降雨作用下南水北调膨胀土渠道稳定性及影响因素

南水北调中线工程膨胀土渠道超过全长的四分之一,降雨是诱发膨胀土渠坡失稳的主要外因.对比分析了考虑非饱和渗流对边坡稳定性的影响,基于有限元方法计算降雨作用下渠道的饱和-非饱和渗流场,分析其边坡的安全系数和位移的变化规律,最后通过正交试验和灰色关联理论对渠道边坡稳定性的影响因素进行敏感性分析.研究结果表明:考虑非饱和渗流下边坡稳定性分析结果更切合工程实际;降雨过程中,边坡浅层一定深度内土体的孔隙水压力迅速增大,这一土体范围随着降雨强度增大和时长增加逐渐向深部扩展;降雨对堤顶向下0～2.5 m范围和一级马道向下0～5 m范围内土体含水率的影响较大,降雨强度的影响大于降雨时长;降雨导致土体吸水膨胀,位移出现轻微的回弹;渠坡的安全系数随着降雨持续逐渐减小,并且降雨强度越大,降幅越大;影响边坡稳定性因素的敏感性排序:黏聚力＞内摩擦角＞饱和渗透系数＞降雨强度＞降雨时长＞土体重度.研究结果可为南水北调工程加强渠道稳定性提供依据.

Analysis of Stability and Influencing Factors of Expansive Soil Channels in the South-to-North Water Diversion Project under Rainfall

The expansive soil channel of the Middle Line South-to-North Water Diversion Project is more than a quarter of its full length, and rainfall is the main external factor causing slope failure of expansive soils. The saturated-unsaturated seepage field of channel under the action of rainfall was calculated, and the change law of safety factor and displacement of the channel slope was analyzed based on the finite element method. Finally, the sensitivity analysis of the influencing factors of the channel slope stability was carried out by orthogonal experiment and grey relational theory. The results show that the pore water pressure of the soil within a certain depth of the shallow slope increases rapidly; the soil swells and the displacement appears slightly rebound due to the rainfall ; the safety factor of the channel slope gradually decreases as the rainfall continues; sensitivity ranking of factors affecting slope stability: cohesion> internal friction angle> saturated permeability coefficient> rainfall intensity> rainfall duration> soil weight.