高陡横坡段桩柱式桥梁双桩基础现场试验研究

为分析高陡横坡段桩柱式桥梁双桩基础承载特性及荷载传递机理,依托湖南省张花(张家界—花垣)高速公路泗溪河一桥#6桩开展了现场试验研究。通过采集施工过程中不同工况条件下桩身应力数据,分析了桩身轴力,桩侧摩阻力以及桩身弯矩分布规律。试验结果表明:试桩桩身所受轴向荷载全部由桩侧摩阻力承担,荷载较小时基本由上部土层承担;坡面以下2~5倍桩径范围内桩土极限摩阻力较小,土层与岩层所提供摩阻力之比随荷载增大而降低;桩顶存在负弯矩,前、后桩与横系梁为受力整体。基于有限杆单元方法建立了双桩结构整体分析模型,并通过反算拟合确定了前、后桩土压力分布规律及大小,计算结果与实测值吻合良好,可为同类工程提供参考。

Field tests on double-pile foundation of bridges in high-steep cross slopes

To analyze the bearing capacity and load transfer mechanism of double-pile bridge foundation in high-steep cross slopes, field tests are carried out located on pier No. 6 in Sixi bridge of Zhangjiajie-Huayuan highway. On the basis of the received measurements of stresses, the distribution rules of the axial force, shaft resistance and moment are obtained. The in-situ results indicate that all the applied loads can be carried by the shaft resistance. In particular, the upper soil layer carries most of the applied loads in the condition that the applied loads are relatively small. The ultimate shaft resistance in the depth whose range varies from 2 to 5 times the pile diameter is very small. The ratio of shaft resistances respectively supported by soils to rocks decreases with the increase of the loads. The negative bending moment occurs near the pile top, and the fact shows that the front pile, back pile as well as tie beam, as an integration, support the external load together. A double-pile analysis model is established based on the finite bar element method, and the distribution form and magnitude of earth pressure are proposed through fitting calculation. The calculated results match well with the measured values, which can provide a reference for similar projects.