Abstract: Mixed sand containing carbonate, as a special geo-material, is mainly distributed in tropical coastal areas. Its unique genesis and composite structure result in different geotechnical engineering characteristics compared to terrigenous sand. Triaxial tests were carried out on the mixed sand with different contents of calcium carbonate under different confining pressures. The testing materials were prepared with coral sand from the South China Sea and silicon sand from the Changjiang River with different mass percentages. The results show that: 1) the peak strength increases approximately linearly with the increase of effective confining pressure and calcium carbonate content; 2) confining pressure and carbonate content are the main parameters influencing the dilatancy characteristics of the mixed sand. The increase of carbonate content results in the transition point between dilation and contraction response and its corresponding axial strain to increase; 3) with the increase of carbonate content, the peak value of cohesion increases linearly and the internal friction angle increase slightly; 4) the relative crushing rate of mixed sand increases with the increase of the calcium carbonate content and confining pressure.

Key words: carbonate mixed sand, calcium carbonate content, shear strength, particle breakage