This study presents a vulnerability assessment methodology that was developed to analyze the Croatian Eastern Adriatic Coast (CEAC), which has extremely complex geomorphology. Local coastal retreat, ...slope instability phenomena, and the influence of marine erosion play a significant role in coastal geohazards in the southeastern coastal area of the Krk Island (Kvarner area, northeastern channel part of the Adriatic Sea). Recent studies emphasize the need to develop an adequate methodology to monitor its evolution and define adequate risk management strategies. The vulnerability analysis was performed on the basis of the available data, taking into account local geological and oceanographic conditions. The coastal vulnerability analysis of the CEAC presents an adaptation of the existing methodology, emphasizing the significance of the geological factor, and providing novel elements of the parameter analysis (i.e., coastal slope, beach width, and significant wave height). This methodology was adapted and improved for the local rocky coast, but can be used on other complex rocky coasts worldwide. The calculated Coastal Vulnerability Index (CVI) around the Stara Baška settlement should be considered to have priority over the vulnerable areas in further monitoring and investigations.
Odabir između 2D i 3D numeričkog modeliranja ovisi prvenstveno o vrstiproblema koji se analizira, potrebama projekta, rokovima, dostupnim resursima teopravdanosti dodatnih ulaganja u složenije ...modele. U radu su prikazani rezultati2D i 3D numeričkih modela izvedbe dionice tunelske cijevi, kako bi se analiziraleosnovne razlike u dobivenim rezultatima i istaknule prednosti upotrebe 3D modela.Na temelju projektne dokumentacije, modeliran je poprečni presjek najnepovoljnijegprofila s najvećim nadslojem materijala. Analize su provedene u računalnimprogramima RS2 i RS3 tvrtke Rocscience. Rezultati su pokazali da je glavna prednost3D modela mogućnost praćenja povećanja radijalnih pomaka s napredovanjemiskopa te realnijeg uvida u efikasnost ugrađene podgrade.
The choice between 2D and 3D numerical modeling depends primarily on the subjectanalysis, project requirements, deadlines, available resources, as well as justificationfor additional investment in complex models. The results of 2D and 3D tunnelnumerical models are presented in order to analyze the fundamental differences andto highlight the 3D model advantages. The models were created on the cross sectionwith the largest overlay, all according to the design documentation. The analyseswere performed using the RS2 and RS3 Rocscience programs. The obtained resultshave shown that the main advantage of the 3D model is the possibility to monitorthe increase of radial displacements with excavation progress, and to provide a morerealistic insight into the efficiency of the installed support elements.
The paper gives a review of conditions and triggers in which landslides occur on flysch slopes in central and northern Istria. The north-eastern
part of the Istrian Peninsula, the so-called Gray ...Istria, consists of Paleogene flysch rock mass. Landslides in this area are usually triggered by heavy rainfall together with human activity which changes slope geometry and assists in retaining surface water in the sliding zone. Briefly, hydrogeological conditions in combination with ground water levels and pore water pressures increase, lead to numerous instability phenomena, during the long and continuous rainfall periods. Instabilities usually include small rotational and translational landslides, and it is seldom that debris flows and rock falls occur. Landslides are evenly evidenced in the first part of winter and the early spring time which corresponds to the second rainfall peak. The analyses performed based on landslide documentation and rainfall historical data, show rainfall trends associated with landslide occurrence. Depending on meteorological, hydrological and geological conditions, cumulative rainfall which triggered landslide activation varies inside a three-month period. The results presented show rainfall trends which serve as characteristic landslide triggers on flysch slopes
in north-eastern part of Istria.
Na kontaktu flišne stijenske mase i vapnenaca, unutar područja središnje i sjeverne Istre te zaleđa Kvarnera evidentirani su brojni geohazardni događaji, a najznačajniji od njih su pojave ...nestabilnosti. U radu je dan pregled značajki područja istraživanja ključnih za pojavu ovog tipa geohazarda. Napravljen je pregled recentnih nestabilnosti i njihovih posljedica kako bi se pokazala motivacija za istraživanje, a i potreba za razvojem cjelovitog sustava upravljanja postojećim problemom. Kroz istraživanje je razvijen koncept integralnog pristupa upravljanju geohazardima, a predloženi okvir mogao bi se kroz različite mehanizme integrirati u sadašnji način funkcioniranja i smanjenje posljedica za postojeće elemente rizika. Predloženi pristup zahtijeva opsežne i mnogobrojne analize, ali određeni elementi mogli bi se implementirati bez većih zahtjeva.
