考虑时间效应的高回填场地不同桩顶荷载基桩受力特性分析

由于基桩在高回填场地的应用不可或缺，考虑在其使用过程中高回填土的蠕变特性对基桩力学特性的影响，利用有限差分软件FLAC3D，并考虑时间效应，对填土厚度为10m，桩径为1m，嵌岩深度为3m的基桩进行桩顶荷载分别为0、0.5MPa、1Mpa、2Mpa、3Mpa和5Mpa的数值模拟分析，得到不同桩顶荷载作用下基桩的受力和变形特征。研究结果表明：桩周填土沉降随时间呈现先加速增加后逐渐趋于平衡的趋势，不同桩顶荷载作用下桩顶位移随时间的变化速率滞后于桩周填土的沉降变形速率；在桩周填土蠕变初期，桩身最大内力加速发展，而桩端阻力在此段时期的增长并没有出现加速增长；随着填土蠕变进入中后期，桩端阻力加速发展，桩侧摩阻力向桩端阻力转移；待桩周填土蠕变稳定后，桩身最大轴力与桩顶荷载呈现正相关，但是桩身轴力附加值随桩顶荷载的增加而减小；增加桩顶荷载桩，桩端阻力及其附加值也随之增大。该研究可为高填土场地桩基的设计施工提供参考。

The foundation piles with different pile tops load considering time effect in high backfill site Analysis of mechanical characteristics

Due to the indispensable application of foundation pile in high backfill site, considering the influence of creep characteristics of high backfill soil on the mechanical properties of foundation pile during its use process, the finite difference software FLAC3D and the time effect are used to calculate the filling thickness of 10m and pile diameter of 1m.The foundation pile with rock-socketed depth of 3m was subjected to numerical simulation analysis with pile top loads of 0, 0.5MPa, 1MPa, 2MPa, 3MPa and 5MPa respectively, and the stress and deformation characteristics of foundation pile under different pile top loads were obtained. The results show that the settlement increases at first and then tends to balance with time, and the rate of pile top displacement changes with time under different pile top loads lags behind the settlement and deformation rate of pile top filling. At the initial stage of creep, the maximum internal force of pile accelerates, but the resistance of pile tip does not increase at this stage. As the creep of fill enters the middle and later stage, the pile tip resistance develops rapidly, and the lateral friction resistance transfers to the pile tip resistance. After the creep stability of the surrounding fill, the maximum axial force of pile is positively correlated with pile top load, but the added value of axial force of pile decreases with the increase of pile top load. Pile tip resistance and its added value also increase with the increase of pile tip load. The study can provide reference for the design and construction of pile foundation in high fill site.