Occurrence of PGE mineralisation in Bangur,Kendujhar district,Odisha

PGE mineralisation of significant grade and extent is reported from Bangur chromite mining area, Kendujhar district, Odisha, located to the south of the well known Baula-Nuasahi ultramafic complex. The hitherto unknown PGE mineralisation is established in a ferritchromit rich breccia zone occurring within Bangur litho-mélange. The mineralized breccia zone is traced for about 550m with a mean width of 12m in NW-SE direction. Chemical analysis of drill core samples by ICP-MS indicates an average ΣPGE content of 3.2 ppm dominated by Pt and Rh. Occurrence of discrete grains of PGM in sizes up to 45 microns is confirmed by SEM-EDX and EPMA study. Delineation of this PGE bearing zone stresses the need for preservation of gangue/matrix of the breccia zone, along with ferritchromit clasts, in the ongoing selective mining of chromite in Bangur.     

Enhancement of Dry Beneficiation of Coal by Air Distributor Design Modification in an Air-Pulsated Stratifier

Natural Resources Research - This study investigated the segregation of organic (maceral) and inorganic (mineral matter or ash) contents of coal in an air stratifier after design modification in...     

Seismic strengthening of RC columns using external steel cage

Steel caging technique is commonly used for the seismic strengthening of reinforced concrete (RC) columns of rectangular cross‐section. The steel cage consists of angle sections placed at corners and held together by battens at intervals along the height. In the present study, a rational design method is developed to proportion the steel cage considering its confinement effect on the column concrete. An experimental study was carried out to verify the effectiveness of the proposed design method and detailing of steel cage battens within potential plastic hinge regions. One ordinary RC column and two strengthened columns were investigated experimentally under constant axial compressive load and gradually increasing reversed cyclic lateral displacements. Both strengthened columns showed excellent behavior in terms of flexural strength, lateral stiffness, energy dissipation and ductility due to the external confinement of the column concrete. The proposed model for confinement effect due to steel cage reasonably predicted moment capacities of the strengthened sections, which matched with the observed experimental values. Copyright © 2009 John Wiley & Sons, Ltd.     

Development of rational models for tunnel blast prediction based on a parametric study

The empirical models available for prediction of the tunnel blast results like pull ratio, specific charge, specific drilling and overbreak have some inherent shortcoming in absence of any parametric study at the backdrop. Hence, the models use different constituting parameters and provide values which differ widely. After a thorough review of literature and field investigations in the drivages of mines and tunnels some parameters were identified. Those parameters were subjected to Multiple Linear Regression analyses to filter out the most influencing ones which represent the rockmass properties, the tunnel configurations and the blast designs. A parameter called Tunnel Blasting Index (TBI) was conceptualized and was expressed in terms of those most influencing parameters. All the blast results observed during the filed investigations could be well related to a single index TBI. Some adjustments on account of shape of the tunnel and joint orientations, which were not addressed in the available models, are suggested in the developed models.     

Gravity wave interaction with floating membrane due to abrupt change in water depth

Using the recently developed expansion formulae for wave structure interaction problems, the scattering of surface water waves by a semi-infinite floating membrane due to abrupt change in bottom topography is analyzed. Both the cases of finite and infinite steps are analyzed. In the present paper, the analysis is based on the linearized theory of water waves and small amplitude membrane response. Combining the linearized kinematic and dynamic surface conditions on the water surface with the dynamic pressure condition on the membrane, a third order differential equation is derived to describe the membrane covered free surface condition. General wave energy relation for wave scattering by floating horizontal membrane is derived by the application of law of conservation of energy flux and alternately by the direct application of Green's second identity. In the floating membrane covered region, the wave energy density is a combination of the kinetic and potential energy density due to the surface gravity waves, and the surface energy density which is due to the existence of the floating membrane on the free surface. Gravity wave transformations due to an abrupt change in bottom topography in the presence of a floating membrane in finite water depth are analyzed based on shallow water approximation. Numerical results are computed and analyzed to understand the wave transformation due to the floating membrane when there is an abrupt change in topography in different cases.     

