基于弱光栅技术的钢管桩静载荷试验

Static load test of steel pipe pile based on weak-reflection fiber gratings

弱反射布拉格光栅感测技术是密集准分布式应变感测技术的一种,并将其应用在海上钢管桩的竖向静载荷试验中。从弱光栅感测技术原理展开,说明弱光栅独特的测试与监测优势。在工程实例中进行竖向静载荷试验,对比利用弱光栅光纤感测技术与分布式光纤感测技术所获竖向静载试验应变数据,试验结果表明在不同荷载下二者所获得的应变相对误差大部分低于50με,在同一荷载下二者所获得的平均误差值不大于30με。通过误差分析来体现弱光栅在静载荷试验中的准确性。由此进一步通过弱光栅计算桩身轴力和侧摩阻力测试结果来反映桩身内力的分布变化规律以及桩身承载特性,即在最大荷载的作用下桩端阻力所承受的荷载不足总荷载的十分之一且侧摩阻力的峰值约在埋深为96.5~108.5m之间。以此说明弱光栅在海上钢管桩实际项目中监测应用的可行性。

The weak-reflection fiber sensing technology is a kind of dense quasi-distributed strain sensing technology, it is applied in the vertical static load test of offshore steel pipe piles. This paper starts from the weak-reflection fiber grating sensing technology, and explains the unique testing and monitoring advantages of weak reflection Bragg gratings.The vertical static load test was carried out in an engineering example, and the strain data of the vertical static load test obtained by using the weak grating fiber sensing technology and the distributed fiber sensing technology were compared.The test results show that the relative error of the strain obtained by the two under different loads is mostly less than 50με, and the average error obtained by the two under the same load is not more than 30 με. The accuracy of weak grating in static load test is reflected by error analysis. Therefore, the test results of axial force and lateral friction resistance of pile are further calculated by weak grating to reflect the distribution and variation of internal force of pile and the bearing characteristics of pile. Under the action of maximum load, the pile tip resistance bears less than one tenth of the total load and the peak value of side friction is about 96.5~108.5 m. This shows the feasibility of weak grating monitoring application in the actual project of offshore steel pipe pile.