路基填土对桥台桩基影响的试验与数值仿真分析

台后路基荷载会使地基软弱下卧层发生压缩和水平移动，致使桥台桩基的受力性状非常复杂。在现场测试结果的基础上，建立了三维有限元模型，模拟了台后路基荷载作用下桥台桩基的受力性状，并与实测结果进行了对比分析。结果表明，有限元计算结果与实测结果较为一致。中间桩排和后排桩桩身最大弯矩与台后路基荷载的关系呈双折线型，与Stewart等提出的一致，但双折线转折点所对应的路基填土荷载并不一致。中间桩排的填土荷载为软土层固结不排水黏聚力强度ccu与土层厚度的加权平均值的3.34倍，后排桩约为2.22倍；前排桩的最大弯矩与路基填土荷载呈线性变化。桩顶变形与台后路基荷载呈非线性关系，可以分为两部分。前排桩桩身最大弯矩位置一直在软土层中，不随台后路基荷载变化；而后排桩桩身最大弯矩位置在台后路基荷载较小时位于软土层中，随着台后路基荷载的增大，最终出现在桩顶。

Field test and 3D FEM studies of bridge abutment on piled foundation subjected to embankment load

Piles supporting bridge abutments on soft clay may be loaded laterally from horizontally soil movements induced by the approach embankment. 3D finite element modeling of piled bridge abutment is set up to explore the behavior of piles induced by embankment load which is compared well with the data from the site monitoring. The results indicate that the bending moment of piles and settlements of bearing platform calculated are consistent with the data from the site monitoring. The curves of the maximum bending moment plotted against the average stress applied by the embankment in the middle pile row and the rear pile row are double broken lines which are consistent with what Stewart, D.P. suggested. However, the average stress corresponding to the threshold (at the intersection of the two lines) do not occur at the same embankment load which are about 3.34 times weighted mean ccu of layered strata in the middle pile row and about 2.22 times weighted mean ccu in rear pile row. The curve of the maximum bending moment plotted against the average stress in front pile row is linear. The deflection of the pile cap plotted against the average stress applied by the embankment doesn’t agree with the curve Stewart, D.P. suggested. The curve obtained in the paper is nonlinear and can be divided into two portions. The maximum bending moment of the front pile row is developed at the upper portion of the clay layer rather than near the pile cap, but that of the rear pile row is developed at the upper portion of the clay layer under low embankment load and then shows the maximum value at the pile head under high embankment load.