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Mousumi Banerjee Jyotisankar Ray Nupur Adhikary Sandip Nandy C. Manikyamba Madhuparna Paul Dola Chakraborty Alireza Eslami 《Journal of the Geological Society of India》2016,88(2):245-255
Malangtoli volcanics of the Singhbhum craton of the eastern Indian shield is one of the important Proterozoic lava suites. Experimental studies on 1 atmosphere pressure constrain the parental magma type and temperature range of crystallization of the parent magma (deduced to be in the range of 1500°C to 1200°C). The experimental studies show that at 1500°C, plagioclase is the first phase to crystallize, followed by few opaques which join along with plagioclase at 1450°C. At subsequent lower temperature (1400°C-1300°C), plagioclase and opaque continue to crystallize. At 1250°C plagioclase and opaque still persist while pyroxene appears first and liquid (glass) still remains. Appearance of opaque minerals (magnetite and illmenite) at both ~1400°C and ~1300°C indicate oscillation of oxygen fugacity in the parent magma, petrographically documented by coarser phenocrysts as well as finer or peripheral tiny grains. Use of tectonic discrimination diagrams (based on discrimination factors F1-F2 and FeOt/MgO vs. TiO2) shows an island arc tholeiitic affinity for Malangtoli volcanic, suggests that the role of proto-plate convergence in Singhbhum architecture played an important role to build up Malangtoli volcanics during Proterozoic. 相似文献
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Ablation processes of snow under a thin dust cover are complicated compared with those under a thick cover, mainly owing to the effects of aggregation (redistribution) of dust particles on the conditions of surface melting. Aggregation of dust particles causes the snow surface to brighten after the initial dust configuration, thus affecting the relationship between initial dust concentration and surface albedo. In order to estimate snow ablation rate under a thin dust cover, we used a composite energy balance model in which the surface albedo is taken as a measured input variable. The estimated results of snow ablation agreed reasonably well with the observation, considering the measurement errors inherited in the snow depressions. Comparison of the two cases, that is, one considering the aggregation of dust particles (observation: albedo variable) and the other without aggregation (assumption: albedo constant), showed that the ablation rates were noticeably lower on the former case. This suggests that the aggregation of dust particles induces a reduction of snow ablation. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Khanal Manoj Adhikary Deepak Balusu Rao Wilkins Andy Belle Bharath 《Geotechnical and Geological Engineering》2022,40(4):1899-1920
Geotechnical and Geological Engineering - Most of the published research on goaf-hole failures are performed using 2D numerical analyses. However, 2D analyses of the goaf-hole failure mechanism,... 相似文献
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The occurrence of foliated rock masses is common in mining environment. Methods employing continuum approximation in describing the deformation of such rock masses possess a clear advantage over methods where each rock layer and each inter‐layer interface (joint) is explicitly modelled. In devising such a continuum model it is imperative that moment (couple) stresses and internal rotations associated with the bending of the rock layers be properly incorporated in the model formulation. Such an approach will lead to a Cosserat‐type theory. In the present model, the behaviour of the intact rock layer is assumed to be linearly elastic and the joints are assumed to be elastic–perfectly plastic. Condition of slip at the interfaces are determined by a Mohr–Coulomb criterion with tension cut off at zero normal stress. The theory is valid for large deformations. The model is incorporated into the finite element program AFENA and validated against an analytical solution of elementary buckling problems of a layered medium under gravity loading. A design chart suitable for assessing the stability of slopes in foliated rock masses against flexural buckling failure has been developed. The design chart is easy to use and provides a quick estimate of critical loading factors for slopes in foliated rock masses. It is shown that the model based on Euler's buckling theory as proposed by Cavers (Rock Mechanics and Rock Engineering 1981; 14 :87–104) substantially overestimates the critical heights for a vertical slope and underestimates the same for sub‐vertical slopes. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Shantanu Kumar Biswal Santosh Kumar Agarwalla Munesh Chandra Adhikary 《Astrophysics and Space Science》2012,337(2):645-650
Some recent experimental observations have been shown that inclusion of electron collisions damping in inertial Alfvén wave
(IAW) dynamics may be important for laboratory as well as space plasmas. This paper presents the numerical simulation of model
equation governing the nonlinear dynamics of IAW in low-beta plasmas. When the nonlinearity arises due to the ponderomotive
