为从宏、细观角度揭示常法向刚度（Constant Normal Stiffness，CNS）条件下锯齿状砂岩-混凝土结构面剪切机制，首先采用湖南大学自主改造的CNS岩石直剪仪开展3组砂岩-混凝土结构面室内剪切试验.在此基础上，采用刚性墙替代法建立与室内试验相应的离散元数值模型，并引入3个显式运动学方程控制砂岩试样运动轨迹从而实现CNS条件加载，将数值模拟与试验结果对比验证了模型的合理性.随后，开展16个工况的数值剪切试验，通过观察剪切裂纹扩展和力链演化形态，从细观角度揭示结构面破坏模式和荷载传递机制，并从宏观角度分析锯齿几何尺寸（半波长λ、起伏角θ）和加载边界条件（初始法向应力σn0、法向刚度K）对剪切强度和法向膨胀的影响.结果表明：剪切裂纹按照“平稳增加—急剧增加—增幅减小”的发展趋势由结构面区域逐渐向岩石内部扩展，结构面破坏模式随起伏角的增大由滑移磨损向剪断破坏过渡，剪切强度随λ、θ、σn0和K的增加呈指数函数型增加.
To reveal the shear mechanism of the zigzag sandstone-concrete interface under constant normal stiffness （CNS） conditions from micro-scale and macro-scale aspects， several direct shear tests for the sandstone-concrete interface were conducted by self-transformation CNS shear apparatus. On this basis， discrete element numerical models simulating laboratory experiments were established by using the rigid wall substitution method. In addition， the motion of the sandstone sample was controlled by three explicit spring-based kinetic equations to ensure the dynamic balance of the system at each time step and realize the CNS loading. The rationality of the models was verified by comparing the numerical simulation and experimental results. Subsequently， 16 cases of numerical shear tests were conducted to further reveal the failure mode and load transfer mechanism of the interface from the micro-scale aspect by observing the micro-crack propagation and force chain evolution， and the effects of asperity geometries （i.e.， half chord-length λ， inclination θ） and boundary conditions （i.e.， initial normal stress σn0， normal stiffness K） on shear strength and dilation were analyzed from the macro-scale aspect. The results indicated that micro-cracks gradually propagated from the interface area to the interior of the rock in a trend of stable increase-rapid increase-decrease in growth rate， and the failure mode of the interface transitioned from wear to shear failure with increasing inclination. The shear strength increased as an exponential function with increasing λ， θ， σn0， and K.
