Study on Monitoring and Early Warning of Karst Collapse Based on BOTDR Technique

Abstract

Brilliouin Optical Time Domain Reflectometer (BOT-DR) is a newly developed measurement and monitoring technique, which utilizes Brilliouin spectroscopy and Optical Time Domain Reflectometer (Jiang et al., 2006;Zhang et al., 2009;Xu et al., 2011) to measure strain generated in optical fibers as distributed in the longitudinal direction. This paper introduces the principle and characters of BOTDR technique firstly, and makes an example of karst collapse monitoring at section K14 of highway from Guilin to Yangshuo. Discussion includes how to use this technique in underlying karst collapse monitoring in karst highway; environmental factors, like temperature and vehicle dynamic load; how to affect the monitoring results; and how to choose optical fiber type and paving region. At last, we compare the results between using BOTDR and geological radar, and conduct the safety diagnosis on the experimental road. The application achievements demonstrate that BOTDR is a viable technique for the karst collapse monitoring.

Distributed fibre optic sensing for sinkhole early warning: experimental study

“…However, they rely on sufficient coupling at the interface between the fibre and the soil, as well as an understanding of the logged strain profile at depth. Monitoring settlements and ground deformation using fibre optic cables is a recent technique (Guan et al, 2013;Klar et al, 2014;Guan et al, 2015;Zhang et al, 2016;Inaudi, 2017) that still requires further understanding and experience of soil-fibre interaction and its effect on the obtained data. The incorporation of fibre optic cables into earthworks could provide significantly improved information on the location, mechanisms, and magnitude of subsurface ground movements in real-time for newly built critical infrastructure over regions with high sinkhole susceptibility.…”

Numerical investigation of fibre-optic sensing for sinkhole detection

“…In situ applications will however be subjected to temperature and moisture content changes, as well as vibrations from human activities (train, road, construction, etc. ), which will pollute the otherwise sensitive DFOS signal (Guan et al, 2015). Temperature changes can typically be corrected by adding a fibre that senses seasonal and daily changes in temperature on a specific channel of the interrogator (Kechavarzi et al, 2016), but this technique might not be sufficient at small strain levels, as needed for this particular application.…”

“…Three different fibre optic sensors were used, both independently and as part of a geogrid, in order to study the sensitivity of those sensor in detecting soil settlements. A recent development in sinkhole detection relies on the use of fibre optic cables, included in the earthwork during construction, sometimes within the use of a geogrid, to monitor ground displacements (Guan et al, 2013;Klar et al, 2014;Zhang et al, 2016;Guan et al, 2015;Inaudi, 2017). This is particularly adapted for long linear infrastructure, such as railways or roads.…”

The Application of Distributed Optical Fiber Sensors (Botda) to Sinkhole Monitoring. Review and the Case of a Damaging Sinkhole in the Ebro Valley Evaporite Karst (Ne Spain)

“…Here, several collapse sinkholes have formed above caverns created by salt solution mining, threatening a major railway. Guan et al (2015) described a 90 m long BOTDR sinkhole monitoring system installed in the Guilin-Yangshuo highway, built upon cavernous limestone mantled by clayey soil. Jiang et al (2016) reported that the Chinese Institute of Karst Geology established in 2006 and 2012 two pilot monitoring sites at Guilin and Guigang of Guangxi province to monitor potential sinkholes along a highway and an oil pipe, respectively.…”

“…Recently, the potential societal risks associated with the construction of transport infrastructure (e.g., vulnerable high-speed railways) in vast sinkhole-prone areas are receiving special attention (Guan et al, 2015;Jiang et al, 2016). A key practical question is whether it would be possible to detect sinkhole-related deformation sufficiently in advance to prevent accidents.…”