At the flysh rock mass and karst contact, in the area of central and northern Istria, as well as Kvarner hinterland, numerous geohazard events have been recorded, the most significant of which the instabilities. This paper gives an overview of the research area key settings, important for this type of geohazards. A review of recent instabilities and their consequences is presented to show the research motivation, as well as the need to develop an integrated management system for managing the existing problem. The concept of an integrated approach for geohazard management has been developed through this research, and the proposed framework could be implemented into the present mode of functioning to reduce the consequences for the existing elements at risk. The proposed approach requires extensive and numerous analysis, but certain elements of this framework could be implemented without major requirements.
Background
Large landslides triggered by rainfall and floods were registered on both sides of the Rječina River Valley, near City of Rijeka, in Croatia, where numerous instability phenomena in the ...past 250 years have been recorded, and yet only some locations have been investigated. The paper presents investigation of the dormant landslide located on the south-western slope, recorded in numerous historical descriptions from 1870. Due to intense and long-term rainfall, the landslide was reactivated in 1885, destroying and damaging houses in the eastern part of the Grohovo Village.
Results
2D stability back analyses have been performed based on landslide features, in order to approximate the position of the sliding surface and landslide dimensions. Because of the very steep landslide topography and the slope covered by unstable debris material, a Remotely Piloted Aircraft System (RPAS) was used to provide the data about the present slope topography. The landslide 3D point cloud was derived using Structure-from-Motion (SfM) photogrammetry. In order to verify the cloud of georeferenced sliding points obtained from images, it was compared with the existing models acquired from terrestrial photogrammetry and laser scanning, showing good accordance and small changes through the years. Based on the classification and Uniaxial Compressive Strength test results, rock mass strength was defined using generalised Hoek-Brown’s failure criteria.
Conclusions
Stability analysis results of the present slope conditions show that the slope is marginally stable for dry conditions, and that the critical seismic coefficient of about 0.14 would generate inertial forces corresponding to the factor of safety equal to 1. Analyses were performed with the purpose to predict the possible reactivation of a dormant landslide, and the presented results could be used in the establishment of an early warning system.
The coastal area around the settlement of Stara Baška (Krk Island, NE channel zone of Adriatic Sea) is in a delicate geodynamic balance. The main causes are the geological structure, hydrological and ...hydrogeological conditions and the direct exposure of the coast to the waves and storm surges. In this paper, the effects of the expected sea level rise on the geological vulnerability of the coast are investigated. Detailed field research was conducted. The complex coastal morphology was surveyed using an Uncrewed Aerial Vehicle (UAV), and the UAV-derived data was used as a 3D point cloud and orthophoto for analysis. In the investigated coastal zone, more resistant Quaternary talus breccias predominate over more susceptible flysch rock mass. One major and two smaller landslides are in a creeping condition and pose a hazard to the surrounding homes. During storm surges, the pocket beaches are completely inundated due to the narrow beach width and waves reach the toe of the slopes. According to the expected sea level rise, coastal processes could become more intense and threaten the current coastal equilibrium. The vulnerability of a large part of the Stara Baška settlement will increase significantly. The conducted research showed the advantages of UAV-derived data for the study of complex rocky coasts and emphasized the need for repeatable UAV surveys.
The studied rock collapse structure is located on the Liburnian coast (Rijeka Bay, channel zone of the NE Adriatic). The relief of the southern part of this coast, with a length of 6.5 km, is a large ...escarpment with very steep to vertical slopes reaching heights of 100 m above sea level, as a result of tectonic movements along the Kvarner fault zone. These events probably led to a sudden relaxation of the highly fractured rock mass. The progressive expansion occurred at locations where previously favourably oriented faults and fissures had formed a polygonal rock collapse resembling a rock-slide which is the focus of this study. Another aim of this study is to reconstruct and explain the complex morphological evolution of the studied landslide, from the pre-failure deformations, through the failure itself, to post-failure displacements, as well as possible future instabilities. Recent techniques to survey the instability, location and to analyse the evolution of the rupture surface and its dimensions were combined (Unmanned Aerial Vehicle, Side Scan Sonar and Remotely Operated Vehicles). The estimated total volume of displaced rock mass is 950,000 m3. The lower part of the instability phenomenon was submerged during the Holocene sea level rise. Since then, a large part of the displaced rock mass has been in a stable position, with sporadic rock falls. However, given unfavourable orientation and discontinuity characteristics, as well as unfavourable environmental influences, possible instabilities might also be expected in the future.
