Inert Rock Research Articles

Characterisation of natural and remoulded Onsøy clay with focus on the influence of mica

Loss of strength caused by the destructuration of sensitive soils has been identified as the trigger of numerous landslides, some of them of devastating proportions. Norwegian sensitive clay deposits are typically found with a mineralogical composition of inert rock flour, including clay-sized chlorite and dioctahedral mica. The present paper presents a cross-scale study conducted on a sensitive clay from Norway with special focus on the role of mica on the material characteristics. Block samples of Onsøy clay obtained from different depths (4–10 m) were characterised and studied in terms of their mechanical properties, fabric and mineralogy. Oedometer compression tests were carried out in a high-pressure oedometer, applying stress up to 25 MPa on samples in an undisturbed and remoulded state. Microstructural investigations were carried out on undisturbed and remoulded samples using cryo-broadionbeam scanning electron microscopy (cryo-BIB-SEM). Mineral composition was analysed using X-ray diffraction on the bulk samples and the fraction ≤2 μm confirming absence of expandable clay minerals (smectites) and kaolinite. Coarse silt sized and irregular shaped particles were dominated by Na-rich and Ca-rich feldspar, quartz, and framboidal pyrite aggregates. A comparison with data sets from several Norwegian sensitive clay deposits showed that the plasticity index of these clays showed a tendency to decrease with an increasing amount of mica when the salinity is lower than 10 g/l. In contrast, for deposits with a salt concentration of more than 10 g/l, a significant increase in the plasticity index was observed with increasing amount of mica. The formation of aggregates was discussed with relation to its impact on the soil mechanical behaviour-

Evaluation of repellent and insecticidal properties of a novel granite dust product in crop protection

Inert rock dusts, such as diatomaceous earth, represent effective products for insect pest management. We investigated the properties of a novel granite dust product in different formulations as a repellent and insecticidal agent against two important horticultural crop pests (Plutella xylostella and Trichoplusia ni). Foliar application of granite dust (dry and in aqueous solution) reduced larval feeding damage of P. xylostella and T. ni on cabbage leaves. In the case of P. xylostella, aqueous formulation of granite dust with surfactant had a significant insecticidal effect on larvae. In oviposition bioassays, adult P. xylostella female insects oviposited significantly fewer eggs on cabbage leaves treated with granite dust than on control leaves. Our results demonstrate, for the first time, the potential use of granite dust as a pest management treatment providing repellent and insecticidal activities exceeding other mineral and dust-based pest management products.

The quantitative studies on gas explosion suppression by an inert rock dust deposit

The traditional defence against propagating gas explosions is the application of dry rock dust, but not much quantitative study on explosion suppression of rock dust has been made. Based on the theories of fluid dynamics and combustion, a simulated study on the propagation of premixed gas explosion suppressed by deposited inert rock dust layer is carried out. The characteristics of the explosion field (overpressure, temperature, flame speed and combustion rate) at different deposited rock dust amounts are investigated. The flame in the pipeline cannot be extinguished when the deposited rock dust amount is less than 12 kg/m3. The effects of suppressing gas explosion become weak when the deposited rock dust amount is greater than 45 kg/m3. The overpressure decreases with the increase of the deposited rock dust amounts in the range of 18–36 kg/m3 and the flame speed and the flame length show the same trends. When the deposited rock dust amount is 36 kg/m3, the overpressure can be reduced by 40%, the peak flame speed by 50%, and the flame length by 42% respectively, compared with those of the gas explosion of stoichiometric mixture. In this model, the effective raised dust concentrations to suppress explosion are 2.5–3.5 kg/m3.

Comparison of the CAS-POL and IOM samplers for determining the knockdown efficiencies of water sprays on float coal dust

ABSTRACTFloat coal dust, generated by mining operations, is distributed throughout mine airways by ventilating air designed to purge gases and respirable dust. Float coal dust poses an explosion hazard in the event of a methane ignition. Current regulation requires the application of inert rock dust in areas subjected to float coal dust in order to mitigate the hazard. An alternate method using water sprays, which have been effective in controlling respirable dust hazards, has been proposed as a way to control float coal dust generated on longwall faces. However, the knockdown efficiency of the proposed water sprays on float coal dust needs to be verified. This study used gravimetric isokinetic Institute of Occupational Medicine (IOM) samplers alongside a real-time aerosol monitor (Cloud Aerosol Spectrometer with polarization; CAS-POL) to study the effects of spray type, operating pressure, and spray orientation on knockdown efficiencies for seven different water sprays. Because the CAS-POL has not been used to study mining dust, the CAS-POL measurements were validated with respect to the IOM samplers. This study found that the CAS-POL was able to resolve the same trends measured by the IOM samplers, while providing additional knockdown information for specific particle size ranges and locations in the test area. In addition, the CAS-POL data was not prone to the same process errors, which may occur due to the handling of the IOM filter media, and was able to provide a faster analysis of the data after testing. This study also determined that pressure was the leading design criteria influencing spray knockdown efficiency, with spray type also having some effect and orientation having little to no effect. The results of this study will be used to design future full-scale float coal dust capture tests involving multiple sprays, which will be evaluated using the CAS-POL.

