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.