岩溶塌陷的光纤传感监测试验研究

An experiment study of monitoring sinkhole collapse by using BOTDR optical fiber sensing technique

通过大型岩溶塌陷物理模型试验室,研究了BOTDR光纤传感技术在岩溶塌陷(或沉陷)监测中的应用。试验中模拟了岩溶水的开采导致塌陷的过程,并实时监测光纤的变形过程及所观测到的土层破坏情况,试验结束后,垂直开挖剖面,检验光纤监测结果的可靠性。结果显示:光纤的应变峰值与土层的扰动、掏空相对应,可判断塌陷发生的位置;由不同层位的光纤应变变化,可判断土层扰动带垂直方向的发展过程;由光纤时间序列的变化趋势,可判断土层扰动带水平方向的发展方向。研究成果表明,BOTDR光纤传感技术监测塌陷的发生是可行的,效果较好。

As a distributed and real time monitor technique, BOTDR gives engineers a great expectation to carry out monitoring and prediction of sinkhole collapse in covered karst areas. This paper introduces the application of BOTDR to measurement of the process of sinkhole collapse in a large-scale modeling experiment. In the test, sinkholes are induced by karst water drainage, and the real time strain change of the optical fiber and soil breakage are measured. In order to analyze the final position of the optical fibers and their relation to the soil deformation, a soil section with optical fibers was excavated after the test. The results show that ① the position of peak strain in optical fibers corresponds to the area of disturbance and cavern formation in the soil, ② the change of optical fiber strain in different soil layers indicates the vertical boundary of disturbed area in soil, ③ the time series of optical fiber strain shows the progress of soil disturbed area formation, and ④ the BOTDR will become a reliable function to monitoring and predicting sinkhole collapse or subsidence, especially along the linear infrastructure constructions, such as highway and railway.