Hydrogeology — Problems with solutions     

K. C. Subhash Chandra 《Journal of the Geological Society of India》2017,90(3):378-378

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Easy to Use Empirical Correlations for Liquefaction and No Liquefaction Conditions     

Abhishek Kumar  B. Vivek Srinivas 《Geotechnical and Geological Engineering》2017,35(4):1383-1407

Considerable damages during an earthquake (EQ) are the consequence of in situ soil losing its shear strength which is popularly known as liquefaction. A number of methodologies are available to quantify the safety of a site against liquefaction occurrence. Widely accepted recent methodologies follow iterative process making it cumbersome for the field engineer. In the present work, empirical correlations are proposed in accordance with widely accepted methodology, analysing the effect of various parameters such as overburden pressure, fines content (FC), factor of safety (FOS) etc. These proposed correlations are easy to use for the designers and the field engineers to determine the liquefaction potential of a site. Considering data from 207 global sites, proposed correlations are validated by comparing with standard methodology. Three different graphical validations are presented supporting that the results based on the proposed correlations are closely matching with the standard methodology. In case a site is found susceptible to liquefaction, so far no correlations are available to determine the shear strength required to be achieved after ground improvement which will ensure no liquefaction during future EQ. Proposed correlations in this work can also be used easily to determine improved shear strength required for a known FOS, FC and EQ magnitude (M) from ground improvement. Two flowcharts explaining the use of proposed correlations to determine FOS of a site and improvement shear strength required for a liquefied site from ground improvement respectively are developed in this work. Based on the second flowchart, determination of shear strength required from ground improvement are done for 45 random sites out of 207 liquefied sites during worldwide EQ in this work.  相似文献   

Flow through the annular space between two porous co-axial elliptic cylinders     

Subhash Chandra Sikdar 《Pure and Applied Geophysics》1973,104(1):473-483

Summary In this paper slow steady motion of fluid, through the annular space between two porous co-axial elliptic cylinders has been studied. There is a suction or injection perpendicular to the walls of the tube; the amount of suction (or injection) per unit length through the outer wall is equal to the amount of injection (or suction) through the inner wall. The pressure gradient along the length of the cylinder is constant. The cylinders are assumed to be large and the distance between them is small. The amount of injection or suction is assumed to be small. Method of perturbation is applied to obtain the velocity distribution.  相似文献   

Improved solar coronal temperature for equal green and red line intensities     

Udit Narain  Suresh Chandra 《Solar physics》1976,47(2):607-609

An improved value of the temperature in the solar corona for equal green and red line intensities is obtained. This temperature is in better agreement with a quoted line-width value than the previous theoretical ones.  相似文献   

Commonwealth view of deep sea mining     

Chandra K. Kumar 《Marine Policy》1982,6(3):239-241

Following the resumed Tenth Session of the Third United Nations Conference on the Law of the Sea (UNCLOS III) the UNCLOS President, Tommy T.B. Koh, declared in a press statement that: ‘The programme of work just adopted by the Conference, spelt out its collective determination that — with or without the United States — delegates intended to bring the Conference to a successful conclusion next spring, and that unlike previous occasions we do not intend to let the commitment slip away from our fingers’.1  相似文献   

Integrated studies for characterization of lineaments used to locate groundwater potential zones in a hard rock region of Karnataka, India     

Subash Chandra  V. A. Rao  N. S. Krishnamurthy  S. Dutta  Shakeel Ahmed 《Hydrogeology Journal》2006,14(5):767-776

An integrated study was carried out to investigate the subsurface geological conditions in a hard rock environment, with the aim of identifying zones with groundwater resource potential. The study, in Bairasagara watershed, Karnataka, India, considered geomorphology, water level, resistivity imaging, self potential, total magnetic field and susceptibility. The signatures due to lineaments have been clearly identified and their role in groundwater movement has been documented. Synthetic simulation methods were used to model the electrical response of the lineament using finite differential modeling scheme. The inverted image of the field data is compared with the synthetic image and iteration were performed on the initial model until a best match was obtained resulting on the generation of the calibrated resistivity image of the subsurface. Resistivity imaging revealed that the dykes are weathered/fractured to a depth of 6–8 m and are compact at deeper levels, and that they behave as barriers to groundwater movement, yet facilitate a good groundwater potential zone on the upgradient side. The results of magnetic surveys were utilized in differentiating granites and dolerite dykes with an insignificant resistivity contrast. Geomorphological expression alone cannot reveal the groundwater potential associated with a lineament. However, characterizing the nature of the feature at depth with integrated geophysical methods provides essential information for assessing that potential.An erratum to this article can be found at  相似文献   

