Experimental Study On Shear Strength Characteristics Of Typical Loess In Taiyuan

Loess is widely distributed in Northwest China.Loess is a Quaternary sediment.Loess has many pores and even visible to the naked eye,vertical joint development,high structural strength when dry,low compressibility,easy sinking by water,lack of bedding and so on.Shanxi is one of the more widely distributed areas of loess.With the continuous advancement of the 13 th Five-Year Plan,the pace of engineering construction has been accelerating,and projects involving loess-like soils have also been increasing.As a result,the nature of loess engineering has also aroused the attention of project builders.Many scholars have conducted in-depth research on the causes,strength characteristics and deformation characteristics of loess,and achieved fruitful results.However,for the construction of foundation engineering,slope engineering and road engineering,there are relatively few studies on the comprehensive effects of moisture content and shear rate on the shear strength of unsaturated loess.Therefore,it is of great practical significance to study the law of soil water content and shear rate on the shear strength of unsaturated loess.Based on the existing achievements,this paper takes the loess samples taken from the construction site of the Qiya Slope Project in Shanxi Province and the Country Garden Slope in Shanxi Province as the research object,and uses the conventional triaxial apparatus to reconstruct the soil of the three groups of soil samples.The undrained shear tests under different shear rates were performed,and the effects of water content,shear rate,and confining pressure on soil strength were analyzed.Direct shear tests were performed on soil samples with different shear rates,and the test data were analyzed.This study draws the following conclusions:(1)The shear rate has a significant effect on the stress-strain curve of undisturbed and remolded soil in triaxial shear test.As the shear rate increases,the corresponding stress-strain curve increases with the shift,and the shear strength also increases.Under the same confining pressure and shear rate conditions,the shear strength of remolded soil increases with the increase of water content,and the reduction of shear strength at low confining pressure is higher than that of confining pressure.(2)In the triaxial test,the shear rate has different effects on the cohesion and the internal friction angle.As the shear rate increases,the cohesive force increases and the magnitude of increase increases from large to small,and the internal friction angle gradually decreases.(3)By analyzing the triaxial shear test data,the relationship between the damage strength of remolded loess,confining pressure and water content,and the relationship between the damage strength of remolded loess and confining pressure and shear rate are obtained.In addition,the relationship between friction angle,cohesion and water content in soil was deduced by the Mohr-Coulomb soil strength failure theory.(4)In the direct shear test,the shear rate has a significant effect on the shear stress-shear displacement curve,and it also has a significant effect on the shear strength index(internal friction angle,cohesion).Under the same moisture content and confining pressure conditions,the shear rate increases,and the cohesion force also increases and the magnitude of the increase is larger,and the influence on the internal friction angle is smaller.(5)For the direct shear test of undisturbed soil samples,During the shear stress-shear displacement curve has obvious peaks,which is a typical softening type.Under the same shear rate and moisture content conditions,the original strength of the loess samples increased with the increase of the applied normal stress.