First Results of a Field Test in Belchatow Brown Coal Mine to investigate Creeping Slopes

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1 Bericht-XXXIV-2009_gesamt_R00.docx Bericht XXXIV, 2009 Rainer Glötzl, Joachim Schneider-Glötzl, Sascha Liehr, Philipp Lenke, Mario Wendt, Katerina Krebber, Luciano Gabino, Jerzy Krywult First Results of a Field Test in Belchatow Brown Coal Mine to investigate Creeping Slopes

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3 Presentation of Glötzl GmbH during VI. International Brown Coal Mining Congress in Belchatow, Sportshotel May 2009 GLÖTZL Gesellschaft für Baumesstechnik mbh Forlenweg 11 Rheinstetten Germany First Results of a Field Test in Belchatow Brown Coal Mine to investigate Creeping Slopes Authors: Rainer Glötzl 1, Joachim Schneider-Glötzl 1, Sascha Liehr 2, Philipp Lenke 2, Mario Wendt 2, Katerina Krebber 2, Luciano Gabino 3, Jerzy Krywult 4 1 Glötzl Gesellschaft für Baumeßtechnik mbh, Forlenweg 11, D Rheinstetten 2 Bundesanstalt fuer Materialforschung und -pruefung (BAM),Unter den Eichen 87, D Berlin 3 Alpe Adria Textil S.r.l., Strada di Salt, 50, IT Remanzacco Udine 4 Jerzy Krywult ENGINEERING, ul. MUSIOŁA 10, PL Katowice ABSTRACT: In the frame of the European Research Program POLYTECT which includes more than 30 partners of Europe and one of India, a geotextile mat with an additional POF Polymer fiber has been developed to detect strain behavior. It is a distributed POF strain sensor technology integrated in this geogrid textile. The new is the measurement of strain fully distributed along the fiber. Installation experiences and first results detecting an opening gap are presented. 1 INTRODUCTION In this presentation I like to introduce these recent research and development results. As mentioned in this European Research Program POLYTECT with many other things also a geotextile mat was developed to investigate and to observe creeping slopes and landslide slopes. The side of the Belchatow brown coal mine The really new is that for geotechnical purposes a system is used which is able to measure strain and temperature continuously distributed along the whole length of the fiber which is integrated in this geogrid. Dateiname: Vortrag International Congress Belchatow 2009.doc Revision-Nr. 5 Speicherdatum: 16/03/09

4 GLÖTZL Gesellschaft für Baumesstechnik mbh Forlenweg 11 Rheinstetten Germany Seite 2 The fiber is a standard PMMA POF which is integrated in the geotextile mat and is able to measure distributed strain behavior on a length of 100 m. New development is a new fiber which is able to measure up to 500 m total length and which will be presented soon. A geogrid mat with integrated PMMA POF. Generally and most known are applications for structural health monitoring. Thevenaz et al. (2001) presented stimulated Brillouin scattering technique with a hydraulic strain resolution up to several tenths of kilometers. Another system is the quasi-distributed fiber sensor as Bragg Grating Systems. Research results and lab tests presented by Liehr et al. showed the system using the OTDR technique. Standard PMMA POF can observe strain up to 40 % but here the time effects by creeping influences of the PMMA POF itself are influencing and changing the results. By these facts which have to be investigated furtheron, the use of this geotextile mat is limited on short-term uses e.g. six to twelve months and the detection of gaps and their localization and the opening speed. All this is made in the frame of the European Project POLYTECT (Polyfunctional Technical Textiles against Natural Hazards). This mat can also be used for strain and deformation in dikes and embankments.

5 GLÖTZL Gesellschaft für Baumesstechnik mbh Forlenweg 11 Rheinstetten Germany Seite 3 2 SEARCH OF A CONVENIENT SITE To carry out a field test, a big point is a convenient construction or site which can be used to test this product under field conditions. The search was running more than one year with different types of sites and was successfully closed with the open-pit brown coal mine in Belchatow. For Glötzl and the POLYTECT group engaged in this field test it was important to find a creeping slope active with a reasonable velocity which allows to detect movements in a reasonable time. Our thanks are addressed to the Directory of the Belchatow Brown Coal Mine for their understanding and support for this new technique. The congress itself is perfectly placed to demonstrate and to present the mat, the results, operating principle a.s.o. Side and installation. location in Belchatow near Lodz, Poland. 3 SENSOR PRINCIPLE The sensor principle short explained is based on the use of the Optical Time Domain Reflectory (OTDR) technique to obtain the backscatter profile of the fiber. Short laser pulses are given into the fiber and the backscattered light for each pulse is recorded as a function of time. The typical measuring time is depending on fiber length and arriving between 1 and 30 meters. In our geotextile grid we used standard PMMA POF with 1 mm core diameter and 2,2 mm coating. The readout unit is an OTDR device from Sunrise Luciol, Switzerland, with a 250 NM light source.

