Abstract: Microbially induced calcite precipitation method, a new soil improvement technology, has a good application prospect in river bank revetment. This study chooses three different particle size ranges of sandy soil for microbial mixture-improved infiltration curing, and conducts unconfined compression tests along with the tests of calcium carbonate content, breakdown rate, and water absorption. Then, we analyse the effects of particle size, infiltration times, and mixing ratio on the curing effect, and investigate the curing mechanism of the mixing method combined with the percolation method. Results show that most of the calcium carbonate generated in the mixing stage plays a pore-filling role and the resulting degree of cementation is low, while the subsequent infiltration and solidification improve soil properties significantly. With a mixing ratio of 2:8 and a particle size range of 0.3 - 0.6 mm, the samples manifest a better curing effect and their compressive strength is increased up to 1.86 MPa. Their calcium carbonate content and compressive strength are increased nonlinearly with the increase in filtration times, while the upper limit of strength increased with particle size. The test results reveal that the lowest disintegration rate is 2% and the lowest water absorption rate is 9.26%. Compared with typical clay soils, the solidified samples have stronger water erosion resistance and certain permeability, indicating a certain application value for river bank protection and construction technology.

Key words: microbially induced calcite precipitation method, particle size, unconfined compressive strength, disintegration rate, water absorption