洞庭湖软土地区大直径超长灌注桩竖向承载力试验研究

以洞庭湖软土地区某特大拱桥主墩桩基础为工程依托 ,进行了一试桩竖向静载荷试验 ,并基于所获得的现场实测数据探讨了软土地区大直径超长灌注桩的荷载传递机理和竖向承载特性。结果表明 ,软土地区大直径超长桩为典型的摩擦桩 ,其竖向承载力主要由桩侧摩阻力提供 ,而桩端阻力往往难以发挥甚至趋于零 ,设计计算时尚应重视桩身压曲稳定分析和桩顶变形验算。同时 ,建议根据上部结构对基础沉降的要求按桩顶容许沉降量来控制超长桩的竖向承载力 ,并基于线弹性 -全塑性桩侧荷载传递模型给出了相应的计算公式 ,以此获得的桩顶荷载位移计算曲线与实测值吻合良好 ,证明了该思路与分析方法的可行性。

LOADING TEST ON THE VERTICAL BEARING CAPACTY OF SUPER-LONG AND LARGE-DIAMETER BORED PILES IN THE SOFT SOIL AREA OF DONGTING LAKE

Based on the vertical loading test results of a super-long and large-diameter bored pile near the main pier of an extra-long arch bridge located in the soft soil area of Dongting Lake, the load transfer mechanism and vertical load bearing behavior of the pile are discussed in depth. The analysis shows that,the super-long piles in the soft clay area behave as typical friction piles,with the vertical bearing capacity being supplied mainly by side friction resistance, and that buckling stability analysis and settlement checking should be carried out in the design process. Furthermore, an idea is presented for identification of the axial bearing capacity of super-long piles in soft clay by using the allowable pile-head settlement,with the relevant calculation formula derived from a linear elastic-full plastic load-transferring model. The calculated load-settlement curve agrees well with the measured one, which proves the feasibility of the proposed method.