Numerical modelling-based pillar strength estimation for an increased height of extraction     

Ashok Kumar  Rakesh Kumar  Arun K. Singh  Sahendra Ram  Pradeep K. Singh  Rajendra Singh 《Arabian Journal of Geosciences》2017,10(18):411

Underground extraction of total thickness of a thick coal seam in single lift by bord and pillar method increases pillar height during retreat. Field studies found that the increase in pillar height affects the depillaring operation adversely, especially, during caving of the strong/massive roof strata. Dilution in strength due to the increased pillar height caused catastrophic failure of barrier pillars and goaf overriding. This warrants a systematic study of pillar strength variation for the different heights of pillar. A review of different pillar strength estimation approaches for an analysis of the dilution in strength of the heightened pillar suggested that numerical modelling provides a better option for such a systematic study. Accordingly, investigations are conducted on simulated models in laboratory adopting a recognised numerical modelling procedure. The observed nature of variations in pillar strengths with the increase in its height in the numerical models and empirical formula is found to be matched. But a mismatch is found between the strength values of the two approaches with an increase in height of the pillar. Considering validity of the empirical formulation in Indian coalfields, a relationship is developed to incorporate a correction in the strength values of the numerical models. The suggested correction on the basis of this simple study of the pillar strength variation would be helpful for the use of the established simulation tool during the depillaring of a thick coal seam.  相似文献   

Recent biogenic traces from the coastal environments of the southern Red Sea coast of Saudi Arabia     

Arun Kumar 《Arabian Journal of Geosciences》2017,10(22):500

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Significance of nearshore wave parameters in identifying vulnerable zones during storm and normal conditions along Visakhapatnam coast,India     

K. V. S. R. Prasad  S. V. V. Arun Kumar  Ch. Venkata Ramu  P. Sreenivas 《Natural Hazards》2009,49(2):347-360

The nearshore parameters, viz., wave runup, wave setup, and wave energy have been estimated during storm and normal conditions of SW monsoon (June–September) and NE monsoon (November–February) by empirical parameterization along Visakhapatnam coast. These results were compared with the field observations during three storms of SW monsoon season in the year 2007. The higher nearshore wave energies were observed at R.K. Beach, Jodugullapalem beach, and Sagarnagar beach during both the seasons. During storm events, the higher wave energies associated with higher wave runups cause severe erosion along the wave convergence zones. The storm wave runups (SWRUs) were higher at R.K. Beach, Palm beach, Jodugullapalem beach, and Sagarnagar Beach. The yearly low wave energy was observed at Lawson’s Bay with lowest wave runup, considered as safest zone. R.K. Beach, Palm beach, and Jodugullapalem beach are identified as vulnerable zones of wave attack. It is noteworthy that in addition to wave energies, wave runups and wave setups also play a vital role in endangering the coast.  相似文献   

Palaeomagnetic and rock magnetic study of charnockites from Tamil Nadu,India, and the ‘Ur’ protocontinent in Early Palaeoproterozoic times     

