Direct simple shear (DSS) testing allows observation of load-deformation response under rotation of the major principal stress plane, which is descriptive of many actual field problems. While the simplicity of the test configuration makes its use popular in research and industry, key uncertainties still remain regarding the interpretation of the laboratory data. This study uses laboratory validated discrete element method (DEM) models to examine the stress transmission in laminar-type direct simple shear devices under drained constant effective stress conditions. The DEM models (comprised of spheres) closely replicate physical specimens of precision chrome steel ball bearings for which the properties (e.g., shape, surface friction, and stiffness) were measured directly. The DEM models were also validated using experimental tests, so that conclusions regarding the system response can be derived with confidence from the available DEM data. The testing program included both loose and dense specimens, allowing for a comparison of the influence of density on stress state which has not been examined in previous simple shear DEM studies. Differences were observed between vertical effective stresses and shear stresses derived from boundary measurements (as commonly carried out in experimental programs) and those derived from force measurements within the DEM specimens. The failure state of the material in simple shear was also examined through Mohr’s circles of stress. The evolution of stresses on both the horizontally and vertically oriented planes were considered so that established methods of direct simple shear interpretation could be critically assessed. For the loose specimens, the angle of shearing resistance can be confidently estimated considering the maximum shear stress acting on the horizontal plane, which is easily inferred from measurements of the shear force during the physical test. This was true considering both internal and boundary calculated stresses. This approach, however, is inaccurate for the dense specimens. Analysis of the particle-scale kinematics of the response illustrates that the deformation field within the central portion of the specimen is in simple shear, although the magnitude of this shearing was significantly larger than what was measured on the boundary. This study and the conclusions derived focus on smooth spherical particle specimens; the objective was to examine the stress distribution within DSS devices and the implications for test interpretation using DEM models that more closely matched the physical laboratory specimens tested than in previous studies. When considered alongside the existing studies, the findings show that there is no broad conclusion that can be applied for all materials and all conditions in simple shear and that interpretation should be carefully tied to the physical conditions simulated.

直接简单剪切（DSS）测试允许观察主主应力平面旋转下的载荷-变形响应，这是许多实际现场问题的描述。尽管测试配置的简单性使其在研究和行业中广为使用，但是关于实验室数据的解释仍存在主要不确定性。这项研究使用实验室验证的离散元方法（DEM）模型来检查层流型直接简单剪切装置在排泄恒定有效应力条件下的应力传递。DEM模型（由球体组成）可以精确复制精密铬钢球轴承的物理样本，并直接对其性能（例如形状，表面摩擦和刚度）进行测量。还使用实验测试验证了DEM模型，这样就可以从可用的DEM数据中可靠地得出有关系统响应的结论。该测试程序包括松散的和密集的试样，可以比较密度对应力状态的影响，而以前的简单剪切DEM研究尚未对此进行检验。从边界测量（通常在实验程序中进行）得出的垂直有效应力和剪切应力与在DEM试样中从力测量得出的垂直有效应力和剪切应力之间观察到差异。还通过莫尔应力圆检查了材料在简单剪切下的破坏状态。考虑了水平和垂直方向上应力的演变，以便可以对直接简单剪切解释的既定方法进行严格评估。对于松散的试样，考虑到作用在水平面上的最大剪切应力，可以确定地估算出剪切阻力的角度，这很容易从物理测试过程中对剪切力的测量中得出。考虑到内部和边界计算的应力，这是正确的。但是，这种方法对于稠密的样本是不准确的。对响应的颗粒运动学的分析表明，试样中心部分的形变场处于简单剪切状态，尽管这种剪切的幅度明显大于在边界处测得的幅度。这项研究和得出的结论集中在光滑的球形颗粒标本上。目的是要检查DSS设备内的应力分布，以及使用DEM模型来检验测试解释的含义，该模型与以前的研究相比，与所测试的物理实验室样本更加匹配。当与现有研究一起考虑时，研究结果表明，尚无广泛的结论可适用于所有材料和简单剪切的所有条件，并且应将解释与模拟的物理条件密切联系。