Axi-symmetric Analysis of Geosynthetic-reinforced Granular Fill-soft Soil System with Group of Stone Columns   总被引：1，自引：1，他引：0  

Kousik Deb  P. K. Basudhar  S. Chandra 《Geotechnical and Geological Engineering》2010,28(2):177-186

The paper presents a mechanical model to predict the behavior of geosynthetic-reinforced granular fill resting over soft soil improved with group of stone columns subjected to circular or axi-symmetric loading. The saturated soft soil has been idealized by spring-dashpot system. Pasternak shear layer and rough elastic membrane represent the granular fill and geosynthetic reinforcement layer, respectively. The stone columns are idealized by stiffer springs. The nonlinear behavior of granular fill and soft soil is considered. Consolidation of the soft soil due to inclusion of stone columns has also been included in the model. The results obtained by using the present model when compared with the reported results obtained from laboratory model tests shows very good agreement. The effectiveness of geosynthetic reinforcement to reduce the maximum and differential settlement and transfer the stress from soft soil to stone columns is highlighted. It is observed that the reduction of settlement and stress transfer process are greatly influenced by stiffness and spacing of the stone columns. It has been further observed that for both geosynthetic-reinforced and unreinforced cases, the maximum settlement does not change if the ratio between spacing and diameter of stone columns is greater than 4.  相似文献   

Magnetic susceptibility mapping of felsic magmatic lithounits in the central part of Bundelkhand Massif,central India     

Santosh Kumar  S. Raju  Manjari Pathak  Abhishek Pandey 《Journal of the Geological Society of India》2010,75(3):539-548

Late Archaean to Palaeoproterozoic felsic magmatic lithounits exposed in the central part of the Bundelkhand massif have been mapped and their redox series (magnetite vs ilmenite series) evaluated based on magnetic susceptibility (MS) data. The central part of Bundelkhand massif comprises of multiple felsic magmatic pulses (∼2600–2200 Ma), commonly represented by coarse grained granite (CGG-grey granite, CPG-pink granite), medium grained pink granite (MPG), fine grained pink granite (FPG), grey and pink rhyolites and granite porphyry (GP). However, the pink colour of these felsic rocks is the result of hydrothermal fluid-flushing leading to potassic alteration of grey granites. MS values of CGG vary from 0.058 to 14.75×10⁻³ SI with an average of 6.35×10⁻³ SI, which mostly represent oxidized type, magnetite series (73%) granites involving infracrustal (igneous) source materials. CPG (av. MS=3.95×10⁻³ SI) is indeed a pink variety of CGG, the original oxidizing nature of which must have been similar to the bulk of CGG, but has been moderately to strongly reduced because of distinctly more porphyritic nature together with partial assimilation of metapelitic (supracrustal) materials, surmicaceous enclaves, carbonaceous material included in the source materials, and to some extent, induced by hydrothermal and later deformational processes. MPG (av. MS= 1.15×10⁻³ SI) as lensoidal stock-like bodies intrudes the CPG and represent both magnetite series (18%) and ilmenite series (82%) granites, which are probably formed by heterogeneous (mixed) source rocks. GP (av. MS=6.26×10⁻³ SI) occur as dykes (mostly trending NE-SW) intrudes the MPG, CPG and migmatites and bears the nature similar to oxidized type, magnetite series granite. FPG (av. MS= 0.666×10⁻³ SI) trending NE-SW occur as lensoid bodies including a large outcrop, is intrusive into both CPG and MPG, and is moderately to very strongly reduced type, ilmenite series granites, which may be derived by the melting of metapelitic crustal sources. FPG hosting microgranular (mafic magmatic) enclaves commonly exhibit high MS values (7.31–10.22×10⁻³ SI), which appear induced by the mixing and mingling of interacting felsic and mafic magmas prevailed in an open system. Grey (av. MS=10.30×10⁻³ SI) and pink (av. MS=6.72×10⁻³ SI) rhyolites represent oxidized type, magnetite series granites, which may have been derived from infracrustal (magmatic) protoliths. Granite series evaluation of felsic magmatic rocks of central part of Bundelkhand massif strongly suggests their varied redox conditions (differential oxygen fugacity) mostly intrinsic to magma source regions and partially modified by hydrothermal and tectonic processes acting upon them.  相似文献   

