Study On The Strength And Deformation Characteristics With Different Stress Path Of Remolded Loess

Loess is loose and porous,with a weakly consolidated special structure,and widely distributed in the northwest of China.With the economic development and construction of the "the Belt and Road Initiatives" in the northwest region,the human activities related to loess are becoming more and more frequent,and a large number of loess landfill slopes are formed.Many scholars have carried out research on the mechanical properties of loess,to explain the mechanism of disaster,which playing a positive role in disaster prevention and reduction work of the loess area.In order to study the deformation and failure law of loess,this paper,based on the previous studies,designs the triaxial shear test of different stress paths as conventional triaxial compression(CTC),triaxial compression(TC),reduced triaxial compression test(RTC),the effects of different stress paths on the mechanical properties of remolded loess were studied.And the micro-structural characteristics of the loess are analyzed by SEM images,and then the failure process of loess is analyzed.The conclusions are as follows:(1)The strength characteristics of the loess are as follows: the remolded loess exhibits strain hardening under the CTC path,while it exhibits weak hardening under the TC and RTC paths,and it shows that CTC path> TC path> RTC path on the shear strength under the same consolidation pressure.Cyclic loading compared to monotonic loading,the soil is compacted,and thus a slight increase in shear strength.(2)The deformation of loess: the remolded loess is the sub-stable structure soil,in the process of deformation and failure,it shows up as the volume contraction,the volume contraction under CTC,TC,RTC path was gradually reduced;for the same stress path,the volume contraction increases with the initial consolidation pressure.The deformation of the soil includes two parts of plastic deformation as shear deformation and dilatation.Remodeling loess at lower stress level loading-unloading-reloading process performance as the volume contraction while loading,and the reversibility of part of dilatation is the main reason of the volume contraction while unloading.The higher the level of stress is shown as the volume contraction while loading and the volume expansion while unloading.(3)Micro-structure characteristics: After the shear stress of different stress paths,according to CTC,TC,RTC order,the degree of particle fragmentation decreases,and the pore content increases in turn.(4)The constitutive model of remolded loess: The Elliptic-Parabolic Yield surface model by Yin Zongze is used to adjust the model parameters according to the test results.It has proved that the model can well describe the deformation characteristics of remolded loess.(5)Analysis of failure process: Under the action of loading,the soil is compressed and compacted at the initial stage of deformation,and its strength is improved to some extent.As the load continues to increase,the particles are continuously cut,rearranged and relative to the slippage,the deformation rate increases steadily,the deformation of the soil to the damage was progressive development,mainly to the axial compression deformation,lateral bulging deformation is small;For the lateral unloading of the deformation behavior,in the early unloading,the soil remains relatively stable with a small amount of deformation.When the lateral constraint is reduced to a critical state,the plastic shear cracks appear in the soil,the structural failure is destroyed,and the deformation of the soil is rapid and the deformation rate is rapidly increasing.