大直径超长后注浆钢筋砼桩身应变分布式光纤监测

Monitoring on axial strain of huge pile by BOTDR technology

后注浆条件下大直径超长桩荷载传递机理十分复杂,而传统监测技术得到的成果不连续,不能准确反映桩基的荷载传递机理。结合工程实例现场静载荷试验,采取BOTDR分布式光纤技术监测桩身应变分布,研究超长桩端阻、侧阻分布。发现桩侧摩阻力呈中间大、两端小的趋势;桩侧负摩阻使摩阻力曲线上出现波峰和波谷交替现象;桩侧摩阻力在桩体下部很难发挥出来,直接把基坑底标高处桩的轴力作为极限承载力是不合理的。

A on- site experiment is carried out on a ease project. The axial strains in piles, which are more than 60 meters long, are monitored in the process of statistic loading with the distributing fiber BOTDR technology. the axial strains of pile are traced down during the process of static loading test, with nine steps of loading. After the axial strain is measured, the axial forces of pile are determined, and the lateral friction forces are also obtained. It reveals that the lateral friction in the deep part of pile is underdeveloped, so the general way to determine the load bearing capacity of pile by deduct the part of friction force over the level of construction pit is unreasonable.