Use of objective analysis to estimate winter temperature and precipitation at different stations over western Himalaya     

Jagdish Chandra Joshi  Ashwagosha Ganju 《Journal of Earth System Science》2010,119(5):597-602

Temperature and fresh snow are essential inputs in an avalanche forecasting model. Without these parameters, prediction of avalanche occurrence for a region would be very difficult. In the complex terrain of Himalaya, nonavailability of snow and meteorological data of the remote locations during snow storms in the winter is a common occurrence. In view of this persistent problem present study estimates maximum temperature, minimum temperature, ambient temperature and precipitation intensity on different regions of Indian western Himalaya by using similar parameters of the neighbouring regions. The location at which parameters are required and its neighbouring locations should all fall in the same snow climatic zone. Initial step to estimate the parameters at a location, is to shift the parameters of neighbouring regions at a reference height corresponding to the altitude of the location at which parameters are to be estimated. The parameters at this reference height are then spatially interpolated by using Barnes objective analysis. The parameters estimated on different locations are compared with the observed one and the Root Mean Square Errors (RMSE) of the observed and estimated values of the parameters are discussed for the winters of 2007–2008.  相似文献   

Statistical analysis of Soft X-ray solar flares during solar cycles 21, 22 and 23     

Navin Chandra Joshi  Neeraj Singh Bankoti  Seema Pande  Bimal Pande  Wahab Uddin  Kavita Pandey 《New Astronomy》2010,15(6):538-546

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The Kinetics of the Interaction Between Iron(III)-Ethylenediaminetetraacetate and Peroxynitrite     

Virender K. Sharma  Ria A. Yngard  Zoltan Homonnay  Abhishek Dey  Chun He 《Aquatic Geochemistry》2010,16(3):483-490

The kinetics of the formation of the purple-colored species between Fe^III-EDTA and peroxynitrite were studied as a function of pH (10.4–12.3) at 22°C in aqueous solutions using a stopped-flow technique. A purple-colored species was immediately formed upon mixing, which had an absorbance maximum at 520 nm. The increase in absorbance with time could be fit empirically by a power function with two parameters a and b. The power equation determined was absorbance = a*t ^b , where a increased linearly with pH and the concentration of peroxynitrite, while b almost remained constant with a value of ~0.25. The molar extinction coefficient ε_520 nm for the colored species was determined as 13 M⁻¹cm⁻¹, which is much lower than ε_520 nm = 520 M⁻¹ cm⁻¹ for the [Fe^III(EDTA)O₂]³⁻, a purple species observed in the Fe^III–EDTA–H₂O₂ system. The results of kinetics and spectral measurements of the present study are briefly discussed and compared with those of the reaction between Fe(III)-EDTA and hydrogen peroxide.  相似文献   

Agricultural cropland extent and areas of South Asia derived using Landsat satellite 30-m time-series big-data using random forest machine learning algorithms on the Google Earth Engine cloud   总被引：1，自引：0，他引：1  

Murali Krishna Gumma  Pardhasaradhi G. Teluguntla  Adam Oliphant  Jun Xiong  Chandra Giri 《地理信息系统科学与遥感》2020,57(3):302-322

