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Calculation of safety factor of slope stability considering the effect of closed air
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摘要: 强降雨导致边坡封闭气体压力的产生，对边坡稳定产生不利影响。现有研究主要考虑封闭气体对入渗的影响，以及当边坡沿湿润锋面滑动时气压对稳定系数的影响。基于封闭气压理论和Green-Ampt模型，建立了同时考虑坡角和气压影响的边坡入渗模型；然后，基于Mohr-Coulomb强度准则和刚体极限平衡法，考虑气压对潜水面之下土体有效应力的降低效应，构建了无限边坡沿潜水面之下的直线滑面滑动时的稳定系数计算模型。最后，通过算例研究了气压力对边坡稳定系数的影响及当滑面位于不同位置时边坡稳定系数的变化规律。结果表明：气压力可显著降低边坡稳定系数；摩擦角越大，黏聚力、滑面深度和坡角越小时，气压力影响越大；降雨入渗过程中，边坡最危险滑面可能位于潜水面之下的直线滑面。Abstract: Intense rainfall always results in the air in soil slopes being closed, and it will decrease the slope stability therefore. The present research mainly focuses on the effect of closed air pressure on infiltration and on the stability safety factor of an infinite soil slope when the slope slides along a plane located at wetting front surface. Firstly, based on the theory of closed air pressure and Green-Ampt model, a slope infiltration model which considers the effect of both air pressure and slope angleon infiltration was developed. Then, combining the Mohr-Coulomb failure criterion and the limit-equilibrium method, a model was established to calculate the stability safety factor (Fsa) of a infinite soil slope. The developed model is suitable for evaluating the Fsa when the slope slides along the plane located under phreatic surface since this model can consider the decreasing effect of closed air pressure on the effective stress of soil under phreatic surface. Finally, the influences of air pressure on infinite soil slope, as well as the variation of Fsa when the slope slides along different planes, were studied. The results indicate that air pressure significantly reduces the slope stability, and the smaller the c' is, the larger the ϕ' is, the smaller the slope angle is, and the shallower the sliding surface is, the more the air pressure affects Fsa. It also shows that the critical sliding surface may locate under the phreatic surface.
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Key words:
- slope /
- safety factor /
- closed air pressure /
- infiltration model
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图 1 不同
$\alpha $ 时的湿润锋深度与时间关系Figure 1. Evolution of
${{\textit{z}}_{\rm{w}}}$ under different$\alpha $ 
图 4 考虑与不考虑气压影响的稳定系数对比
Figure 4. Comparison of Fs with and without considering air pressure
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