S. Mondal  J.D.A. Piper  L. Hunt  G. Bandyopadhyay  S. Basu Mallik 《Journal of Asian Earth Sciences》2009,34(4):493-506

Palaeomagnetic and magnetomineralogical results are reported from charnockites in basement terrane at the eastern sector of the WSW–ENE granulite belt of South India. Magnetite is the dominant ferromagnet identified by rock magnetic and optical study; it is present in several phases including large homogeneous titanomagnetites and disseminated magnetite in microfractures linked to growth stages ranging from primary charnockite formation to uplift decompression and exhumation within the interval ～2500–2100 Ma. Several components of magnetization are resolved by thermal demagnetization and summarized by four pole positions; in the northern (Pallavaram) sector these are P1 (33°N, 99°E, dp/dm = 8/9°) and P2 (79°N, 170°E, dp/dm = 3/6°), and in the southern (Vandallur) sector they are V1 (23°N, 116°E, dp/dm = 8/9°) and V2 (26°S, 136°E, dp/dm = 5/10°). These magnetizations are linked to uplift cooling of the basement and unblocking temperature spectra suggest acquisition sequences P1 → P2 and V1 → V2 in each case implying movement of the shield from higher to lower palaeolatitudes sometime between 2500 and 2100 Ma. Palaeomagnetic poles from the cratonic nuclei of Africa, Australia and India all identify motion from higher to lower palaeolatitudes in Early Palaeoproterozoic times, and this is dated ～2400 and ～2200 Ma in the former two shields. The corresponding apparent polar wander (APW) segments match the magnetization record within the charnockite basement terranes of southern India to yield a preliminary reconstruction of the ‘Ur’ protocontinent, the oldest surviving continental protolith with origins prior to 3000 Ma. Although subject to later relative movements these nuclei seem to have remained in proximity until the Mesozoic break-up of Gondwana.  相似文献   

Aquifer characteristics and its modeling around an industrial complex,Tuticorin, Tamil Nadu,India: A case study   总被引：3，自引：0，他引：3  

N. C. Mondal  V. S. Singh  R. Rangarajan 《Journal of Earth System Science》2009,118(3):231-244

Anthropogenic pollution of shallow groundwater resources due to industrial activities is becoming a cause of concern in the east coastal belt of the state of Tamil Nadu, India. Integrated hydrogeological, geophysical and tracer studies were carried out in the coastal region encompassing an industrial complex. The objective has been to gain knowledge of aquifer characteristics, ascertaining groundwater movement and its flow direction, which would in turn reveal the possibility of contamination of groundwater regime and its better management. The results of multi-parameters and model study indicate that the velocity of groundwater flow ranges from 0.013 m/d to 0.22m/d in and around the industrial complex in upstream western part of the catchment and 0.026 m/d to 0.054m/d in the downstream eastern part, near the coast. These parameters are vital for the development of groundwater management scheme.  相似文献   

Implications of kHz quasi-periodic brightness oscillations in X-ray binaries for neutron star structure     

Arun V. Thampan  Dipankar Bhattacharya  Bhaskar Datta 《Monthly notices of the Royal Astronomical Society》1999,302(4):L69-L73

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In-orbit Performance of UVIT and First Results     

S. N. Tandon  J. B. Hutchings  S. K. Ghosh  A. Subramaniam  G. Koshy  V. Girish  P. U. Kamath  S. Kathiravan  A. Kumar  J. P. Lancelot  P. K. Mahesh  R. Mohan  J. Murthy  S. Nagabhushana  A. K. Pati  J. Postma  N. Kameswara Rao  K. Sankarasubramanian  P. Sreekumar  S. Sriram  C. S. Stalin  F. Sutaria  Y. H. Sreedhar  I. V. Barve  C. Mondal  S. Sahu 《Journal of Astrophysics and Astronomy》2017,38(2):28

The performance of the ultraviolet telescope (UVIT) on-board AstroSat is reported. The performance in orbit is also compared with estimates made from the calibrations done on the ground. The sensitivity is found to be within \(\sim \)15% of the estimates, and the spatial resolution in the NUV is found to exceed significantly the design value of \(1.8^{\prime \prime }\) and it is marginally better in the FUV. Images obtained from UVIT are presented to illustrate the details revealed by the high spatial resolution. The potential of multi-band observations in the ultraviolet with high spatial resolution is illustrated by some results.  相似文献   

Response of infaunal macrobenthos to the sediment granulometry in a tropical continental margin–southwest coast of India     

K.A. Jayaraj  P. Sheeba  Josia Jacob  C. Revichandran  P.K. Arun  K.S. Praseeda  P.A. Nisha  K.A. Rasheed 《Estuarine, Coastal and Shelf Science》2008,77(4):743-754

