边坡变形的分布式光纤监测试验研究及实践

布里渊光时域反射计(BOTDR)是一项新型光电传感仪器,可对沿光纤的轴向应变进行分布式监测。该技术采用光纤作为传感和传输介质,具有良好的抗干扰、长距离、可植入性和分布式监测等特点。本文总结了近几年来分布式光纤在边坡工程中监测的工程实践和试验研究结果。实践表明,将光纤传感器铺设在加固边坡的锚杆和框架梁中,在加固边坡的同时进行安全监测,可以取得良好的效果;而将光纤直接铺设在边坡浅层土体中进行监测,可以及时对边坡安全提供预警,但往往不利于长期监测。本文还介绍了将光纤传感器布设在用于加固边坡的土工织物中进行安全监测的室内试验研究。实验证明,不同的光纤类型、布设方法、土工织物性能等都会对监测结果产生影响。最后分析了分布式光纤监测在岩土工程监测中的应用前景,以及今后研究的关键技术问题。

Distributed Fiber Monitoring Test and Its Application to Slope Deformation

Brillouin Optical Time-Domain Reflectometer (BOTDR), a newly developed distributed fiber optic sensing technique, has some unique functions such as distributed, long distance, anti-electromagnetic interference, and waterproof, and is very suitable and useful to the monitoring and early-warning of geo-logical engineering such as slope engineering. There have been many tests and practices of which the dis-tributed fiber optic sensing technique had been successfully applied to geotechnical engineering. However, for a soil slope, the layout of fiber sensors will greatly affect the monitored data. In this paper, the experi-ence of lab tests and practical applications that BOTDR was applied to monitor the deformation of a soil slope were introduced. In a case of the reinforced soil slope, the fiber sensors were tried to be embedded into soil anchors and frame beams, which shows the result of strain can well reflect the deformation cha-racteristics of the slope. Another case of a highway slope, the fiber sensors were directly buried into a shallow soil layer of the slope, the location of strain anomalies in monitoring data can well reflect the loca-tion of soil surface failure, but this method does not fit for long time monitoring, because too much defor-mation of fiber sensor will cause fiber sensors broken down. And a lab test in which fiber sensors were em-bedded into geotextiles used for slope reinforcement were also introduced in this paper, which shows the monitoring results were mainly affected by the type and the layout of the fiber sensors, and the properties of the geotextiles. Lab tests and engineering practices show that the distributed fiber optic sensing tech-nique can be well used in slope safety monitoring through proper layout method and data processing. At last, the prospects.and future key issues were discussed.