降雨对路堤斜坡稳定性影响的时间效应

以某高速公路填筑试验路堤为例，基于非饱和土渗透及强度理论，采用渗流场与应力场、稳定性计算耦合的方法，对两种不同透水特性的路堤在降雨过程中孔隙水压力和稳定性系数随时间变化的特点及规律进行较为深入的探讨。结果表明，（1）透水性能较好的路堤斜坡下部降雨入渗要强于斜坡上部，透水性能较差的路堤斜坡，雨水往往以近似于均匀的形式入渗；（2）透水能力强的路堤斜坡在短暂的超强降雨或者强度较低但持续时间超长的降雨过程中，其最小稳定性系数易于出现滞后现象，一般滞后0.5～3 d，透水能力差的路堤斜坡最小稳定性系数有显著滞后特点，一般滞后7～15 d；（3）总降雨量一定、雨强大于等于50 mm/d条件下透水能力强斜坡能达到的最小稳定性系数随降雨时间增长而降低，而透水能力差的斜坡最小稳定性系数受雨强和降雨时间共同影响。

Time effect on stability of embankment slope due to rainfall

Based on the permeability and strength theory of unsaturated soil, this study used two expressway embankments consisting of soil with significantly different permeabilities as examples to investigate the variations in pore water pressure and stability coefficient of the embankments during different rainfalls. The results show: (1) The rainfall infiltrates better in lower parts than upper parts of the embankment formed with high permeability soils; however, it infiltrates almost equably in the surface of embankment formed with less permeability soils. (2) The minimum stability coefficient of the embankment slope with high permeability occurred normally after rainfall about 0.5-3 days during the short and high intense rainfall process, or less intense and longtime rainfall process. And the minimum stability coefficient of embankment with less permeability lag behind rainfall more obvious, normally lagging 7-15 days behind rainfall. (3) When the total rainfall is constant, the minimum stability coefficient of the embankment slope with high permeability decrease as rainfall intensity increase. The embankments with low permeability are influenced by both rainfall intensity and duration.