Timotej Verbovšek

Influences of Aquifer Properties on Flow Dimensions in Dolomites

The paper focuses on analyses and correlations of flow dimensions in different dolomite aquifers in Slovenia. Flow dimensions are obtained through the reinterpretation of 72 pumping tests with the generalized radial flow model, based on the fractional flow dimension. The average value of flow dimensions is 2.16 for all dolomites. A study of flow dimensions in individual aquifers categorized according to their lithological properties shows that higher dimensions occur in massive late-diagenetic Cordevolian and Anisian dolomites compared with bedded Main, Baca, and especially Lower Triassic dolomites, which contain a greater proportion of noncarbonate minerals. Partially penetrating wells have higher flow dimensions than fully penetrating wells. Flow dimensions are poorly correlated with hydraulic conductivities of fractures. When comparing the quantities of major dissolved minerals, obtained by hydrogeochemical inverse modeling, with the values of flow dimensions, the Cordevolian and Anisian dolomites are found to exhibit the highest values of both dissolved dolomite and flow dimensions, indicating that greater dissolution occurs at higher flow dimensions. For other aquifers, data points are more scattered and the correlation is mostly poor. When compared with three-dimensional fractal dimensions of fracture networks, there is no correlation with flow dimensions. However, almost all the values of flow dimensions are lower than the corresponding fractal dimensions in dolomites (average D= 2.77), possibly indicating the channeling of flow within the available space of the fracture networks, consequently reducing the flow dimensions.

Monitoring of the Stogovce Landslide Slope Movements with GEASENSE GNSS Probes, SW Slovenia

Open image in new window Landslide Stogovce had been triggered by an extreme precipitation event in September 2010, and destroyed a local road. Measurements in inclinometers along the newly constructed road have indicated movements in 2011 and 2016. GEASENSE GNSS probes, which were installed on the landslide body below the new road, have also measured movements in range of several cm/month in the 2012–mid 2015 period, with cumulative movement of 45 cm in this period. Depth to the slip surface was from 13 to 25 m, and groundwater occurs in most of the boreholes, approximately half meter above the slip surface. The displaced material has been also detected by the calculation of surface difference in GIS, from the 2010 and 2014 lidar DEMs. The displaced material is composed mostly of debris of fractured Upper Triassic limestone and dolomite and weathered flysch, and due to its measured movements, is still capable of being transformed into a debris flow.

Mass Movement Processes of Quaternary Deposits in the Vipava Valley, SW Slovenia

Slope sediments of the Vipava Valley represent a complex sedimentary system deposited by very different mechanisms of transport and sedimentary processes that are controlled by a specific lithological and tectonic structure as well as climate conditions of the valley. Varying intensities and dynamics of mass movement processes in this area during the recent geological history (late Pleistocene and early Holocene) influenced the spatial distribution of slope sediments.

Using the Intensity Values from Terrestrial Laser Scanner (TLS) for Determining Lithology of Flysch Rock Mass in Southwest Slovenia

Heterogeneous rock mass, such as flysch is represented by individual lithological units with different geomechanical parameters. The heterogeneity of the rock mass affects its geotechnical behaviour, which causes difficulties in slope stability, as well as in underground construction. Development of modern ground-based remote sensing techniques, enables measurement and positioning of distant objects. Terrestrial Laser Scanner (TLS) has been in the past years successfully integrated in acquisition of geological features. In case of pulsed TLS, the scanner emits short pulsed beam of light and measures the time-of-flight from reflected object surface in order to compute the distance from objects. The resulted point cloud is georeferenced in the post-processing phase. Terrestrial Laser Scanner also records the intensity of reflectance, which depends on the properties of the scanned surface. Flysch rock mass can be followed in SW Slovenia, therefore a lithology profile in quarry Elerji was chosen to test the applicability of TLS in characterising the heterogeneous rock mass. The selected quarry wall was lithologically logged and scanned with TLS. Some samples along the profile have been collected for X-ray diffraction analysis of minerals. The analysis of point cloud included the examination of differences between intensity values for individual lithological units and determination of parameters, affecting the value. The resulted intensity intervals for sandstones and marlstones have been empirically tested on the same profile with relatively positive results. Findings and further analysis would help geologists determine the general engineering geological properties of flysch rock mass in the field, as well as geomechanical conditions for faster and more accurate decisions in providing support types in underground construction, defining slope stability and long-term solutions for stabilisation of rock wall.

