Landslide types in the Slani Potok gully, Croatia

The Slani Potok gully (0.48 km2) is situated in the central part of the Vinodol Valley (64.57 km2) in Croatia, and it was formed in the Eocene flysch deposits. So far, the area of Slani Potok has been mainly referred in the scientific literature as being subjected to unusually intense soil erosion processes (i.e., ‘’excessive erosion’’), associated with landslides. However, the landslides were never investigated in detail, given the available research methods only involved field investigations. Therefore, the landslide types according to the most commonly used landslide classifications have remained undetermined. In this paper, landslide types in the Slani Potok gully are presented, identified and mapped based on the visual interpretation of seven different LiDAR topographic derivatives computed from the 1 x 1 m DTM available from March 2012. The geomorphological historical landslide inventory of the Slani Potok gully was created, consisting of 181 landslide phenomena. Landslides cover 69 % of the area (0.33 km2) of the Slani Potok gully. The size of the smallest landslide is 65 m2, and of the largest is 10,563 m2. Landslides are very small to moderate-small, shallow to moderate-shallow, and mainly successive in distribution. Most of the landslides initiate along the margins of the gully channel walls, and extend to the gully channel bottom. Such a large number of identified landslides, as well as their specific spatial arrangement within the gully, indicates that sliding processes predominantly affect the morphologic development of the Slani Potok gully, and that the soil erosion is the secondary process in the study area.</p

Construction of Zagrad foundation pit in Rijeka

Prikazana je gradnja građevne jame kompleksa "Zagrad" u Rijeci. Iskop građevne jame u stijenskoj masi proveden je osiguranjem zasjeka štapnim sidrima i odgovarajućim podgradnim sustavima. Zbog složenih geotehničkih uvjeta na lokaciji neposredno okruženoj postojećim građevinama, bilo je nužno pomno kontrolirati izvođenje radova. Uspostavljenim sustavom promatranja i mjerenja podgradnih sustava osigurano je provođenje naknadnih analiza i potprojektiranja tijekom izvedbe radova.The foundation pit construction for the Zagrad complex in Rijeka is presented. The excavation of the foundation pit in the rock mass was conducted by protecting the side hill cut with rock bolts and appropriate support systems. The realization of this work had to be strictly supervised due to complex geotechnical conditions at this construction site closely surrounded by existing structures. Early establishment of an appropriate system for the support system monitoring and checking enabled subsequent analyses and design during realization of the work

Excavation of Open Pit “Zagrad” in Rijeka, Croatia, A Case History

On the location Zagrad in Rijeka, Croatia, an open pit has been designed and constructed for the purpose of building the garageaccommodation- business complex. The location of the open pit is situated in the central area of the town Rijeka, and closely surrounded by the existing accommodation buildings, a traffic line and a railway. The open pit was designed and constructed four levels below the terrain surface, adjacent to the existing buildings and a traffic line. To secure the open pit walls during excavation, a support system with the selfdrilling rock bolts for the reinforcing of the rock mass and reinforced concrete grid structure on the excavated surface was designed. This paper presents the construction method for the open pit, with the application of active design concept during works execution. It also presents the set-up system for measuring, observing and monitoring of the support system behavior. This enabled, on the basis of the measurement results and performed back analysis, an active designing of the suitable support system during works execution, for the in situ conditions of the rock mass in excavation. Performed back analysis showed need for the additional correction in the correlation between deformation characteristics of the rock mass and rock mass classification

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

Soil-Water Characteristic Curve of Residual Soil from a Flysch Rock Mass

Depending on the nature of the material and suction range, laboratory measurements of the soil-water characteristic curve (SWCC) can be time-consuming and expensive, especially for residual soils, in which a wide range of particle sizes and soil structures typically results in SWCCs that cover a wide range of suction. Investigations of the SWCCs of residual soil from flysch rock masses are rare, and so far, no results were presented in the literature which were obtained by performing measurements on undisturbed specimens. In this paper, a detailed examination of water retention characteristics is performed for a specific type of residual soil (CL) formed by the weathering of a flysch rock mass. Measurements performed by using different techniques and devices on intact specimens were successfully combined to obtain the SWCC during both drying and wetting processes, under different stress conditions, and from saturated to air-dried conditions. Used procedures are suitable for the determination of SWCCs of soils that undergo volume changes during the drying or the wetting process, since instantaneous volumetric water content can be determined. Results presented in this paper can be used to assess the influence of desaturation of the residual soil covering flysch slopes during dry summer periods by providing key-in material properties required to analyze the transient rainfall infiltration process

Sedimentacijski procesi u akvatorijima luka smještenih na ušćima rijeka

U radu je tretirana problematika gradnje luka i lučkih sadržaja kao i osiguranja potrebnih prostora (dubina) u akvatorijima luka smještenim na lokacijama gdje vodotoci prolaze kroz luku ili njenu neposrednu blizinu. Najizraženiji negativni utjecaji vodotokova na luke su sedimentacijski procesi koji uzrokuju smanjenje dubine u lučkom akvatoriju što utječe na plovnost te otežavaju temeljenje i gradnju lučkih objekata. U radu je, na primjeru triju sjevernojadranskih hrvatskih luka: Rijeke, Raše i Plomina, prikazan međuodnos vodnog okruženja (voda iz rijeka: Rječine, Raše i Boljunčice) i spomenutih luka u kontekstu prisutnih sedimentacijskih procesa. Prikazom i analizom navedenih primjera u radu se ističe važnost sagledavanja problematike utjecaja donosa nanosa na lučki akvatorij ukoliko je on lociran u području ušća vodotoka. Ukazuje se i na problematiku proširenja postojećih lučkih površina na lokacijama recentnih naslaga u području ušća pojedinih vodotokova te daju preporuke za monitoring, planiranje i provođenje potrebnih aktivnosti vezanih uz navedenu problematiku, a koje treba uzeti u obzir pri kompleksnom planiranju takvih luka

