Abstract: To widen the expressway built on soft soil is an important subject in expressway construction engineering. Taking the widening project of Hang-Yong Expressway as background, the influence of additional stress in the foundation generated by the new embankment is analyzed. Based on Mohr-Coulomb model, regularity of settlement and deformation of old and new embankments are analyzed and compared with the measured data. Tension occurs in pavement due to the non-uniform settlement of the new and old embankments. Time for pavement can be determined by post construction differential settlement.