Structural marine soft soil layer is widely distributed in coastal region

which brings lots of potential disasters. Soft soil subgrade in the Jiangsu provincial section of an expressway is studied in this research. A new method

to obtain constitutive parameters of undisturbed soil of Shanghai model by consolidation test results of compressed soil is proposed. The subgrade settlement is simulated by soil-water coupled FEM software. The effect of soil structure

permeability and thickness of soft soil layer on subgrade settlement are analyzed. The results show that the stronger the initial soil structure is

the larger pore pressure and subgrade settlement are in loading stage. With the gradual destruction of soil structure after completion of construction

it is positively correlated with the amount of layer compression and soil structural parameters. The permeability affects settlement and settling time as well. The lower the permeability is

the larger total subgrade settlement and more proportion of post-construction settlement are. Thickness of the soft soil can also affect settlement and settling time. The thicker the soil layer is

the larger subgrade settlement and longer settling time are.