The improved shear strength calculation method in direct shear test

Direct shear test is broadly used to get the strength of soil, joints, and specific material in the field of geotechnical engineering because its simple structure and easier operation. But the current direct shear strength calculation does not concern on the variation of the shearing surface during the test, has no regard for the effects of the shearing area on the shear strength, so the test result is not the really strength of the samples. To discovery the affection of the shearing surface on the direct shear strength, three different calculation methods of shear surface and its affection on the shear strength were put forward based on the new mathematical model and large number of experimental with improvement direct shear apparatus, the new calculation method makes the result more accuracy and closer to the really shear strength of the samples.