Surficial sediment samples, collected from the continental margin of the southwest coast of India in July 2004, were examined for the grain size and soft-bottom macrobenthic fauna, to understand the sediment granulometry and its effect on the faunal distribution. Samples were collected using Smith-McIntyre Grab, from 20 to 200 m depth range, consisting of mid-shelf, outer shelf and slope. Fine-grained sediment located in the mid shelf and supported low faunal abundance. Polychaetes constituted the bulk of the fauna. Feeding guild changed with depth and sediment granulometry. Coexistence of deposit feeders and carnivores in outer shelf and deposit feeders and filter feeders in the slope region indicated the effective utilization of different food resources. In general, richness and diversity were high in the southern region. Depth wise, the diversity and abundance were relatively high in the 50–75 m depth range. Correlation and BIO-ENV analysis showed that combination of different factors such as sediment texture, sediment sorting and depth were found to influence the distribution of macrobenthos. Hence, spatial variations observed in benthic community were presumably linked to the variations in sediment granulometry and the energy level conditions prevailing in the area.  相似文献   

Improvement of groundwater quality due to fresh water ingress in Potharlanka Island, Krishna delta, India   总被引：1，自引：0，他引：1  

N. C. Mondal  V. S. Singh  V. K. Saxena  R. K. Prasad 《Environmental Geology》2008,55(3):595-603

Hydrochemical study had been carried out on the groundwater resources of Potharlanka Island, Krishna delta, India. Groundwater samples were collected and analyzed at 42 sites in December 2001 and October 2006. A comparative study of hydrochemical data indicates: groundwater is mildly alkaline with a pH of 7.0–8.2; electrical conductivity (EC) varies from 605 to 5,770 μS/cm in December 2001, and 652–5,310 μS/cm in October 2006. More than 62% of the groundwater samples in 2006 have TDS value <2,000 mg/l, which is within permissible limit of potable water, but 57% of the samples in 2001, are higher than the maximum permissible limit. Extremely low HCO₃/Cl and variable high Mg/Ca (molar ratios) had been indicated the transformation of the fresh groundwater aquifer systems to saline in 2001. Groundwater of this Island is mainly classified as Na–Cl and mixed types. A high percentage of Na–Cl type of these waters indicates the possibility of seawater ingression/intrusion process during 2001 and comparatively mixed water type indicates the dilution activities of groundwater. Excessive withdrawal of groundwater has caused the increase of saline water intrusion. Improvement of groundwater quality in this Island due to artificial recharge structures made by NGRI under RGNDWM project and affects of the flood due to heavy rainfall of the months of September–October 2005 are discussed in this paper.  相似文献   

Groundwater prospects evaluation based on hydrogeomorphological mapping using high resolution satellite images: A case study in Uttarakhand     

Md. Surabuddin Mondal  A. C. Pandey  R. D. Garg 《Journal of the Indian Society of Remote Sensing》2008,36(1):69-76

Water is the most important natural resource which forms the core of the ecological system. The advent of remote sensing has opened up new vistas in groundwater prospect evaluation, exploration and management. The groundwater resources of the study area, Rishikesh region of Garhwal Himalayas, are under threat due to population pressure caused by expanding tourism in this region. This entails sustainable and judicious use of this precious resource. The groundwater prospect evaluation in Rishikesh region has been attempted based on hydrogeomorphological mapping of the area consisting of thematic maps of hydrogeomorphology, geology, drainage, lineament, slope and relief using high resolution IRS-1C LISS III and PAN merged satellite images. The Rishikesh region exhibits diverse hydrogeomorphological conditions where the groundwater regime is controlled mainly by topography and geology. A probability-weighted approach has been applied during overlay analysis in ArcMap GIS environment. The overlay analysis allows a linear combination of weights of each thematic map with respect to ground water potential. Good groundwater prospects dominate in the area with more than 50% of the study area showing moderate to excellent potential. The study shows that the remote sensing and geoinformatics techniques can be applied effectively for groundwater prospect evaluation.  相似文献