Slope Instability Monitoring by using Distributed Optical Fiber

Abstract

Mass movements are often associated with periods of heavy rainfall that penetrate the ground causing a reduction in its shear strength parameters and generating instabilities that can lead to rupture. These instabilities when in densely populated areas can cause catastrophic occurrences with loss of human life and environmental and economic damage. This article discusses the results of ground strain measurement obtained by using a special optical cable and a Distributed Temperature and Strain Sensor (DTSS) unit. The optical cable was installed on a slope in São Paulo state, Brazil. Optical fiber technology allows instantaneous and periodic monitoring of surface strain evolution that occurs over a wide area, complementing traditional geotechnical instrumentation, made up of punctual and manual measurements, which is prone to error and requires more time for verification. The optical cable used for this study acts as an intrinsic sensor, where the cable itself acts as a sensor element, thus performing the function of receiving and transmitting information, unlike other sensors, called extrinsic, which only transmit information from a point sensor. The optical fiber sensor used are lightweight, malleable and immune to electromagnetic interference, making them ideal because they are rugged and allow for practical control and reliable results. For the optical cable analyzed for this article, the maximum strain variation and maximum strain relief values were 1528.29 microstrains and -2867.69 microstrains, respectively.