Opto-Dielectrometric Sensor for Measuring Total Incombustible Content in Underground Coal Mines

Coal dust produced during underground coal-mining, i.e., float dust, which deposits throughout the coal mine, can be feedstock for coal dust explosions. To prevent these explosions, inert rock dust (limestone dust) is applied to roof, floor, and rib areas of a coal mine. The ratio of incombustible mass (rock dust + incombustible content of coal dust) divided by total mass of the deposited dust is defined as the total incombustible content (TIC) of the deposited dust within the mine. Regulations require that a minimum TIC ratio (80%) to be maintained for safe working conditions inside the mine. This paper presents design, fabrication, and experimental results for a real-time sensing module, which uses continuous optical and dielectrometry methods to measure the TIC of the deposited float dust/rock dust. The optical sensor determines the TIC of the deposited dust based on optical reflection, which is described by modified Beer Law. We present an extension of the Bouguer-Beer–Lambert Law to find the relation between the reflectivity of a layer of known thickness (obtained by interdigital dielectrometry sensor) of a dust mixture to the ratio of each constituent. We also present the experimental results from testing the sensor prototypes in a realistic laboratory test bed that is subjected to the deposition of the coal dust/rock dust mixture. The sensor performance and stability at different humidity levels is evaluated and the accuracy of the results is compared with the currently established best practices for measuring TIC in underground coal mines.

Characterization of airborne float coal dust emitted during continuous mining, longwall mining and belt transport.

Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. If deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coal dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float coal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float coal dust to respirable dust ranged from 10.3 to 13.8. The ratios measured on the longwall face were between 18.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8.

Comparative life cycle assessment and economic analysis of typical flue-gas cleaning processes of coal-fired power plants in China

The life cycle environmental impacts of widely used flue-gas cleaning processes, including limestone-gypsum wet flue-gas desulfurization (FGD), selective catalytic reduction denitration (SCR) and electrostatic precipitators (ESP), are compared. The abbreviations FGD, SCR and ESP in this article refer in particular to the above listed processes. Energy consumption, resource consumption and emission inventories of each life cycle phase are established. The potentials of five environmental impact categories, namely, global warming, acidification, nutrient enrichment, photochemical ozone formation, soot and ashes are finally obtained. The current paper reveals that the total energy consumption and resource consumption are dominated by the process operation. The three processes are compared and it is found that to achieve equal environmental burden reductions, the SCR process consumes more energy and approximately the same amount of air and inert rock as the FGD. But the water consumption of the FGD is much higher than the SCR. The ESP process consumes both the least energy and the least resource in general. The economic assessment indicates that the performance of the ESP process tends to be the best and the FGD follows when equally invested.

How Porosity Increases During Incipient Weathering of Crystalline Silicate Rocks

Weathering of bedrock to produce porous regolith, the precursor to biologically active soil and soluble mineral nutrients, creates the life-supporting matrix upon which Earth’s Critical Zone—the thin surface layer where rock meets life—develops (Ollier 1985; Graham et al. 1994; Taylor and Eggleston 2001). Water and nutrients locked up in low porosity bedrock are biologically inaccessible until weathering helps transform the inert rock into a rich habitat for biological activity. Weathering increases the water-holding capacity and nutrient accessibility of rock and regolith by increasing porosity and mineral surface area, affecting the particle-size distribution, and enhancing ecosystem diversity (Cousin et al. 2003; Certini et al. 2004; Zanner and Graham 2005). Especially in areas where soils are thin and climate is dry, the water stored in weathered rock is essential to ecosystem productivity and survival (Sternberg et al. 1996; Zwieniecki and Newton 1996; Hubbert et al. 2001; Witty et al. 2003). Removal of soluble material during weathering decreases the concentrations of major elements such as Ca, Na, and Mg and the overall mass of the solid, decreasing the bulk density and increasing porosity. These chemical and physical changes result in decreased uniaxial compressive strength and elastic moduli of the rock and increased infiltration of water through the weathered rock (Tugrul 2004). Porosity in intact bedrock is comprised of inter- and intra-granular pores developed during (re-) crystallization in igneous and metamorphic rocks or diagenesis in sedimentary rocks. As we conceptualize it, the conversion of low-permeability bedrock to regolith generally begins due to the transport of meteoric water into protolith through the large-scale fractures that are present as a result of regional tectonic factors or exhumation (Wyrick and Borchers 1981; Molnar et al. 2007). In zones near the fractures, water can infiltrate into the low-porosity rock …

The age of radiance: the epic rise and dramatic fall of the atomic era

Radiation is a complex and paradoxical concept: staggering amounts of energy flow from seemingly inert rock and that energy is both useful and dangerous. While nuclear energy affects our everyday lives-from nuclear medicine and food irradiation to microwave technology-its invisible rays trigger biological damage, birth defects, and cellular mayhem. From the end of the nineteenth century through the use of the atomic bomb in World War II to the twenty-first century's confrontation with the dangers of nuclear power, Nelson illuminates a pageant of fascinating historical figures: Enrico Fermi, Marie and Pierre Curie, Albert Einstein, FDR, Robert Oppenheimer, and Ronald Reagan, among others. He reveals many little-known details, including how Jewish refugees fleeing Hitler transformed America from a country that created light bulbs and telephones into one that split atoms; how the most grotesque weapon ever invented could realize Alfred Nobel's lifelong dream of global peace; how emergency workers and low-level utility employees fought to contain a run-amok nuclear reactor, while wondering if they would live or die. Brilliantly fascinating and remarkably accessible, The Age of Radiancetraces mankind's complicated and difficult relationship with the dangerous power it discovered and made part of civilization.

