软基桥头路基填筑对桥台桩的影响

Effects of Embankment Load on Piled Bridge Abutments on Soft Clay

为考察台后路堤荷载导致的地基软弱下卧层压缩和水平移动作用下的桥台桩基受力性状,建立了桥台桩基的三维有限元模型,验证了其合理性,并通过设置桩-土接触单元分析了桥头路基填筑对桥台桩基受力性状的影响。结果表明:由于桩的"遮拦效应",前排桩桩-土"绕流"现象较后排桩更为明显;同时,桩的阻拦作用使桩周土体位移值较自由土场预测值偏小;桩-土相对位移较大时桩平均侧向压力与桩-土相对位移呈非线性关系;每级荷载下最大桩侧土压力约为路堤荷载的74%;路堤荷载大小与桩身最大弯矩值的关系与基桩所处位置有关,并非简单的双折线关系;在影响桩身弯矩因素中,软土层力学性质对桩身弯矩影响较桩身模量更为明显;桩在受轴向力和侧向力耦合作用下,桩基础的承载力会有所提高,但不明显。

In order to investigate the behavior of the piled bridge abutments, caused by the compression and horizontal displacement of the soft substratum due to embankment load, a 3 D FE model of the abutment pile foundation was established and proved to be reasonable. Then, the effects of embankment load on the behavior of piled bridge abutment were analyzed using a pile- soil contact element. The results show that the pile-soil bypassing phenomenon of the front piles is more obvious than that of the back piles because of shielding effect~ the intercepting effect of the piles makes the displacement of the soil around the piles smaller than the predicted value of the free soil field~ as the pile-soil relative displacement becomes larger, there exists a nonlinear relationship between the mean lateral pressure and the pile-soil relative displacement~ the maximum lateral pressure is about 740/00 of the embankment load under each load level~ the relationship between the embankment load and the maximum moment value of the piles is not the simple double broken line relationship but relates with the location of the piles; among all thefactors that affect the moment value of the piles, the mechanical properties of the soft soil plays a more important role than the modulus of piles and when the axial force and lateral force coupled, the bearing capacity of the pile foundation can be upgraded slightly.