Vertical uplift resistance of close-spaced shallow rectangular group anchor plates embedded in sand     

R. Ganesh 《Marine Georesources & Geotechnology》2020,38(9):1070-1081

Abstract

This study describes an analytical solution for determining the ultimate vertical uplift resistance of a group of two and multiple number of close-spaced shallow rectangular anchor plates embedded horizontally in sand. The analysis was performed by using an upper bound theorem of limit analysis with the employment of the kinematically admissible three-dimensional (3D) rigid wedge collapse mechanisms. Results are obtained in terms of dimensionless uplift factors F_γ and F_q due to the components of soil self-weight and surcharge pressure acting on the ground surface for a wide range of parameters. It was found that the magnitude of uplift factors decreases substantially with a decrease in the clear spacing between the anchors, soil friction angle, and embedment ratio, and an increase in the aspect ratio of anchors. Further, it was noticed that when the clear spacing between the anchors is greater than or equal to the certain critical value, the interaction effect of anchors vanishes and the magnitude of uplift factors associated with a group of anchors becomes equal to that of single isolated anchors. The present solutions are found to compare reasonably well with those theoretical, numerical, and experimental results available in the literature.  相似文献   

Arsenic-enriched aquifers: Occurrences and mobilization of arsenic in groundwater of Ganges Delta Plain, Barasat, West Bengal, India     

Sandeep Kar  Jyoti Prakash Maity  Jiin-Shuh Jean  Chia-Chuan Liu  Bibhash Nath  Huai-Jen Yang  Jochen Bundschuh   《Applied Geochemistry》2010,25(12):1805-1814

Hydrogeochemical characteristics and elemental features of groundwater and core sediments have been studied to better understand the sources and mobilization process responsible for As-enrichment in part of the Gangetic plain (Barasat, West Bengal, India). Analysis of water samples from shallow tubewells (depth 24.3–48.5 m) and piezometer wells (depth 12.2–79.2 m) demonstrate that the groundwater is mostly the Ca-HCO₃ type and anoxic in nature (mean Eh_SHE = 34 mV). Arsenic concentrations ranged from <10–538 μg/L, with high concentrations only present in the shallow to medium depth (30–50 m) of the aquifer along with high Fe (0.07–9.8 mg/L) and relatively low Mn (0.15–3.38 mg/L) as also evidenced in core sediments. Most groundwater samples contained both As(III) and As(V) species in which the concentration of As(III) was generally higher than that of As(V), exhibiting the reducing condition. Results show lower concentrations of NO₃, SO₄ and NO₂ along with higher values of DOC and HCO₃, indicating the reducing nature of the aquifer with abundant organic matter that can promote the release of As from sediments into groundwater. Positive correlations of As with Fe and DOC were also observed. The presence of DOC may actively drive the redox processes. This study revealed that reduction processes of FeOOH was the dominant mechanism for the release of As into the groundwater in this part of the Ganges Delta plain.  相似文献   

Electrical resistivity investigation of the arsenic affected alluvial aquifers in West Bengal,India: usefulness in identifying the areas of low and high groundwater arsenic   总被引：1，自引：1，他引：0  

Bibhash Nath  Sukumar Basu Mallik  Doris Stüben  Debashis Chatterjee  Laurent Charlet 《Environmental Earth Sciences》2010,60(4):873-884

This study aims at finding out possible relation between lithology and spatial pattern of dissolved arsenic (As) in groundwater around Chakdaha municipality, West Bengal, India. Satellite image, coupled with electrical resistivity survey and borehole drilling helps to delineate surface and sub-surface lithological framework of the As affected alluvial aquifers. The satellite imagery demonstrate that the high As area are presumably under active flood plain environment (low-lying areas), that constantly receive organics due to periodic flooding. Thick low resistive (fine-grained) layer was observed at the top around the high As areas, which, however, not found in low As areas. The result suggests that hydraulic properties of the surface/sub-surface soil/sediment have an important control on the fate and transport of As in the aquifer. This study demonstrates that electrical resistivity tools can be effectively used for the reconnaissance survey in characterizing the plausible lithological framework of an alluvial aquifer containing As.  相似文献   

Comments on ‘Volatile displacement of Meghalaya coals — A pointer to explore low sulphur coals’ by P Behera <Emphasis Type="Italic">(J. Earth Syst. Sci., 116, April 2007, 137–142)</Emphasis>     

Rabindra Nath Hota 《Journal of Earth System Science》2009,118(2):175-177

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Erratum to: A study of lightning activity over land and oceanic regions of India     

Asha Nath  G. K. Manohar  K. K. Dani  P. C. S. Devara 《Journal of Earth System Science》2009,118(6):735

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Contribution of galaxies to the background hydrogen-ionizing flux     

Julien E. G. Devriendt  Shiv K. Sethi  Bruno Guiderdoni  & Biman B. Nath 《Monthly notices of the Royal Astronomical Society》1998,298(3):708-718

We estimate the evolution of the contribution of galaxies to the cosmic background flux at 912 Å by means of a semi-analytic model of galaxy formation and evolution. Such modelling has been quite successful in reproducing the optical properties of galaxies. We assume that high-redshift damped Lyman α systems are the progenitors of present-day galaxies, and we design a series of models that are consistent with the evolution of cosmic comoving emissivities in the available near-infrared, optical, ultraviolet and far-infrared bands along with the evolution of the neutral hydrogen content and average metallicity of damped Lyman α systems. We use these models to compute the galactic contribution to the Lyman-limit emissivity and background flux for 0 ≃  z  ≤ 4. We take into account the absorption of Lyman-limit photons by H  I and dust in the interstellar medium of the galaxies. We find that the background Lyman-limit flux due to galaxies might dominate (or be comparable to) the contribution from quasars at almost all redshifts if the absorption by H  I in the interstellar medium is neglected. Such H  I absorption would result in a severe diminishing of this flux — by almost three orders of magnitude at high redshifts and by one to two orders at z  ≃ 0. Though the resulting galaxy flux is completely negligible at high redshifts, it is comparable to the quasar flux at z  ≃ 0.  相似文献   

