Rudarsko-geološko-naftni zbornik (The Mining-Geological-Petroleum Bulletin)

Petrological characteristics of clastic sedimentary rocks from the St. Barbara ore mine in Rude near Samobor

Šime Bilić, Vesnica Garašić — Fri, 22 Jan 2021 00:00:00 +0100

In the scope of this research, the petrographic and geochemical analyses of clastic sedimentary rocks from the St. Barbara, copper and iron ore mine in Rude near Samobor, have been made, aiming to classify and determine the provenance and environment of formation of clastic sedimentary rocks, as well as the influence of hydrothermal fluids on their properties. Eight samples were collected in total from different locations in the mine. Six of those samples have been studied in detail. The results showed structural and geochemical variability and uneven hydrothermal alteration intensity in the samples. Based on petrographic analyses, three rocks are classified as sublithoarenite, quartz arenite and quartz greywacke. Three of the samples are classified as ore breccia, ore sandstone, and ore silt-sandstone due to the pronounced hydrothermal alterations and ore mineralisation. Comprehensively, petrographic and geochemical analyses indicate that the source rocks of the investigated clastic sedimentary rocks were felsic (La/Sc = 0.9-6.2; Th/Sc = 1.3-2.4), most probably sedimentary, possibly resedimented rocks. The extent of source rock weathering was very high (Chemical Index of Alteration CIA = 52.1 - 81.3%) and the geotectonic position of the sedimentary basin was very likely to be at the passive continental margin.

Elevated selenium levels in vegetables, fruits, and wild plants affected by the Raša coal mine water chemistry

Fri, 22 Jan 2021 00:00:00 +0100

Selenium (Se), an essential trace element that is toxic when humans and animals are exposed to it in excess, is ubiquitous in coal. For centuries, superhigh-organic-sulfur (SHOS) Raša coal, enriched in S, Se, U, V, and Mo, was mined and processed across the Mediterranean Raša Bay area, located in the Istrian peninsula (in the northern Adriatic Sea, Croatia). There is concern that Raša coal mine water is contaminating local water, soil, and crops. The aim of this monitoring study was to determine the levels of Se and selected potentially toxic trace (As, Cd, Cu, Cr, Mo, Pb, U, V, and Zn), and minor (Fe and Mn) elements in Raša coal mine water, surface water, and associated vegetables, one fruit, and wild plants. Levels of Se in coal mine water were increased (up to 12 µg/L) compared to the maximum allowed water Se (10 µg/L). Compared to an EU average soil Se (1.15 mg/kg), Raša garden soil showed a 5-fold increase in Se. Compared to Croatian and Greek vegetable Se levels (low to normal), Raša vegetables showed a 20-fold, and a 50-fold increase in Se, respectively. Although approximative only, estimates of daily intake (EDI) of Se for mixed Raša vegetables (n = 21) showed a high level (0.055 mg/day). Namely, recommended dietary allowances (RDA) of Se for females and males are 0.055 mg/day, and 0.070 mg/day, respectively. The EDI values of the analyzed vegetables contributed to average RDA levels as follows: garlic (183%), turnip (154%), parsley (147%), onion and gourd (76%), lettuce (74%), kale (62%), radicchio (51%), and potato (20%). Although the calculated EDI for the analyzed Raša vegetables was 1/8 the toxic dose (>0.4 mg/day), these results call for further research on the dietary and nutritional status of the residents in terms of Se.

An investigation on the effects of micro-parameters on the strength properties of rock

Fri, 22 Jan 2021 00:00:00 +0100

Rocks are formed from particles and the interaction between those particles controls the behaviour of a rock’s mechanical properties. Since it is very important to conduct extensive studies about the relationship between the micro-parameters and macro-parameters of rock, this paper investigates the effects of some micro-parameters on strength properties and the behaviour of cracks in rock. This is carried out by using numerical simulation of an extensive series of Uniaxial Compressive Strength (UCS) and Brazilian Tensile Strength (BTS) tests. The micro-parameters included the particles’ contact modulus, the contact stiffness ratio, bond cohesion, bond tensile strength, the friction coefficient and the friction angle, and the mechanical properties of chromite rock have been considered as base values of the investigation. Based on the obtained results, it was found that the most important micro-parameters on the behaviour of rock in the compressive state are bond cohesion, bond tensile strength, and the friction coefficient. Also, the bond tensile strength showed the largest effect under tensile conditions. The micro-parameter of bond tensile strength increased the rock tensile strength (up to 5 times), minimized destructive cracks and increased the corresponding strain (almost 2.5 times) during critical stress.

