Diatomites belonging to a list of raw materials used in the EU criticality assessment are essential to many industrial applications due to a unique combination of their physical properties, i.e. porous and permeable structure, high specific surface area and adsorption capacity, low density and thermal conductivity, and chemical inertness. The present study was undertaken to analyse the relationships between the pore network characteristics, petrophysical parameters, and mineralogical variability of the Lower Miocene diatomites from the Jawornik deposit (Skole Unit, the Polish Outer Carpathians, SE Poland). Five varieties of the diatomites, distinguished on the basis of the macroscopic features, i.e., colour and fracturing effects, have been investigated by SEM, chemical and XRD analysis, mercury intrusion porosimetry, helium pycnometry, and the Vickers hardness tests. Significantly differing are two varieties. The light-coloured, massive and block-forming diatomites (variety BL) consist mainly of poorly cemented siliceous skeletal remains of diatoms, and represent the rocks with high total porosity (38-43%), low bulk density (1.28-1.38 g/cm 3) and low microhardness (10.7 HV 0.3). The dark-gray silicified diatomites with a platy or prismatic splitting (variety PD) reveal obscured microfossils of diatoms and are the most compact and hard rocks (80.8 HV 0.3), with poor total porosity (17-24%) and higher bulk density (1.70-1.78 g/cm 3). The spatial distribution of the field identifiable rock varieties allows selective exploitation of the diatomites with the predictable petrophysical characteristics that define their future use.
WprowadzenieKamienie dekoracyjne i architektoniczne s¹ najczêoeciej wydobywane w formie bloków, czyli bry³ skalnych o prostopad³ooeciennych kszta³tach i wymiarach, zapewniaj¹cych objê-tooeae odpowiedni¹ dla maj¹cych powstaae rzeŸb, p³yt ok³adzinowych czy elementów konstrukcji budowlanych. Wielkooeae bloków i ich zawartooeae w skalnej masie zale¿y od intensywnooeci p³aszczyzn podzielnooeci i ich orientacji. Udzia³ materia³u blocznego w ocenianej objêtooeci górotworu zwany jest blocznooeci¹ geologiczn¹, zaoe odniesiony do ilooeci wydobytego urobku -blocznooeci¹ górnicz¹. W obu przypadkach wyra¿any jest on w procentach i stanowi istotny parametr z³ó¿ surowców skalnych zaliczanych do kamieni blocznych i ³amanych (dawniej drogowych i budowlanych), gdy¿ jest podstaw¹ w³aoeciwego ich wykorzystania przy zastosowaniu odpowiednich metod eksploatacji. Ma to istotne znaczenie dla optymalizacji wydobycia, albowiem pozyskiwanie kamienia ³amanego zwi¹zane jest zwykle z intensywnym u¿yciem bryzantycznych materia³ów wybuchowych, których stosowanie przyczynia siê do powstawania nowych p³aszczyzn podzielnooeci i zaniku mo¿liwooeci pozyskiwania bloków.W Polsce po³udniowo-wschodniej u¿ytkowanie materia³ów kamiennych od wczesnego oeredniowiecza wi¹¿e siê z rozwojem myoeli technicznej, sztuki i architektury. Wielkooeae
The complex pore space considerably affects the unique properties of diatomite and its significant potential for many industrial applications. The pore network in the diatomite from the Lower Miocene strata of the Skole nappe (the Jawornik deposit, SE Poland) has been investigated using a fractal approach. The fractal dimension of the pore-space volume was calculated using the Menger sponge as a model of a porous body and the mercury porosimetry data in a pore-throat diameter range between 10,000 and 10 nm. Based on the digital analyses of the twodimensional images from thin sections taken under a scanning electron microscope at the backscattered electron mode at different magnifications, the authors tried to quantify the pore spaces of the diatomites using the box counting method. The results derived from the analyses of the pore-throat diameter distribution using mercury porosimetry have revealed that the pore space of the diatomite has the bifractal structure in two separated ranges of the pore-throat diameters considerably smaller than the pore-throat sizes corresponding to threshold pressures. Assuming that the fractal dimensions identified for the ranges of the smaller pore-throat diameters characterize the overall pore-throat network in the Jawornik diatomite, we can set apart the distribution of the pore-throat volume (necks) and the pore volume from the distribution of the pore-space volume (pores and necks together).
Analiza mechaniki procesu rozdrabniania surowców mineralnych w kruszarkach i wysokocioenieniowych prasach walcowych WprowadzenieProces rozdrabniania ska³ wywo³any jest przez naprê¿enia wewnêtrzne, których wielkooeae przekracza wartooeci graniczne. Naprê¿enia wewnêtrzne s¹ pochodn¹ oddzia³ywañ krusz¹cych, takich jak oeciskanie, udar, zginanie, oecinanie itp. Wynik rozdrabniania w konkretnej kruszarce jest uzale¿niony od w³aoeciwooeci wytrzyma³ooeciowych ziaren danego surowca, a tak¿e od charakteru oddzia³ywañ krusz¹cych. W ka¿dej kruszarce wystêpuje wiele oddzia³ywañ krusz¹cych, z których jedno, zale¿nie od typu kruszarki, ma znaczenie dominuj¹ce. W kruszarkach udarowych czy m³otkowych dominuj¹ce znaczenie posiada udar. W kruszarkach szczêkowych, sto¿kowych, walcowych i prasach walcowych wystêpuje g³ównie oeciskanie, ale tak¿e oecinanie i zginanie. Dlatego korzystne jest wielorakie oddzia³ywanie elementów kruszarek na rozdrabniany materia³. St¹d na przyk³ad wa¿ny jest kszta³t powierzchni szczêk kruszarek szczêkowych, ukszta³towanie powierzchni sto¿ków kruszarek sto¿kowych, ukszta³towanie powierzchni walców kruszarek i pras walcowych.Charakter i wielkooeae odkszta³ceñ zale¿y od typu i wielkooeci przy³o¿onych si³ (naprê¿eñ), dlatego ska³y charakteryzuj¹ siê ró¿n¹ wytrzyma³ooeci¹, zale¿nie od sposobu przy³o¿enia obci¹¿enia. Orientacyjne zale¿nooeci pomiêdzy wytrzyma³ooeci¹ na oeciskanie R c , zginanie R g , oecinanie R t i rozci¹ganie R r, przedstawiaj¹ siê nastêpuj¹co (Majcherczyk 1989):
The sandstones with a laminated structure are common building materials. Lamination is macroscopically expressed as colour and grain size variations observed both in the deposit and within individual beds; therefore, the properties of such sandstones are diverse depending on the spatial distribution of the binding mass and framework components. For the terrestrial sandstones of different genesis, four types of laminae have been distinguished based on petrographic studies. They have a siliceous binder or a mixed ferruginous–siliceous–argillaceous binder with different proportions of these components. In laminae of types I–III, the grain framework is built mainly of quartz grains, and in type IV, it is accompanied by numerous lithoclasts and feldspars. Knoop hardness and CERCHAR abrasivity were tested in each lamina variety, and the results were correlated with the equivalent quartz content and the longitudinal ultrasonic wave velocity measured perpendicular and parallel to the lamination. The proposed research methodology was not used in previous studies on terrestrial laminated sandstones. The results explain a strong dependence between mineral composition, structure of laminae, and technical parameters of rocks. The knowledge of this relationship facilitates the selection of rocks that meet the relevant technical requirements and helps to optimally manage the resources of sandstone deposits.
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