Rheological Behaviors of Structural Soft Soil in Dongting Lake Area

Thick soft soil layers are widely distributed in inland lake areas and southeast coastal regions in China and the natural soft soil shows entirely different characteristics with remoulded soil due to the existence of structural characteristic. The structural characteristics of soft soil have been a research focus and difficult problem in geotechnical engineering and engineering practice. By taking the structural soft soil in Dongting Lake area as the research object, the indoor one-dimensional (1D) consolidation rheological test was conducted to fit and analyze the test data. Moreover, the analytical solution under the 1D consolidation was deduced according to fitted rheological constitutive model to reveal the rheological behaviors of structural soft soil under different stress levels. The research results showed that the soft soil of the lake area has a stress threshold. The threshold is 0 at a low stress level, and the rheological behavior of soft soil complies with the law of Schiffman model and soft soil has a low consolidation rate. At a high stress level, the stress threshold is close to a constant and in this context, the rheological behavior of soft soil conforms to the law of Nishihara model with a rapid consolidation rate of soft soil. The consolidation rate of the soft soil in the lake area accelerates with the increase of the stress threshold while slows down with the growth of pre-stressed loads. Therefore, it can be concluded that different settlement calculation methods need to be used according to the imposed loads during the engineering construction in the lake area with structural soft soil.