Independent component analysis for UXO detection in highly cluttered environments     

Chandra S. Throckmorton  Stacy L. Tantum  Yingyi Tan  Leslie M. Collins   《Journal of Applied Geophysics》2007,61(3-4):304-317

Statistical signal processing techniques have shown progress in discriminating UXO from clutter when the objects occur in isolation. Under this condition, only a single object contributes to the measured sensor data. For multiple closely spaced subsurface objects, however, the unprocessed sensor measurement is a mixture of the responses from several objects. Consequently, the unprocessed measurements cannot be used directly to discriminate UXO from clutter. In this paper, we implement independent component analysis (ICA), a well-established blind source separation (BSS) technique, to recover the unobserved object signatures from the mixed measurement data obtained by simulating electromagnetic induction (EMI) sensor data, and then use the recovered signatures for UXO/clutter discrimination. Discrimination performance depends on multiple factors, including the number of clutter objects in proximity to the UXO, the separation distance between the UXO and clutter, and the number of mixed measurements available. Simulation results are presented illustrating the impact of these factors on discrimination performance.  相似文献   

Upper mantle anisotropy beneath northeast India–Asia collision zone from shear-wave splitting analysis     

Devajit Hazarika  Dilip Kumar Yadav  V. Sriram  Abhishek Rai 《International Journal of Earth Sciences》2013,102(7):2061-2076

Teleseismic earthquake data recorded by 11 broadband digital seismic stations deployed in the India–Asia collision zone in the eastern extremity of the Himalayan orogen (Tidding Suture) are analyzed to investigate the seismic anisotropy in the upper mantle. Shear-wave splitting parameters (Φ and δt) derived from the analysis of core-refracted SKS phases provide first hand information about seismic anisotropy and deformation in the upper mantle beneath the region. The analysis shows considerable strength of anisotropy (delay time ~0.85–1.9 s) with average ENE–WSW-oriented fast polarization direction (FPD) at most of the stations. The FPD observed at stations close to the Tidding Suture aligns parallel to the strike of local geological faults and orthogonal to absolute plate motion direction of the Indian plate. The average trend of FPD at each station indicates that the anisotropy is primarily originated by lithospheric deformation due to India–Asia collision. The splitting data analyzed at closely spaced stations suggest a shallow source of anisotropy originated in the crust and upper mantle. The observed delay times indicate that the primary source of anisotropy is located in the upper mantle. The shear-wave splitting analysis in the Eastern Himalayan syntaxis (EHS) and surrounding regions suggests complex strain partitioning in the mantle which is accountable for evolution of the EHS and complicated syntaxial tectonics.  相似文献   

Correction to: Application of analytical hierarchy process (AHP) for flood risk assessment: a case study in Malda district of West Bengal,India     

Abhishek Ghosh  Shyamal Kumar Kar 《Natural Hazards》2018,92(1):369-379

Flow pulsations in two-phase and single-phase near-critical fluids are considered as a possible source of ultra-low-frequency seismo-electromagnetic variations. The conditions for generation and suppression of density wave instability in the crust are analyzed and the surface electromagnetic effect due to streaming potential generation is estimated. The upper limit of amplitude of magnetic field variations due to density wave instability is about 0.1 nT for single-phase supercritical and 1 nT for two-phase flow oscillations in the frequency range \(10^{-4}{-}10^{-2}~\) Hz for the temperature gradients and spatial scales possible during strike slip events. The signal is characterized by a decaying amplitude with typical relaxation time of about several quasi-periods. The possibility of generation of very low-frequency flow pulsations in two-phase fluids via individual bubble evolution and interaction with external acoustic waves is discussed.  相似文献   

Correction to: Vulnerability assessment through index modeling: a case study in Muriganga–Saptamukhi estuarine interfluve,Sundarban, India     

Abhishek Ghosh  Sutapa Mukhopadhyay 《Arabian Journal of Geosciences》2018,11(8):179

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