Journal Articles

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    Association of chlorophyll in a multi-parametric shallow marine environment off the Karnataka-Kerala coast
    (2011) Raghavan, B.R.; Shylini, S.K.; Deepthi, T.; Kumaraswami, M.; Ashwini, S.; Chauhan, P.; Raman, M.; Venkat Reddy, D.
    Cluster analysis is a useful data analyzing method to obtain detailed information on the state of the shallow marine environment. The objective of this analysis is to appreciate the clustering patterns of the data of case II shallow marine environment of the eastern Arabian Sea. R-mode cluster analysis was resorted to appreciate the relation of the physical, chemical and biological oceanographic parameters represented as dendograms. A set of 14 parameters were retrieved from seven seasons of the coastal waters from Bekal (North Kerala) to Karwar (North Karnataka). This study exhibits diverse clustering patterns reflecting the heterogeneous behavior of the surface waters of the shallow Arabian Sea enforced by the physical, chemical and biological oceanography of the shallow marine environment. © 2011 CAFET-INNOVA technical society. All right reserved.
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    Evaluation of suitability of garnetiferous biotite gneiss for M-sand production - A case study
    (CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Anand, R.S.; Venkat Reddy, D.V.
    Natural sand are weathered and worn out particles of rocks and are of various grades or size depending on the accounting of wearing. The main natural and cheapest resource of sand is river. River sands are mined from river beds and sand mining has disastrous environmental consequences. Rivers in the southwest coast of India are under immense pressure due to various kinds of human activities among which indiscriminate extraction of construction grade sand is the most disastrous one. The situation is rather alarming in the rivers of Kerala. Indiscriminate of sand has depleted the natural resource and ravaged the rivers of the State. Since sand mining from river caused a lot of environmental issues, the Government has banned mining of the same. Thus, river sand is becoming a scarce commodity and hence exploring alternatives to it has become imminent. The artificial sand (M-sand) produced by proper machines can be a better substitute to river sand. Rock crushed to the required grain size distribution is termed as Manufactured sand (M-Sand). The most common rock in the quarries of Trivandrum is Garnetiferous Biotite gneiss (GBG), followed by Charnockite, Leptynite etc. In present investigation, suitability of the available GBG in Trivandrum area, to be used for m-sand production is verified. For this, a case study was done at Cheriyakonni quarry. The rocks were collected from ‘Metarock Pvt. Ltd.’ m-sand manufacturing plant which collects rock Cheriyakonni quarry, which is rich in GBG. The result of the study gives the best size and best proportion of GBG for m-sand production. © 2014 CAFET-INNOVA TECHNICAL SOCIETY.
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    A geological and geotechnical investigation of some rocks in Trivandrum area, Kerala, India
    (CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2015) Anand, R.S.; Venkat Reddy, D.
    In the Indian stone industry, possessing huge reserves of about 1,690 million cum dimensional stone deposits, geological and geotechnical parameters of commercial rock deposit plays a significant role in the economic exploitation of quality commercial rock deposits. The success of the commercial stone industry solely depends upon the availability of large reserves of defect free raw materials. An attempt is made here to study the geological and geotechnical properties of different rocks from Trivandrum area, Kerala. A variety of rock samples from different parts of Trivandrum are subjected to study petrographic, physical and strength parameters. Geological studies reveals that inherent geological discontinuities in rock deposits like multiple joints, weathering, foliations and variations in color of the rocks etc. lead to huge wastage of resources, because such rocks are not suitable for any engineering purpose. The geotechnical studies conducted gives an idea about the physical and strength properties of the rocks. The result of the study gives the rock which has maximum favorable properties for use in construction engineering applications, out of the available ones in the study area. © 2015 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
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    Assessment of coastal water quality along south west coast of India using multile regression analysis on satellite data
    (National Institute of Rural Development Rajendranagar Hyderabad 500 030, 2018) Jose, D.M.; Mandla, V.R.; Subbarao, S.S.V.; Rao, N.S.; Moses, S.A.
    The coastal waters being the ultimate receiver of all the wastes, shows a declining trend in its quality. It is of immense importance to know the extent of pollution for its monitoringandmanagemenlMeasurementofdissolvedoxygen (DO), biologicaloxygen demand (BOD), pH and fecal coliform (FC) are vital in water quality monitoring and assessment studies. Usually these parameters are determined by analysing water samples collected from various locations. Since this is tedious and expensive, it is limited to small scales. In this paper, an effort has been made to quickly assess the quality of coastal waters of Kerala directly from the satellite imagery by estimating National Sanitation Federation Water Quality Index (NSFWQI) along with DO, BOD, pH and FC. Multiple linear regression is used to develop statistically significant models using Sea Surface Temperature (SST) and Remote Sensing Reflectance (Rrs) from Moderate Resolution Imaging Spectroradiometer (MODIS) and in-situ data available on DO, BOD, pH and FC. The models when validated showed good correlation between in situ values and predicted values with r values ranging from 0.73 (p=0.001) for DO to 0.89 for NSFWQI (p=0.018). Spatial maps are generated showing the distribution of these parameters along the coast. The parameters in the study are checked to see if they are in compliance with the standards. The study gives models to estimate the daily distribution of these parameters along the coast using MODIS data. Thus, appropriate control measures could be adopted to limit the effect on susceptible rural population. © 2019 JPR Solutions. All rights reserved.
