Abstract: Centrifugal model tests are carried out on marshy and lacustrine soft soil embankments treated by vacuum combined with surcharge preloading and reinforced by composite foundation with cement deep mixed columns, respectively. The variations of settlement and earth pressures in two centrifugal models are compared. The reinforcement effects are analyzed in an attempt to determine a suitable reinforcement method for marshy and lacustrine soft soil. Results conclude that under the same condition, the consolidation settlement of embankment treated by vacuum combined with surcharge preloading increases more rapidly than that reinforced by cement deep mixed columns: the consolidation degree reaches over 80% on the 30^th day and more than 90% on the 90^th day, yet with smaller earth pressures at each monitoring point. Moreover, the sectional settlement distribution of embankment treated by vacuum combined with surcharge preloading is more even, but the differential settlement is large in the late test period. The reinforcement effect of vacuum combined with surcharge preloading is better than composite foundation with cement deep mixed columns because post-construction settlement of the former is half of the latter. In addition, measurement of moisture content before and after centrifugal test suggest that the reinforcement depth of vacuum combined with surcharge preloading extends over ten meters in marshy and lacustrine soft soil. The settlement fitting equations of the two centrifugal models are both exponential functions, which fit well with monitored settlement curves and can be used to predict the long-term consolidation settlement of embankment. In conclusion, vacuum combined with surcharge preloading is superior to composite foundation with cement deep mixed columns.

Key words: marshy and lacustrine soft soils, centrifugal model test, vacuum combined with surcharge preloading, composite foundation with cement deep mixed columns, consolidation settlement