Geohydrological evaluation of upper agniar and vellar basins,tamil nadu: An integrated approach using remote sensing,geophysical and well inventory data     

S Palanivel  A Ganesh  T Vasantha Kumaran 《Journal of the Indian Society of Remote Sensing》1996,24(3):153-168

The present paper focuses mainly on the assessment of groundwater availability in the Upper Agniar and Vellar basins. The remote sensing data was used to map the geomorphological units and structural pattern. The integration of geomorphology and structural pattern with geophysical and well inventory data reveals that shallow groundwater occurrence is controlled by geomorphological characteristics whereas at intermediate depth faults/fractures control the yield of groundwater. The study has also indicated that the eastern part of the basins is more favourable for groundwater development than the western part.  相似文献   

Detection of seismic reflections from seismic attributes through fractal analysis   总被引：5，自引：0，他引：5  

Sankar Kumar Nath  Pawan Dewangan 《Geophysical Prospecting》2002,50(3):341-360

The concept of fractals is used here for the identification of seismic reflectors with special emphasis on thin‐bed delineation, which is generally overlooked during standard data processing. A new fractal analysis scheme is applied to both synthetic and real field seismic data. The fractal dimensions of the three seismic attributes – amplitude, phase, and instantaneous frequency – have been analysed and evaluated. A change in fractal dimension is found to occur whenever there is a reflection. However, the resolution in the delineation of reflectors varies, depending on the attribute under consideration and the method of fractal dimension estimation used. Fractal analysis is performed on both noise‐free and noisy synthetic data to establish the noise tolerance limit for both the ‘divider method’ and the ‘Hurst method’. It is then tested with different peak frequencies of the source wavelet to establish the criteria for using the divider method and the Hurst method. The divider method is found to be suitable for high peak frequency source wavelets (> 25 Hz), while the Hurst method is best suited for low peak frequency source wavelets (< 25 Hz). Finally, when applied to the digitally processed and migrated field seismic data, it could even delineate reflectors which otherwise went undetected on the migrated time section.  相似文献   

Slake durability and mineralogical properties of some pyroclastic and sedimentary rocks   总被引：1，自引：0，他引：1  

Ganesh Dhakal  Tetsuro YonedaMasaji Kato  Katsuhiko Kaneko 《Engineering Geology》2002,65(1):31-45

Slake durability of rocks is an important property of rock-mass and rock-materials in geotechnical practice. The slake durability of rocks is closely related to their mineralogical composition. In this paper, mineralogical examinations and slake durability tests for argillaceous clastic rocks, especially pyroclastic rocks, sandstones and mudstones of Neogene Tertiary age from Japan, were performed in order to assess the slake durability and rock alteration process of these rocks as well as to understand the relationship between mineralogy and durability.The mineral composition and textural features of the rocks were studied by means of optical microscopy (OM), X-ray diffractometry (XRD), electron microprobe analysis (EPMA), and scanning electron microscopy (SEM). In addition, the slake durability test was carried out by using the standard testing method of ISRM [Int. J. Rock Mech. Min. Sci. 16 (1979) 148] in distilled water and in the aqueous solutions with dissolved electrolytes of NaCl and CaCl₂.The pyroclastic rocks and tuffaceous sandstone, rich in di-octahedral and tri-octahedral Fe smectite, respectively, show distinctively different slaking behaviors. The pyroclastic rocks show relatively high slaking (Id₂=55.5% and Id₁₀=10.5%) than the tuffaceous sandstone (Id₂=94.1% and Id₁₀=87.8%, refer to text for Id₂ and Id₁₀). This difference in the slake durability observed in these rocks is due to the microscopic occurrences of smectite present in the interspaces between the particles (pyroclastic rocks) and zeolite cementing the interspaces (tuffaceous sandstone) as alteration minerals. In addition, the durability results of tuffaceous sandstone show that the slake durability decreases as the degree of weathering increases (weathered material Id₂=88.7% and Id₁₀=65.3%). Furthermore, two mudstones of Miocene and Pliocene ages, having different clay mineral compositions (smectite vs. illite+chlorite), show the lowest and the highest slake durability among the tested clastic rocks. Hard mudstone shows the highest (Id₂=98.1% and Id₁₀=95.5%) while the soft mudstone shows the lowest (Id₂=33.9% and Id₆=0.4%.) slake durability. Thus, the slake durability of pyroclastic and sedimentary rocks is greatly affected by their mineral composition and texture, and is closely related to their alteration history. Slake durability is also affected by the kind of dissolved electrolyte and its concentration in the aqueous solution, providing some useful information for geotechnical practice.  相似文献   

A study of self-similar cylindrical MHD shock waves in monochromatic radiation     

Onkar Nath 《Astrophysics and Space Science》1989,158(1):163-167

It is never too strange to expect that an eventual fifth repulsive interaction may also be mediated by a spin-2 field. On the other hand, it is highly unlikely that a spin-1 field may mediate an attractive force.  相似文献