be 3 times that of the content of calcium ion in concentrated seawater, so that the calcium ion in cementation liquid can be effectively used to produce precipitation. The best reinforcement effect can be obtained by using the cement injection velocity of 2 mL/min to reinforce 5 cm sand column samples. After reinforcement, the unconfined compressive strength of the sand column sample can reach 653 kPa, which takes 4.5 days. Increasing the batch of bacterial injection cannot effectively improve the reinforcement effect of the sand column.

Key words: microbial induced calcium precipitation, sand column reinforcement, seawater