钻孔压灌桩的超弱光纤光栅应变场监测方法

Ultra-weak fiber grating strain field monitoring method for bored piles

提出了一种在长螺旋钻孔压灌桩中引入超弱光纤光栅的应变场监测方法。分析了超弱光纤光栅多点应变传感原理,设计了一种定点式标距1 m的超弱光纤光栅光缆,对灵敏度进行了标定,在10000με范围内的平均应变灵敏度为1.15 pm/με。在广州市有轨电车试验桩项目中,采用预拉力方式将光缆与钢筋笼结合后埋设,经过28天固化后对多根长螺旋钻孔压灌桩进行了静载测试和分析。试验表明,超弱光纤光栅传感系统工作频率1 Hz,应变精度1可实现对桩基应变场的多点、大量程、高精度的线性监测,验证了超弱光纤光栅传感器在桩基监测中的可行性。

Pressure grouting pile is a kind of"green pile"with high quality,low cost and noise-free.In this paper,the strain field monitoring method of ultra-weak fiber Bragg grating is introduced into long spiral pressure grouting pile for the first time.the principle of ultra-weak fiber Bragg grating multi-point strain sensing and the demodulation system are analyzed,and a fixed-point gauge length 1 m ultra-weak fiber Bragg grating optical cable is designed,and the sensitivity is calibrated.the average strain sensitivity of the optical cable in the range of 0 to10000μεis 1.15 pm/με.in the Guangzhou Tram Test Pile Project,the pre-tension technology was used to combine the optical cable with the steel cage and then buried.after 28 days of curing,the static load test of several long spiral pressure grouting pile is carried out,and one pile is analyzed in detail.the test shows that the sensing system can monitor the strain distribution of pile foundation under different loads on line,and obtain the axial force of pile body through the strain distribution,which verifies the feasibility of Ultra-weak fiber Bragg grating sensor in pile foundation monitoring.