Geotechnical properties in relation to grain-size and mineral composition: case study landslide in the Rječina Valley (Croatia)

Investigated landslide is the largest active mass movement along the Croatian coast, situated on the north-eastern slope in the central part of the Rječina Valley (north-eastern coastal part of Adriatic Sea, Croatia). Slopes in this valley are formed in siliciclastic rocks - flysch, while limestone rock mass is visible on the cliffs around the top of the river valley. The slopes are at the limit of a stable equilibrium state, and mass movement phenomena have been recorded since 19th century. Samples for laboratory testing were taken from the flysch bedrock, weathered zone and slope formations, and were recovered to provide specimens for data on their mineralogical, physical and geotechnical properties. Correlation between mineralogical and geotechnical properties and their influence on sliding processes are presented in this paper. Clay fraction in samples ranges from 17 % to 38 %. Clay activity of the tested samples is from 0.45 to 0.89, and the residual friction angle varies from 13.0° to 17.7°. These results correspond to the presence of kaolinite and illite groups of clay mineral. Mineral composition and decrease in strength of fine-grained soil materials, due to the increase of pore water pressures, contributes to the slope movements.  </span

Conditions and triggers of landslides on flysch slopes in Istria, Croatia

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

Estimation of 99mTc-ciprofloxacin accumulation indexes in bone and joint bacterial infections

Background/Aim. 99mTc-ciprofloxacin is a radiopharmaceutical preparation sintetized to improve diagnostic accuracy of bacterial infections in human tissues. It is mostly applied in diagnosis of bone and joint infections. Many papers have confirmed its sensitivity to infection, but newer papers argued its specificity. The aim of this study was to compare the results of visual analysis of scintigrams to semiquantitative calculations of accumulation indexes with the assumption that calculation of indexes would improve the specificity for bone and joint infections. Methods. We examined 40 patients, 25 with confirmed bone and joint bacterial infections and 15 patients with bone and joint diseases without bacterial infection. Scintigraphy was performed 5 minutes, 1, 4 and 24 hours after intravenous (iv) injection of 99mTc-ciprofloxacin. Scintigrams were analyzed visually and by calculation and comparation of accumulation indexes values. Results. Visual sensitivity was 94%, but specificity only 47%. Index calculation achieved much higher specificity (100% after 1, 4 and 24 hours for cut off value of 1.50). All basic index values (5 min) in the patients with infections increased in 24 hours. In 8 patients without infection occurred a slight increase and in 7 patients decrease of basic index values. Conclusion. Calculation of accumulation index values is needed in the use of 99mTc-ciprofloxacin scintigraphy as it is the only way to improve specificity for bacterial bone infections. Visual interpretation of results is sensitive, but not specific due to accumulation of the drug in a high percent of non infected bone and joint lesions

Integral Approach to Geohazard Management at Flysch-Karst Contact

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

Određivanje jednoosne tlačne čvrstoće vapnenaca

The most used parameter in rock engineering practice is the Uniaxial Compressive Strength (UCS). It is often estimated on the field or trough Index-to-strength conversion factors proposed by various researchers for a specific rock type. The research presented in the paper involved field estimation of Uniaxial Compressive Strength using Schmidt rebound hammer and Point Load laboratory testing on limestone rock samples. The results of the estimated UCS were compared to the Uniaxial Compression Strength laboratory testing results on limestone specimens taken from the same location, in order to compare corresponding UCS of limestone rocks. These results can contribute to better estimation of the local design parameters, when direct determination of the UCS in the laboratory is not possible, rather than adopting the values from around the world case studies.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

Large gravitational collapse structure on a rocky coast (Kvarner, NE Adriatic Sea)

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