Study On Consolidation Creep Characteristics And Model Of The Benggang Soil

The consolidation creep characteristics of the collapsed soil are the key to the instability of the collapsed wall.Accurate analysis of the differences in the consolidation creep characteristics of the collapsed soil under different conditions is particularly important for the study of the occurrence and development of the Benggang.Therefore,this study combines the indoor one-dimensional consolidation creep test and consolidation creep theoretical model to analyze the consolidation and creep characteristics of different layers soil of typical Benggang under different initial dry density conditions and consolidation pressure,and establishes a consolidation creep model suitable for the Benggang soil for numerical simulation.The main conclusions are as follows:（1）The strain change process of the Benggang soil has obvious nonlinear characteristics,which can be divided into instantaneous strain stage,decaying creep stage and stable creep stage.The instantaneous strain and decaying creep strain account for 89%of the total strain,and the stable creep strain accounts for about 11%;The stress-strain relationship of collapsed soil conforms to the hyperbolic model（R²>0.9632）.（2）After 60min,the Benggang soil completely enters the secondary consolidation（creep）stage.The stable creep rate is shown as the debris layer being greater than the sand soil layer being greater than the red soil layer,the viscosity coefficient being greater than the sand soil layer being greater than the debris layer,and the secondary consolidation coefficient being generally greater than the red soil layer and the sand soil layer.All these indicate that the creep rate of the lower soil mass is greater than that of the upper soil mass,which is an important reason for the collapse of the collapsed wall.（3）The inflection point pressure of consolidation compression of the Benggang soil is 400k Pa,which is suitable for use as the consolidation pressure in engineering.The consolidation coefficient of the Benggang soil decreases with the increase of consolidation pressure on the whole,the consolidation coefficient of the sand layer and the debris layer is greater than that of the red soil layer,and the consolidation coefficient of remolded soil increases with the increase of initial dry density on the whole;Classification according to compression coefficient a_1-2,the Benggang soil belongs to medium-high compressibility soil.The variation range of the red soil layer a_1-2 is 0.20～1.27MPa^-1,and that of the sand layer is0.46～1.02MPa^-1,and that of the debris layer is 0.22～1.18MPa^-1.（4）The fractional Burgers model can well describe the consolidation and creep process of the Benggang soil;In model parameters,₀ and₁are increases linearly with the increase of stress,and₀ of remolded soil and₁ of undisturbed soil are also increases linearly with the increase of stress;Theαandβof the red soil layer and the sand layer have certain dispersion with the change of stress,and that of the debris layer are good fitting with four-parameter equation.The numerical simulation is carried out by compiling the UMAT subroutine of the fractional Burgers model,and the results are in good agreement with the experimental data,which can be used to simulate and predict the consolidation and creep process of the Benggang soil.