湿地湖泊相软土加固方案及固结沉降离心模型试验研究

为研究湿地湖泊相软土的软基加固方案及固结沉降规律,分别进行真空堆载联合预压和水泥土搅拌桩复合地基加固湿地湖泊相软土路基的离心模型试验,对比分析2种方案的沉降发展和土压力变化情况。试验结果表明:相同条件下,真空堆载联合预压固结沉降发展更快,第30天固结度达到80%以上,第90天达到90%以上,且各测点土压力值更小;真空堆载联合预压下路堤横断面沉降分布更均匀,但后期沉降差较大,真空堆载联合预压的工后沉降约为水泥土搅拌桩复合地基的一半,加固效果更好;由含水率测试可知,真空堆载联合预压的影响深度至埋深10 m以下;2个模型的沉降拟合公式都为指数型函数,与实际沉降拟合较好,可预测长期的固结沉降。真空堆载联合预压方案优于水泥土搅拌桩复合地基加固方案。

Centrifugal Model Test on Reinforcement Methods and Consolidation Settlement of Marshy and Lacustrine Soft Soils

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.