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Abstract: The use of geothermal energy, which comes from both deep geothermal systems and the shallow underground, has been developing rapidly in the last few decades. The purpose of the paper is to present the results of measurements of the thermal properties of all rock samples and sediments that were available from boreholes, two tunnels and numerous surface locations in Slovenia in the period from 1982 to the end of 2022. In relation to the shallow geothermal potential, a special effort is needed to characterize the thermal properties of the rocks and sediments and to implement thermal energy transfer technology. In this sense, knowledge of the thermal conductivity of rocks and sediments is required to assess the possibility of low-enthalpy heat exchange in a given local area. The largest number of measurements was taken to determine thermal conductivity. Determinations of thermal diffusivity were carried out on a much smaller number of rock and sediment samples, as well as determinations of radiogenic heat production in rocks. The results of thermal conductivity measurements on 430 samples from 119 wells, 20 samples from two tunnels and 156 samples from surface locations are shown. The highest thermal conductivities are shown by samples of dolomite, quartz conglomerate and conglomerate, phyllonite, quartz phyllite and gneiss, while the lowest are measured in sediments such as clay, lignite with clay, peat and dry sand. The determined radioactive heat generation is the lowest for milonitized dolomite and highest for dark grey sandstone with shale clasts. Our results are comparable to those already published worldwide, and they could be the basis for the possible future Slovenian standard for the thermal properties of measured rocks and sediments.
Keywords: thermal conductivity, thermal diffusivity, borehole, tunnel, surface, rock, sediment, radioactive heat generation, Slovenia
Published in DiRROS: 15.01.2024; Views: 157; Downloads: 78
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Abstract: The alpine environment is characterized by complex geology, high-energy terrain, deeply incised river valleys with high erosional potential, extreme weather conditions and dynamic geomorphic processes. Such settings provide favourable conditions for the formation of composite landslides rather than individual slope mass movement phenomena. As an example, we present the kinematics of the composite landslide Urbas in the North of Slovenia which developed in the complex geological and morphological settings characteristic of the alpine environment. The research combines several monitoring techniques and involves the integration of both surface and subsurface displacements measured in the landslide area. The results indicate that the composite sliding process consists of several simultaneous and interrelated types of movements occurring in different segments of the unstable mass that are governed by different mechanisms of displacements, such as rockfall, sliding and debris flow. The kinematic characteristics of a deep-seated landslide that formed in such conditions vary spatially, but is rather homogenuous vertically, indicating translational type of movement. Spatial kinematic heterogeneity is primarily related to the diverse terrain topography, reflecting in different displacement trends. Based on the revealed kinematic proprieties of the sliding material, the sediment discharge illustrates the sliding material balance which estimates the volume of the retaining material that represents the potential for slope mass movement events of larger scales.
Keywords: composite landslide, alpine conditions, kinematics, monitoring, sediment discharge
Published in DiRROS: 15.12.2022; Views: 617; Downloads: 171
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Abstract: Mining waste deposits (MWDs) represent significant and constant pollution source for the environment worldwide, thus it is very important to identify and diminish their environmental impacts. The aim of this study was to determine long-term environmental impacts and their temporal variations of MWDs in Pb–Zn mining districts in Slovenia and assess stability of potentially harmful element (PHE)-bearing phases in stream water. The results showed that investigated MWDs are important source of PHEs in stream sediments and that PHEs mostly occur as fine-grained and liberated PHE-bearing ore minerals. MWDs have generally stronger impact on sediments of smaller streams draining MWDs and main streams close to their confluences, however, fine-grained PHE-bearing material is transported along major watercourses over long distances causing regional pollution. Main ore minerals are mostly soluble in stream water. However, measured PHE leaching potential of MWDs is negligible. PHE levels in stream waters are thus low, demonstrating that drainage of MWDs predominantly contributes to PHE pollution in solid particulate form. Possible long-term remediation solution that would reduce environmental impact is recovery of metals from fine grain size fractions of MWDs, which could become an effective practice in sustainable management of historical MWDs. However, further studies of MWDs’ secondary resource potential, processing technology and evaluation of environmental aspects of extraction are needed.
Keywords: metals, stream sediment, stream water, characterisation, mineral solubility
Published in DiRROS: 03.03.2022; Views: 676; Downloads: 510
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