Effect Of Freeze-thaw Cycles On Shear Strength Of Loess And The Influence Of Shallow Slope Stability

In the seasonally frozen soil area,the shallow soil body of the loess slope will undergo shallow collapse and collapse under repeated freezing and thawing,which will cause great harm to the construction of the project and the safety of people’s lives and property.At present,there are few research results on the stability and mechanical properties of shallow soils varying with the number of freeze-thaw cycles when shallow collapse occurs on loess slopes,and further research is needed.By referring to domestic and foreign literatures,one-dimensional freeze-thaw cycle test,water content test,triaxial test,direct shear test and other indoor tests were carried out on loess to study the moisture content within the soil with the number of freeze-thaw cycles during the freeze-thaw cycle Changes and the mechanical properties of soils with different water content before and after freeze-thaw change with the number of freeze-thaw cycles.Based on the test results,the modified Janbu method was used to compare and analyze the safety factors of the slopes obtained in different tests,and the effect of repeated freezing and thawing on the stability of the shallow soil of the loess slope was obtained.The geotechnical analysis software FLAC^3D was used to analyze the influence of freeze-thaw action on the stability of shallow soils on loess slopes and compared with the revised Janbu method.The stability of the solution changes with the water content and the number of freeze-thaw cycles.The specific research results of this article are as follows:1.Through the moisture content test,it is concluded that under the same freeze-thaw conditions,when w=8.5%,the maximum aquifer of the loess does not change with the increase of freeze-thaw times;when w≥10.5%,the maximum aquifer of the loess follows the freeze The increase in the number of melts gradually migrated upward and eventually remained stable.The higher the initial moisture content of the sample,the less the number of freeze-thaw cycles required for the moisture in the loess to migrate and remain stable under the action of freeze-thaw.2.The triaxial test of low confining pressure was carried out on freeze-thaw loess,and the influence of confining pressure on the mechanical parameters of freeze-thaw loess was analyzed.Based on Moore-Coulomb’s theorem,the shear strength parameters of loess were determined,and it was found that the shear strength parameters of loess were affected by the number of freeze-thaw cycles and the initial moisture content.When w=8.5%,the cohesion of the loess increases first with the increase of freeze-thaw cycles,and then decreases;when w≥10.5%,the cohesion of the loess decreases with the increase of freeze-thaw cycles trend.Under each initial water content condition,the internal friction angle of loess showed a decreasing trend as the number of freeze-thaw cycles increased.3.The direct shear test was carried out on the freeze-thaw loess,and the shear strength parameters of the loess maximum aquifer and the following soil layers under various freeze-thaw conditions were combined with the moisture content test to determine that the shear strength of the loess maximum aquifer was affected by the freeze-thaw effect.The largest,the highest degree of degradation of shear strength parameters.Finally,the variation of the shear strength parameters of the largest aquifer in the loess under repeated freeze-thaw cycles is analyzed.4.Based on the results of the triaxial test and the direct shear test,the modified Janbu method was used to compare and analyze the changes of the safety factors of the shallow soil layers of the loess slope under repeated freezing and thawing to determine the potential of the shallow soil bodies The sliding surface is the largest aquifer of the soil.According to the comparison results,the changes of the potential sliding surface of the shallow soil in the loess slope in the actual project under repeated freeze-thaw.5.Geotechnical analysis software FLAC^3D was used to analyze the change of safety factor of shallow soils with different initial moisture contents under the action of repeated freezing and thawing.The simulation results are compared with the calculation results of the modified Janbu method to further verify the effect of freezing and thawing on the stability of shallow soils on the loess slope.