In order to obtain a better understanding of the load transfer mechanism of open-ended tubular piles driven into weak rocks, numerical analysis is conducted to study the internal and external shaft frictions, base resistance and the stress distribution pattern in the surrounding rock mass. Meanwhile, since pile shoes are often applied when driving to the rock layer, a common inner pile shoe attached to the open-ended tubular pile was analysis and compared with the pile without a shoe. In this study, the discrete element method (DEM), which can mimic rock grains and the interaction between grains, is adopted due to its ability to simulate large deformation problems such as pile penetration process. The flat-joint model that allows partial damage at the contact interface was employed to replicate the discrete nature of the rock mass. The rock behaviour was calibrated against triaxial test results for a pyroclastic weak rock, and then the calibrated rock was employed for the simulation of pile penetration. A 30° segment of the true-scale model was simulated using the DEM with a height of 3 m and a radius of 1.5 m, which was composed of about 557,000 particles. Initial stresses were applied at the boundary of the testing chamber, while the side of the chamber was discretised into several sections with increasing horizontal stresses with depth to establish the at rest condition. Numerical results for penetration of an open-ended tubular pile show that the external shaft resistance of the pile with inner pile shoe increased approximately linearly as the pile penetrated deeper. In addition, the internal shaft friction was notably less than the external shaft friction for both piles with and without a shoe. Plugging was observed for both piles with and without a driving shoe. The inner pile shoe allowed the pile partial plugging to occur at shallower penetration depth. This study sheds a light on the load transfer mechanism of the open-ended tubular piles and the effect of the shoe on the axial capacity of the piles in weak rocks.

为了更好地理解开端管桩打入软弱岩石的荷载传递机制，通过数值分析研究了围岩体中的内外轴摩擦力、基础阻力和应力分布模式。同时，由于打入岩层时往往要使用桩靴，因此对普通的内桩靴安装在开口管桩上的情况进行了分析，并与没有桩靴的桩进行了比较。在这项研究中，离散元法（DEM）可以模拟岩石颗粒和颗粒之间的相互作用，因为它能够模拟大变形问题，例如桩穿透过程。允许接触界面部分损坏的平接模型被用来复制岩体的离散特性。针对火山碎屑弱岩的三轴试验结果对岩石行为进行了校准，然后将校准后的岩石用于桩穿透模拟。使用高度为 3 m、半径为 1.5 m 的 DEM 模拟了真实比例模型的 30° 段，该 DEM 由大约 557,000 个粒子组成。初始应力施加在测试室的边界，而测试室的侧面被离散成几个部分，随着深度的增加水平应力，以建立静止状态。开口管桩穿透的数值结果表明，随着桩的穿透深度，带有内桩靴的桩的外轴阻力近似线性增加。此外，对于有和没有鞋的桩，内部轴摩擦明显小于外部轴摩擦。有和没有驱动靴的两个桩都观察到堵塞。内桩靴允许在较浅的穿透深度处发生桩部分堵塞。本研究揭示了开口管桩的荷载传递机制以及鞋对软弱岩石中桩的轴向承载力的影响。