Improvement of super deep and soft ground under embankment of expressway with combination method of vacuum and preloading

The embankment of an expressway is constructed by material whose anti deformation ability is very bad, and its fill height is larger than 6 m. The ground contains a muddy clay with thickness of 20 m and water content of 43%~70%. For the stability and settlement of embankment, combination method of vacuum and preloading is adaped to improve the foundation. It is indicated that the improvement effect is very obvious. Compared with preloading, the period of construction can be decrease halfly, the settlement of roadbed reduced 10%. The strength of soil is increased by more than 2 times. The consolidation degree of soil is larger than 95% after the embankment of height of 6.7 m is filled and vacuum preloading is constructed for 2 months. The displacement of foundation soil is smaller than 1.0 mm/d during the construction of embankment, and the embankment and ground soil is stable. The settlement of roadbed is smaller than 20 cm during the operation. The experience can be referenced to the other and similar engineerings.