force and Joule heating driven density perturbations, the model equation turns out to be a modified nonlinear Schr?dinger
equation (MNLS). The electron collisions are introduced only in the electron momentum equation. The damped localized structures
of IAW with sidebands are obtained. Also, the effect of collisional damping on power spectra of magnetic fluctuations with
different scaling laws has been studied. These turbulent structures may be responsible for particle acceleration in laboratory
and space plasmas. 相似文献
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Technical Note 总被引：10，自引：0，他引：10
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Layered rock masses can be modelled either as standard, orthotropic continua if the layer bending can be neglected or as Cosserat continua if the influence of layer bending is essential. This paper presents a finite element smeared joint model based on the Cosserat theory. The layers are assumed to be elastic with equal thickness and equal mechanical properties. All the cosserat parameters are expressed through the elastic properties of layers, layer thickness and joint stiffness. Plastic-slip as well as tensile-opening of layer interface (joint) are accounted for in a manner similar to the conventional non-associative plasticity theory. As an application, the behaviour of an excavation in a layered rock mass is examined. The displacement and stress fields given by smeared joint models based on the Cosserat continuum and the conventional anisotropic continuum approaches are compared with those obtained from the discrete joint model. The conventional anisotropic continuum model is found to break-down completely when the effective shear modulus in the direction parallel to layering is low in comparison to the shear modulus of the intact layer, whereas the Cosserat model is found to be capable of accurately reproducing complex load–deflection patterns irrespective of the differences in shear moduli. © 1998 John Wiley & Sons, Ltd. 相似文献
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Optimal design of rain gauge network in the Middle Yarra River catchment,Australia 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Rainfall data are a fundamental input for effective planning, designing and operating of water resources projects. A well‐designed rain gauge network is capable of providing accurate estimates of necessary areal average and/or point rainfall estimates at any desired ungauged location in a catchment. Increasing network density with additional rain gauge stations has been the main underlying criterion in the past to reduce error and uncertainty in rainfall estimates. However, installing and operation of additional stations in a network involves large cost and manpower. Hence, the objective of this study is to design an optimal rain gauge network in the Middle Yarra River catchment in Victoria, Australia. The optimal positioning of additional stations as well as optimally relocating of existing redundant stations using the kriging‐based geostatistical approach was undertaken in this study. Reduction of kriging error was considered as an indicator for optimal spatial positioning of the stations. Daily rainfall records of 1997 (an El Niño year) and 2010 (a La Niña year) were used for the analysis. Ordinary kriging was applied for rainfall data interpolation to estimate the kriging error for the network. The results indicate that significant reduction in the kriging error can be achieved by the optimal spatial positioning of the additional as well as redundant stations. Thus, the obtained optimal rain gauge network is expected to be appropriate for providing high quality rainfall estimates over the catchment. The concept proposed in this study for optimal rain gauge network design through combined use of additional and redundant stations together is equally applicable to any other catchment. © 2014 The Authors. Hydrological Processes published by John Wiley & Sons Ltd. 相似文献
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Manoj Khanal Deepak Adhikary Chandana Jayasundara Rao Balusu 《Geotechnical and Geological Engineering》2016,34(1):217-235
This paper investigates various multiseam mining related parameters using mine site specific data and numerical simulations. Two important mining effects—subsidence and stress—are analysed for different possible mining layouts. A geological mine dataset has been used to generate a numerical model. The predicted surface subsidence magnitude and surface profile have been compared under different scenarios to assess potential options in multiseam mining strategies. The effects that seam separation distances, mining offset, panel layout and panel orientation each have on surface subsidence and chain pillar stress magnitude have been investigated. The numerical simulation shows that ascending or descending mining directions have little impact on controlling the surface subsidence in multiseam mining and predicted an almost identical maximum stress development at the chain pillars. Numerical simulations infer that the orientation of the top panels control the subsidence profile. 相似文献