Theoretical Concept to Understand Plan and Design Smooth Blasting Pattern   总被引：1，自引：0，他引：1  

S. K. Mandal  M. M. Singh  S. Dasgupta 《Geotechnical and Geological Engineering》2008,26(4):399-416

Considering different mechanical cutting tools for excavation of rock, drilling and blasting is said to be inexpensive and at the same time most acceptable and compatible to any geo-excavation condition. Depending upon strength properties of in-situ rock mass, characteristics of joint pattern and required quality of blasting, control blasting techniques viz., pre-split and smooth blasting are commonly implemented to achieve an undamaged periphery rock-wall. To minimize magnitude of damage or overbreak, the paper emphasized that in-situ stresses and re-distribution of stresses during the process of excavation should be considered prior to selection of explosive parameters and implementation of any suitable blast pattern. Rock structure being not massive in nature, the paper firstly explains the influence of discontinuities and design parameters on smooth-wall blasting. Considering the empirical equations for estimation of stress wave’s magnitude and its attenuation characteristics through transmitting medium, the paper has put forward a mathematical model for smooth blasting pattern. The model firstly illustrates that rock burden for each hole should be sub-divided into thin micro strips/slabs to understand the characteristics of wave transmission through the medium and lastly with the help of beam theory of structural dynamics have put forward a mathematical model to analyze and design an effective smooth blasting pattern to achieve an undamaged periphery rock-wall.  相似文献   

Evidence of Superposed Metamorphism from the Gokavaram Area, Eastern Ghats Belt, and its Relation with the Kemp Land Coast, East Antarctica     

Somnath Dasgupta  Pulak Sengupta  Supratim Pal  Masato Fukuoka 《Gondwana Research》1999,2(2):227

In this paper, we compare the petrological histories of the Kemp Land Coast (east Antarctica), and Gokavaram area (Eastern Ghats), that were supposed to have been juxtaposed. The area around Gokavaram is dominated by different varieties of paragneisses (pelitic, quartzofeldspathic, and calcareous composition) with relatively minor amounts of orthogneisses (mafic, enderbitic, and granitic composition). The rocks were involved in three major phases of deformation, and were finally affected by localised shear movement. On the basis of reaction textures, well preserved in high Mg-Al granulites, and calc-silicate granulites, and geothermobarometric data we deduce a polymetamorphic evolution of the rocks. Following an early M₁ metamorphism culminating at 9.2–9.4 kbar, > 950°C, the rocks cooled nearly isobarically down to 850°C. During a subsequent M₂ metamorphism, near isothermal decompression to 5–6 kbar occurred. This was followed by near isobaric cooling down to 600–650°C. M₃ is a weak amphibolite facies overprint, largely restricted to late shears, which involved hydration as well. Available radiometric data from this area can be interpreted in terms of partial resetting of U-Pb systematics in older sphenes due to M₃ metamorphism at ca. 550 Ma. Despite the absence of sufficient isotopic data on the Eastern Ghats granulites, we document a remarkable similarity in the petrological history of the two supposedly erstwhile neighbours.  相似文献   

Seismic active earth pressure on walls with bilinear backface using pseudo-dynamic approach   总被引：2，自引：0，他引：2  

Sreevalsa Kolathayar  Priyanka Ghosh   《Computers and Geotechnics》2009,36(7):1229-1236

This paper presents a study on the seismic active earth pressure behind a rigid cantilever retaining wall with bilinear backface using pseudo-dynamic approach. The wall has sudden change in inclination along its depth and a planar failure surface has been considered behind the retaining wall. The effects of a wide range of parameters like soil friction angle, wall inclination, wall friction angle, amplification of vibration, variation of shear modulus, and horizontal and vertical seismic accelerations on the active earth pressure have been explored in the present study. Unlike the Mononobe-Okabe method, which incorporates pseudo-static analysis, the present analysis predicts a nonlinear variation of active earth pressure along the wall. The results have been compared with the existing values in the literature.  相似文献   

Erratum to: Exposure of developing countries to sea-level rise and storm surges     

Susmita Dasgupta  Benoit Laplante  Siobhan Murray  David Wheeler 《Climatic change》2011,106(4):581

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Examining the Effect of Ancillary and Derived Geographical Data on Improvement of Per-Pixel Classification Accuracy of Different Landscapes     

Uttam Kumar  Anindita Dasgupta  Chiranjit Mukhopadhyay  T. V. Ramachandra 《Journal of the Indian Society of Remote Sensing》2018,46(3):407-422

