Research On One-dimensional Consolidation Creep Characteristics And Constitutive Model Of Soft Soil

Urban rail transit has been developing rapidly in recent years,and in just over 20 years,the total length of urban rail transit in China has jumped to the first place in the world.The coastal cities are developing rapidly and their rail transit development is the focus of China’s rail transit development.However,soft clay is widely distributed in coastal areas with obvious aging properties.Thus its creep characteristics will cause serious post-construction settlement problems in the number of projects.Therefore,it is particularly important to study the creep characteristics of soft soil in our coastal cities.The research on the creep characteristics of soft soil in Ningbo can help to the research of the soil in other coastal areas.The soil samples studied in this paper are from the construction site of the Ningbo rail transit project.The indoor tests are completed in the geotechnical laboratory of the Zhejiang Engineering Survey and Design Institute.One-dimensional consolidation creep test,direct shear test,and particle analysis test are carried out for soft soils of different depths in Ningbo.The influence of preloading on the creep characteristics of soft soil is studied through the above tests.The influence of different stress states on the average viscosity coefficient of soft soil is studied,and its internal mechanism is also analyzed.By discussing the effect of soil particle size on the average viscosity coefficient,it is found that the soil with a higher proportion of small particle size has a smaller average viscosity coefficient.The stress-strain relationship of soft soil in the Ningbo area shows obvious non-linear characteristics.Different from preloaded soft soil,the non-preloaded soft soil shows obvious non-linear characteristics.According to the creep characteristics of Ningbo soft soil in the laboratory test,a five-element nonlinear constitutive model is established by introducing nonlinear elastic modulus based on the linear constitutive model.The five-element linear constitutive model and the five-element nonlinear constitutive model are fitted with the data of the one-dimensional consolidation creep test respectively.The results suggest that the linear constitutive model can be used when the consolidation pressure is small,and the nonlinear constitutive model can be used when the consolidation pressure is large.An empirical model suitable for the stable creep stage of soft soil in the Ningbo area is established,and the strain deviation error between the model and the test data is less than 5%.The settlement deformation of soft soil in the Ningbo area during the stabilization creep phase can be predicted simply and conveniently by this empirical model.The results of this paper are helpful to practical engineering problems.