The interface between soil and structure can be referred to as a soil-structure system, and its behavior plays an important role in many geotechnical engineering practices. In this study, results are presented from a series of monotonic direct shear tests performed on a sand-structure interface under constant normal stiffness using the discrete element method (DEM). Strain localization and dilatancy behavior of the interface is carefully examined at both macroscopic and microscopic scales. The effects of soil initial relative density and normal stress on the interface shear behavior are also investigated. The results show that a shear band progressively develops along the structural surface as shear displacement increases. At large shear displacement a unique relationship between stress ratio and void ratio is reached in the shear band for a certain normal stress, indicating that a critical state exists in the shear band. It is also found that the thickness and void ratio of the shear band at the critical state decreases with increasing normal stress. Comparison of the DEM simulation results with experimental results provides insight into the shear behavior of a sand-structure interface and offers a means for quantitative modeling of such interfaces based on the critical state soil mechanics.

土壤与结构之间的界面可以称为土壤-结构系统，其行为在许多岩土工程实践中起着重要作用。在这项研究中，结果是通过使用离散元方法（DEM）在恒定法向刚度下在砂结构界面上进行的一系列单调直接剪切试验得出的。在宏观和微观尺度上都仔细检查了界面的应变局部化和剪胀行为。还研究了土壤初始相对密度和法向应力对界面剪切行为的影响。结果表明，随着剪切位移的增加，剪切带沿着结构表面逐渐发展。在较大的剪切位移下，对于一定的法向应力，在剪切带中达到了应力比和空隙比之间的唯一关系，这表明在剪切带中存在临界状态。还发现临界状态下剪切带的厚度和空隙率随法向应力的增加而减小。将DEM模拟结果与实验结果进行比较，可以深入了解砂土结构界面的剪切行为，并为基于临界状态土壤力学的此类界面的定量建模提供了一种手段。