Analysis and Improvement of Oblique Shear Phenomenon of Direct Shear Apparatus

Direct shear test is an important method to test the shear strength of soil. But the phenomenon of "oblique shear" often appears in the process of test, the soil sample subjected to eccentric pressure and uneven stress distribution, which affect the stability and accuracy of the test. This paper, starts from the construction of the direct shear apparatus, found that the relative displacement between the upper shear box and the axial pressure rod, is one important cause of "oblique shear". Set the steel ring between the lower shear box and the push rod, dose not affect the shear force measurement and can completely fix the upper shear box. There is no relative displacement between the upper shear box and the rod used to apply axial pressure after improvement, and no the phenomenon of "oblique shear". The experimental results are more stable and the coefficient of variation is smaller. The improvement scheme of the direct shear apparatus is simple, the improvement effect is obvious, and the stability and accuracy of the direct shear test are improved.