Abstract: Soil is a product of nature, and influenced by factors such as sedimentation process, sedimentation conditions, and sedimentation environment. The engineering characteristic parameters of soils have variability, resulting in various indicator parameters obtained from the exploration sampling points being unable to describe the engineering characteristics of the soil layer within the scope. Based on the expressway construction project in Lixiahe area, this paper uses the random field theory to conduct the probability statistical analysis on the variability of engineering characteristic parameters of the lagoon soft soils in this area and summarizes the statistical results of variability of mechanical indexes and deformation indexes of soft soil in other regions in China. The analysis shows that the variability of physical properties indicators of soft soil in the Lixia River lagoon phase is low, while the variability of the mechanical and deformation properties indicators is relatively high. There is an obvious trend component along the depth direction, which has a significant impact on variability. After removing the trend component, the coefficient of variation can be reduced by about half.

Key words: Soft Soils, Engineering Characteristic Parameters, Variability, Probability Statistics