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Item Monitoring Spatial and Temporal Scales of Shoreline Changes in the Cuddalore Region, India(Elsevier, 2018) Subbarayan, S.; Kulithalai Shiyam Sundar, K.S.S.; Vishnuprasath, S.R.Coastal zones are constantly undergoing changes in shape and environment due to natural processes and anthropogenic interventions. The study of shoreline change has become a matter of great concern in recent years. The measurement of shorelines is a key factor in coastal zone construction. A shoreline change study was carried out for a 33-km stretch of the Cuddalore coast between Gadilam and the Vellar River. Satellite images (2000, 2005, 2010, and 2015) were taken as an input dataset in a GIS platform. Automatic shoreline delineation was attempted by a masking technique using ENVI software. In this study, the modification of normalized difference water index (MNDWI) method extracted the raster shoreline-based contrast value of coastal pixels and thresholding techniques for segmenting water and land regions. DSAS software and reference digitized shoreline boundary data were used for the analysis of shoreline changes. End point rate (EPR) and net shoreline movement determination showed the northern part of the Uppanar River mouth under erosion (region A to C and E) and sediment deposition at an accretion rate of 7.6. m/year from EPR and 114. m from NSM. The maximum shoreline erosion rate was -. 3.8. m/year from EPR and -. 57. m from NSM. From these attempts and results, a methodical approach for detection and monitoring of shoreline changes on spatial and temporal scales of interest have been suggested. © 2019 Elsevier Inc. All rights reserved.Item Slope stability studies of excavated slopes in lateritic formations(Springer, 2019) Shivashankar, R.; Thomas, B.C.; Krishnanunni, K.T.; Venkat Reddy, D.V.The study area for this paper is coastal Karnataka in India, which has laterites and lateritic soils. The soil stratification in this area mainly consists of lithomargic clay, which is a product of laterization, sandwiched between the hard and porous weathered laterite crust at the top and the hard granite or granitic gneiss underneath. This lithomargic clay, locally called as ‘shedi soil’ behaves as dispersive soil and is also highly erosive. In the first stage of this study, laboratory erosion studies are conducted by using the hole erosion test apparatus on controlled shedi soil samples. Erosion observed in the HET is accelerated due to slaking irrespective of dispersive nature of the soil. Erosion problems were also dealt with using a stabilizer, calcium lignosulfonate and resulted in high increase in its erosion resistance. In the second stage of this study, slope stability studies of excavated slopes in lateritic formations are conducted considering intensity of rainfall, ponding and seepage, apart from the usual geotechnical parameters. The slopes steeper than 60° are not stable in the case of shedi soil considered here. © Springer Nature Singapore Pte Ltd 2019.Item Monitoring Spatial and Temporal Scales of Shoreline Changes in the Cuddalore Region, India(Elsevier, 2019) Subbarayan, S.; Kulithalai Shiyam Sundar, K.S.S.; Vishnuprasath, S.R.Coastal zones are constantly undergoing changes in shape and environment due to natural processes and anthropogenic interventions. The study of shoreline change has become a matter of great concern in recent years. The measurement of shorelines is a key factor in coastal zone construction. A shoreline change study was carried out for a 33-km stretch of the Cuddalore coast between Gadilam and the Vellar River. Satellite images (2000, 2005, 2010, and 2015) were taken as an input dataset in a GIS platform. Automatic shoreline delineation was attempted by a masking technique using ENVI software. In this study, the modification of normalized difference water index (MNDWI) method extracted the raster shoreline-based contrast value of coastal pixels and thresholding techniques for segmenting water and land regions. DSAS software and reference digitized shoreline boundary data were used for the analysis of shoreline changes. End point rate (EPR) and net shoreline movement determination showed the northern part of the Uppanar River mouth under erosion (region A to C and E) and sediment deposition at an accretion rate of 7.6m/year from EPR and 114m from NSM. The maximum shoreline erosion rate was −3.8m/year from EPR and −57m from NSM. From these attempts and results, a methodical approach for detection and monitoring of shoreline changes on spatial and temporal scales of interest have been suggested. © 2019 Elsevier Inc. All rights reserved.Item Failures Investigation of Marine Propellers in Corrosive Environments(Springer Nature, 2021) Mirashi, V.U.; Johnson, S.; Hegde, S.; Vijayan, V.; Cadambi, S.Marine corrosion failure of fishing boat propellers made of cast Nickel Aluminium Bronze were investigated. Specimens extracted from the corroded propellers were characterized by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The alloy comprises several Fe3Al (κ1, κ2, κ4), NiAl (κ3) type intermetallic precipitates and β’ martensite embedded in Cu-rich α-matrix. Transverse sections of the corroded region showed two distinct zones; a non-uniform top oxide layer and a partially corroded zone with selective corrosion of the β’ martensite which run parallel to the κ3 precipitates. From the microstructural analysis it is adjudged that the aggressive local corrosion of the matrix is preceded by cracking of the oxide by erosion, cavitation, etc., A slow growth of the oxide layer follows that reduces the corrosion rate. However, the corrosion cycle repeats on erosion or cracking of the oxide layer when the propeller is used in marine waters. Coupon specimens immersed in actual marine conditions is presented that supports the above theory. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.