大直径管桩-钢管复合桩基承载特性现场试验研究

Field Test of Bearing Properties of Large Diameter Tubular Pile-SteelPipe Composite Pile Foundation

为研究大直径管桩-钢管复合桩基承载特性,依托温州港状元岙港区码头二期工程桩基建设,选取工程桩S1、S2为试验桩,分别开展了竖向静载和水平静载原位试验,测得竖向静载的截面应变值ε,及水平静载下桩顶水平位移Y、桩顶转角θ;计算了竖向静载时不同截面桩身轴力Q axial、桩端阻力Q pu、桩侧摩阻力Q s,及水平静载时泥面处桩的水平位移Y 0、泥面处桩的转角θ0;分析了竖向静载及水平静载过程中桩顶位移S随着竖向荷载Q的改变而变化的规律,以及竖向刚性系数K、不同截面桩身轴力Q axial和桩侧摩阻力Q s的变化规律。研究表明:竖向静载下桩顶荷载-桩顶位移(Q-S)曲线呈缓变形;试桩S1、S2竖向承载力均不小于10500 kN,满足工程设计要求;桩侧摩阻力Q s随桩入土深度z的增加而逐渐发挥,其分布形式呈“驼峰型”;在最大竖向静载Q max下,试桩S1、S2桩端荷载分担比分别为9.55%、8.45%,均属端承摩擦桩;在水平静载H下,试桩S1、S2的水平承载力均满足设计要求;试桩S1、S2的桩身最大弯矩M max分别为820、1038 kN·m,均出现在泥面以下3.0 m附近。大直径管桩-钢管复合桩能满足项目工程要求。

In order to study the bearing characteristics of the large diameter tubular pile-steel pipe composite pile foundation,relying on the construction of the pile foundation of the second phase of the wharf in the Zhuangyuan'ao port area of Wenzhou Port,the engineering piles S1 and S2 were selected as the test piles to carry out the vertical static load and horizontal static load test respectively.The vertical static load section strain value ε and pile top displacement Y,pile top rotation angle θ under horizontal static load were measured.The pile axial force Qaxial,pile tip resistance Qpu and pile side friction Qs under vertical static load as well as the mud displacement Y 0 and angleθ0 at the mud surface under horizontal load were calculated.The variation law of pile top displacement S changing with horizontal load Q in the process of vertical static load and horizontal static load was analyzed,as well as the variation law of vertical stiffness coefficient K,axial force value Qaxial and pile side resistance Qs at different pile elevation were analyzed.The research shows that the Q-S curve of pile foundation shows slow deformation under vertical static load test;the vertical bearing capacity of test pile S1 and S2 is not less than 10,500 kN,which can well meet the requirements of engineering design;the lateral friction resistance of the pile gradually develops with the increase of embedded depth z of pile body,and its distribution form is“hump-shaped”;under the maximum vertical load Qmax,the test pile S1 and S2 pile tip load ratios are 9.55% and 8.45% respectively,which represents as friction pile;under the horizontal load H,the horizontal bearing capacity of test pile S1 and S2 meets the design requirements;and the maximum bending moment of S1 and S2 is 820 kN·m and 1,038 kN·m respectively,both of which occur at about 3.0 m below the mud surface.It is proved that the large diameter tubular pile-steel pipe composite pile foundation can meet the engineering requirements of the project.