3rd Regional Symposium on Landslides in the Adriatic-Balkan Region – Ljubljana, Slovenia

The Adriatic-Balkan Network of International Consortium on Landslides (ICL ABN) was established in January 2012 as one of eight regional and thematic networks of the International Consortium on Landslides (ICL) to promote its activities as well as the activities of the International Programme on Landslides (IPL). The ICL ABN encompasses eight institutions (Table 1). The common interests behind the establishment of this regional network on landslides are outlined in Mihalić Arbanas et al. (2012a) as follows: (1) alignment of professional and scientific resources at the regional level by initiating and implementing joint bilateral or multilateral projects with participants from the region; (2) sharing of information and knowledge; (3) enhancing education and training through the exchange of scientists and professionals between regional institutions, establishing courses and schools on landslides for young researchers, and educating public and local administrations; and (4) development of regionally harmonized strategies for landslide hazard/risk prevention and mitigation. ICL ABN joint activities began in early 2012 with the preparation of a review on a wide range of subjects relevant for landslide research and mitigation in Croatia, Serbia, and Slovenia (Mihalić Arbanas et al. 2012b, c). One of the main tasks of the ICL AdriaticBalkan Network is the organization of a biannual symposium for geoscientists, engineers, professionals, and decision-makers concerned with landslide hazards and risks and their impact on society, both in the Adriatic-Balkan region and worldwide. The 1st Regional Symposium on Landslides in the Adriatic-Balkan Region was held in March 2013 in Zagreb (Croatia) where more than 110 participants from 12 countries (Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Japan, Kosovo, Macedonia, Slovenia, Serbia, Romania, Russia, and Vietnam) presented 77 scientific papers about landslides as well as other topics related to landslide science and practice. The 2nd Regional Symposium on Landslides in the Adriatic-Balkan Region followed in 2015 in Belgrade (Serbia). A wide range of landslide topics was presented in the Symposium sessions with more than 100 participants from 13 countries (Bosnia and Herzegovina, Croatia, Germany, Greece, Italy, Japan, Macedonia, Montenegro, Romania, The Russian Federation, Serbia, Slovenia and Switzerland). The cover pages of the 1st and 2nd ReSyLAB Abstract proceedings (Mihalić Arbanas and Arbanas 2014; Abolmasov et al. 2017) are presented in Fig. 1. The 3rd Regional Symposium on Landslides in the AdriaticBalkan Region (3rd ReSyLAB) will be held on 11–13 October 2017 in Ljubljana (Slovenia) organized by the Geological Survey of Slovenia and University of Ljubljana (Faculty of Civil and Geodetic Engineering and Faculty of Natural Sciences and Engineering). The symposium aims to gather the ICL ABN members, as well as other respected experts, professionals, geoscientists, engineers, professionals, decision-makers, and researchers from the region and beyond (including both the academic and industrial spheres)

Spatial distribution and origin of coalbed gases at the working faces of the Velenje Coal Basin, Slovenia, since the year 2000

Abstract Geochemical and isotopic monitoring of coalbed gases at the excavation fields of mining areas in Velenje Coal Basin, Slovenia, has been ongoing since the year 2000 with the aim of obtaining better insights into the distribution and origin of coalbed gases. Results from the mining areas Pesje and Preloge (active excavation fields) are presented here from the year 2000 up to the present. Composition and origin of coalbed gases were determined using mass spectrometry at the Jožef Stefan Institute. From a larger database of geochemical samples, 119 samples were used for analysis and spatial presentation in a geographical information system (GIS) environment. We have used geochemical (CH4, CO2 and N2) and isotopic (δ13CCO2 and δ13CCH4) tracers for geochemical and isotopic characterisation of coalbed gases from the active excavation fields. Concentrations of CO2 and the carbon dioxide–methane indices in the southern part of the basin are higher than in the northern part of the basin due to the vicinity of the active Šoštanj Fault. The value of δ13CCH4 at the active excavation field indicates a bacterial origin, with values greater than –50‰, and only some boreholes show elevated δ13CCH4 quantities as a consequence of the CO2 reduction process in Velenje Coal Basin. The value of δ13CCO2 indicates the bacterial and endogenic origin of carbon.

3rd Regional Symposium on Landslides in the Adriatic-Balkan Region (3rd ReSyLAB)—a final report

The 3rd Regional Symposium on Landslides in the Adriatic-Balkan Region (3rd ReSyLAB) was held in Ljubljana, Slovenia, from June 11 to 13, 2017, with 70 participants from nine countries (Austria, Bosnia and Hercegovina, Croatia, Czech Republic, Italy, Republic of Macedonia, Serbia, Slovenia, Spain)—scientists, engineers, researchers, students, experts, politicians, and other decision-makers working in the area of landslide risk reduction in the region. The ReSyLAB is a biannual event organized by the Adriatic-Balkan Network of the International Consortium on Landslides (ICL ABN). Being an important form of activities of this ICL regional network comprising of six ICL members from four countries, it was also a contribution of the International Consortium on Landslides (ICL) to the implementation of the Sendai Framework for Disaster Risk Reduction 2015–2030. This article reports on the main outcomes of the 3rd ReSyLAB Symposium. Altogether, 41 abstracts were published in the symposium book of abstracts, and the symposium proceedings with over 20 reviewed full papers are under preparation to be printed early in 2018. During the 3rd ReSyLAB, a five invited keynote lectures have been presented, and 28 oral presentations are given to the audience. An important part of the symposium was a Round Table entitled “Enhancing cooperation between landslide research community and end users.” On the last day of the symposium, over 30 experts participated in two post-symposium study tours in Slovenia.

