Abstract: To investigate the effect of the radius of the spherical heads of the indenter on the results of a point load test, this study uses a discrete element model based on the flat joint contact for numerical simulation. Results show that the discrete element model based on the flat joint model can accurately describe the damage process and size effects of rocks under point loads. Damage of rock samples under the loading of different radii of the indenter can be characterized as vertical splitting damage, and the larger the radius of the indenter is, the larger the damage area. Values of the point load strength of rock samples increase with increasing the radius of the indenter and obey a power function relationship. The results of this study provide a theoretical basis for the selection of the spherical heads of indenters in point load tests and tool design for mechanical rock breaking.

Key words: discrete element method, flat joint model, point load strength, size effect

摘要： 为探明点荷载试验中压头半径对试验结果的影响，采用基于平直节理接触的离散元模型进行数值仿真研究。研究结果表明：基于平直节理的离散元模型能够准确呈现岩石在点荷载作用下的破坏过程和尺寸效应；在不同半径的压头加载作用下，岩样破坏形式均为竖向劈裂破坏，且压头半径越大，破坏面积越大；岩样点荷载强度的测量值随着压头半径的增大而增大，服从幂函数关系。研究结果可为点荷载试验中压头的选择、机械破岩中刀具的设计提供理论依据。

关键词: 离散元法，平直节理模型，点荷载强度，尺寸效应