Abstract: Study on the phase transition properties and rheological model of submarine sediments during rheological testing is of great significance to the safety assessment for submarine structures. Using the soft clay in South China Sea, five group samples with different water contents were prepared, and a series of rheological tests under different temperature was carried out using the MCR302 rheometer. The results show that shear stress increases rapidly then increases slowly with increasing shear rate, while apparent viscosity decreases rapidly then decreases slowly. The shear stress and apparent viscosity decrease with increase in water content, and they increase with decrease in temperature. Phase transition happens in soft clay during shearing and can be divided into static and dynamic yield stresses, and the models for static and dynamic yield stresses were established on the basis of experimental results. In addition, Dual-Bingham rheological model considering effects of water content and temperature for soft clay from South China Sea was established, and the efficiency of model was verified. The results of this paper can provide basic model for the numerical analysis of submarine structure stability in South China Sea.

Key words: soft clay in South China Sea, phase transition, water content, temperature, rheological model