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Overview of Activities at Duće and Omiš Pilot Sites (CROSBI ID 606842)

Prilog sa skupa u zborniku | sažetak izlaganja sa skupa | međunarodna recenzija

Vlastelica, Goran ; Miščević, Predrag ; Fukuoka, Hiroshi ; Furuya, Gen ; Kordić, Branko Overview of Activities at Duće and Omiš Pilot Sites // Book of abstracts/4th workshop of the Japanese -Croatian project on Risk Identification and Land-Use Planning for Disaster Mitigation of Landslides and Floods in Croatia / Vlastelica, Goran ; Andrić, Ivo ; Salvezani, Daša (ur.). Split: Fakultet građevinarstva, arhitekture i geodezije Sveučilišta u Splitu, 2013. str. 23-24

Podaci o odgovornosti

Vlastelica, Goran ; Miščević, Predrag ; Fukuoka, Hiroshi ; Furuya, Gen ; Kordić, Branko

engleski

Overview of Activities at Duće and Omiš Pilot Sites

Dalmatia region in Croatia has dozens of registered active rockfall zones. Virtually whole area along main coastal road from city of Split to town of Omiš is a potential danger zone for inhabitants and community infrastructure. Almost every year, in periods after heavy rain and/or considerable low air temperature, many sudden rockfalls in this area are recorded. Stabilizing and managing the entire area without localising potential threats would require considerable funding, which private owners and local communities cannot afford, so more suitable method for forecasting and detecting potential rockfalls is needed. For this study a specific location named Luka in Duće area and a part of old town centre of Omiš are selected as pilot sites. Slope over Luka location is made of Eocene flysch, which is covered by a relatively thin and hard layer of breccia. Main component of flysch is marl, a rock material which is prone to weathering when submitted to atmospheric agents. As a result of weathering, surface formed of weaker marl is eroded with rain and the layer of harder breccia remains like “cantilever”. With time cracks start to form on the top of the cliff and parts of breccia start to fall off in large blocks. The cliffs over the town of Omiš are in the karstificated geological formation made mainly of limestone. Stabilizing the entire slopes in town area without localising potential threats would require considerable funding, which private owners and local community cannot afford, so a more cost-effective method to localise priorities should be found. One of them could be the proposed method that uses LiDAR technology. LiDAR (Light Detection and Ranging) is an optical remote sensing technology used in Terrestrial Laser Scanners. TLS is often used to perform periodical monitoring in large landslide and rockfall areas. In this study Optech ILRIS-3D with enhanced range was used at both pilot sites. First scan with ILRIS-3D was made in September 2011, however at that time a serial malfunction was noticed. After repairment in Canada, scanning started again in April 2012 and it was repeated five times in a 3-6 month intervals to this day. The first scan for both pilot sites was georeferenced and it will be used as a reference scan for comparison of all future periodical monitoring at this location. Comparison of the two scans was made by using IM Survey module of Polyworks software. As an example of comparison a large block removal was used to test the methodology of comparing sequential datasets (Fig. 1). On this figure the differences between two scans starting from 10 cm up to 4 m, from a 300 meters distant standpoint of the instrument, are clearly observed. With these results the morphology of the slope, block size and shape can be obtained very precisely and which can then be used in rockfall analysis. To detect smaller displacements of blocks (in the scale of millimetre to couple of centimetres) prior to its detachment, data should be acquired from standpoints closer to the cliff. However, this shortening of the range to the target raises the question of practical usage of this method for this and especially for even larger sites. Except for detecting unstable blocks at steep slopes, this temporal model of surveying can certainly be applied for observing erosion process in soft rock (similar to marl in this area) or as an additional tool for creating rockfall inventory for this area. That would be a long-term project (minimum 10 – 20 years with yearly periodical scanning), however the results of which could be used for the purpose of detailed hazard mapping of the wider area than this pilot sites, and for sure help us to better understand the process of rock fall in this region. In combination with previous methodologies, results obtained by a spectrometer could be used for better understanding some of triggering factors for rockfalls in these materials. In this project a non-destructive quantitative measurements of material reflectance were performed using portable field spectrometer TerraSpec 4 Hi-Res (ASD Inc., USA). All the measurements were made in the Geotechnical laboratory of the Faculty of Civil Engineering, Architecture and Geodesy. The measured wavelength region TerraSpec 4 ranges from 380 – 2500 nm which mean that covers a visible (400-700 nm) and near-infrared (700-2500 nm) regions. The first laboratory tests with spectrometer suggest the relative quantity of the carbonate mineral group can be detected (in this area it consists mostly of calcite) and also there is a high possibility that they could be correlated with other testing procedures (such as calcimetry of XRD analysis). Therefore, spectrometer as portable device, unlike previously mentioned, can find it application in very fast in-situ measurements of those properties.

rockfall; TLS; LiDAR; VIS-NIR spectroscopy

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Podaci o prilogu

23-24.

2013.

objavljeno

Podaci o matičnoj publikaciji

Book of abstracts/4th workshop of the Japanese -Croatian project on Risk Identification and Land-Use Planning for Disaster Mitigation of Landslides and Floods in Croatia

Vlastelica, Goran ; Andrić, Ivo ; Salvezani, Daša

Split: Fakultet građevinarstva, arhitekture i geodezije Sveučilišta u Splitu

978-953-6116-46-1

Podaci o skupu

4th Project Workshop of the Japanese-Croatian Project on "Risk Identification and Land-Use Planning for Disaster Mitigation of Landslides and Floods in Croatia"

predavanje

12.12.2013-14.12.2013

Split, Hrvatska

Povezanost rada

Geologija, Građevinarstvo