Anisotropic and impulsive neutron emissions from brittle rocks under mechanical load

The aim of the present research work is to investigate the emission of neutrons from inert materials subjected to mechanical load. If confirmed, this emission can be seen as a proof of the existence of piezonuclear reactions, i.e. nuclear reactions of fission induced by pressure. This investigation was performed by loading specimens of granite under uniaxial compression till failure and recording the emissions through passive dosimeters. In the present work, the experimental setup was designed and realised, in accordance with what is described in the literature as concerns neutron emissions from inert rock specimens under compressive uniaxial loads. The proper functioning of dosimeters was verified and the experimental functional procedure with radioactive sources was described in the paper. The preliminary experimental activity of the measurement of the background level of neutrons was performed describing the set up allowing it. Finally, the functional tests with radioactive sources, measurement of background values and neutron emission tests during the monoaxial destructive compression tests of the granite specimen were compared and discussed.

Development of Design Criteria for Denitrifying Treatment Wetlands

Subsurface wetlands are well suited for on-site applications because they provide odor and vector control and they mitigate public access issues (U.S. EPA, 1993). Artificial subsurface wetlands are typically designed with an inert rock medium, can be either planted or unplanted, and are designed so that the water flows below the surface of the wetlands through the porous medium. The medium provides a surface area for the growth of bacterial films but inhibits the carbon cycling from plant debris because the packing material prevents the plant debris from reaching the water. As a result, subsurface wetlands are only marginally successful at removing nitrogen from wastewater. The nitrogen removal that does occur is the result of plant assimilation and microbial denitrification that utilizes any remaining carbon source in the influent and from plant decay (Kadlec and Knight, 1996). To increase the denitrification performance, an alternative carbon source is required. Gersberg et al. (1983) demonstrated that the addition of carbon, in the form of methanol, stimulated bacterial denitrification and increased nitrate removal efficiencies to 95%. Based on previous research, it has been found that a variety of organic solids can be used simultaneously as media and as a carbon source to support the denitrification process. These include plant biomass (Gersberg et al., 1983), cotton burr and mulch compost (Su and Puls, 2007), wheat straw (Aslan and Turkman, 2003), sawdust (Robertson and Cherry, 1995; Schipper et al., 1998), and woodchips (Healy et al., 2005; Robertson et al., 2009). Schipper et al. (1998) demonstrated that porous groundwater treatment walls amended with sawdust were successful in removing nitrate from contaminated groundwater. Robertson et al. (2005) demonstrated that the proprietary Nitrex filters, which utilize a nitrate reactive material, produced septic tank effluent nitrate removal rates of up to 96%, remaining effective for at least five years, but removal rates were diminished during the winter months. The temperature of the water in a wetland system can significantly affect the rate of denitrification (Kadlec and Knight, 1996). The use of a readily available organic medium in a constructed subsurface wetland as a method for denitrification of nitrified septic tank effluent has not been investigated. This title belongs to WERF Research Report Series . ISBN: 9781843395331 (eBook)

Biot poroelasticity of a chemically active shale

The Biot theory of poroelasticity relates the strain ε of a porous material to changes of the applied stress σ and of the pore pressure p . Additional osmotic effects are present in some rocks, such as shales. This paper modifies the thermodynamic arguments used by Biot in order to include the chemical potentials μ r of all the chemical species within the pore fluid. In the limit in which salt is unable to move into or out of the shale, the deformation depends only on the chemical potential μ w of the water and the applied stress. In the limit of a chemically inert rock, the standard Biot analysis is obtained, and the pore pressure p is again the important variable. Real shales lie somewhere between these two limits.

Cementation Effects in Frictional Materials

Cementation effects are studied on the basis of three series of drained triaxial compression tests on compacted soil, soil‐cement, and mortar. The frictional materials have the same gradation curve and the same water content, and the specimens are produced using the same compactive effort and have nearly the same initial, total density. The only difference between the three sets of specimens is the amount of cement exchanged with inert rock flour. Increasing cement contents produces increasing cohesion and tensile strength as well as increasing friction angle at low confining pressures. The curvature of the failure envelopes increases with cementation, and the failure envelopes are parallel at medium confining pressures. At high confining pressures, they cross each other such that the compacted soil becomes stronger than the two cemented soils. Analyses of the strengths show that this behavior can be explained in terms of the different compressibilities and different rates of dilation observed for the three frictional materials.