The effects of dilatancy on the collapse dynamics of granular materials in air or in a liquid are studied experimentally and numerically. Experiments show that dilatancy has a critical effect on the collapse of granular columns in the presence of an ambient fluid. Two regimes of the collapse, one being quick and the other being slow, are observed from the experiments and the underlying reasons are analyzed. A two-fluid smoothed particle hydrodynamics model, based on the granular-fluid mixture theory and the critical state theory, is employed to investigate the complex interactions between the solid particles and the ambient water. It is found that dilatancy, resulting in large effective stress and large frictional coefficient between solid particles, helps form the slow regime. Small permeability, representing large inter-phase drag force, also retards the collapse significantly. The proposed numerical model is capable of reproducing these effects qualitatively.

中文翻译：

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膨胀和压实对沉水颗粒柱倒塌的影响

通过实验和数值研究了膨胀对颗粒材料在空气或液体中坍塌动力学的影响。实验表明，在周围流体存在的情况下，膨胀对粒状柱的坍塌具有关键影响。从实验中观察到了两种崩溃状态，一种是快速的，另一种是缓慢的，并分析了根本原因。基于颗粒-流体混合理论和临界状态理论的双流体平滑颗粒流体动力学模型被用来研究固体颗粒与环境水之间的复杂相互作用。研究发现，膨胀作用导致固体颗粒之间的有效应力和摩擦系数大，有助于形成慢速状态。渗透率小，代表相间阻力大，也显着延缓了坍塌。所提出的数值模型能够定性地再现这些影响。