{"id":506,"date":"2013-09-26T14:28:34","date_gmt":"2013-09-26T12:28:34","guid":{"rendered":"http:\/\/wp.unil.ch\/risk\/?p=506"},"modified":"2013-09-26T17:00:57","modified_gmt":"2013-09-26T15:00:57","slug":"line-rouyet-monitoring-and-characterization-of-rock-slope-instabilities-in-norway-using-gb-insar","status":"publish","type":"post","link":"https:\/\/wp.unil.ch\/risk\/line-rouyet-monitoring-and-characterization-of-rock-slope-instabilities-in-norway-using-gb-insar\/","title":{"rendered":"Line Rouyet: Monitoring and characterization of rock slope instabilities in Norway using GB-InSAR."},"content":{"rendered":"

Line Rouyet<\/em>
\n Co-supervisors:\u00a0Prof. Michel Jayboyedoff,\u00a0Dr. Marc-Henri Derron<\/em>
\n Experts:\u00a0Dr. Lene Kristensen,\u00a0MSc. Cl\u00e9ment Michoud<\/em><\/p>\n

The master thesis named \u201cMonitoring and characterization of rock slope instabilities in Norway using GBInSAR\u00a0(Ground-Based Interferometric Synthetic Aperture Radar)\u201d aims (1) to improve the knowledge about\u00a0the advantages and limitations of a GB-InSAR system (\u00a9LiSALab-Ellegi) for the monitoring of instable rock slopes;\u00a0(2) to contribute to the understanding of two large rock instabilities, especially in terms of behavior and\u00a0geometry.<\/p>\n

The work includes (1) the processing and interpretation of GB-InSAR data for two main case studies of major\u00a0rockslides in Norway, as well as for a third test case involving rockfalls; (2) the comparison of GB-InSAR results\u00a0with other available monitoring data (GPS, crack\/extenso-meters, lasers-reflectors, tiltmeters and\u00a0meteorological data), as well as the integration of structural analyzes (using Terrestrial and Aerial Laser\u00a0Scanning data); (3) the global synthesis of the results and the comparison with the conclusions of precedent\u00a0studies in order to reach the two objectives previously highlighted.<\/p>\n

The first case study is the site of Indre Nordnes (Troms County, northern Norway) which is affected by a large\u00a0rockslide above Lyngenfjord generating a significant risk of tsunami. Its volume is estimated to be around 10-15 millions of m3. Two intermittent GB-InSAR campaigns were performed in summer 2011 and their results\u00a0are compared and integrated with the large monitoring database available since the end of 2007 for the\u00a0crackmeters, the beginning of 2010 for the GPS, since mid-2011 for the extensometers and tiltmeters.<\/p>\n

Generally, the results show that the rockslide is slow (6-7 mm\/year) with accelerations during the thaw\u00a0periods (May-June). The year 2011 is an exception with an important acceleration in June (up to 14 mm in\u00a0only 2 weeks according to GB-InSAR data). These values can be related to the exceptionally high temperatures\u00a0in 2011. Moreover, GB-InSAR data allow giving new information about the extent and the repartition of\u00a0movements of instable area. Finally, thanks to the structural analyzes two discontinuities sets are supposed to\u00a0be mainly involved in the sliding. It suggests a stair-steps geometry of the sliding surface.<\/p>\n

The second case study is the large B\u00f8ra\/Mannen area (M\u00f8re of Romsdal County, western Norway), which\u00a0includes the rockslide of Mannen (15-25 millions of m3) as well as the B\u00f8ra plateau located on the southwest\u00a0side of Mannen. Because B\u00f8ra area showed some signs of activity, intermittent GB-InSAR campaigns were\u00a0performed in summer 2011 and 2012. Their results are compared and integrated with the large monitoring\u00a0database including GPS campaigns between 2003 and 2010 on B\u00f8ra plateau, various in situ data in Mannen\u00a0since the end of 2010 and permanent GB-InSAR data since the beginning of 2010. This second GB-InSAR\u00a0system is located about 2 km more northeastern than the one of B\u00f8ra and aims to monitor the Mannen\u00a0rockslide. It has the advantage to be in overlap with the B\u00f8ra GB-InSAR view and to provide continuous\u00a0images between 2010 and 2013.<\/p>\n

