Abstract: It is of great practical significance to study the engineering characteristics and settlement rules of soft ground. Based on the laboratory test results and observed data of settlement deformation of soft ground of Suining-Ziyang expressway in Sichuan Province, the engineering characteristics and settlement rules are analyzed. Some conclusions are drawn as follows: (1) the soft clay is uniformly distributed composed of high- and low-liquid limit clay. Its physical parameters are lower than those in part of the coastal areas of China, but its mechanical parameters are higher; (2) the main physical and mechanical parameters of the soft clay have a linear correlation. According to the correlation, the physical and mechanical parameters can be forecasted and controlled; (3) the consolidation coefficient has a nolinear to linear decrease as the stress increases. The creep of the soft clay is nonlinear and time-dependent. There are three types of creep curves, and thus the primary and secondary compressions can be distinguished; (4) the mathematical relationships between the settlement and the thickness of the soft clay are proposed based on the observated data of soft soil subgrade treated by plastic drainage plates and stone columns.