Abstract: The deep-sea sediment is exploited in the Pacific C-C district by our research group. Its physico-mechanical properties are studied by analysis of laser particle size, test of liquid and plastic limit, tests of nitrogen adsorption, consolidation and direct shear, and its mineral compositions and microstructures are analyzed by X-ray diffraction(XRD) and scanning electronic microscope(SEM) methods, respectively. Test results show that the deep-sea sediment is clay soil with predominant silt. It has properties of high liquid limit, high plasticity, high specific surface area, high consolidation coefficient, low compressive modulus and low shear strength, which easily results in slip and subsidence of the deep-sea mining machine. It is mainly composed of montmorillonite, quartz, feldspar, mica, chlorite and serpentine, with sheet-linked microstructure of silt and microbial debris filling with honeycomb flocculation microstructure of clay mineral together. The simulative soil substituting for the deep-sea sediment should be prepared based on the mineral composition, particle size, water content, specific surface area and shear strength as well as liquid limit, plastic limit and microstructure of the deep-sea sediment. The research results can provide an important basis for walking-characteristic study and optimization design of the deep-sea mining machine.

Key words: physical properties, mechanical properties, mineral composition, microstructure, deep-sea sediment