Water-sand inrush is one of the most destructive disasters for underground structures buried in saturated erodible soils. The related upward propagation of ground disturbance has not been well understood so far. In this study, a series of numerical simulations were performed to investigate such disturbance propagation behavior. Typical dual-stratum geological condition was modeled since this was the most common condition where water–sand inrush disasters had been widely reported previously. The numerical simulations applied discrete particles to model the lower sand layer, continuum mechanics to model the overlying clay layer, and Darcy’s law to model the underground water flow, with solid–fluid coupling considered. The simulation results were reported and were compared with available data from the literature. It was found that the sand and water loss rates were highly dependent on location of the inrush opening, which was attributed to the different local porosity near the opening, a result of the particle-scale fluid–solid coupling. A funnel-type sand flowing pattern can be identified, and the upward propagation of ground disturbance can be described by evolution of a loosening ellipse that outlines the extent of ground experiencing displacement. As the water–sand inrush proceeded, the tendency of vertical alignment of the loosening ellipse suggests an increasing role of gravity relative to the fluid–solid coupling force in driving particle motion. The ground disturbance propagation was accompanied with localization in strain rate, dissipative work, and particle spin rate. The non-uniform ground displacement was accompanied with re-distribution of stress in the form of continuously evolving soil arches. The cross-stratum soil arch can lead to unloading process at the stratum interface and consequently cause upper payer instability.

中文翻译：

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在双层地质条件下，水-沙突入式地表扰动向缺陷隧道中向上扩展


突水沙是埋在饱和可侵蚀土壤中的地下结构最具破坏性的灾害之一。到目前为止，地面扰动的相关向上传播尚未得到很好的理解。在本研究中，进行了一系列数值模拟来研究这种扰动传播行为。对典型的双层地质条件进行建模，因为这是以前广泛报道的突水灾害的最常见情况。数值模拟应用离散粒子对下层砂层进行建模，使用连续介质力学对上覆粘土层进行建模，并使用达西定律对地下水流进行建模，同时考虑了固-液耦合。报告了模拟结果并与文献中的可用数据进行了比较。研究发现，沙子和水的损失率在很大程度上取决于突增开口的位置，这归因于开口附近不同的局部孔隙率，这是颗粒尺度流固耦合的结果。可以识别出漏斗状的沙子流动模式，并且可以通过一个松散的椭圆的演变来描述地面扰动的向上传播，该椭圆勾勒出地面发生位移的程度。随着水-沙突流的进行，松散椭圆垂直排列的趋势表明，相对于流固耦合力，重力在驱动粒子运动中的作用越来越大。地面扰动传播伴随着应变率、耗散功和粒子自旋速率的定位。不均匀的地面位移伴随着应力的重新分配，形式为不断发展的土拱。 跨层土拱可导致地层界面处的卸荷过程，从而导致上层支付方不稳定。