The micromechanical mechanism of upward pipe-soil interaction in unsaturated soil remains unresolved. This study investigates the upward pipe-soil interactions in dry and unsaturated granular soil througha sequence of coupled discrete element method and finite element method (DEM-FEM) simulations. The capillary suction effect was simulated using the Johnson-Kendall-Roberts (JKR) adhesive model, while the pipe segment was simulated with finite element mesh. A comparison was conducted between the behaviors of pipes and soil in dry, unsaturated soils at various depths of burial. The findings reveal that discontinuity and large deformation in unsaturated granular soil can be modeled successfully. In addition, the capillary suction effect on the stress and deformation of pipes is effectively explained by the wide contact force distribution and the weak particle collision behaviors around pipes. Meanwhile, the study identifies differences in soil arching effects as the essential reason behind the different modes of soil deformation in dry and unsaturated soils. Moreover, an exploration of particle-scale behaviors yields several conclusive mechanistic modes of upward pipe-granular soil interaction at different burial depths. The study demonstrated that suction in unsaturated granular soil significantly improves the upward pipe-soil interaction force and changes the failure mode of pipe-soil interactions.

中文翻译：

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非饱和颗粒土中向上管-土相互作用行为的微观力学分析


非饱和土中向上管-土相互作用的微观力学机制仍未解决。本研究通过一系列耦合离散元法和有限元法 （DEM-FEM） 模拟研究了干燥和非饱和颗粒土中向上的管-土相互作用。使用 Johnson-Kendall-Roberts （JKR） 胶粘剂模型模拟毛细管抽吸效应，而管段则使用有限元网格模拟。对不同埋藏深度的干燥、非饱和土壤中管道和土壤的行为进行了比较。研究结果表明，可以成功地模拟非饱和颗粒土中的不连续性和大变形。此外，毛细管吸力对管道应力和变形的影响可以用较宽的接触力分布和管道周围的微弱粒子碰撞行为来有效解释。同时，该研究发现土壤拱起效应的差异是干燥和非饱和土壤中土壤变形模式不同的主要原因。此外，对颗粒尺度行为的探索产生了不同埋藏深度向上管道-颗粒土壤相互作用的几种决定性的机制模式。研究表明，在不饱和颗粒土中吸力显著提高了向上的管-土相互作用力，并改变了管-土相互作用的破坏模式。