黄土山区高陡边坡水毁对桥梁桩基安全影响研究

Influence of High and Steep Slope Washout on Bridge Pile Foundation Safety in Loess Hilly Area

为全面了解黄土山区高陡边坡水毁对桥梁桩基安全的影响,在对山西省典型黄土山区4条高速、174座桥梁下部全面调查的基础上,依据黄土地区现场桩基静载试验,应用FLAC3D建立黄土山区高陡边坡地形桥梁桩基有限差分模型,分析了高陡边坡水毁崩塌对桩基承载特性的影响,揭示了桩基承载力、桩侧摩阻力、桩端阻力及有效桩长变化规律。研究表明:随着临坡距的减小,桩基承载力不同程度降低,临坡距越小,桩基承载力影响越大;桩基承载力降低主要是由于桩侧土体缺失导致桩侧摩阻力无法完全发挥,桩端阻力影响不大;临坡距越小,斜坡失效桩长越大,有效桩长变短;高陡边坡水毁显著改变了摩擦桩的承载特性,危及桥梁下部结构及运营安全。

For comprehensively understand the influence of high and steep slope washout on bridge pile foundation safety in loess hilly area,based on widely investigation on 4 expressways,174 bridges in typical hilly area of Shanxi province,on the basis of on-site pile static loading test in loess area,bridge pile foundation finite difference model with high and steep slope in loess area were built by software FLAC 3D ,and analyzed the influence of washout & collapse of high and steep slope on pile foundation bearing behavior,announced the change law of ultimate bearing capacity,pile lateral friction ,tip resistance and effective length of pile. The study shows that ultimate bearing capacity of pile foundation are decreased to different degree with the decreased slope distance,the shorter slope distance,the higher influence of ultimate bearing capacity;the ultimate bearing capacity decrease mainly due to the loss of lateral soil,which result in pile lateral friction not fully bring into play,tip resistance has little difference;the shorter slope distance,the longer failure pile length,and shorter effective length of pile;the washout of high and steep slope make significant difference on bearing behavior of friction pile,which jeopardize the bridge substructure and operating safety.