The low permeability of discharged muck must last for at least tens of minutes to avoid water spewing during earth pressure balance (EPB) shield tunneling; however, foam, which is usually added to soil to reduce its permeability, has its own unique time‐varying characteristics. Thus, it is important to predict the stable time of permeability of foam‐conditioned soil for EPB shield tunneling. Based on theories of the effective permeation channel of pure foam and fluid mechanics, a constant is proposed to predict the duration of the initial period during which the coefficient of permeability of the conditioned soil remains stable. A series of large‐scale permeation tests were carried out to determine the duration of the initial stable period for various foam‐conditioned soils, and it was verified that the predicted results were in good agreement with the measured results. Furthermore, based on the constant, practical concepts, including duration reference curves, optimum fineness, optimum porosity and critical particle size, are proposed for the spewing control of EPB shield tunneling.

中文翻译：

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基于渗透常数的泡沫条件土渗透稳定性计算模型

排出的泥土的低渗透性必须持续至少数十分钟​​，以防止在土压平衡（EPB）盾构隧道施工期间涌出水；但是，通常添加到土壤中以降低其渗透性的泡沫具有其独特的时变特性。因此，对于EPB盾构隧道施工，预测泡沫条件土壤渗透性的稳定时间很重要。基于纯泡沫的有效渗透通道理论和流体力学，提出了一个常数来预测条件土壤的渗透系数保持稳定的初始阶段的持续时间。进行了一系列大规模的渗透测试，以确定各种泡沫条件土壤的初始稳定期的持续时间，验证了预测结果与实测结果吻合良好。此外，基于不变的实用概念，包括持续时间参考曲线，最佳细度，最佳孔隙率和临界粒径，提出了用于EPB盾构隧道喷水控制的方法。