This research focuses on the analysis of soil-water interaction at the carbonate-flysch contact on the Istrian peninsula in Croatia. As a result of the interaction of surface and groundwater and the ...position of flysch and carbonate rocks in the geotechnical profile, two problems occur in the study area: numerous instabilities and the occasionally high turbidity of drinking water. As an example, the St. Ivan spring was considered. The paper presents a complex mechanism of groundwater circulation in geological structures at carbonate-flysch contacts, differences in runoff through karst aquifers and flysch rocks during heavy rainfall under current and predicted (climate change) conditions, and the mentioned geohazards as a result of extreme precipitation. The analyses carried out showed the decisive influence of the existing geological structure on the dynamics of infiltration and precipitation runoff, as well as the risks of pronounced spring water turbidity and instability events. The main drivers of these geohazards are continuous long-term precipitation for landslides and intense daily precipitation for turbidity. Possible consequences of climate change are the increase in precipitation intensity, amount and higher variation, which subsequently brings risks such as the increase in maximum runoff, i.e., the expected more frequent occurrence of high turbidity and the more frequent occurrence of higher cumulative precipitation triggering instabilities in the area.
Određivanje jednoosne tlačne čvrstoće vapnenaca Vračević, Doris; Dugonjić Jovančević, Sanja; Peranić, Josip ...
Zbornik radova (Građevinski fakultet Sveučilišta u Rijeci),
12/2019, Volume:
XXII, Issue:
1
Paper, Journal Article
Peer reviewed
Open access
Najčešće korišten parametar u stijenskom inženjerstvu je jednoosna tlačna čvrstoća (UCS). Često se procjenjuje na terenu ili pomoću korelacija s indeksom čvrstoće u točki predloženih od strane ...različitih istraživača za određen tip stijene. Istraživanja prikazana u radu uključuju terenska ispitivanja jednoosne tlačne čvrstoće Schmidtovim čekićem i laboratorijskog ispitivanja indeksa čvrstoće opterećenjem u točki na uzorcima vapnenačkih stijena. Rezultati procijenjenih UCSa uspoređeni su s laboratorijskim ispitivanjem jednoosne tlačne čvrstoće na uzorcima vapnenaca, uzetih sa iste lokacije, kako bi se usporedili rezultati za odgovarajući UCS vapnenačkih stijena. Ovi rezultati mogu pridonijeti boljoj procjeni lokalnih projektnih parametara kada određivanje točne vrijednosti UCS u laboratoriju nije moguće, no ne i usvajanju vrijednosti dobivenih analizom slučajeva iz ostatka svijeta.
The constant threat from landslides in the northeastern part of Istria, Croatia, calls for the need to apply accurate and reliable methods in landslide hazard assessment in order to prevent landslide ...damage and to set an early warning system if necessary. Furthermore, landslide susceptibility and hazard assessment enable optimal area management and regional urban planning. The study area is in the northeastern and central part of the Istrian Peninsula, well known as an area of frequent, small and shallow slope instability phenomena. Landslide susceptibility assessment in the area around the city of Buzet was performed using a deterministic landslide susceptibility model in the LS-RAPID software. LS-RAPID was developed to analyze stability at one single location, but the performed analysis has shown that LS-RAPID can be used as a powerful tool in landslide susceptibility and hazard assessment on regional scale. The objective of this paper is to establish the influence of the runout potential on the enlargement of the landslide-susceptible zones, due to expansion of the failure area around the initial failure zone. Performed analysis of rainfall return periods shows the frequency of landslide occurrence and provides the possible correlation with the time component of landslide hazard in the area.
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