GIS-assisted classification of litho-geomorphological units using Maximum Likelihood Classification, Vipava Valley, SW Slovenia

In the Vipava Valley (SW Slovenia), various types of mass movements occur in a geologically and geomorphologically diverse setting. These comprise various types of landslides, creep, and Quaternary slope deposits of carbonate blocks and recent scree deposits. A general geological setting is represented as Mesozoic carbonate overthrust on Paleogene flysch (alternations of mostly sandstones and marlstones), resulting in steep slopes and mass movements. Our study is based on the automatic classification of various litho-geomorphological units including slope deposits, alluvial deposits, steep carbonate cliffs, flysch, two carbonate plateaus, and Quaternary deposits, based on supervised Maximum Likelihood Classification. Several polygons were used for training in the broader valley area, and later, the method was applied to automatically classify the complete area into the abovementioned six units. For input layers, we used data for elevation, slope, terrain ruggedness index (TRI), and curvature. Results show that generally, the method is suitable for classification of the litho-geomorphological units including slope deposits. However, comparison with a more detailed map, comprising mapped various mass movements indicated that the method correctly predicts high Trnovo plateau carbonates, steep carbonate slopes, translational carbonate blocks, and fossil rock avalanche deposits, and alluvial deposits, but is not able to clearly distinguish between flysch and more recent slope deposits of gravel and breccia due to their similar elevation, TRI, and slope values. The Slano blato mudflow and Stogovce landslide are not recognized. Therefore, this automatic classification can be carefully used to create a guidance map of general occurrences of litho-geomorphological units including slope deposits before going to the field, with the aim of delineation of slope deposits so they can be further studied in detail later in the field. However, such a map cannot be used as a direct substitute map for the geological and geomorphological map obtained in the field due to impossibility in distinguishing among the units with the same properties (elevation, slope, and TRI values).

Determination of rock type and moisture content in flysch using TLS intensity in the Elerji quarry (south-west Slovenia)

Terrestrial laser scanning (TLS) was performed in tectonically undisturbed flysch in the Elerji quarry (south-west Slovenia), which represents heterogeneous rock mass with alternation of marlstone and sandstone beds. A 9.3-m-thick lithological profile was measured in detail and then compared to TLS values of reflected intensity and mineralogical composition of general marlstones and sandstones. The results showed distinguishable differences between the intensity values of marlstones and sandstones, as these two groups were found to be statistically different. It was also possible to discriminate these units with regard to their moisture content, as different values were observed for combinations of lithology and moisture content. Correlations of intensity and RGB (red, green, blue) values for the mineralogical composition of marlstones and sandstones revealed a good correlation of intensity with combined calcite and quartz content; however, such correlation is valid only for sandstones due to their bigger grain size. Larger quartz grains can scatter the laser beam and lower the correlation. The results showed that acquiring data from heterogeneous rock mass using TLS could be used for the geotechnical engineering classification of distant, inaccessible outcrops and excavated faces, based on the well-established RMR (Rock Mass Rating) and GSI (Geological Strength Index) rock mass classification systems. Both RMR and GSI classification systems classify rock mass based on rock composition, structure and surface conditions of discontinuities. Lithological segmentation of heterogeneous rocks presents, therefore, an important input parameter for their further classification.

Comparison of hydraulic conductivities by grain-size analysis,pumping, and slug tests in Quaternary gravels, NE Slovenia

Abstract Hydraulic conductivities (K) can be obtained from pumping and slug tests as well as grain size analysis. Although empirical methods for such estimations are longstanding, there is still insufficient comparison of K values among the various approaches. Six grain-size analysis methods were tested on coarse-grained alluvial sediments from 12 water wells in NE Slovenia. Values of K from grainsize methods were compared to those of pumping tests and slug tests. Six grain-size methods (USBR, Slichter, Hazen, Beyer, Kozeny-Carman, and Terzaghi) were used for comparison with the Theis and Neuman pumping test method and the Bouwer-Rice method for slug tests. The results show that the USBR (US Bureau of Reclamation) method overestimates K values and there is no correlation with other results, so its use is not advised. Conversely, whilst the Slichter method gives much lower estimates of K, it is the only one to completely fulfill the grain size requirements. Other methods (Hazen, Beyer, Kozeny- Carman, and Terzaghi) result in intermediate values and are similar to the Slichter method; however they should be used for smaller-sized sediments. Due to their high transmissivity and small radius of inffiuence, slug tests should be avoided in the analysis of gravels, as they only test a small portion of the aquifer compared to pumping tests. This is confirmed by the low correlation coefficients between hydraulic conductivities obtained from pumping tests and slug tests.