考虑动水压力的改进 Bishop 法及其在岸坡稳定性评价中的应用

抽水蓄能电站岸坡在周期性水位变动下易发生变形失稳, 危及库区人民生命财产安全。为评价水库运行期的岸坡稳定性, 文章提出一种基于改进 Bishop 法的稳定性评价方法, 通过引入取矩中心及其确定方法, 使其适用于包括圆弧滑动面在内的任意形状的滑动面, 其次在评价库水位变动对岸坡稳定性时引入了动水压力的计算公式。以 Fredlund 的考题为例, 通过与 Spencer 法和 Morgenstern-Price 法进行对比验证了该方法的可行性, 对不同库水位变化情况下的安全系数进行敏感性分析。结果表明: 改进 Bishop 法计算得到的规律与 Morgenstern-Price 法基本保持一致, 而该方法与 Morgenstern-Price 法计算的安全系数最大偏差为 0.4; 此外由于考虑了动水压力, 与传统方法相比, 计算结果更准确地反映了边坡稳定性。将改进 Bishop 法应用于周宁抽水蓄能电站下库区某岸坡的分析, 结果表明, 在未考虑动水压力时, 该岸坡的安全系数为 1.287, 与描述的失稳迹象相符, 而在考虑了动水压力后, 安全系数降低了 0.272, 说明在水库运行期间, 该岸坡存在较大的失稳潜力。改进的 Bishop 法可以更加准确地评价抽水蓄能电站水库运行期岸坡的稳定性, 为科学评价岸坡稳定性提供依据。

The bank slope of pumped storage power station is prone to deformation and instability under periodic water level changes, which endangers the safety of people's life and property in the reservoir area. In order to evaluate the bank slope stability of reservoir during operation, a stability evaluation method based on improved Bishop method is proposed. This method introduces the center of moment taking and its determination method, which makes it suitable for any shape of sliding surface including circular sliding surface. The calculation formula of hydrodynamic pressure is also introduced when evaluating the stability of bank slope under the changes of reservoir water level. Taking Fredlund's test questions as an example, the feasibility of the proposed method was verified through comparison with Spencer's method and Morgenstern-Price method. The sensitivity analysis of the safety factor under different reservoir water level changes was carried out. It is found that the law calculated by the improved Bishop method is basically consistent with that calculated by Morgenstern-Price method, and the maximum deviation in the safety factor calculated by the improved Bishop method and Morgenstern-Price method is 0.4. In addition, considering the hydrodynamic pressure, the calculated results can reflect the slope stability more accurately than the traditional method. The improved Bishop method was applied to the analysis of a bank slope in the lower reservoir area of Zhouning Pumped Storage Power Station. The calculated results show that the safety factor of the bank slope is 1.287 when the hydrodynamic pressure is not considered, which is consistent with the described signs of instability. However, taking into account the hydrodynamic pressure, the safety factor is reduced by 0.272. This means that there is a great instability potential of the bank slope during the operation of the reservoir. Therefore, the improved Bishop method can more accurately evaluate the bank slope stability of pumped storage power station reservoir during operation, and provide a basis for scientific evaluation of bank slope stability.