The role of fault reactivation in the development of tropical montane lakes

This work details the role of fault reactivation in the development of tropical montane lakes by using basin morpho-structural analysis and seismostratigraphic studies. The upland lakes are severely faulted sinkholes, whose faults penetrate the Quaternary sedimentary units. Four main stages are related to the lake formation: (i) an Early Proterozoic tectonic deformation of the rocks along the southern border of the Carajás Structure, where the lake is placed; (ii) differential erosion by – and building of – the formation of the South Carajás Hill; (iii) Fe-rich crust formation by weathering and gravitational collapse faults following the E–W plateau border and the start of Violão Lake formation during the Pliocene–Pleistocene; and (iv) episodic fault-fracture reactivation by gravitational collapse causing pulses of subsidence in the lake and outlining its faulted borders. Dissolution of the lateritic crust and erosion by runoff drainage under wet climate conditions were coeval with fault activities, which allowed the deposition of relatively thick clastic deposits organized in three main seismostratigraphic units associated with major lake-level fluctuations. Initial fault reactivation under low-level water started lacustrine basin development with deposition of prograding fan deltas related to the main drainage. A second fault reactivation by gravitational collapse increased the lake accommodation space and resulted in the deposition of fine-grained sediments from dilute interflows or overflows until 36 000 cal year BP. At about 31 000 cal year BP, rapid decreases in the lake water level under redox conditions at the sediment/water interface allowed widespread siderite formation. A third gravitational collapse episode was responsible for the increase in the lake area and depth and the returning of clastic/organic deposition up to the present. This tropical montane lake can be seen as a representative example for understanding the formation of other upland lakes controlled by fault reactivation. © 2020 John Wiley & Sons, Ltd.     

Beach monazites from Alleppey: A window to the Trivandrum Block,Southern India

Detrital monazites can be used to reconstruct the tectonothermal history of their provenance. Dating of beach monazites from Alleppey by EPMA U-Th-Pb_total technique using the centroid method demonstrates that the ages recorded by even a small number of 28 analyses from a single thin section grain mount can potentially reveal a considerable portion of the tectonothermal history of the Trivamdrum block. Three monazite populations were identified that yielded ages 605 ± 9, 575 ± 23 and 548 ± 11 Ma, which have their more or less exact counterparts reported from the Trivandrum Block. One monazite grain yielded random Paleoproterozoic ages ranging from 1756 Ma to 1345 Ma representing similar ages which earlier have been interpreted as due to differential Pb-loss from >2000 Ma monazites during the late Neoproterozoic-Cambrian metamorphism.     

Aerosol physical characteristics at Bhubaneswar, East coast of India

Physical characterization of atmospheric aerosols was carried out using various equipments like Grimm's spectrophotometer, Aetholometer and Microtops-II at Bhubaneswar, a coastal city in the east coast of India. Meteorological parameters were recorded on-line with an automatic weather station, which showed weather relatively free from extreme events with high humidity during the period. The pre-monsoon months showed an increase in aerosol mass in the higher size ranges. The black carbon (BC) showed maximum values during winter which may be due to various anthropogenic activities like biomass burning and forest fire as well as dry conditions conducive to transport from far off places. The α values representing aerosol size distribution and β values showing the total aerosol concentration in vertical air column rose simultaneously in pre-monsoon months to attain maximum values during February–March 2008. The AOD was also correlated with PM-10 and BC concentrations.     

Efficacy of neural network and genetic algorithm techniques in simulating spatio‐temporal fluctuations of groundwater

Groundwater modelling has emerged as a powerful tool to develop a sustainable management plan for efficient groundwater utilization and protection of this vital resource. This study deals with the development of five hybrid artificial neural network (ANN) models and their critical assessment for simulating spatio‐temporal fluctuations of groundwater in an alluvial aquifer system. Unlike past studies, in this study, all the relevant input variables having significant influence on groundwater have been considered, and the hybrid ANN technique [ANN‐cum‐Genetic Algorithm (GA)] has been used to simulate groundwater levels at 17 sites over the study area. The parameters of the ANN models were optimized using a GA optimization technique. The predictive ability of the five hybrid ANN models developed for each of the 17 sites was evaluated using six goodness‐of‐fit criteria and graphical indicators, together with adequate uncertainty analyses. The analysis of the results of this study revealed that the multilayer perceptron Levenberg–Marquardt model is the most efficient in predicting monthly groundwater levels at almost all of the 17 sites, while the radial basis function model is the least efficient. The GA technique was found to be superior to the commonly used trial‐and‐error method for determining optimal ANN architecture and internal parameters. Of the goodness‐of‐fit statistics used in this study, only root‐mean‐squared error, r² and Nash–Sutcliffe efficiency were found to be more powerful and useful in assessing the performance of the ANN models. It can be concluded that the hybrid ANN modelling approach can be effectively used for predicting spatio‐temporal fluctuations of groundwater at basin or subbasin scales. Copyright © 2014 John Wiley & Sons, Ltd.