Using soda residue (SR)-ground granulated blast furnace slag (GGBS)-carbide slag (CS) and cement as solidifiers of sludge, the dry-wet durability of solidified sludge under capillary immersion and full immersion in seawater are conducted, and the influence laws and mechanisms of different immersion methods on the durability of solidified silt under seawater erosion environment are investigated. The results show that: SR-GGBS-CS solidified sludge shows better dry-wet durability than cement solidified sludge when cement dosage equals GGBS dosage. Generally, the samples in full immersion mode are damage severely, and show a high mass loss rate and low unconfined compressive strength. However, the strength of the sample in capillary immersion mode is lower than that in full immersion mode when the solidifier dosage and dry-wet cycles increase. The corrosive ions rising with the capillary water cause salt crystallization and the formation of Thaumasite, which deepens the inhomogeneity and damage for the samples under the coupling effects of multiple dry-wet cycles and seawater. Therefore, the adverse effect of capillary immersion on the dry-wet durability of solidified sludge gradually exceeds that of full immersion, and the zone above groundwater is the weakest.

In order to reveal the impact of the coupling effect of dry-wet cycles and erosion on the properties of solidified silt, dredged silt was solidified with soda residue, slag and carbide slag as solidifying agents. The appearance, unconfined compressive strength and damage of solidified silt were studied under the coupling effect of capillary infiltration wetting-drying cycles and erosion environments such as distilled water, seawater and magnesium sulfate, and the coupling action laws, mechanisms and optimal solidifying agent dosages were explored. The results show that the coupling effect of magnesium sulfate erosion and wetting-drying cycles results in the most serious appearance damage and the most significant reduction in strength of the specimens. Increasing the slag content can improve the durability of the solidified silt. When the slag contents are 20% and 15%, respectively, the soda residue content should not exceed 25% and 35%. The coupling effect of seawater and magnesium sulfate erosion with multiple wetting-drying cycles causes the specimens to quickly reach the damage and failure state with the increase of strain. The coupling effect of seawater erosion and wetting-drying cycles leads to the formation of more ettringite and NaCl crystals in the specimens. With the increase in the number of cycles, the NaCl crystals increase, the inhomogeneity of the specimens is enhanced, and the numbers of mesopores and macropores increase. The coupling effect of magnesium sulfate erosion and wetting-drying cycles results in the reduction of hydration products such as calcium silicate hydrate. Expansive CaSO₄·2H₂O precipitates when the soda residue content is too high, leading to a decline in the durability of solidified silt. The coupling effect of capillary infiltration wetting-drying cycles and erosion causes serious macroscopic and microscopic damages to solidified silt.