6 GLÖTZL Gesellschaft für Baumesstechnik mbh Forlenweg 11 Rheinstetten Germany Seite 4 4 INSTALLATION Our partner in the frame of POLYTECT, AAT Alpe Adria Textil, was preparing a geogrid like mat with a length of 10 meters and a width of 4 meters. The POF was integrated in the center cover, the long length with ending lengths of 4 meters. Fixing and installation of the geogrid mesh

7 GLÖTZL Gesellschaft für Baumesstechnik mbh Forlenweg 11 Rheinstetten Germany Seite 5 After long discussions and argumentation we decided to place the mat close to the high point street along the brown coal mine. Picture xx is showing the localization and the already visible gaps. The section we have chosen was in the area of a creeping slope already found in the past and long-term observed with vertical inclinometers. The sliding surface is about 50 meters down. Before placing the mat, all greens have been removed. The mat itself was placed after a function control at the site and laid down on the installation field without strengthening the mat. A cover of overburden of sand material was used with a height of 10 to 12 cm only. Placing of the geogrid on the surface of the slope area

8 GLÖTZL Gesellschaft für Baumesstechnik mbh Forlenweg 11 Rheinstetten Germany Seite 6 A further installation technique will be sprayed resin to fix and a mat for example placed on an inclined slope to have fixation over the total surface and not only some fixing points. After installation a first zero measurement was done by the colleagues of the BAM and also training with our colleagues of Budokop was carried out. The training was continued with a second measurement next day and after this our Polish colleagues continued these measurements independently. Next picture is showing the different measurements and will be explained and compared with the visible gap movements. We all know that a lot of the additional measurements and further research have to be done but today we only like to present these first results in regard of localization and increase of the gap. Only a short comment: Already in the measurement of 17. November last year we can see that the increase is slightly and not according the opening. Here we can see this as an additional influence by creeping. So, the increase in loss is reduced by this creeping and relaxation effects of this Polymer material. Measuring unit OTDR (Optical Time Domain Reflector)

9 GLÖTZL Gesellschaft für Baumesstechnik mbh Forlenweg 11 Rheinstetten Germany Seite 7 5 CONCLUSION First result seeing opening of a gap (courtesy BAM, Berlin) The introduced distributed strain sensor technique and the integrated fiber into textile for geotechnical uses. The first results are exciting and interesting. The further needs in longer fibers and in relaxation research are identified. Further tests have been foreseen in spring time also in Belchatow and also in the frame of the POLYTECT RESEARCH PROGRAM. First result seeing opening of a gap (courtesy BAM, Berlin)

10 GLÖTZL Gesellschaft für Baumesstechnik mbh Forlenweg 11 Rheinstetten Germany Seite 8 6 ACKNOWLEDGEMENT The presented investigations are financially supported by the European Commission within the 6 th framework program and are carried out in the project POLYTECT Polyfunctional Technical Textiles against Natural Hazards (NMP2-CT ). The authors gratefully thank for the financial support and the valuable cooperation of all partners involved. We also thank the Directors of the brown coal pit for providing the possibility for this field test. 7 REFERENCES The team and the group is saying thank you for your attention Frogatt, M and Moore, j High-spatial-resolution distributed strain measurement in optical fiber with Rayleigh scatter. Applied Optics, 37: Husdi, IR, Nakamura, K and Ueha, S Sensing characteristics of plastic optical fibers measured by optical time domain reflectometry. Measurement Science and Technology, 15: Liehr, S., Lenke, P., Krebber, K., Seeger, M., Thiele, E., Metschies, H., Gebreselassie, B., Münich, JC and Stempniewski, L Distributed strain measurement with polymer optical fibers integrated into multifunctional geotextiles. Proc. of SPIE, Vol. 7003: Liehr, S., Lenke, P., Wendt, M. and Krebber, K., Perfluorinated graded-index polymer optical fibers for distributed measurement of strain. Proc. Of POF Conference. Thevenaz, L., Facchini, M, Fellay, a., Nikles, M and Robert, P Field tests of distributed temperature and strain measurement for smart structures. Lasers and Electro-Optics. CLEO/Pacific Rim, Glötzl, R., Schneider-Glötzl, J., Eine neue Geotextilmessmatte mit verteilter Sensortechnik im Einsatz. 5. Freiberger GEOTECHNIK-Kolloquium am 04. & 05. Juni 2009.

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