Experimental Study On Consolidation Rheological Properties Of Cangzhou Coastal

The distribution of soft clay in the world is very wide,and the distribution areas are mostly coastal cities.Coastal cities have rapid economic development,and a lot of accompanying infrastructure projects have been put into construction.The evaluation of the mechanical properties of soft clay,especially the time-dependent mechanical and deformation characteristics,is of great significance to the long-term stability of the project.This paper takes Cangzhou coastal soft clay as the research object,and conducts a series of experimental studies on its rheological properties.The specific content is as follows.1.One-dimensional consolidation instrument was used to carry out experimental research on the one-dimensional rheological properties of Cangzhou coastal soft clay.Under the condition of graded loading,the deformation law of the soft clay in the area under different preloading conditions is studied.The tests show that the rheological deformation of Cangzhou coastal soft clay is nonlinear.Under the preload load,the amount of creep deformation decreases,and the greater the level of preload load,the smaller the creep deformation amount.The pre-compressive load will affect the primary and secondary consolidation stages.The pre-compressive load is small,and the deformation is divided into two stages: primary consolidation and secondary consolidation.The pre-compressive load increases and the deformation is mainly creep deformation.The initial porosity is affected by the preload.The larger the preload,the smaller the initial porosity.Under the same preload,the secondary consolidation system first increases and then decreases as the vertical load level increases;at the same vertical stress level,the greater the preload load level,the smaller the secondary consolidation coefficient.Using one-dimensional consolidation instrument to carry out experimental research on one-dimensional rheological properties of Cangzhou coastal soft clay.Under the condition of graded loading,the deformation law of the soft clay in the area under different preloading conditions is studied.2.Under hierarchical loading,a three-axis rheometer was used to experimentally study the three-dimensional rheological properties of Cangzhou coastal soft clay,and its deformation law under different drainage conditions and different confining pressure conditions was studied.The larger the confining pressure,the shorter the time for vertical deformation to reach stability,and the smaller the final creep deformation.The confining pressure level will affect the primary and secondary consolidation deformation stages.The greater the confining pressure,the shorter the time to enter creep deformation.The level ofconfining pressure also affects the yield stress.The greater the confining pressure,the greater the yield stress.Under different drainage conditions,the rheological characteristics of Cangzhou coastal soft clay are different.When the level of partial stress is small,the creep deformation under drainage is greater,and when the level of partial stress is large,the creep deformation is greater under undrained condition.Under undrained conditions,the isochronous curve of deviatoric stress and vertical strain is nonlinear and has a significant yield point.The deformation phase of soil samples under undrained conditions can be regarded as viscoelastic and viscoplastic deformation.Under drainage conditions,the relationship between the deviating stress and the isochronous curve of vertical strain shows a linear relationship,and the deformation of soil samples is mainly viscoelastic deformation.Based on the triaxial rheological test results,establish a theoretical model and an empirical model that can reflect the rheological laws of Cangzhou coastal soft clay.The theoretical model in this paper chooses the ellipse-parabolic double yield surface model considering rheological properties,and the empirical model is improved based on the traditional Singh-Mitchell empirical model,so as to better describe the deformation law of soft clay in the region Model.3.Based on the triaxial rheological test results,establish a theoretical model and an empirical model that can reflect the rheological laws of Cangzhou coastal soft clay.The yield surface rheological model is based on the oblong-parabola double yield surface model proposed by Professor Yin Zongze,and it is established by the influence of time.The model parameters are determined by conventional triaxial tests and triaxial rheological tests.The empirical model is improved based on the traditional Singh-Mitchell empirical model,and the exponential relationship reflecting stress and strain is replaced by a hyperbolic function relationship,so that the deformation law of soft clay in the area can be better described.The parameters of the empirical model were determined by triaxial rheological test data analysis.4.Validate the model by inversion calculation.The deformation law under 150 kPa confining pressure was verified.The verification results show that the double-yield surface rheological model is better than the description of the body strain change in reflecting the variation law of the partial strain with time,and the verification results under the drainage conditions are more accurate.The modified Singh-Mitchell empirical model can better reflect the deformation law when the partial stress water is low,but when the partial stress level exceeds 80%,the calculation result is greater than the actual measurement result.Compared with the empirical model,the calculation results of the double yield surface rheological constitutive model are more accurate and the applicability is more extensive.At the same time,from the verification results,the rheological constitutive model established in this paper has certain applicability and can provide a certain reference for the engineering practice in the soft clay area of Cangzhou.