Study On Shear Creep Characteristics And Model Of Saturated Cohesive Soil

In recent decades,high speed railways and underground railways have been built on the cohesive soils of coastal areas.Clayey soil's behavior is highly time-dependent,and the resulting in long term defferential settlemant under loading,which may cause track irregularity,damage track structure and reduce its service life.Therefore,a correct understanding of the deformation time characteristics of cohesive soil is of great significance for guiding the underground and infrastructure construction and operation and maintenance of the area.In this paper,the shear creep behavior of cohesive soil is studied through indoor triaxial shear creep test.The main contents and achievements are as follows.1.Triaxial shear creep test of the original soil under multistage loading shows that the deformation of the original soil presents the characteristics of nonlinear attenuation creep,and there are obvious rapid growth,slow growth and stable three stages,and the higher the load level,the longer the deformation reaches the stable time.The division of primary and secondary consolidation stages of silty clay under different loading conditions was tried by both curve characteristic method and pore pressure dissipation method.The results show that the t_EOP determined by the former is smaller than that determined by the latter.With the higher load level,the greater the starting point of secondary consolidation is t_EOP,it is suggested that the curve characteristic method be used to divide the primary and secondary consolidation,and the pore pressure dispersion corresponding to the time of determination of the original soil is about 80%.2.Triaxial shear creep tests under different loading modes and different confining pressure of the remolded soil showed that the deformation of the remolded soil also showed the characteristics of nonlinear attenuation creep.When using curve characteristic method to divide primary and secondary consolidation,The pore pressure dispersion of 400kPa under confining pressure is about 75%,and the pore pressure dispersion of 600kPa under confining pressure is about 85%.The higher the confining pressure is,the smaller the final deformation is.The more the step loading is,the smaller the final deformation is.The deformation capacity of intact soil is higher than that of remolded soil under the same load.3.Based on the test,a hyperbolic creep model describing cohesive soil is established.The parameters of total stress creep and effective stress creep are discussed respectively for undisturbed soil and remolded soil.?1?From the total stress creep analysis,the shear stress level and the initial void ratio are the main factors affecting the creep model parameters.Generally speaking,A_s?strain parameter?is directly proportional to D_r?stress level?,which is inversely proportional to e₀?initial void ratio?,while B_s is also affected by soil structure.?2?Effective stress creep analysis shows that A_s is positively correlated with D_r,and is influenced by structure,while B_s is also affected by soil structure.4.The hyperbolic creep model is suitable for intact soil and remolded soil.The total stress creep is good,and the parameter value rule is good,which is convenient for engineering application.