Shear Strength Anisotropy Of Undisturbed Malan ?Q₃? Loess In Shanxi Based On Triaxial Compression Test

Loess is a special type of soil with macroporosity,water sensitivity and vertical joint development.Loess is widely distributed,accounting for approximately 6.6%of the global surface area,and is widely distributed in Central Europe,Southern Europe,Asia,Central America,Northwestern Africa,Africa,Northern Russia,Argentina,Australia,and New Zealand^[3-7].Among them,loess is the most widely distributed in China.With the development of social economy,the implementation of the“Western Development”strategy and the“One Belt and One Road”strategy,the quantity and scale of infrastructure construction and project construction in the loess area have been continuously increasing,and research on the mechanical properties of loess has become increasingly urgent.The unique structure formed during the deposition and evolution of loess makes the mechanical properties of loess distinctly different in different directions.As for the study of mechanical properties of loess,specimens prepared in the vertical direction are currently used,and the deformation and failure characteristics of loess cannot be fully reflected.Shear strength is an important mechanical property of loess,which has been widely used in landslide stability evaluation,deformation analysis and engineering control design.In this experiment,the undisturbed and undrained triaxial compression tests were carried out in the vertical and horizontal directions of the Malan Loess from Shanxi Province.The deformation and failure characteristics were investigated.The results show that there is significant anisotropy in the shear behavior of the undisturbed Loess in Shanxi,where the ground is buried at a depth of 4 meters,in the dry state:under the 50kPa confining pressure,the deviatoric stress peak values and elastic modulus values of the vertical specimens are smaller than that of the horizontal specimens.As to the failure strain values,it is opposite,the values of vertical specimens are larger.Under the confining pressures of 100,150,and 200 kPa,the peak deviator stress and elastic modulus of the vertical specimens are larger than that of horizontal specimens,and the failure strain values of vertical specimens are smaller.With the increase of confining pressure,the deviated stress peak value,failure strain value and elastic modulus of the vertical specimens gradually increase;the deviated stress peak value and failure strain value of the horizontal specimens gradually increase,while the elastic modulus values decrease gradually.In the dry state,the cohesion of the vertical specimen is smaller than that of the horizontal specimen,and the internal friction angle is larger than that of the horizontal specimen.In low confining pressure,the shear strength of the vertical specimen is less than the shear strength of the horizontal specimen,while in high confining pressure,shear strength of the vertical specimens is greater than that of the horizontal specimens.In low principal stress,the shear strength of the vertical specimen is less than that of the horizontal specimen,while the shear strength of the vertical specimen is greater than that of the horizontal specimen in high principal stress.