Soil shearing strength can not only evaluate the sensitivity of soil erosion

but also is an important parameter to reflect the tillage performance of cultivated-layer. There are some differences in soil shearing strength indexes under different shearing modes. In this paper

the soil of purple soil sloping farmland was taken as the research object

the laboratory triaxial and direct shearing test method were used to study the bulk density and water content on remolded purple soil. The effect on shearing strength of the cultivated-layer soil was analyzed

and the differences between the two test methods were analyzed. The results showed that: (1) The soil cohesion (c) of the purple soil sloping farmland increased with the increasing of the bulk densities(ρd) and decreased with the increasing of water contents (w). The maximum cohesive forces of the triaxial and direct shearing tests were 32.33 and 21.78 kPa respectively

both of which occurred under bulk density of 1.4 g/cm3 and water content of 10%. The internal friction angle (φ) of the cultivated-layer increased with the increasing of the bulk densities and decreased with the increasing of the water contents. The maximum internal friction angles of the triaxial and direct shearing tests were 22.67° and 29.11° respectively

under bulk density of 1.4 g/cm3 and water content of 10%. (2) Under the same confining pressure

the maximum principal stress difference of the cultivated-layer soil increased with the increasing of the bulk densities

and decreased with the increasing of water contents. Under the same bulk density and water content

the maximum principal stress difference of the cultivated-layer soil increased with the confining pressure. (3) The interaction of soil bulk density and water content in the cultivated-layer had a significant effect on cohesion and internal friction angle(P<0.05). The optimum soil bulk density—water content condition for the shear strength of the soil in sloping farmland was 1.4 g/cm3—10%.(4) Different shearing modes affected the shearing strength index of the soil. The soil cohesion of the cultivated-layer was greater or closer to the direct shearing test under the triaxial test conditions

while the soil internal friction angle was significantly lower than the direct shearing test result. This was mainly related to the difference between the two shearing test principles.