Overall, a good concordance is found between the results of the two GB-InSAR systems. In the overlap part, a\u00a0coherent and progressive pattern is highlighted in the middle of the slope. During the August 2011 campaign,\u00a0positive displacements (increasing of distance between the GB-InSAR and the target) are recorded and exceed\u00a0+8 mm in two weeks. With data integration at long-term, it is shown that this part is affected by large\u00a0variations and inversions of movements, which can be related to seasons. These effects could be linked to\u00a0water circulation in the rock slope, but the explanations are not yet clear.<\/p>\n

For the Mannen rockslide, it is possible to distinguish two parts with different behaviors in terms of velocities\u00a0and orientations of movement. It highlights that the most upper and southwestern part is the most active (>20 mm\/year). Otherwise, thanks to the structural analyzes three discontinuities sets are supposed to be\u00a0mainly involved in the sliding.<\/p>\n

For B\u00f8ra area, GB-InSAR recorded higher displacements (25-90 mm\/year) than those estimated from GPS\u00a0<\/span>campaigns (mainly no significant displacements with a maximum velocity of 14.6 mm\/year). In any case, it\u00a0appears that the area is generally moving slowly and quite regularly.<\/p>\n

Finally, high variations at short-term and long-term are visible on the interferograms which cast doubts on the\u00a0data quality. A case of loss of coherence probably due to snowfalls in October is also detected. This underlines\u00a0the high potential of researches to improve the removing of atmospheric effects and the capability of the GBInSAR\u00a0in case of external perturbations.<\/p>\n

The third test case of Sunndals\u00f8ra-Oppd\u00f8lsstranda (site C along the road 70 between the two localities, M\u00f8re\u00a0of Romsdal County, western Norway) is studied in order to improve the knowledge of the potential of GBInSAR\u00a0for the detection and analysis of rockfalls. Between April 2010 and October 2011, five GB-InSAR\u00a0campaigns were performed and give information about a rockfall event of 15-20 m3 which occurred the 8th of\u00a0June 2011. The results confirm the capability of the system to record precursor movements to failure, but\u00a0highlighted also various operational limitations.<\/p>\n

Overall, the joined analysis of the three different case studies allows having a good overview of the potential\u00a0and limitations of the GB-InSAR system. Moreover, because of their respective advantages and limitations (in\u00a0terms of kind of recorded information, temporal sampling, accuracy, spatial coverage, etc.), it appears that\u00a0the GB-InSAR and the in situ monitoring devices have a good complementarity. The integration of their results\u00a0therefore allows giving new inputs about the behavior and geometry of the Indre Nordnes and B\u00f8ra\/Mannen\u00a0sites.<\/p>\n","protected":false},"excerpt":{"rendered":"

Line Rouyet Co-supervisors:\u00a0Prof. Michel Jayboyedoff,\u00a0Dr. Marc-Henri Derron Experts:\u00a0Dr. Lene Kristensen,\u00a0MSc. Cl\u00e9ment Michoud The master thesis named \u201cMonitoring and characterization of rock slope instabilities in Norway using GBInSAR\u00a0(Ground-Based Interferometric Synthetic Aperture … <\/p>\n","protected":false},"author":1341,"featured_media":888,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[73758],"tags":[58407],"class_list":{"0":"post-506","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-masters_completed","8":"tag-58407"},"_links":{"self":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/posts\/506","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/users\/1341"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/comments?post=506"}],"version-history":[{"count":0,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/posts\/506\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/media\/888"}],"wp:attachment":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/media?parent=506"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/categories?post=506"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/tags?post=506"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}