Abstract: Calcareous silt interlayer with uneven thickness and disjunct distribution, is normally generated inside the building foundation during South China Sea Island reef reclamation project. Until now, investigation on the mechanical behavior of calcareous silt soils in the high-salt sea environment are scarcely carried out. In this paper, a series of direct shear tests, laser particle size analysis, Zeta potential analysis and SEM tests were respectively performed to study effects of water-salt ratio on shearing behaviors of calcareous silt soils. Experimental results demonstrated that the shear strength and internal friction angle of calcareous silt firstly decreased and then increased with the increase of water-salt ratio, but the cohesive force of soils showed an opposite pattern. When entering to the supersaturation stage of salt content, the shear strength and internal friction angle continuously increased with increasing water-salt ratio, while the cohesive force monotonically decreased. Microstructural test results revealed that, the increase in salt content can improve the aggregation of silty soil particles and reduce the particle surface potential, but this phenomenon becomes not significant at higher salt contents. After entering the supersaturation stage, salt crystals were formed inside the soils, which could improve the bonding degree between particles and promote lubrication of particle contact surfaces by wrapping fine particles.

Key words: calcareous silt, water-salt ratio, shear behavior, particle size analysis, Zeta potential analysis