北京城市副中心站综合交通枢纽工程试验桩静载试验数据分析

Static Load Testing Data of Tentative Piles for the Transportation Hub of Beijing Sub-Center Station

试验桩静载测试是施工前为桩基设计提供依据的重要手段。针对北京城市副中心站综合交通枢纽项目试验桩直径大、桩身长、承载力高的特点,基于16根试验桩的静载检测成果,分析其采用扩底、桩侧和桩底注浆等施工工艺对承载力的影响。采用振弦式传感器测读钢筋应变量,得到桩身检测截面轴力分布并计算各土层的侧摩阻力。这些成果表明,各测试断面轴力随荷载增加而增大,而在同级荷载水平下轴力随着深度增加逐渐减小。此外,侧摩阻力的发挥随荷载增大而增加,扩底及桩侧注浆等措施使得基桩承载力明显提高。

The static load test of tentative piles is an important means to provide the basis for the design of a pile foundation before construction. This paper focuses on testing results of 16 piles with a large diameter,super-long and high loading for the comprehensive transportation hub project at Beijing Urban Sub-Center Station. The influences of construction techniques for piles such as the bottom expansion,pile side and bottom grouting on the bearing capacity are discussed. Strains of steels are measured by the vibrating wire gauge installed along with the reinforced steels in these piles. Furthermore,the axial force against depth of each test section is derived and the side friction resistance at the pile-soil interface is calculated. Based on these results,the axial force of each test section increases as the load increases,whereas the axial force at each section gradually decreases from top to bottom under the same level of the load. In addition,the side friction resistance increases with the increase of the load,and the bearing capacity of piles is improved significantly when some techniques such as bottom expansion and side grouting are facilitated.