Simplified analysis method for the bank slope stability with the influence of water level plummet
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摘要: 水位骤降是影响岸坡稳定的主要外在因素,但现有计算方法均需通过渗透力或孔隙水压力计算或者渗流场与应力场耦合分析来考虑水位下降对岸坡产生的渗流作用,计算过程较复杂,不便于工程设计人员采用。为了便于分析水位骤降对岸坡稳定性的影响,通过对岸坡任一点考虑渗透力与否的应力状态进行对比分析,得到将渗透力对岸坡稳定性影响简化为抗剪强度参数黏聚力降低的这一等效关系,并将此等效关系与强度折减法相结合,建立岸坡稳定性简化计算模型,提出了水位骤降影响下岸坡稳定性简化分析方法,并将该简化分析方法与已有分析方法进行对比分析。结果表明:该简化分析方法结果与岸坡全局临界滑移场(GCSF)方法、Geostudio的Slope/W模块方法及传统极限平衡分析方法计算均质岸坡稳定性所得安全系数相差分别为2.6%、3.5%和3.5%。可见,所建立的简化方法与已有分析方法的结果吻合较好;进一步采用该简化方法与全局临界滑移场(GCSF)方法计算存在软弱夹层的非均质岸坡,所得安全系数相差3.1%。这表明该简化方法计算水位骤降影响下均质、非均质岸坡稳定性均具有较好的可靠性和适用性。Abstract: Water level plummet is one of the main external factors affecting the stability of bank slope, however, the existing calculation methods need to consider the seepage effect of water level drop on bank slope through the calculation of seepage force or pore water pressure or the coupling analysis of seepage field and stress field, which are complicated and inconvenient for engineering designers to adopt. In order to analyze the influence of water level plummet on the stability of bank slope conveniently, the stress state of one point in the bank slope with and without considering seepage force was analyzed, and an equivalent relationship that the influence of seepage force on bank slope stability could be seen as the decrease of the parameter of cohesion c was obtained. Combining this equivalent relationship with the strength reduction method, a simplified calculation model of bank slope stability was established, and then a simplified stability analysis method for bank slope stability under the influence of water level plummet was proposed. The homogeneous bank slope stability analyses were carried out by the simplified analysis method in this paper, the bank slope globally critical slip field (GCSF) method, Geostudio's Slope/W module method and the traditional ultimate equilibrium methods respectively, and the results show that the safe factors calculated by the above-mentioned methods are in good agreement, with the differences of 2.6%, 3.5% and 3.5% respectively. Then the heterogeneous bank slope stability analyses were carried out by the simplified analysis method in this paper and the slope globally critical slip field (GCSF) method respectively. The results show that the safe factors calculated by the two methods are also in good agreement, with the difference of 3.1%. It is indicated that the simplified calculation method proposed in this paper for homogeneous and heterogeneous bank slope stability analysis is reliable and feasible.
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表 1 岸坡安全系数
Table 1. Safety factors of bank slope
计算方法 瑞典圆弧法 Bishop法 Janbu法 不平衡推力法 GCSF Slope/W 本文简化方法 安全系数 1.19 1.17 1.06 1.12 1.17 1.18 1.14 -
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