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    SEM and XRD investigations on lithomargic clay stabilized using granulated blast furnace slag and cement
    (Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2019) C. Sekhar, D.; Nayak, S.
    Lithomargic clay soil is found along the western coast of southern India extending from Cochin to Goa below hard lateritic soil varying in large depths. This soil is problematic as it loses its strength upon saturation and is mainly consisting of silt size particles. Granulated blast furnace slag is a by-product from the iron industry available in large quantities. Since it has high percentage of CaO (i.e. 30–45%), it has latent hydraulic properties. Laboratory experiments were conducted to improve the strength properties of lithomargic clay by replacing soil with varying percentages of GBFS. Lithomargic clay stabilised with 25% GBFS was found to be the optimum. Further addition of 2 and 4% cement to the optimised slag–soil mix improves the strength properties significantly. SEM and XRD analyses were carried out to observe the microstructural changes in the stabilised soil. The reason for the improvement in strength was established through SEM and XRD. C-S-H, C-A-S-H and few other similar compounds were responsible in improving the strength properties by filling the voids between the soil particles. From the quantitative EDS analysis, it was concluded that the strength improvement was due to the increase in Ca:Si ratio and decrease in Al:Ca ratio. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group.
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    Local site effect incorporation in probabilistic seismic hazard analysis – A case study from southern peninsular India, an intraplate region
    (Elsevier Ltd, 2019) Shreyasvi, C.; Venkataramana, K.; Chopra, S.
    The inclusion of local site effects into seismic hazard analysis is an important issue and has been attempted previously in both deterministic and probabilistic manner. The present study is an attempt to combine the local site response with the standard probabilistic seismic hazard analysis. The site response was computed by performing an equivalent linear analysis in the frequency domain. The input soil profiles for the analysis were taken from the borehole data of the North Kerala region (one of the Southerly states in India). The uncertainty in estimating the shear velocity profile (VS) has been addressed by applying multiple VS–N correlations. The variability in the choice of input motions has been reduced by selecting multiple ground motions representing distinct hazard levels (return period of 50–2000 years). The uniform hazard spectrum developed for the host reference site conditions has been adjusted to the target region and the input motions are scaled accordingly. The analyzed soil profiles were categorized into three distinct soil types namely ‘Sand’, ‘Clay’ and ‘All soil’ based on the predominant soil content. The empirical amplification equation as a function of input rock spectral acceleration (Sa r) was developed for each soil type. ‘Sand’ exhibits nonlinear behavior for Sa r > 0.1 g whereas ‘clay’ demonstrates sustained amplification at longer periods. The average spectral amplification observed is 3 for ‘All soil’, 5 for ‘clay’ and 3.5 for ‘sand’ in the study region. The regionally developed amplification function aids in transforming a Ground Motion Prediction Equation (GMPE) from generic to site-specific. The modified GMPE is integrated with the regional seismic source model to estimate site-specific probabilistic seismic hazard. The study produces site-specific spectrum and surface hazard maps which can be of direct use to planners and designers in creating a seismic resilient built environment. © 2019 Elsevier Ltd
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    Laterites and lateritic soils: Geology, engineering properties and problems
    (International Association of Lowland Technology 1 Honjo Saga 840-8502, 2020) Shivashankar, R.; Thomas, B.C.
    Lateritic soils are abundantly available in the Konkan belt in the western coast of peninsular India, in the four southern states namely - Kerala, Karnataka, Goa and Maharashtra. Along with heavy rainfall (annual rainfall of 2000mm - 4000mm), the region is characterised by high humidity and little variation in temperatures. The typical stratification in lateritic areas consists of soft to hard lateritic crust at the top - about 3m thick, underlain by a layer of lithomargic clay (8 to 10m thick) underlain by parent rock, which is granitic gneiss. This paper briefly discusses the following aspects of lateritic soils (a) geotechnical properties, including those of laterites, lithomargic clays, lateritic lithomarges and lithomargic laterites (b) erosion studies from hole erosion tests (c) slope stability problems of excavated slopes in lateritic formations (d) role of vegetation i.e. turfing and/or trees on slopes in the stability of slopes. It is concluded that lateritic soils, especially lithomargic clays and lateritic lithomarges (1) behave somewhat like dispersive soils. (2) They are highly erosive by nature, especially lithomargic clays with higher content of sand and silt (3) Stability of both excavated and embankment slopes depends on good drainage control. Providing berms and vegetation on slopes adds to stability of slopes. © 2020 International Association of Lowland Technology. All rights reserved.
