Microstructure properties of soft soils under marine, interactive marine, and river-lake facies sedimentary environments

The marine environment has an important influence on the microscopic and macroscopic properties of soft soils, which are different from other types of soft soils. This paper discussed the microscopic properties of marine, interactive marine, and river-lake facies soft soils and their relationship to macroscopic parameters. Geotechnical tests and field emission scanning electron microscope (FESEM) tests for three types of soft soils were carried out to study the influences of sedimentary environments on microstructure and macroscopic properties; the microstructure parameters were obtained by image processing technology and fractal theory; quantitative relationships between microstructure parameters and the macroscopic physical parameters were analyzed by multiple regression analysis methods. The results show that three sedimentary environments lead to significant differences in the microstructure of soft soils, particularly in the marine environment, with the soil particles being mostly flake stacked under marine sedimentation, flocculated in interactive marine, and agglomerated in river-lake facies. The fractional dimensions of the pores, soil particles distribution and the pore shape are 1.54, 1.78 and 1.43, respectively, the largest for the interactive marine soft soils. The probability entropies of soil particles in marine, interactive marine, and river-lake are 0.43, 0.47, and 0.53, respectively, which get bigger in order. The highest pore complexity is found in the interactive marine soft soils. The relationship formula between macroscopic physical parameters and microstructure parameters was established. It reveals that the physical parameters are expressed by joint action of pore distribution fractional dimension, soil particles probability entropy, pore shape fractional dimension and soil particles shape fractional dimension.