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随着穿越中国西部山区等复杂地形的公路桥梁越来越多,黄土沟壑地形桥梁桩基受到较复杂外荷载作用的问题也越来越凸显,同时由于桩周土体缺失效应,桩侧土体呈现出不对称性,侧摩阻力在靠近坡面侧土体中很难得到有效发挥,从而降低了桩基的竖向承载能力。结合西部黄土沟壑地形斜陡坡的工程地质特点,参考陕北黄土地区已建或在建桥梁工程项目的地勘资料,采用MIDAS FEA中桩土界面的接触分析进行有限元数值模拟,计算分析了黄土沟壑地形斜陡坡对桩基承载力的影响,总结了坡度、临坡距这2个主要因素对桩基极限承载力的影响规律。研究结果表明:桩基极限承载力与坡度呈反比例关系,坡度为30°时,桩基承载力较平坡桩基承载力下降了13.2%,桩侧摩阻力下降了18.3%,桩端阻力下降了2.3%;坡度为70°时,桩基承载力较平坡桩基承载力下降了46.7%,桩侧摩阻力下降了64.0%,桩端阻力下降了9.8%;随着临坡距的增加,桩端阻力变化微小,桩侧阻力增加明显,临坡距由D(桩基直径)增加至8D时,桩端阻力占极限承载力的比例由59%下降到49%,且基本保持稳定;而桩侧阻力在临坡距由D变为2D时,桩侧阻力增加了25%。在工程实践中,坡度因素不容忽视,研究结果可为相关地区桥梁桩基设计和施工提供参考。
With more and more highways and bridges passing through complicated terrains in the western part of China, the problem that the pile foundation of the loess gully terrain bridge is subject to more complicated external loads also becomes more and more prominent. Due to the lack of soil around the pile, Showing the asymmetry, lateral friction near the slope side of the soil is difficult to effectively play, thereby reducing the vertical bearing capacity of the pile. According to the engineering geology characteristics of the steep slopes in the loess gully area in western China, with reference to the geological survey data of the existing or under construction bridges in the loess region of northern Shaanxi, the finite element numerical simulation is conducted by using the contact analysis of the MIDAS FEA pile-soil interface, The influence of slope with steep gully slope on the bearing capacity of pile foundation is summarized. The influence of two main factors such as slope and slope on the ultimate bearing capacity of pile foundation is summarized. The results show that the ultimate bearing capacity of pile is inversely proportional to the slope. When the slope is 30 °, the bearing capacity of pile foundation is reduced by 13.2% compared with the pile foundation of pile slope, the friction of pile side is decreased by 18.3% and the resistance of pile tip is decreased 2.3%. When the slope is 70 °, the bearing capacity of pile foundation is reduced by 46.7% compared with that of plain pile, the friction of pile side is decreased by 64.0% and the resistance of pile tip is decreased by 9.8%. With the increase of the slope distance , The change of pile tip resistance is small and the pile lateral resistance increases obviously. When the slope distance increases from D (diameter of pile foundation) to 8D, the ratio of pile end resistance to ultimate bearing capacity decreases from 59% to 49%, and remains basically stable. On the other hand, when the slope resistance changes from D to 2D, the pile side resistance increases by 25%. In engineering practice, the slope factor can not be ignored, and the research results can provide references for the design and construction of bridge pile foundation in related areas.