Effects of chemical conditions on the engineering properties and microscopic characteristics of Tianjin dredged fill

Chemical conditions have significant effects on the engineering properties and microscopic characteristics of the dredged fill. In this study, a series of laboratory tests were conducted to investigate the engineering properties and microscopic characteristics of the dredged fill under different chemical conditions. In addition, the micromechanism of the effect of chemical conditions on the engineering properties of the dredged fill is revealed. Under alkaline conditions, the undrained shear strength and structural yield stress increased by 50.33 and 145 kPa, respectively. The particle morphology was transformed from a granular and flaky structure to an agglomerated structure, and the surface-to-surface connection was the main form of intergranular connection. These changes reflect the enhancement of the intergranular cementation strength of the dredged fill by the generated insoluble substances and suggest that adding a certain amount of alkaline materials is an effective method to improve the engineering properties of dredged fill. Under acidic conditions, the undrained shear strength was significantly decreased, while the compressibility was notably increased. The cementation between soil particles was severely damaged due to the corrosion of hydrogen ions, leading to an increase in the number of large-diameter pores in the dredged fill and a deterioration of the microstructural characteristics. Under saline conditions, the undrained shear strength was reduced by 5 kPa, and the compressibility was increased. No distinct agglomerated structures were formed due to the dispersion of the internal particles of the dredged fill, and the soil skeleton effect was not notable.