Effective conservation and management of natural resources requires up-to-date information of the land cover (LC) types and their dynamics. Multi-resolution remote sensing (RS) data coupled with additional ancillary topographical layers (both remotely acquired or derived from ground measurements) with appropriate classification strategies would be more effective in capturing LC dynamics and changes associated with the natural resources. Ancillary information would make the decision boundaries between the LC classes more widely separable, enabling classification with higher accuracy compared to conventional methods of RS data classification. In this work, we ascertain the possibility of improvement in classification accuracy of RS data with the addition of ancillary and derived geographical layers such as vegetation indices, temperature, digital elevation model, aspect, slope and texture, implemented in three different terrains of varying topography—urbanised landscape (Greater Bangalore), forested landscape (Western Ghats) and rugged terrain (Western Himalaya). The study showed that use of additional spatial ancillary and derived information significantly improved the classification accuracy compared to the classification of only original spectral bands. The analysis revealed that in a highly urbanised area with less vegetation cover and contrasting features, inclusion of elevation and texture increased the overall accuracy of IKONOS data classification to 88.72% (3.5% improvement), and inclusion of temperature, NDVI, EVI, elevation, slope, aspect, Panchromatic band along with texture measures, significantly increased the overall accuracy of Landsat ETM+ data classification to 83.15% (7.6% improvement). In a forested landscape with moderate elevation, temperature was useful in improving the overall accuracy by 6.7 to 88.26%, and in a rugged terrain with temperate climate, temperature, EVI, elevation, slope, aspect and Panchromatic band significantly improved the classification accuracy to 89.97% (10.84% improvement) compared to the classification of only original spectral bands, suggesting selection of appropriate ancillary data depending on the terrain.  相似文献   

Analyzing the effect of atmospheric trace elements on selected plant species     

Priyanka Sharma  Shailender Kumar  Abhinav Garg  Chirashree Ghosh 《Environmental Earth Sciences》2015,74(12):7793-7800

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Characterizing spatial variability of soil properties in salt affected coastal India using geostatistics and kriging   总被引：2，自引：0，他引：2  

Rahul Tripathi  A. K. Nayak  Mohammad Shahid  R. Raja  B. B. Panda  S. Mohanty  Anjani Kumar  B. Lal  Priyanka Gautam  R. N. Sahoo 《Arabian Journal of Geosciences》2015,8(12):10693-10703

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Conservation And Conflicts In The Sundarban Biosphere Reserve,India          下载免费PDF全文

Priyanka Ghosh 《Geographical review》2015,105(4):429-440

The Sundarban Biosphere Reserve in West Bengal, India, is part of the largest mangrove forest ecosystem in the world. The reserve is a world heritage site and the last refuge for the endangered Bengal tiger at a crucial time when global climate change threatens their existence. The mangrove ecosystem and wildlife conservation have become the priority for the state government of West Bengal. However, in becoming so, the state government imposes restrictions on catching fish in the core and buffer areas of the biosphere reserve, which intensify fishermen's everyday resource‐access struggles in the mangrove forest. This paper examines the conflict between local fishermen and conservation needs, broadening the understanding of human‐environment relationships in the Sundarbans region of India.  相似文献   

Seismic vertical uplift capacity of horizontal strip anchors using pseudo-dynamic approach     

Priyanka Ghosh 《Computers and Geotechnics》2009,36(1-2):342-351

This paper presents the pseudo-dynamic analysis to determine the seismic vertical uplift capacity of a horizontal strip anchor using upper bound limit analysis. However, in the literature, the pseudo-static approach was used by few researchers to compute the seismic vertical pullout resistance, where the real dynamic nature of earthquake accelerations cannot be considered. Under the seismic conditions, the values of the unit weight component of uplift factor f_γE are determined for different magnitudes of soil friction angle, soil amplification, embedment ratio and seismic acceleration coefficients both in the horizontal and vertical directions. It is observed that the uplift factor f_γE decreases significantly with the increase in seismic accelerations and amplification but increases with the increase in embedment ratio. The results are compared with the existing values in the literature and the significance of the present methodology for designing the horizontal strip anchor is discussed. In presence of vertical earthquake acceleration and amplification of vibration, the present values of f_γE compare reasonably well with the existing pseudo-static values obtained by modifying the horizontal acceleration coefficient.  相似文献   

Inverted metamorphic sequence in the Sikkim Himalayas: crystallization history, P–T gradient and implications     

S. Dasgupta  J. Ganguly  S. Neogi 《Journal of Metamorphic Geology》2004,22(5):395-412

The metapelitic rocks of the Sikkim Himalayas show an inverted metamorphic sequence (IMS) of the complete Barrovian zones from chlorite to sillimanite + K‐feldspar, with the higher grade rocks appearing at progressively higher structural levels. Within the IMS, four groups of major planar structures, S₁, S₂ and S₃ were recognised. The S₂ structures are pervasive throughout the Barrovian sequence, and are sub‐parallel to the metamorphic isograds. The mineral growth in all zones is dominantly syn‐S₂. The disposition of the metamorphic zones and structural features show that the zones were folded as a northerly plunging antiform. Significant bulk compositional variation, with consequent changes of mineralogy, occurs even at the scale of a thin section in some garnet zone rocks. The results of detailed petrographic and thermobarometric studies of the metapelites along a roughly E–W transect show progressive increase of both pressure and temperature with increasing structural levels in the entire IMS. This is contrary to all models that call for thermal inversion as a possible reason for the origin of the IMS. Also, the observation of the temporal relation between crystallization and S₂ structures is problematic for models of post‐/late‐metamorphic tectonic inversion by recumbent folding or thrusting. A successful model of the IMS should explain the petrological coherence of the Barrovian zones and the close relationship of crystallization in each zone with S₂ planar structures along with the observed trend(s) of P–T variation in Sikkim and in other sections. A discussion is presented of some of the available models that, with some modifications, seem to be capable of explaining these observations.  相似文献