ABSTRACT

The South Asia (India, Pakistan, Bangladesh, Nepal, Sri Lanka and Bhutan) has a staggering 900 million people (~43% of the population) who face food insecurity or severe food insecurity as per United Nations, Food and Agriculture Organization’s (FAO) the Food Insecurity Experience Scale (FIES). The existing coarse-resolution (≥250-m) cropland maps lack precision in geo-location of individual farms and have low map accuracies. This also results in uncertainties in cropland areas calculated from such products. Thereby, the overarching goal of this study was to develop a high spatial resolution (30-m or better) baseline cropland extent product of South Asia for the year 2015 using Landsat satellite time-series big-data and machine learning algorithms (MLAs) on the Google Earth Engine (GEE) cloud computing platform. To eliminate the impact of clouds, 10 time-composited Landsat bands (blue, green, red, NIR, SWIR1, SWIR2, Thermal, EVI, NDVI, NDWI) were derived for each of the three time-periods over 12 months (monsoon: Days of the Year (DOY) 151–300; winter: DOY 301–365 plus 1–60; and summer: DOY 61–150), taking the every 8-day data from Landsat-8 and 7 for the years 2013–2015, for a total of 30-bands plus global digital elevation model (GDEM) derived slope band. This 31-band mega-file big data-cube was composed for each of the five agro-ecological zones (AEZ’s) of South Asia and formed a baseline data for image classification and analysis. Knowledge-base for the Random Forest (RF) MLAs were developed using spatially well spread-out reference training data (N = 2179) in five AEZs. The classification was performed on GEE for each of the five AEZs using well-established knowledge-base and RF MLAs on the cloud. Map accuracies were measured using independent validation data (N = 1185). The survey showed that the South Asia cropland product had a producer’s accuracy of 89.9% (errors of omissions of 10.1%), user’s accuracy of 95.3% (errors of commission of 4.7%) and an overall accuracy of 88.7%. The National and sub-national (districts) areas computed from this cropland extent product explained 80-96% variability when compared with the National statistics of the South Asian Countries. The full-resolution imagery can be viewed at full-resolution, by zooming-in to any location in South Asia or the world, at www.croplands.org and the cropland products of South Asia downloaded from The Land Processes Distributed Active Archive Center (LP DAAC) of National Aeronautics and Space Administration (NASA) and the United States Geological Survey (USGS): https://lpdaac.usgs.gov/products/gfsad30saafgircev001/.  相似文献   

A new exploration tool: Quantitative core characterization     

Carl H. Sondergeld  Chandra S. Rai 《Pure and Applied Geophysics》1993,141(2-4):249-268

We will describe a new laboratory system which was designed to be highly automated and portable while maintaining quality. Driving this design was the recognition of the temporal dependence of physical properties. It becomes apparent that some sedimentary rocks, particularly shales, degrade and disaggregare so completely that mechanical or elastic properties cannot be measured. This temporal dependence displays a time scale much shorter than normal weathering but greater than the time for stress relief. A system was designed to permit field characterization of freshly recovered core material. A benefit of automation and portability is a marked increase in measurement efficiency. The attributes of this system permit rapid characterization of a large number of fresh cores in remote, frontier exploration areas. This feature can significantly reduce prospect evaluation time. Statistically significant rock property databases can be created in a short period of time.  相似文献   

Rayleigh waves in an inhomogeneous medium     

Prakash Chandra Singh 《Pure and Applied Geophysics》1972,98(1):87-101

Summary Dispersion in Rayleigh waves is discussed for semi-infinite media with = ₁(1 ± cos s z) and = ₁(1 ± cosh s z), being the rigidity of the medium. A few workers tried with the above Fourier type of model but failed to find the dispersive nature. Because they neglected s due to the complexity of the calculation they arrived at a non dispersive frequency equation. This difficulty is removed in this paper and a dispersive frequency equation is obtained which shows both direct and inverse dispersion. The second model leads to non-convergent solution forz but shows many interesting results which are also discussed.  相似文献   

Turam response of a permeable inhomogeneous cylindrical conductor surrounded by a thin shell     

Janardan G. Negi  Chandra P. Gupta  U. Raval 《Pure and Applied Geophysics》1972,97(1):137-145

Summary Electromagnetic response characteristics of an inhomogeneous permeable cylinder surrounded by a thin insulated concentric dissipative shell is obtained in presence of a line-source of current. The 3-layer boundary value problem is solved by assuming the thickness of the shell to be much smaller than the skin-depth in the shell. Numerically computed results are presented in the form of argand diagrams to examine the influence of the shell parameters (conductivity and its proximity with the core) and magnetic contrast. The multi-frequency response of the system is also given which resolves the two conducting layers and analyzes the frequency dependence of screening behavior of the shell.N.G.R.I. Contribution No. 282.  相似文献   

On temperatures in the crust: The effect of temperature dependence of conductivity     

Rishi Narain Singh  Sheel Chandra Jain 《Pure and Applied Geophysics》1970,80(1):267-270

Summary An analysis is made to ascertain the effect of conductivity variation with temperature on the temperatures within the crust. It shows that this effect is very small and can safely be neglected.  相似文献