Hydraulic fracturing design improvements by proppant flowback mitigation method application during hydrocarbon production

Temirlan Jatykov, Bimurat Sagindykov, Kuralay Bimuratkyzy — Fri, 22 Jan 2021 00:00:00 +0100

Proppant flowback after hydraulic fracturing treatment is quite a serious challenge that causes damage to both downhole and surface equipment, leading to unwanted workovers and production suspension, or other negative outcomes. Some special methods including preventive as well as corrective measures already exist in the industry to overcome the proppant flowback problems. However, there is no clear guidance on how to choose the method for certain conditions, particularly during the hydraulic fracturing design stages. Therefore, the authors conducted a comprehensive review of fourteen preventive technologies to systematize them and to propose an initial decision-making approach. The following methods were considered in this paper: Resin Coated Proppants (RCP), RCP with Activator, RCP with Nanoparticles, Proppant with Liquid Resin Systems (LRS), Proppant with Surface Modification Agents (SMA), Proppant with Proppant Consolidation Aid (PCA), Cylindrical Proppant, Microfibers, Thermoset Resin Fibers, Thermoset Film Strips, Deformable Isometric Particles (DIP), Expandable Proppants, Polymer Surface Modified Proppants, and In-situ Formulated Proppants. The review reveals physical, chemical, and technological properties of each method to select criteria for effective screening. So, the reader could find the appropriate proppant flowback mitigation method corresponding to a particular reservoir and the well conditions during the initial hydraulic fracturing design stages.

Injury Analysis of Iran’s Mining Workplaces

Mohammad-Javad Rahimdel — Fri, 22 Jan 2021 00:00:00 +0100

Mining is a high-risk industry that exposes operators and workers to a high level of occupational health and safety hazards caused by vehicle accidents, blasting, or collapse. This paper aims to analyse the serious and fatal accidents in Iran’s mines over a six-year period, from 2012 to 2017. The data sources were the statistical results of the occupational accidents reported by the National Statistical Centre of Iran and the importance measure of incidents defined by the questionnaires received from the mine safety and health experts. This research presents a model for the prioritization of the mining workplace based on the weighted injury risk of the occupational incidents in the mining industry. The results of this work show that the coal mines of Iran have the highest work-related incidence rate which requires special safety attention. Moreover, the total temporary disability risk is currently at the lowest level in all mining activities, while the fatality risk has significantly increased in the coal mines in recent years. The results obtained from this study are helpful to detect the dangerous mining workplaces and to protect workers from workplace hazards by considering the safety guidelines.

Evaluating the Sawability of Rocks by Chain-Saw Machines using the PROMETHEE Technique

Fri, 22 Jan 2021 00:00:00 +0100

One of the most significant factors in the estimation of dimension stone quarry cost is the production rate of rock cutting machines. Evaluating the production rate of chain-saw machines is a very significant and practical issue. In this research, it has been attempted to evaluate and select the suitable working-face for a quarry by examining the maximum production rate in the Dehbid and Shayan marble quarries. For this purpose, field studies were carried out which included measuring operational characteristics of the chain-saw cutting machine, the production rate and sampling for laboratory tests from seven active case studies. Subsequently, the physical and mechanical properties of rocks including: Uniaxial Compressive Strength (UCS), Brazilian Tensile Strength (BTS), Los Angeles abrasion, quartz content, water absorption percentage, porosity, Schmidt hardness and grain size for all sample measurements were studied after transferring the samples to a rock-mechanics laboratory. Finally, the sawability of the quarried working-faces was evaluated using the PROMETHEE multi-criteria decision-making (MCDM) model according to the physical and mechanical properties. The results of the study indicated that the number 1 and 5 working-faces from the Dehbid and Shayan quarries are the most suitable working-faces in terms of production rate with the maximum recorded production values (4.95 and 3.1 m²/h), and with net flow rates (2.67 and -0.36) respectively.

