Research On Mechanical Properties And Constitutive Model Of Saline Soil Stabilized By Lime And As

Carbonate impregnated soils are widespread on the Songnen Plain in the deep seasonal permafrost zone.The engineering properties of the soil under the long-term freezing and salt coupling have heavily influenced the regional construction and economic development of the local area.In permafrost regions affected by freeze-thaw cycles,the mechanical properties of saline soil show more obvious deterioration than that in non-permafrost regions.Inorganic modification has been widely used in the operation of infrastructure as the most economical and effective method to improve soil mechanical properties.However,the mechanical properties of saline soil in permafrost regions are restricted by complex influencing factors,resulting in strong nonlinear mechanical characteristics,which are difficult to be simulated by traditional models.One of the main tasks in permafrost mechanics is therefore the construction of an inorganically improved intrinsic model of saline soils in cold regions.This paper is based on the project of the Key Laboratory of Permafrost Engineering,"Research on Freeze-thaw Characteristics of Carbonate-stained Soil in Northeast China(SKLFSE201919).In order to solve the engineering problems caused by the coupling of freezing and salt in cold regions,firstly,this paper uses orthogonal test,variance analysis,range analysis and SPSS software analysis to obtain the optimal mix ratio of lime-fly-ash-cement improve saline soil in cold regions.Unconfined compressive strength test and consolidated-undrained triaxial shear test were carried out on the basis of the optimum mix proportion considering the environmental temperature,age,salt content,freezing temperature threshold and freeze-thaw cycles.Based on Weibull distribution,a mathematical equation with high reliability was established to describe the combined effect of freeze-thaw cycle and confining pressure on strength change,and the constitutive equation of solidified saline soil was constructed.The unconfined compression strength test results showed that the unconfined compressive strength(UCS)of the solidified saline soils at an age of 14 days can reach 75% of the maximum UCS,which basically meets the engineering construction requirements.The range of the rate of strength loss as affected by salinity was 16.2% to 75.65%,while the salt-freezing coupling effect amplified the rate of strength loss.Affected by increasing salinity,the rate of strength loss of frozen soils was magnified by a factor of 1.2 to 3.7compared to thawing soils.Likewise,the CU triaxial shear test showing that the rate of strength loss of shear strength was amplified by the coupling effect of FTCs and salt erosion.With the increasement of FTCs,the strain threshold of Young’s modulus was gradually pushed backward...