2D DEM analysis of the interactions between bio-inspired geo-probe and soil during inflation–deflation cycles
2D DEM analysis of the interactions between bio-inspired geo-probe and soil during inflation–deflation cycles
复制标题
膨胀-通货紧缩循环期间仿生地质探测器与土壤之间相互作用的二维 DEM 分析
作者：
Yifei Ma;T. Matthew Evans;Douglas D. Cortes
锥入度试验和标准贯入试验可能是现场调查土壤特性最通用的技术。由于探头与土壤之间的摩擦，使探头穿过土壤需要很大的下压力。受到蠕虫在挖掘隧道时使身体符合机械上最有利的形状的能力的启发，一种创新的自挖掘地质探测器被开发出来并在实验室环境中部署。与蠕虫扩张身体的能力类似，安装在刚性锥体后面的软气球通过定期施加压力或真空来充气或放气，以改变锥体的穿透阻力。实验室实验显示出令人鼓舞的结果，即新型地质探针可以更有效地穿透土壤。然而，气球-土壤-锥体界面的相互作用很复杂，尚未完全了解。这项数值研究的重点是地质探测器在气球充气和放气期间的行为。开发了二维离散元模型，以提供对地质探测器与土壤之间相互作用的微观力学的粒子级洞察。首先进行基线模拟，以研究膨胀和通货紧缩期间大块土壤的破坏机制。此外，还分析了气球-土壤和土壤-锥体界面处的接触力，以显示穿透阻力的变化。对位移场、剪切应变场和接触力链进行数值研究，以获得对工具-土壤相互作用的基本了解。然后，通过进行灵敏度分析来研究气球位置和覆盖应力对探头行为的影响。这项研究提供了一种数值技术来研究实验室测试中无法实现的工具-土壤相互作用。仿真结果的实施可以将实验室规模的测试外推到更广泛的应力和边界条件。
The cone penetration test and the standard penetration test are perhaps the most versatile techniques for investigating soil properties in-situ. Advancing the probe through the soil requires substantial downforce due to friction between the probe and the soil. Inspired by the ability of worms to conform their body to the most mechanically advantageous shape while tunneling, an innovative self-excavating geo-probe has been developed and deployed in a laboratory environment. Analogous to a worm’s ability to expand its body, a soft balloon mounted behind a rigid cone is inflated or deflated by applying pressure or vacuum periodically to alter the cone penetration resistance. Laboratory experiments have shown promising results that the new geo-probe can penetrate the soil more efficiently. However, the interactions at balloon–soil–cone interfaces are complex and not fully understood. This numerical study focuses on the behavior of the geo-probe during balloon inflation and deflation. A two-dimensional discrete element model is developed to provide particle-level insight into the micromechanics of the interactions between the geo-probe and the soil. A baseline simulation is first conducted to study the failure mechanisms of the bulk soil during inflation and deflation. Additionally, the contact forces at balloon–soil and soil–cone interfaces are analyzed to show the variation of penetration resistance. The displacement field, shear strain field, and contact force chains are numerically investigated to gain a fundamental understanding of the tool–soil interaction. Then, the effect of balloon locations and overburden stresses on the behavior of the probe are studied by performing sensitivity analyses. This study provides a numerical technique to study the tool–soil interactions that was inaccessible in laboratory test. Implementation of the simulation results enables extrapolation of bench-scale testing to a wider range of stresses and boundary conditions.