Sedimentacijski procesi u akvatorijima luka smještenih na ušćima rijeka

U radu je tretirana problematika gradnje luka i lučkih sadržaja kao i osiguranja potrebnih prostora (dubina) u akvatorijima luka smještenim na lokacijama gdje vodotoci prolaze kroz luku ili njenu neposrednu blizinu. Najizraženiji negativni utjecaji vodotokova na luke su sedimentacijski procesi koji uzrokuju smanjenje dubine u lučkom akvatoriju što utječe na plovnost te otežavaju temeljenje i gradnju lučkih objekata. U radu je, na primjeru triju sjevernojadranskih hrvatskih luka: Rijeke, Raše i Plomina, prikazan međuodnos vodnog okruženja (voda iz rijeka: Rječine, Raše i Boljunčice) i spomenutih luka u kontekstu prisutnih sedimentacijskih procesa. Prikazom i analizom navedenih primjera u radu se ističe važnost sagledavanja problematike utjecaja donosa nanosa na lučki akvatorij ukoliko je on lociran u području ušća vodotoka. Ukazuje se i na problematiku proširenja postojećih lučkih površina na lokacijama recentnih naslaga u području ušća pojedinih vodotokova te daju preporuke za monitoring, planiranje i provođenje potrebnih aktivnosti vezanih uz navedenu problematiku, a koje treba uzeti u obzir pri kompleksnom planiranju takvih luka

Quality control for rock anchors

U radu se opisuju laboratorijski pokusi čupanja štapnih sidara sa 48 raznih injekcijskih smjesa, uz mjerenje akustične emisije. Pokazuje se da se novim mjerenjem i predloženim analitičkim postupkom može odrediti sila koja je blizu sile sloma, tako da štapno sidro i dalje ostaje upotrebljivo za ojačanje stijenske mase. Mjerenje akustične emisije može se preporučiti za in situ kontrolu kvalitete štapnih sidara, uz novi doprinos kvaliteti aktivnoga geotehničkog projektiranja.Laboratory rock-anchor pullout test with 48 different grouts, and with the acoustic emission measurement, is described in the paper. It is demonstrated that the force close to the failure point can be determined by the new measurement and the proposed analytical procedure, so that the rock anchor will remain usable for rock mass strengthening purposes. Acoustic emission measurements can be recommended for the in situ rock anchor quality control, as a novel qualitative improvement of active geotechnical design practices

A complex landslide in the Rječina Valley: results of monitoring 1998-2010

Results of landslide monitoring undertaken between 1998–2010 on the north-eastern slope of the central part of Rječina Valley in front of Grohovo village (north-eastern coastal part of Adriatic Sea, Croatia) are presented. This is the largest regional active landslide. The slopes around the Rječina riverbed are formed in siliciclastic sedimentary rocks with flysch characteristics. The bedrock is mostly covered with unstable slope formations. A limestone rock mass is visible on the cliffs around the top of the river valley. The landslide is complex and retrogressive, with 13 sliding bodies. It occurred in December 1996 by displacement of an initial landslide body where movement had been registered in the 19th century. The limestone mega-blocks and separated rocky towers on the top of the slope have also moved, which is an atypical phenomenon of the flysch slopes in the area of Rijeka. After initial sliding ceased, and major movements subsided, monitoring of benchmark movements from 1998 until 2010 determined further maximum displacements on the upper part of the slope, and minimum movement in the lower part. The area of the Rječina Valley from the Valići Dam to the Pašac Bridge was selected as a pilot area in the framework of the Croatian-Japanese bilateral joint research project. Monitoring results provided the basis of establishing an early warning system for possible landslide occurrence and estimating the degree of landslide risk.</p

A complex landslide in the Rječina Valley: results of monitoring 1998-2010

Results of landslide monitoring undertaken between 1998–2010 on the north-eastern slope of the central part of Rječina Valley in front of Grohovo village (north-eastern coastal part of Adriatic Sea, Croatia) are presented. This is the largest regional active landslide. The slopes around the Rječina riverbed are formed in siliciclastic sedimentary rocks with flysch characteristics. The bedrock is mostly covered with unstable slope formations. A limestone rock mass is visible on the cliffs around the top of the river valley. The landslide is complex and retrogressive, with 13 sliding bodies. It occurred in December 1996 by displacement of an initial landslide body where movement had been registered in the 19th century. The limestone mega-blocks and separated rocky towers on the top of the slope have also moved, which is an atypical phenomenon of the flysch slopes in the area of Rijeka. After initial sliding ceased, and major movements subsided, monitoring of benchmark movements from 1998 until 2010 determined further maximum displacements on the upper part of the slope, and minimum movement in the lower part. The area of the Rječina Valley from the Valići Dam to the Pašac Bridge was selected as a pilot area in the framework of the Croatian-Japanese bilateral joint research project. Monitoring results provided the basis of establishing an early warning system for possible landslide occurrence and estimating the degree of landslide risk.</p