DBPapers
DOI: 10.5593/SGEM2014/B12/S2.023

COMPARISON OF RESULTS OF TWO METHODS OF FIBRE OPTICS DEFORMATION MONITORING IN GEOTECHNICS

K. Capova, J. Zalesky, M. Zalesky
Wednesday 1 October 2014 by Libadmin2014

References: 114th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-08-7 / ISSN 1314-2704, June 19-25, 2014, Book 1, Vol. 2, 171-178 pp

ABSTRACT
The paper introduces selected results of applications fiber optics deformation monitoring in geotechnics. Series of Fiber Bragg Gratings sensors and Brillouin Optical Time Domain Analysis were used for monitoring of a side slope deformations of an open cast mine. These monitoring technologies with developed ways of protection of fibers / optic cables, installation procedures and data evaluation were tested under laboratory conditions and in the underground research center of the Czech Technical University in Prague prior to on site deployment. The first type of applications was used for the surface monitoring of the potentially unstable area installed just below the ground surface. The outputs of these applications were the determination of the active part in the monitored area, the deformation development in time in selected lines drawn through the potentially unstable areas. The check of the assumption of so called reference part of the installation was provided with use of the Global Navigation Satellite System (GNSS), which is sufficiently accurate for larger deformations. Extensometer tape and laser distometer were used for cross-checking the monitored results. The second type of application was instrumentation of fiber optics into two boreholes. The boreholes are usually vertical and have to be deep enough. The common condition is the fixing of the lower end of the borehole to the stable area which is not and is not going to be affected by any deformations and therefore may be considered as the so called fixed end. An independent check of the measurement results is provided by the simultaneous accurate line-wise geotechnical 3-D monitoring. The gathered results are discussed and evaluated from the points of view of problems connected with data interpretation, sensitivity and repeatability of deformation sensing in cases of our developed methods of in-situ fiber optics applications.

Keywords:geotechnical monitoring, deformation monitoring, BOTDA, FBG, fibre optics, slope stability