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光纤传感技术是滑坡监测领域较新的方法,通过在白水河滑坡前缘采用定点固定加直接埋设的方式并行布设应变式光纤和温度补偿式光纤,开展地表变形监测。根据PPP-BOTDA分布式光纤理论,对应变式光纤和温度补偿式光纤的应变数据进行温度补偿处理,得到光纤因变形而引起的实际应变。利用巴特沃斯低通滤波去噪方法,比较4组不同采样频率下的滤波效果及残差,确定滤波器阶数n和截止频率Wn。为表征2次监测数据之间的差异,选取光纤2次监测曲线与固定横轴的面积差作为评判指标,获取光纤沿线面积差,得到面积差与光纤应变差异程度之间为正相关关系,同时与野外实测数据进行对比分析。结果表明,采用PPP-BOTDA技术进行滑坡地表变形监测时,利用巴特沃斯滤波器进行去噪处理,并采用应变面积差表征光纤应变差异程度的分析结果,与野外空间地理位置上吻合度较高,对光纤技术在滑坡监测中的应用具有一定的借鉴意义。
Optical fiber sensing technology is a new method in the field of landslide monitoring. Surface strain monitoring is carried out by arranging strain-type optical fiber and temperature-compensated optical fiber in parallel by fixed-point fixing and direct embedding in the front of Baishuhe landslide. According to the theory of PPP-BOTDA distributed optical fiber, the strain data of strain fiber and temperature compensated fiber are temperature compensated, and the actual strain of fiber due to deformation is obtained. Using Butterworth low-pass filter denoising method, the filter efficiency and residual at different sampling frequencies are compared to determine the filter order n and the cut-off frequency Wn. In order to characterize the differences between the two monitoring data, the difference between the monitored area of the optical fiber twice and the area of the fixed horizontal axis was selected as the evaluation index to obtain the area difference along the optical fiber. The area difference was positively correlated with the degree of optical fiber strain difference. And the field measured data for comparative analysis. The results show that when using PPP-BOTDA to monitor the deformation of landslide, we use Butterworth filter to denoise and analyze the degree of fiber strain difference based on strain area difference, which is in good agreement with the geographic location of the field , Which has some reference to the application of optical fiber technology in landslide monitoring.