Laboratory tests on the strengthening of wet-mix shotcrete lining with the use of nanomaterials

Fri, 22 Jan 2021 00:00:00 +0100

Adding nanomaterials to concrete extends the size range of constituent particles well into nano-scale dimensions, which could help the compacting of particles in cement-based materials. Regarding the differences between shotcrete and cast concrete, in this study, the properties of shotcrete with nano and micro-silica and nano-clay were experimentally studied. The micro and nanomaterials have been added at different percentages (6%, 9%, and 12%) to a shotcrete paste. The comparison was based on the uniaxial compressive strength, flexural strength, tensile strength, and porosity tests of different specimens. The results indicated that the maximum increase in compressive, flexural, and tensile strengths of shotcrete was related to 12% nano-SiO₂, while for 12% nano-clay, all of these strengths were decreased at 28 days. The optimum percentage for shotcrete substitution by nano-clay was established to be 6%. Also, the application of the nanomaterials led to a decrease in the water absorption and porosity of shotcrete. Eventually, the results revealed that the improvement of mechanical properties by the introduction of the nanomaterials in shotcrete could be satisfactory.

Determination of Methane Desorption Zone for the design of a drainage borehole Pattern (Case Study: E4 Panel of the Tabas Mechanized Coal Mine, Iran)

Ali Hosseini, Mehdi Najafi — Fri, 22 Jan 2021 00:00:00 +0100

Underground coal mining is known as one of the major sources of methane emissions which mainly occurs after underground coal extraction. Rock strata in-situ methane can potentially be the most significant hazard in coal mining operations. To prevent or minimize the risks of methane emissions, methane drainage approaches have been adopted by coal mines. Rock mass methane drainage is the most efficient and effective approach toward controlling methane hazards as it prevents and reduces the frequency of methane emissions, outflows into the working area and sudden outbursts of methane and rocks. The method includes drilling boreholes from the tailgate side to the unstressed zone in the roof and floor strata above and below a working coal seam. The coal seam gas content in Tabas Parvadeh I is estimated to be about 16 m³/t, which is relatively high. Based on exploration data, five distinct coal seams have been identified (B1, B2, C1, C2 and D) at the coal deposit and currently C1 is being worked. Considering the high value of C1 gas content and surrounding rocks, the Methane Drainage System (MDS) has been utilized for gas drainage. This paper tries to determine the desorption area which is essential and helpful for the selection of an effective drilling pattern into the adjacent coal seams. In this study, the methane drainage zone in the E4 panel of the Tabas coal mine was calculated using experimental equations and a drainage borehole pattern was determined.

Optimization of Chalcopyrite Galvanic Leaching in the Presence of Pyrite and Silver as Catalysts by using Response Surface Methodology (RSM)

Fri, 22 Jan 2021 00:00:00 +0100

In this research, dissolution of chalcopyrite concentrate is modelled and optimized using Response Surface Methodology (RSM). Also, effective parameters in the leaching process such as the amount of pyrite, silver ions, redox potential and initial concentration of acid are comprehensively studied. Central Composite Design (CCD) methodology is chosen as the design matrix to predict the optimum level of the parameters. In the next step, it will be proven that in the presence of silver ions, pyrite effectiveness is improved and also the chalcopyrite dissolution rate is increased considerably. Using the result of quadratic programming, a rotation speed of 1000 rpm, a pyrite/chalcopyrite mass ratio of 3:1, the amount of 150 ppm silver ion, a solution potential set point of 470 mV, at 800°C and 25 g/L initial acid concentration are the optimal level of the selected parameters wherein the maximum copper extraction with more than 95% in less than 10 hours can be accessible.

An overview and future prospects of Croatian geotechnological heritage

Zlatko Briševac, Ana Maričić , Vladislav Brkić, Vladi Bralić — Fri, 22 Jan 2021 00:00:00 +0100

Industrial heritage plays an important role in the economical, historical, and cultural identity of contemporary European society. A significant part of the industrial heritage consists of historical buildings which have remained after mining and petroleum exploitation. Moreover, industrial heritage can be also nurtured in countries in which mining and petroleum activities are not fully developed. It is inevitably associated with geological heritage. Furthermore, geological heritage is essential for a better understanding of nature, its wider appreciation and better protection. Mining has always played a significant industrial role, but it has recently lost its significance due to increasing environmental requirements regarding the European green deal and transforming the economy for a sustainable future. However, old mining and petroleum heritage sites can become attractions and they can contribute to the development of tourism and the community itself. A new term “geotechnological heritage”, presented in this paper, is related to mining, geological and petroleum heritage due to their significant interaction. This paper presents the used and unused touristic potential of heritage on selected sites in the Republic of Croatia. In addition, an analysis of the Croatian undervalued geotechnological heritage has been performed after the exploitation of stone and other nonmetallics, coal, metals, and petroleum. Unlike Croatia, the potential of geotechnological heritage has been recognized and exploited in most European countries. Therefore, Croatia has a great opportunity to develop heritage based on the experience of more successful members of the European Union.