An investigation on the kerf width in abrasive waterjet cutting of granitic rocks

This paper presents an experimental and statistical study on the kerf width, used instead of the width of the cut in abrasive waterjet (AWJ) cutting. Pre-dimensioned granitic rocks were sampled for the experimentations designed by using Taguchi orthogonal arrays. The effects of the AWJ operating variables on the kerf width were studied and the rock properties were correlated with the kerf widths. Additionally, predictive models for the kerf widths were developed using multi-variable regression analysis and the developed models were verified through some statistical tests. The results demonstrated that the standoff distance and the traverse speed have significant effects on the kerf widths. The results also showed that water absorption, unit weight, microhardness, the maximum grain size of rock-forming minerals, and mean grain size of the rock have significant correlations with the kerf widths of the tested rocks. Furthermore, the modeling results revealed that the predictive models derived from rock properties, can be successfully used as a practical guideline.     

Recycling of abrasives in abrasive water jet cutting with different types of granite

The cost of abrasives has restricted usage of abrasive water jet (AWJ) technology in natural stone cutting applications. However, recycling of the abrasives makes the technology more economical, effective, and environmentally friendly. In this study, significant rock properties affecting the recycling of abrasives in AWJ cutting of granites are investigated. Abrasive mass percentage above 106 μm (AMP_106μm) is considered as a performance criterion in terms of recycling of abrasives since these abrasives can be effectively reused in the rock cutting applications. The study reveals that a considerable amount of used abrasives is in a reusable form. Among the rock properties, the microhardness is statistically determined as the most significant rock property affecting the AMP_106μm. It is also concluded that theAMP_106μm can be explained with high accuracy by the proposed model including the microhardness, the quartz content, and the plagioclase content.     

Quasi‐static analysis of elastic behavior for some systems having higher fracture densities

Elastic behavior of geomechanical systems with interacting (but not intersecting) fractures is treated using generalizations of the Backus and the Schoenberg–Muir methods for analyzing layered systems whose layers are intrinsically anisotropic due to locally aligned fractures. By permitting the axis of symmetry of the locally anisotropic compliance matrix for individual layers to differ from that of the layering direction, we derive analytical formulas for interacting fractured regions with arbitrary orientations to each other. This procedure provides a systematic tool for studying how contiguous, but not yet intersecting, fractured domains interact, and provides a direct (though approximate) means of predicting when and how such interactions lead to more dramatic weakening effects and ultimately to failure of these complicated systems. The method permits decomposition of the system elastic behavior into specific eigenmodes that can all be analyzed, and provides a better understanding about which of these specific modes are expected to be most important to the evolving failure process. Copyright © 2009 John Wiley & Sons, Ltd.     

Investigation on the Levels of Heavy Metals,Polycyclic Aromatic Hydrocarbons,and Polychlorinated Biphenyls in Sewage Sludge Samples and Ecotoxicological Testing

This article reports the levels of heavy metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) in sewage sludges taken from two wastewater treatment plants (WWTPs) in Konya (Turkey) as well as their toxicity. The concentrations of heavy metals, including Cd, Cr, Cu, Ni, Pb, Zn in sludge samples from plant #2 did not exceed the limits described in both Turkish and European Union (EU) regulations. The similar result was observed in samples obtained from plant #1, except for sludge taken in May 2010. The ΣPAHs concentration ranging from 960 to 7680 µg/kg dry matter shows that sewage sludges from plant #1 could be used for agricultural purpose. However, sewage sludges from plant #2 (ΣPAHs: 1077–17 509 µg/kg dry matter) was not suitable for using in agriculture. The concentrations of ΣPCBs in all investigated sludges from plant #1 (7.46–709.36 µg/kg dry matter) and plant #2 (14.12–788.47 µg/kg dry matter) were lower than the limits reported in Turkish and EU regulations. The probable sources of PAHs and PCBs in sludges were also determined. The ecotoxicological tests examined on Vibrio fischeri and Lepidium sativum organisms showed that sludges from plant #1 had no significant toxic effect, while sludges from plant #2 had acute toxic property. Finally, all the results showed that sewage sludges from plant #1 had potential for being used in agriculture.     

Distribution and chemical speciation of heavy metals in the surficial sediments of the Bak?r?ay and Gediz Rivers, Eastern Aegean

The pollution of aquatic ecosystem by heavy metals has assumed serious proportions due to their toxicity and accumulative behaviour. The toxicity and fate of the water borne metal is dependent on its chemical form and therefore quantification of the different forms of metal is more meaningful than the estimation of its total metal concentrations. A five-step sequential extraction procedure was applied for the determination of the distribution of seven elements (Pb, Cr, Cu, Mn, Zn, Ni, Fe) in sediment samples collected from Bakır?ay and Gediz Rivers. According to this study, the results of metals are mostly retained in the residual, oxidizable and reducible fractions. Based on the chemical distribution of metals, we found that Cr, Zn, Cu and Ni are the most non-mobile metals. Pb is the metal that showed the highest percentages in the residual and reducible fractions. Mn is present in the higher percentages in the reducible and carbonate fractions. However, Fe is present in the greatest percentages in the residual fraction, which implies that these metals are strongly linked to the sediments. The risk assessment code as applied to the present study shows that about 12.3–26.9 and 15.7–33.5% of manganese at most of the sites exist in carbonate fraction in the Bakır?ay and Gediz Rivers, respectively. Therefore, Mn comes under the medium risk category in the Bakır?ay and high-risk category in the Gediz River. Speciation pattern of Cu, Zn, Pb, Cr, Ni, Fe shows low to medium risk to aquatic environment health in both rivers.     

Curie Point Depth Investigation of Central Anatolia,Turkey

The residual aeromagnetic total field intensity anomalies in central Anatolia were calculated from the regional aeromagnetic anomalies surveyed by the Mineral Research and Exploration (MTA) of Turkey. The residual aeromagnetic data were analyzed to produce Curie point estimates by the method of OKUBO et al. (1985). The Curie point depth of central Anatolia varies from 7.9 km and 22.6 km. The shallowest Curie point depths were observed around the Cappadocia and Erciyes Volcanic complexes in central Anatolia. A good correlation was deduced between the Curie point depths and the heat-flow data measured previously, which is most certainly important for the geothermal resources of the region. The shallow Curie point depths also correlate well with the hot spring locations in central Anatolia.