Abstract：Numerical method combined with field investigation is employed to explore the sliding failure mechanism of Taihua highway embankment during construction，which is built on soft soils and the soft soils are improved with stone columns. The analytical results show that the original design using stone columns to improve soft soils is not acceptable because the undrained shear strength of the soft soils is too low to confine the stone columns efficiently. As a result，no completed stone columns are formed in the soft soils，with which the high rate of embankment filling causes the sliding failure of the embankment slope. In addition，a treatment method by using rigid concrete tube-pile is presented. For the compression stiffness of pile is greater than those of soft soils，most of the embankment loads are borne by piles，and the remaining load is carried by the soft soils，which allow the embankment to be built in a single stage without further endangering of undrained failure of soft soils and the settlement of embankment can be reduced. Numerical analysis and field monitoring results both demonstrate that the soft soils treated by using rigid concrete tube-pile is successful.
