| Loess is mainly distributed in the central and western regions of my country,covering an area of about 635,000 km2,accounting for about 7%of our country’s land area.The loess covering area of Qinghai Province is about 24,800 km2,accounting for about 3.9%of the national loess[1].In recent years,with the introduction of the"The Belt and Road"initiative,has been paid to the construction of the loess area,especially in infrastructure construction under dynamic loads such as railways,research on loess is mainly concentrated in places outside Qinghai,such as Xi’an,Taiyuan,and Lanzhou.In addition,studies have shown that the engineering mechanical properties of loess are different due to different areas.Therefore,it is necessary to conduct experimental research on the engineering mechanical properties of loess in the Haibei area of Qinghai.Based on the method of combining indoor experiment and numerical simulation,this paper explores the engineering mechanical properties of loess in Haibei area of Qinghai,and uses the GDS standard stress path test system（ADVTTS）to conduct triaxial shear tests under different stress paths to study the effects of consolidation state,confining pressure and the stress path on the strength and stress-strain characteristics of undisturbed loess;the two-way GDS dynamic triaxial test system（DYNTTS）is used to perform dynamic triaxial tests on undisturbed loess under different initial stress states and loading conditions,Study the effects of consolidation stress ratio,cyclic dynamic stress ratio,loading frequency,dynamic stress,confining pressure and water content on the dynamic characteristics of undisturbed loess.Taking into account the climatic characteristics of the borrowing place and the diversity of traffic loads,the article sets freeze-thaw Dynamic triaxial test under cyclic and dynamic confining pressure;and analyze the macro-mechanical properties of the sample from a microscopic point of view through the scanning electron microscope;use the ABAQUS finite element software to simulate the indoor dynamic triaxial test,in order to compare and verify the test results.Main conclusions:（1）The stress-strain curve of the undisturbed loess in the triaxial shearing process shows a strain-softening type.When the strain reaches 2%to3%,the stress-strain curve of the sample has a peak,which is the breaking strength of the sample.Under the condition of the same axial deviator stress,the axial deformation of the sample in the conventional triaxial compression（CTC）test is smaller than that in the triaxial compression（TC）test with a constant average principal stress p,and the former will fail the intensity is significantly higher than the latter.The increase in consolidation stress ratio and confining pressure can reduce the deformation of the sample and increase the strength.（2）The rebound strain decreases with the increase of consolidation stress ratio and loading frequency,and increases with the increase of cyclic dynamic stress ratio,confining pressure,dynamic stress and water content.The axial cumulative strain increases with Consolidation stress ratio,cyclic dynamic stress ratio,confining pressure,dynamic stress and water content increase with the increase,but decrease with the increase of loading frequency.The change of the modulus of resilience with the number of cycles is basically the same under different test conditions.In the initial stage of loading,the modulus of resilience increases rapidly with the number of vibrations,and then changes with the number of vibrations.It basically reaches a stable state when it reaches 500 times.The modulus of resilience increases with the increase of consolidation stress ratio and loading frequency,and decreases with the increase of cyclic dynamic stress ratio,confining pressure,dynamic stress and water content.（3）The effect of freeze-thaw cycles on the remodeled loess backbone curve is affected by the change of water content,but the overall trend is that as the number of freeze-thaw cycles increases,the backbone curve gradually decreases,and the water content has a greater impact on the backbone curve of remodeled loess When the water content increases from 10.0%to 16.0%,the backbone curve changes from strain-softening to strain-hardening,and this change is not affected by the number of freeze-thaw cycles.As the number of freezing and thawing increases,the severity of soil damage increases,and the strength and modulus attenuate.After freezing and thawing reach a certain number of times,the strength and modulus of the soil increase to a certain extent.（4）Using ABAQUS finite element software to simulate indoor tests,it has a high degree of fit,and the errors meet the requirements of allowable values. |
