3D Discrete Element Method Simulations of a Laminar-Type Simple Shear Apparatus

Abstract

The direct simple shear test was developed as an element test in which, in principle, a uniform simple shear strain field was applied to a sample. In the intervening years a number of shortcomings have been identified with this testing apparatus, most notably the exact stress conditions within the sample are not known. However the test itself is not overly complex, and it is thought to better represent true in situ conditions when compared with the triaxial test. In particular, it allows for smooth rotation of the principal stress orientation, which is common in many practical geotechnical conditions. Consequently, simple shear testing remains a popular method to advance understanding of soil response. This paper documents a fundamental study of the direct simple shear apparatus using the discrete element method (DEM). A series of stacked cylindrical walls were used to simulate a laminar-type simple shear cell. The prototype simulations presented showed localized stress differences for the loose and dense samples. The DEM data also allows for direct determination of the strength parameters, stress path, and the angle of noncoaxiality. All simulations exhibited noncoaxial behavior. The loose sample showed less principal stress axis rotation and the principal axes' orientations became coincident at lower shear strains. © 2014 American Society of Civil Engineers.