Research On Melt-sinking Characteristics Of Unsaturated Saline Soil Based On Elasto-viscoplastic Model

With the implementation of the “The Belt and Road” national strategy recently,China is preparing to infrastructure construction such as highway,railway,inevitably based on the salted soil.Soil salinity is a common soil which causes disease with high frequency.It is mainly manifested in poor compact-ability at drying status,hardly achieves the schedule.However,bearing capacity will decrease and deforms obviously at wetting status.The disease caused by soaking water threatens the safe operation of the highway and railway every moment.It is of great value and significance to establish a method for predicting the melt-sinking deformation of saline soil for controlling engineering risk and evaluating operation safety.In this paper,the empirical equation of the melt-sinking deformation have been revealed basing on laboratory experiment for the disease of Second Double Line of Lanzhou-Xinjiang railway.The empirical formula is introduced to elasto-viscoplastic unsaturated soil model,which has formed melt-sinking model of saline soil based on elasto-viscoplastic unsaturated constitutive model.Finally,the numerical simulation of one dimensional laboratory experiment is carried out,in addition,the model is extended to two dimensions and the two-dimensional numerical simulation of field test for engineering example is verified.The main contents and conclusions of this paper are as follows.(1)The improvement of the experimental device had been carried out to expand the study on the deformation range of saline soil.The results show that the compression and melk-sinking deformation of the saline soil are mainly influenced by the vertical load,the salt content and the degree of compaction.The collapse coefficient increases with the increase of the axial pressure and decreases with the increase of the degree of compaction and increases with the increase of salt content.The empirical formula of dissolving deformation is an exponential type with two parameters,which are the maximum strain and the strain rate.(2)Based on the elasto-viscoplastic constitutive model of unsaturated soil,the empirical formula of settlement and deformation of saline soil is introduced,and the related parameters of soil subsidence are added to the soil structure failure.The main characteristics of this model are as follows: the effect of soil matrix suction on soil deformation and the influence of settlement deformation on soil structure.(3)Basing on the simulation of one dimensional consolidation room,it found that the viscoplastic constitutive model was ideal for the simulation of unsaturated soil.Empirical formula of the melt-sinking of salted soil with exponential type can be more reasonably reacted to one-dimensional test in laboratory(4)It is feasible to verify the constitutive model in the case of two dimensions from the simulation results of matrix suction,melt-sinking deformation and the law of water migration.Finally,the results of numerical analysis of an engineering found simulation results of Second Double Line of Lanzhou-Xinjiang railway are basically consistent with the actual.