干旱和局部渗水对膨胀土渠堤稳定性影响研究

Effect of drought and partial seepage on stability of expansive soil canal embankments

为探究膨胀土渠堤表面风干、地下水位升高和侧坡渗水等因素对其稳定性的影响,防控由此引发的现场灾害,开展了填方渠坡室内模型试验,研究了南水北调渠堤膨胀土含水量波动对渠坡变形和裂缝发育规律的影响,分析了边坡变形值、裂缝长度宽度与含水率、时间和渗水位置的关系,揭示了膨胀土含水量波动的致灾过程和时空发育规律。试验结果表明:(1)旱季坡面水分蒸发导致渠坡表层200 mm深度内首先产生垂直坡表面的“V”形簇状纵向裂缝,后逐渐水平发育,坡面最大沉降值为4 mm, 15 d后沉降趋于稳定;(2)雨季渠堤下部地基水位抬升使渠堤底部膨胀土发生显著膨胀,渠堤整体抬升3.32 mm;(3)在渠堤侧坡渗水中心点附近土体含水量上升8%以上,坝堤内自由水沿纵横向不均匀扩散而引起土体各向不均匀膨胀变形,并在右坡坡脚处产生长400 mm、宽14 mm的宽大裂缝;(4)基于膨胀系数的地基变形计算公式可以较好地预测渠坡浸水后各位置的变形量,有助于依据土体含水量判别各点的变形状态,为渠堤稳定性分析提供参考。

To investigate the influence of surface air drying,groundwater level rising and side slope seepage on the expansive soil embankment,and prevent the on-site disasters caused by them,a laboratory model test was conducted to study the influence of fluctuations in water content of the expansive soil on the deformation and crack development of the embankment of the South-to-North Water Diversion Project.The relationships between slope deformation,crack length,crack width and water content,time and seepage location were analyzed.The disaster-causing process and spatio-temporal development law of water content fluctuation of expansive soil were revealed.The test results showed that:①Evaporation causes the first V-shaped cluster of vertical longitudinal cracks on the slope surface at a depth of 200 mm,and then the cracks gradually develop horizontally with a maximum settlement value of 4 mm,while reach stability after 15 days.②Elevation of the water level at the foundation in the rainy season cause significant expansion of the expansive soil at the bottom,and the embankment is elevated by 3.32 mm.③The water content of the soil near the seepage center on latera canal slope increases by more than 8%.Free water in the embankment spread unevenly along the vertical and horizontal direction,causing the uneven expansion and deformation of the soil in all directions.And a wide crack of 400 mm in length and 14 mm in width was generated.④The calculation formula of foundation deformation based on the expansion coefficient can better predict the deformation at each location after the canal embankment submerged in water.It helps to discern the deformation state at each point based on the moisture content of the soil and provides a reference for the analysis of embankment stability.