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    Bivariate Drought Characterization of Two Contrasting Climatic Regions in India Using Copula
    (American Society of Civil Engineers (ASCE), 2021) Sajeev, A.; Deb Barma, S.; Mahesha, A.; Shiau, J.-T.
    This study aims to construct the multiple time-scale joint distributions of drought duration and severity using two-dimensional copulas and compare the drought characteristics in India's two contrasting climate regions: the arid Rajasthan and humid, tropical Kerala. The drought occurrences were defined by the standardized precipitation index (SPI) with a threshold below -0.8 at time scales of 3, 6, 12, and 24 months for 1900-2016. Significant correlations were noted between the drought severity and drought duration in both regions. The Clayton copula gave a better fit than other copulas for modeling the dependence among the observed drought duration and severity. The results indicate that the probability of short-term droughts (SPI-3 and SPI-6) is more significant than those of long-term droughts (SPI-12 and SPI-24) for an identical drought event in both regions. Also, the probability of severe drought events with greater duration and severity for long-term droughts (SPI-12 and SPI-24) is higher in Kerala than that in western Rajasthan. For all the time-scale SPIs, the conditional probability of drought severity for a given duration exceeding a threshold showed an increasing trend in both regions. Furthermore, the conditional probability of the drought duration given the severity for short-term droughts is greater than that of the long-term droughts for the same drought event. For short-term droughts, the conditional return period of an identical drought event is lower in Kerala than in western Rajasthan. In contrast, the conditional return period of long-term droughts is lower in western Rajasthan. Additionally, copula-based nonexceedance conditional distributions for the major crops were established based on rainfall. © 2020 American Society of Civil Engineers.
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    Long-Term Climate Variability and Drought Characteristics in Tropical Region of India
    (American Society of Civil Engineers (ASCE), 2021) Vijay, A.; Sivan, S.D.; Mudbhatkal, A.; Mahesha, A.
    This work reports climate change signals and long-Term trend analysis of climate variables, meteorological drought, and extreme climate indexes over the tropical state of Kerala in India. The trend analysis reveals statistically significant decrease of annual and southwest monsoon rainfall (as much as 63 mm and 55 mm per decade, respectively). A decrease in number of annual rainy days (up to 2.8 days/decade) is also reported. Temperature trend analysis indicates an increasing trend with as high as 1.3°C/decade. The spatio-Temporal variation of extreme climate indexes across Kerala shows a decreasing trend of extreme precipitation indexes and an increasing trend of extreme temperature indexes. R95 and R95p decreased in northern and southern Kerala whereas R5 index increased in central and southern regions. Warm days have significantly increased whereas cold days exhibit a decreasing trend across the state. The increase in warmer nights is statistically significant whereas colder nights are decreasing in central and southern regions. Meteorological drought using Standardized Precipitation Index (SPI) reveals increasing occurrence of droughts in Kerala with higher frequencies over southern and central Kerala. © 2021 American Society of Civil Engineers.
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    Copula-Based Frequency and Coincidence Risk Analysis of Floods in Tropical-Seasonal Rivers
    (American Society of Civil Engineers (ASCE), 2021) Muthuvel, D.; Mahesha, A.
    The conventional method of univariate flood frequency analysis based solely on peak flow (Q) overlooks the influence of other characteristic flood variables, such as the accumulated volume (V) of the flood and the duration (D) of flood events. A copula-based multivariate model that represents the joint behavior of these dependent flood variables could aid in computing joint return periods of flood events in tropical, seasonal rivers of India. In connection with the potential locations of high flood risk among west-flowing rivers, multivariate flood frequency analysis was performed on the Bharatapuzha, Periyar, and Chaliyar Rivers of the state of Kerala, India. A comparison of univariate return periods with multivariate return periods reveals that the intersection of flood variables corresponding to a 20-year univariate return period yields a trivariate return period of 91 years at Bharatapuzha and 144 years at Periyar and Chaliyar. The return period by the union of such flood variables is 10 years. The choice of flood variables and their combination depend on the problem at hand. Additionally, basinwise confluence flood frequency models are built with the peak flow at each stream as the random variables show their spatial interdependencies using conditional probabilities and return periods. The copula-based flood coincidence risk model captures the temporal aspect of the co-occurrence of flood peaks in a basin's streams. The co-occurrence of annual flood peaks between the stream pairs of the Bharatapuzha, Periyar, and Muvathapuzha basins is the highest toward the end of July with probabilities of approximately 2.2×10-4 (at the Kumbidi and Mankara stations), 3×10-4, and 1×10-3, respectively. A trio of copula-based multivariate flood frequency, confluence flood frequency, and flood coincidence risk models could be used to design safe and economic hydrologic infrastructure. © 2021 American Society of Civil Engineers.