Abstract: In the artificial made land project, the soft marine cohesive soils usually require improvement and the vacuum preloading is a frequently used soil improvement method. Before the vacuum can be applied, a layer of black fine sand is applied over the soft mucky clay so that a working platform can be created for the construction equipment. This paper presents the cementation of black fine sand by using MicrobialInduced Calcite Precipitation (MICP) method to reduce the thickness of the sand without reducing the bearing capacity. The effect of solution set up time, concentration and the velocity on the MICP sand cementation is evaluated by analysis the calcium ion utilization, distribution of calcium carbonate in the solidified sand column and the unconfined compressive strength. The results indicate that it is feasible to use MICP method for the rapid sand cementation. The solidified sand column can reach an unconfined compressive strength of 1.91 MPa in a short period of time. The results also show that the unconfined compressive strength has an index relationship with the concentration of calcium carbonate in the solidified sand column. The best result from the solution with 3 hour set up time, concentration of 0.75M with a velocity of 10ml/min.

Key words: Microbial-Induced Calcite Precipitation, Cementation of Sand, Utilization Ratio of Calcium Ion, Unconfined Compressive Strength